From 7b2a6b214b891f0da742f946e69a070127f9469c Mon Sep 17 00:00:00 2001
From: Dhruv Manilawala <dhruvmanila@gmail.com>
Date: Mon, 12 Feb 2024 20:36:20 +0530
Subject: [PATCH] Preview minimal f-string formatting

---
 .../ruff/expression/fstring.options.json      |   8 +
 .../test/fixtures/ruff/expression/fstring.py  | 142 ++++
 .../src/comments/placement.rs                 |  22 +
 crates/ruff_python_formatter/src/context.rs   |  85 +-
 .../src/expression/expr_f_string.rs           |  18 +
 crates/ruff_python_formatter/src/options.rs   |   9 +
 .../src/other/bytes_literal.rs                |   2 +-
 .../src/other/f_string.rs                     | 108 ++-
 .../src/other/f_string_element.rs             | 229 ++++++
 crates/ruff_python_formatter/src/other/mod.rs |   1 +
 .../src/other/string_literal.rs               |   2 +-
 crates/ruff_python_formatter/src/preview.rs   |   5 +
 .../ruff_python_formatter/src/string/mod.rs   |  30 +-
 ...bility@cases__preview_long_strings.py.snap |  22 +-
 ...__preview_long_strings__regression.py.snap |  35 +-
 .../format@expression__fstring.py.snap        | 746 +++++++++++++++++-
 16 files changed, 1411 insertions(+), 53 deletions(-)
 create mode 100644 crates/ruff_python_formatter/resources/test/fixtures/ruff/expression/fstring.options.json
 create mode 100644 crates/ruff_python_formatter/src/other/f_string_element.rs

diff --git a/crates/ruff_python_formatter/resources/test/fixtures/ruff/expression/fstring.options.json b/crates/ruff_python_formatter/resources/test/fixtures/ruff/expression/fstring.options.json
new file mode 100644
index 00000000000000..e3c32249eeffb6
--- /dev/null
+++ b/crates/ruff_python_formatter/resources/test/fixtures/ruff/expression/fstring.options.json
@@ -0,0 +1,8 @@
+[
+  {
+    "preview": "enabled"
+  },
+  {
+    "preview": "disabled"
+  }
+]
diff --git a/crates/ruff_python_formatter/resources/test/fixtures/ruff/expression/fstring.py b/crates/ruff_python_formatter/resources/test/fixtures/ruff/expression/fstring.py
index 017d243f1f08ea..1e51406fc91023 100644
--- a/crates/ruff_python_formatter/resources/test/fixtures/ruff/expression/fstring.py
+++ b/crates/ruff_python_formatter/resources/test/fixtures/ruff/expression/fstring.py
@@ -62,3 +62,145 @@
 x = f'''a{""}b'''
 y = f'''c{1}d"""e'''
 z = f'''a{""}b''' f'''c{1}d"""e'''
+
+# F-String formatting test cases (Preview)
+
+# Simple expression with a mix of debug expression and comments.
+x = f"{a}"
+x = f"{
+    a = }"
+x = f"{ # comment
+    a }"
+x = f"{   # comment
+    a = }"
+
+# Remove the parentheses as adding them doesn't make then fit within the line length limit.
+# This is similar to how we format it before f-string formatting.
+aaaaaaaaaaa = (
+    f"asaaaaaaaaaaaaaaaa { aaaaaaaaaaaa + bbbbbbbbbbbb + ccccccccccccccc + dddddddd } cccccccccc"
+)
+# Here, we would use the best fit layout to put the f-string indented on the next line
+# similar to the next example.
+aaaaaaaaaaa = f"asaaaaaaaaaaaaaaaa { aaaaaaaaaaaa + bbbbbbbbbbbb + ccccccccccccccc } cccccccccc"
+aaaaaaaaaaa = (
+    f"asaaaaaaaaaaaaaaaa { aaaaaaaaaaaa + bbbbbbbbbbbb + ccccccccccccccc } cccccccccc"
+)
+
+# This should never add the optional parentheses because even after adding them, the
+# f-string exceeds the line length limit.
+x = f"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa { "bbbbbbbbbbbbbbbbbbbbbbbbbbbbb" } ccccccccccccccc"
+x = f"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa { "bbbbbbbbbbbbbbbbbbbbbbbbbbbbb" = } ccccccccccccccc"
+x = f"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa { # comment
+                                             "bbbbbbbbbbbbbbbbbbbbbbbbbbbbb" } ccccccccccccccc"
+x = f"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa { # comment
+                                             "bbbbbbbbbbbbbbbbbbbbbbbbbbbbb" = } ccccccccccccccc"
+
+# Multiple larger expressions which exceeds the line length limit. Here, we need to decide
+# whether to split at the first or second expression. This should work similarly to the
+# assignment statement formatting where we split from right to left in preview mode.
+x = f"aaaaaaaaaaaa { bbbbbbbbbbbbbb } cccccccccccccccccccc { ddddddddddddddd } eeeeeeeeeeeeee"
+
+# The above example won't split but when we start introducing line breaks:
+x = f"aaaaaaaaaaaa {
+        bbbbbbbbbbbbbb } cccccccccccccccccccc { ddddddddddddddd } eeeeeeeeeeeeee"
+x = f"aaaaaaaaaaaa { bbbbbbbbbbbbbb
+                    } cccccccccccccccccccc { ddddddddddddddd } eeeeeeeeeeeeee"
+x = f"aaaaaaaaaaaa { bbbbbbbbbbbbbb } cccccccccccccccccccc {
+        ddddddddddddddd } eeeeeeeeeeeeee"
+x = f"aaaaaaaaaaaa { bbbbbbbbbbbbbb } cccccccccccccccccccc { ddddddddddddddd
+                                                            } eeeeeeeeeeeeee"
+
+# But, in case comments are present, we would split at the expression containing the
+# comments:
+x = f"aaaaaaaaaaaa { bbbbbbbbbbbbbb # comment
+                    } cccccccccccccccccccc { ddddddddddddddd } eeeeeeeeeeeeee"
+x = f"aaaaaaaaaaaa { bbbbbbbbbbbbbb
+                    } cccccccccccccccccccc { # comment
+                                            ddddddddddddddd } eeeeeeeeeeeeee"
+
+# Here, the expression part itself starts with a curly brace so we need to add an extra
+# space between the opening curly brace and the expression.
+x = f"{ {'x': 1, 'y': 2} }"
+# Although the extra space isn't required before the ending curly brace, we add it for
+# consistency.
+x = f"{ {'x': 1, 'y': 2}}"
+x = f"{ {'x': 1, 'y': 2} = }"
+x = f"{  # comment
+    {'x': 1, 'y': 2} }"
+x = f"{    # comment
+    {'x': 1, 'y': 2} = }"
+
+# But, in this case, we would split the expression itself because it exceeds the line
+# length limit so we need not add the extra space.
+xxxxxxx = f"{
+    {'aaaaaaaaaaaaaaaaaaa', 'bbbbbbbbbbbbbbbbbbbbbb', 'ccccccccccccccccccccc'}
+}"
+# And, split the expression itself because it exceeds the line length.
+xxxxxxx = f"{
+    {'aaaaaaaaaaaaaaaaaaaaaaaaa', 'bbbbbbbbbbbbbbbbbbbbbbbbbbb', 'cccccccccccccccccccccccccc'}
+}"
+
+# Triple-quoted strings
+# It's ok to use the same quote char for the inner string if it's single-quoted.
+f"""test {'inner'}"""
+f"""test {"inner"}"""
+# But if the inner string is also triple-quoted then we should preserve the existing quotes.
+f"""test {'''inner'''}"""
+
+# Comments
+
+# No comments should be dropped!
+f"{ # comment 1
+    # comment 2
+    foo # comment 3
+    # comment 4
+}"  # comment 5
+# comment 6
+
+# Conversion flags
+#
+# This is not a valid Python code because of the additional whitespace between the `!`
+# and conversion type. But, our parser isn't strict about this. This should probably be
+# removed once we have a strict parser.
+x = f"aaaaaaaaa { x !  r }"
+
+# Even in the case of debug expresions, we only need to preserve the whitespace within
+# the expression part of the replacement field.
+x = f"aaaaaaaaa { x   = !  r  }"
+
+# Combine conversion flags with format specifiers
+x = f"{x   =   !  s
+         :>0
+
+         }"
+# This is interesting. There can be a comment after the format specifier but only if it's
+# on it's own line. Refer to https://github.com/astral-sh/ruff/pull/7787 for more details.
+# We'll format is as trailing comments.
+x = f"{x  !s
+         :>0
+         # comment
+         }"
+
+x = f"""
+{              # dangling comment 1
+ x =   :.0{y # dangling comment 2
+           }f}"""
+
+# Here, the debug expression is in a nested f-string so we should start preserving
+# whitespaces from that point onwards. This means we should format the outer f-string.
+x = f"""{"foo " +    # comment 1
+    f"{   x =
+
+       }"    # comment 2
+ }
+        """
+
+# Mix of various features.
+f"{  # dangling comment 1
+    foo # after foo
+   :>{
+          x # after x
+          }
+    # dangling comment 2
+    # dangling comment 3
+} woah {x}"
diff --git a/crates/ruff_python_formatter/src/comments/placement.rs b/crates/ruff_python_formatter/src/comments/placement.rs
index 2d958ebee98f33..b6709473e83610 100644
--- a/crates/ruff_python_formatter/src/comments/placement.rs
+++ b/crates/ruff_python_formatter/src/comments/placement.rs
@@ -289,6 +289,28 @@ fn handle_enclosed_comment<'a>(
             }
         }
         AnyNodeRef::FString(fstring) => CommentPlacement::dangling(fstring, comment),
+        AnyNodeRef::FStringExpressionElement(_) => {
+            // Handle comments after the format specifier (should be rare):
+            //
+            // ```python
+            // f"literal {
+            //     expr:.3f
+            //     # comment
+            // }"
+            // ```
+            //
+            // This is a valid comment placement.
+            if matches!(
+                comment.preceding_node(),
+                Some(
+                    AnyNodeRef::FStringExpressionElement(_) | AnyNodeRef::FStringLiteralElement(_)
+                )
+            ) {
+                CommentPlacement::dangling(comment.enclosing_node(), comment)
+            } else {
+                handle_bracketed_end_of_line_comment(comment, locator)
+            }
+        }
         AnyNodeRef::ExprList(_)
         | AnyNodeRef::ExprSet(_)
         | AnyNodeRef::ExprListComp(_)
diff --git a/crates/ruff_python_formatter/src/context.rs b/crates/ruff_python_formatter/src/context.rs
index b5dc85fcb3039d..d3dc848daa6ccf 100644
--- a/crates/ruff_python_formatter/src/context.rs
+++ b/crates/ruff_python_formatter/src/context.rs
@@ -1,11 +1,22 @@
 use crate::comments::Comments;
-use crate::string::QuoteChar;
+use crate::string::{QuoteChar, StringQuotes};
 use crate::PyFormatOptions;
 use ruff_formatter::{Buffer, FormatContext, GroupId, IndentWidth, SourceCode};
 use ruff_source_file::Locator;
 use std::fmt::{Debug, Formatter};
 use std::ops::{Deref, DerefMut};
 
+/// Location of the expression which is currently being formatted.
+#[derive(Copy, Clone, Debug, Default)]
+pub(crate) enum ExpressionLocation {
+    /// The expression is inside an f-string, in the replacement field i.e., `f"foo {x}"`.
+    ///
+    /// The containing `StringQuotes` is surrounding f-string quote information.
+    InsideFString(StringQuotes),
+    #[default]
+    Other,
+}
+
 #[derive(Clone)]
 pub struct PyFormatContext<'a> {
     options: PyFormatOptions,
@@ -22,6 +33,7 @@ pub struct PyFormatContext<'a> {
     /// quote style that is inverted from the one here in order to ensure that
     /// the formatted Python code will be valid.
     docstring: Option<QuoteChar>,
+    expression_location: ExpressionLocation,
 }
 
 impl<'a> PyFormatContext<'a> {
@@ -33,6 +45,7 @@ impl<'a> PyFormatContext<'a> {
             node_level: NodeLevel::TopLevel(TopLevelStatementPosition::Other),
             indent_level: IndentLevel::new(0),
             docstring: None,
+            expression_location: ExpressionLocation::Other,
         }
     }
 
@@ -86,6 +99,14 @@ impl<'a> PyFormatContext<'a> {
         }
     }
 
+    pub(crate) fn expression_location(&self) -> ExpressionLocation {
+        self.expression_location
+    }
+
+    pub(crate) fn set_expression_location(&mut self, expression_location: ExpressionLocation) {
+        self.expression_location = expression_location;
+    }
+
     /// Returns `true` if preview mode is enabled.
     pub(crate) const fn is_preview(&self) -> bool {
         self.options.preview().is_enabled()
@@ -332,3 +353,65 @@ where
             .set_indent_level(self.saved_level);
     }
 }
+
+pub(crate) struct WithExprLocation<'a, B, D>
+where
+    D: DerefMut<Target = B>,
+    B: Buffer<Context = PyFormatContext<'a>>,
+{
+    buffer: D,
+    saved_location: ExpressionLocation,
+}
+
+impl<'a, B, D> WithExprLocation<'a, B, D>
+where
+    D: DerefMut<Target = B>,
+    B: Buffer<Context = PyFormatContext<'a>>,
+{
+    pub(crate) fn new(expr_location: ExpressionLocation, mut buffer: D) -> Self {
+        let context = buffer.state_mut().context_mut();
+        let saved_location = context.expression_location();
+
+        context.set_expression_location(expr_location);
+
+        Self {
+            buffer,
+            saved_location,
+        }
+    }
+}
+
+impl<'a, B, D> Deref for WithExprLocation<'a, B, D>
+where
+    D: DerefMut<Target = B>,
+    B: Buffer<Context = PyFormatContext<'a>>,
+{
+    type Target = B;
+
+    fn deref(&self) -> &Self::Target {
+        &self.buffer
+    }
+}
+
+impl<'a, B, D> DerefMut for WithExprLocation<'a, B, D>
+where
+    D: DerefMut<Target = B>,
+    B: Buffer<Context = PyFormatContext<'a>>,
+{
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.buffer
+    }
+}
+
+impl<'a, B, D> Drop for WithExprLocation<'a, B, D>
+where
+    D: DerefMut<Target = B>,
+    B: Buffer<Context = PyFormatContext<'a>>,
+{
+    fn drop(&mut self) {
+        self.buffer
+            .state_mut()
+            .context_mut()
+            .set_expression_location(self.saved_location);
+    }
+}
diff --git a/crates/ruff_python_formatter/src/expression/expr_f_string.rs b/crates/ruff_python_formatter/src/expression/expr_f_string.rs
index dcbb85520e9d1b..76af5630c707f5 100644
--- a/crates/ruff_python_formatter/src/expression/expr_f_string.rs
+++ b/crates/ruff_python_formatter/src/expression/expr_f_string.rs
@@ -48,6 +48,24 @@ impl NeedsParentheses for ExprFString {
     ) -> OptionalParentheses {
         if self.value.is_implicit_concatenated() {
             OptionalParentheses::Multiline
+        // TODO(dhruvmanila): Ideally what we want here is a new variant which
+        // is something like:
+        // - If the expression fits by just adding the parentheses, then add them and
+        //   avoid breaking the f-string expression. So,
+        //   ```
+        //   xxxxxxxxx = (
+        //       f"aaaaaaaaaaaa { xxxxxxx + yyyyyyyy } bbbbbbbbbbbbb"
+        //   )
+        //   ```
+        // - But, if the expression is too long to fit even with parentheses, then
+        //   don't add the parentheses and instead break the expression at `soft_line_break`.
+        //   ```
+        //   xxxxxxxxx = f"aaaaaaaaaaaa {
+        //       xxxxxxxxx + yyyyyyyyyy
+        //   } bbbbbbbbbbbbb"
+        //   ```
+        // This isn't decided yet, refer to the relevant discussion:
+        // https://github.com/astral-sh/ruff/discussions/9785
         } else if AnyString::FString(self).is_multiline(context.source()) {
             OptionalParentheses::Never
         } else {
diff --git a/crates/ruff_python_formatter/src/options.rs b/crates/ruff_python_formatter/src/options.rs
index 8deaf926e41125..7b74c7b0d5a3cc 100644
--- a/crates/ruff_python_formatter/src/options.rs
+++ b/crates/ruff_python_formatter/src/options.rs
@@ -466,3 +466,12 @@ pub enum PythonVersion {
     Py311,
     Py312,
 }
+
+impl PythonVersion {
+    /// Return `true` if the current version supports [PEP 701].
+    ///
+    /// [PEP 701]: https://peps.python.org/pep-0701/
+    pub fn supports_pep_701(self) -> bool {
+        self >= Self::Py312
+    }
+}
diff --git a/crates/ruff_python_formatter/src/other/bytes_literal.rs b/crates/ruff_python_formatter/src/other/bytes_literal.rs
index 63011c2e3e6cff..42ed8d81c4d789 100644
--- a/crates/ruff_python_formatter/src/other/bytes_literal.rs
+++ b/crates/ruff_python_formatter/src/other/bytes_literal.rs
@@ -17,7 +17,7 @@ impl FormatNodeRule<BytesLiteral> for FormatBytesLiteral {
                 Quoting::CanChange,
                 &locator,
                 f.options().quote_style(),
-                f.context().docstring(),
+                f.context(),
                 is_hex_codes_in_unicode_sequences_enabled(f.context()),
             )
             .fmt(f)
diff --git a/crates/ruff_python_formatter/src/other/f_string.rs b/crates/ruff_python_formatter/src/other/f_string.rs
index eb5458c1c83247..4f626325108072 100644
--- a/crates/ruff_python_formatter/src/other/f_string.rs
+++ b/crates/ruff_python_formatter/src/other/f_string.rs
@@ -1,9 +1,15 @@
+use ruff_formatter::write;
 use ruff_python_ast::FString;
 use ruff_text_size::Ranged;
 
 use crate::prelude::*;
 use crate::preview::is_hex_codes_in_unicode_sequences_enabled;
-use crate::string::{Quoting, StringNormalizer};
+use crate::preview::is_pep_701_enabled;
+use crate::string::{
+    choose_quotes, Quoting, StringNormalizer, StringPart, StringPrefix, StringQuotes,
+};
+
+use super::f_string_element::FormatFStringElement;
 
 /// Formats an f-string which is part of a larger f-string expression.
 ///
@@ -25,27 +31,85 @@ impl<'a> FormatFString<'a> {
 impl Format<PyFormatContext<'_>> for FormatFString<'_> {
     fn fmt(&self, f: &mut PyFormatter) -> FormatResult<()> {
         let locator = f.context().locator();
+        let comments = f.context().comments().clone();
+
+        if !is_pep_701_enabled(f.context()) {
+            let result = StringNormalizer::from_source(self.value.range(), &locator)
+                .normalize(
+                    self.quoting,
+                    &locator,
+                    f.options().quote_style(),
+                    f.context(),
+                    is_hex_codes_in_unicode_sequences_enabled(f.context()),
+                )
+                .fmt(f);
+            self.value.elements.iter().for_each(|value| {
+                comments.mark_verbatim_node_comments_formatted(value.into());
+            });
+            return result;
+        }
+
+        let string = StringPart::from_source(self.value.range(), &locator);
+
+        // TODO(dhruvmanila): This could probably be simplified for Python 3.12 specifically
+        // as same quotes can be re-used inside an f-string.
+        let quotes = choose_quotes(
+            &string,
+            &locator,
+            self.quoting,
+            f.options().quote_style(),
+            f.context(),
+        );
+
+        let is_multiline =
+            memchr::memchr2(b'\n', b'\r', locator.slice(self.value).as_bytes()).is_some();
+        let context = FStringContext::new(string.prefix(), quotes, is_multiline);
+
+        // Starting prefix and quote
+        write!(f, [string.prefix(), quotes])?;
+
+        format_with(|f| {
+            f.join()
+                .entries(
+                    self.value
+                        .elements
+                        .iter()
+                        .map(|element| FormatFStringElement::new(element, context)),
+                )
+                .finish()
+        })
+        .fmt(f)?;
+
+        // Ending quote
+        quotes.fmt(f)
+    }
+}
+
+#[derive(Clone, Copy, Debug)]
+pub(crate) struct FStringContext {
+    prefix: StringPrefix,
+    quotes: StringQuotes,
+    is_multiline: bool,
+}
+
+impl FStringContext {
+    const fn new(prefix: StringPrefix, quotes: StringQuotes, is_multiline: bool) -> Self {
+        Self {
+            prefix,
+            quotes,
+            is_multiline,
+        }
+    }
+
+    pub(crate) const fn quotes(self) -> StringQuotes {
+        self.quotes
+    }
+
+    pub(crate) const fn prefix(self) -> StringPrefix {
+        self.prefix
+    }
 
-        let result = StringNormalizer::from_source(self.value.range(), &locator)
-            .normalize(
-                self.quoting,
-                &locator,
-                f.options().quote_style(),
-                f.context().docstring(),
-                is_hex_codes_in_unicode_sequences_enabled(f.context()),
-            )
-            .fmt(f);
-
-        // TODO(dhruvmanila): With PEP 701, comments can be inside f-strings.
-        // This is to mark all of those comments as formatted but we need to
-        // figure out how to handle them. Note that this needs to be done only
-        // after the f-string is formatted, so only for all the non-formatted
-        // comments.
-        let comments = f.context().comments();
-        self.value.elements.iter().for_each(|value| {
-            comments.mark_verbatim_node_comments_formatted(value.into());
-        });
-
-        result
+    pub(crate) const fn should_remove_soft_line_breaks(self) -> bool {
+        !self.is_multiline
     }
 }
diff --git a/crates/ruff_python_formatter/src/other/f_string_element.rs b/crates/ruff_python_formatter/src/other/f_string_element.rs
new file mode 100644
index 00000000000000..3ccea0c780b015
--- /dev/null
+++ b/crates/ruff_python_formatter/src/other/f_string_element.rs
@@ -0,0 +1,229 @@
+use std::borrow::Cow;
+
+use ruff_formatter::{format_args, write, RemoveSoftLinesBuffer};
+use ruff_python_ast::{
+    ConversionFlag, Expr, FStringElement, FStringExpressionElement, FStringLiteralElement,
+};
+use ruff_text_size::Ranged;
+
+use crate::comments::{dangling_open_parenthesis_comments, trailing_comments};
+use crate::context::{ExpressionLocation, NodeLevel, WithExprLocation, WithNodeLevel};
+use crate::prelude::*;
+use crate::preview::is_hex_codes_in_unicode_sequences_enabled;
+use crate::string::normalize_string;
+use crate::verbatim::suppressed_node;
+
+use super::f_string::FStringContext;
+
+/// Formats an f-string element which is either a literal or a formatted expression.
+///
+/// This delegates the actual formatting to the appropriate formatter.
+pub(crate) struct FormatFStringElement<'a> {
+    element: &'a FStringElement,
+    context: FStringContext,
+}
+
+impl<'a> FormatFStringElement<'a> {
+    pub(crate) fn new(element: &'a FStringElement, context: FStringContext) -> Self {
+        Self { element, context }
+    }
+}
+
+impl Format<PyFormatContext<'_>> for FormatFStringElement<'_> {
+    fn fmt(&self, f: &mut PyFormatter) -> FormatResult<()> {
+        match self.element {
+            FStringElement::Literal(string_literal) => {
+                FormatFStringLiteralElement::new(string_literal, self.context).fmt(f)
+            }
+            FStringElement::Expression(expression) => {
+                FormatFStringExpressionElement::new(expression, self.context).fmt(f)
+            }
+        }
+    }
+}
+
+/// Formats an f-string literal element.
+pub(crate) struct FormatFStringLiteralElement<'a> {
+    element: &'a FStringLiteralElement,
+    context: FStringContext,
+}
+
+impl<'a> FormatFStringLiteralElement<'a> {
+    pub(crate) fn new(element: &'a FStringLiteralElement, context: FStringContext) -> Self {
+        Self { element, context }
+    }
+}
+
+impl Format<PyFormatContext<'_>> for FormatFStringLiteralElement<'_> {
+    fn fmt(&self, f: &mut PyFormatter) -> FormatResult<()> {
+        let literal_content = f.context().locator().slice(self.element.range());
+        let normalized = normalize_string(
+            literal_content,
+            self.context.quotes(),
+            self.context.prefix(),
+            is_hex_codes_in_unicode_sequences_enabled(f.context()),
+        );
+        match &normalized {
+            Cow::Borrowed(_) => source_text_slice(self.element.range()).fmt(f),
+            Cow::Owned(normalized) => text(normalized).fmt(f),
+        }
+    }
+}
+
+/// Formats an f-string expression element.
+pub(crate) struct FormatFStringExpressionElement<'a> {
+    element: &'a FStringExpressionElement,
+    context: FStringContext,
+}
+
+impl<'a> FormatFStringExpressionElement<'a> {
+    pub(crate) fn new(element: &'a FStringExpressionElement, context: FStringContext) -> Self {
+        Self { element, context }
+    }
+}
+
+impl Format<PyFormatContext<'_>> for FormatFStringExpressionElement<'_> {
+    fn fmt(&self, f: &mut PyFormatter) -> FormatResult<()> {
+        let FStringExpressionElement {
+            expression,
+            debug_text,
+            conversion,
+            format_spec,
+            ..
+        } = self.element;
+
+        let comments = f.context().comments().clone();
+
+        if let Some(debug_text) = debug_text {
+            token("{").fmt(f)?;
+
+            // If debug text is present in a f-string, we'll mark all of the comments
+            // in this f-string as formatted.
+            comments.mark_verbatim_node_comments_formatted(self.element.into());
+
+            write!(
+                f,
+                [
+                    text(&debug_text.leading),
+                    suppressed_node(&**expression),
+                    text(&debug_text.trailing),
+                ]
+            )?;
+
+            // Even if debug text is present, any whitespace between the
+            // conversion flag and the format spec doesn't need to be preserved.
+            match conversion {
+                ConversionFlag::Str => text("!s").fmt(f)?,
+                ConversionFlag::Ascii => text("!a").fmt(f)?,
+                ConversionFlag::Repr => text("!r").fmt(f)?,
+                ConversionFlag::None => (),
+            }
+
+            if let Some(format_spec) = format_spec.as_deref() {
+                write!(f, [token(":"), suppressed_node(format_spec)])?;
+            }
+
+            token("}").fmt(f)
+        } else {
+            let dangling_item_comments = comments.dangling(self.element);
+            let (dangling_open_parentheses_comments, trailing_format_spec_comments) =
+                dangling_item_comments.split_at(
+                    dangling_item_comments
+                        .partition_point(|comment| comment.start() < expression.start()),
+                );
+
+            let item = format_with(|f| {
+                let line_break_or_space = match expression.as_ref() {
+                    // If an expression starts with a `{`, we need to add a space before the
+                    // curly brace to avoid turning it into a literal curly with `{{`.
+                    //
+                    // For example,
+                    // ```python
+                    // f"{ {'x': 1, 'y': 2} }"
+                    // #  ^                ^
+                    // ```
+                    //
+                    // We need to preserve the space highlighted by `^`.
+                    Expr::Dict(_) | Expr::DictComp(_) | Expr::Set(_) | Expr::SetComp(_) => {
+                        Some(soft_line_break_or_space())
+                    }
+                    _ => None,
+                };
+
+                let f = &mut WithExprLocation::new(
+                    ExpressionLocation::InsideFString(self.context.quotes()),
+                    f,
+                );
+
+                write!(f, [line_break_or_space, expression.format()])?;
+
+                // Conversion comes first, then the format spec.
+                match conversion {
+                    ConversionFlag::Str => text("!s").fmt(f)?,
+                    ConversionFlag::Ascii => text("!a").fmt(f)?,
+                    ConversionFlag::Repr => text("!r").fmt(f)?,
+                    ConversionFlag::None => (),
+                }
+
+                if let Some(format_spec) = format_spec.as_deref() {
+                    let elements =
+                        format_with(|f| {
+                            f.join()
+                                .entries(format_spec.elements.iter().map(|element| {
+                                    FormatFStringElement::new(element, self.context)
+                                }))
+                                .finish()
+                        });
+                    write!(
+                        f,
+                        [
+                            token(":"),
+                            elements,
+                            trailing_comments(trailing_format_spec_comments)
+                        ]
+                    )?;
+                }
+
+                line_break_or_space.fmt(f)
+            });
+
+            let inner = format_with(|f| {
+                let mut buffer = RemoveSoftLinesBuffer::new(f);
+
+                if dangling_open_parentheses_comments.is_empty() {
+                    if self.context.should_remove_soft_line_breaks() {
+                        write!(buffer, [group(&soft_block_indent(&item))])
+                    } else {
+                        write!(f, [group(&soft_block_indent(&item))])
+                    }
+                } else {
+                    if self.context.should_remove_soft_line_breaks() {
+                        write!(
+                            buffer,
+                            [group(&format_args![
+                                dangling_open_parenthesis_comments(
+                                    dangling_open_parentheses_comments
+                                ),
+                                soft_block_indent(&item),
+                            ])]
+                        )
+                    } else {
+                        write!(
+                            f,
+                            [group(&format_args![
+                                dangling_open_parenthesis_comments(
+                                    dangling_open_parentheses_comments
+                                ),
+                                soft_block_indent(&item),
+                            ])]
+                        )
+                    }
+                }
+            });
+
+            let mut f = WithNodeLevel::new(NodeLevel::ParenthesizedExpression, f);
+
+            write!(f, [token("{"), inner, token("}")])
+        }
+    }
+}
diff --git a/crates/ruff_python_formatter/src/other/mod.rs b/crates/ruff_python_formatter/src/other/mod.rs
index d07339f717cbf5..2aace837913c4f 100644
--- a/crates/ruff_python_formatter/src/other/mod.rs
+++ b/crates/ruff_python_formatter/src/other/mod.rs
@@ -7,6 +7,7 @@ pub(crate) mod decorator;
 pub(crate) mod elif_else_clause;
 pub(crate) mod except_handler_except_handler;
 pub(crate) mod f_string;
+pub(crate) mod f_string_element;
 pub(crate) mod f_string_part;
 pub(crate) mod identifier;
 pub(crate) mod keyword;
diff --git a/crates/ruff_python_formatter/src/other/string_literal.rs b/crates/ruff_python_formatter/src/other/string_literal.rs
index c8120721241cb3..69fd6069e82f00 100644
--- a/crates/ruff_python_formatter/src/other/string_literal.rs
+++ b/crates/ruff_python_formatter/src/other/string_literal.rs
@@ -63,7 +63,7 @@ impl Format<PyFormatContext<'_>> for FormatStringLiteral<'_> {
             self.layout.quoting(),
             &locator,
             quote_style,
-            f.context().docstring(),
+            f.context(),
             is_hex_codes_in_unicode_sequences_enabled(f.context()),
         );
 
diff --git a/crates/ruff_python_formatter/src/preview.rs b/crates/ruff_python_formatter/src/preview.rs
index 712a7da4170881..f4a63921549c17 100644
--- a/crates/ruff_python_formatter/src/preview.rs
+++ b/crates/ruff_python_formatter/src/preview.rs
@@ -81,3 +81,8 @@ pub(crate) const fn is_multiline_string_handling_enabled(context: &PyFormatConte
 pub(crate) const fn is_format_module_docstring_enabled(context: &PyFormatContext) -> bool {
     context.is_preview()
 }
+
+/// Returns `true` if the [`PEP 701`](https://github.com/astral-sh/ruff/issues/7594) preview style is enabled.
+pub(crate) fn is_pep_701_enabled(context: &PyFormatContext) -> bool {
+    context.is_preview()
+}
diff --git a/crates/ruff_python_formatter/src/string/mod.rs b/crates/ruff_python_formatter/src/string/mod.rs
index 2d68054a421e41..e821103695c1ef 100644
--- a/crates/ruff_python_formatter/src/string/mod.rs
+++ b/crates/ruff_python_formatter/src/string/mod.rs
@@ -4,7 +4,7 @@ use std::iter::FusedIterator;
 use bitflags::bitflags;
 use memchr::memchr2;
 
-use ruff_formatter::{format_args, write};
+use ruff_formatter::{format_args, write, FormatContext};
 use ruff_python_ast::{
     self as ast, Expr, ExprBytesLiteral, ExprFString, ExprStringLiteral, ExpressionRef,
 };
@@ -13,6 +13,7 @@ use ruff_source_file::Locator;
 use ruff_text_size::{Ranged, TextLen, TextRange, TextSize};
 
 use crate::comments::{leading_comments, trailing_comments};
+use crate::context::ExpressionLocation;
 use crate::expression::expr_f_string::f_string_quoting;
 use crate::expression::parentheses::in_parentheses_only_soft_line_break_or_space;
 use crate::other::f_string::FormatFString;
@@ -326,18 +327,12 @@ impl StringNormalizer {
         quoting: Quoting,
         locator: &'a Locator,
         configured_style: QuoteStyle,
-        parent_docstring_quote_char: Option<QuoteChar>,
+        context: &PyFormatContext<'_>,
         normalize_hex: bool,
     ) -> NormalizedString<'a> {
         let raw_content = locator.slice(self.0.content_range());
 
-        let quotes = choose_quotes(
-            &self.0,
-            locator,
-            quoting,
-            configured_style,
-            parent_docstring_quote_char,
-        );
+        let quotes = choose_quotes(&self.0, locator, quoting, configured_style, context);
 
         let normalized = normalize_string(raw_content, quotes, self.0.prefix(), normalize_hex);
 
@@ -475,7 +470,7 @@ pub(crate) fn choose_quotes(
     locator: &Locator,
     quoting: Quoting,
     configured_style: QuoteStyle,
-    parent_docstring_quote_char: Option<QuoteChar>,
+    context: &PyFormatContext<'_>,
 ) -> StringQuotes {
     // Per PEP 8, always prefer double quotes for triple-quoted strings.
     // Except when using quote-style-preserve.
@@ -525,7 +520,7 @@ pub(crate) fn choose_quotes(
         // Overall this is a bit of a corner case and just inverting the
         // style from what the parent ultimately decided upon works, even
         // if it doesn't have perfect alignment with PEP8.
-        if let Some(quote) = parent_docstring_quote_char {
+        if let Some(quote) = context.docstring() {
             QuoteStyle::from(quote.invert())
         } else if configured_style.is_preserve() {
             QuoteStyle::Preserve
@@ -536,6 +531,19 @@ pub(crate) fn choose_quotes(
         configured_style
     };
 
+    let quoting =
+        if let ExpressionLocation::InsideFString(f_string_quotes) = context.expression_location() {
+            if (f_string_quotes.is_triple() && !string.quotes().is_triple())
+                || context.options().target_version().supports_pep_701()
+            {
+                quoting
+            } else {
+                Quoting::Preserve
+            }
+        } else {
+            quoting
+        };
+
     match quoting {
         Quoting::Preserve => string.quotes(),
         Quoting::CanChange => {
diff --git a/crates/ruff_python_formatter/tests/snapshots/black_compatibility@cases__preview_long_strings.py.snap b/crates/ruff_python_formatter/tests/snapshots/black_compatibility@cases__preview_long_strings.py.snap
index a589aeffed92e2..e95632baa85c1f 100644
--- a/crates/ruff_python_formatter/tests/snapshots/black_compatibility@cases__preview_long_strings.py.snap
+++ b/crates/ruff_python_formatter/tests/snapshots/black_compatibility@cases__preview_long_strings.py.snap
@@ -902,7 +902,7 @@ log.info(f"""Skipping: {'a' == 'b'} {desc['ms_name']} {money=} {dte=} {pos_share
  )
  
  dict_with_lambda_values = {
-@@ -524,61 +383,54 @@
+@@ -524,65 +383,58 @@
  
  # Complex string concatenations with a method call in the middle.
  code = (
@@ -941,7 +941,7 @@ log.info(f"""Skipping: {'a' == 'b'} {desc['ms_name']} {money=} {dte=} {pos_share
  log.info(
 -    "Skipping:"
 -    f" {desc['db_id']} {foo('bar',x=123)} {'foo' != 'bar'} {(x := 'abc=')} {pos_share=} {desc['status']} {desc['exposure_max']}"
-+    f'Skipping: {desc["db_id"]} {foo("bar",x=123)} {"foo" != "bar"} {(x := "abc=")} {pos_share=} {desc["status"]} {desc["exposure_max"]}'
++    f'Skipping: {desc["db_id"]} {foo("bar", x=123,)} {"foo" != "bar"} {(x := "abc=")} {pos_share=} {desc["status"]} {desc["exposure_max"]}'
  )
  
  log.info(
@@ -981,6 +981,18 @@ log.info(f"""Skipping: {'a' == 'b'} {desc['ms_name']} {money=} {dte=} {pos_share
  )
  
  log.info(
+-    f"""Skipping: {"a" == 'b'} {desc["ms_name"]} {money=} {dte=} {pos_share=} {desc["status"]} {desc["exposure_max"]}"""
++    f"""Skipping: {"a" == "b"} {desc["ms_name"]} {money=} {dte=} {pos_share=} {desc["status"]} {desc["exposure_max"]}"""
+ )
+ 
+ log.info(
+@@ -590,5 +442,5 @@
+ )
+ 
+ log.info(
+-    f"""Skipping: {'a' == 'b'} {desc['ms_name']} {money=} {dte=} {pos_share=} {desc['status']} {desc['exposure_max']}"""
++    f"""Skipping: {"a" == "b"} {desc["ms_name"]} {money=} {dte=} {pos_share=} {desc["status"]} {desc["exposure_max"]}"""
+ )
 ```
 
 ## Ruff Output
@@ -1394,7 +1406,7 @@ log.info(
 )
 
 log.info(
-    f'Skipping: {desc["db_id"]} {foo("bar",x=123)} {"foo" != "bar"} {(x := "abc=")} {pos_share=} {desc["status"]} {desc["exposure_max"]}'
+    f'Skipping: {desc["db_id"]} {foo("bar", x=123,)} {"foo" != "bar"} {(x := "abc=")} {pos_share=} {desc["status"]} {desc["exposure_max"]}'
 )
 
 log.info(
@@ -1422,7 +1434,7 @@ log.info(
 )
 
 log.info(
-    f"""Skipping: {"a" == 'b'} {desc["ms_name"]} {money=} {dte=} {pos_share=} {desc["status"]} {desc["exposure_max"]}"""
+    f"""Skipping: {"a" == "b"} {desc["ms_name"]} {money=} {dte=} {pos_share=} {desc["status"]} {desc["exposure_max"]}"""
 )
 
 log.info(
@@ -1430,7 +1442,7 @@ log.info(
 )
 
 log.info(
-    f"""Skipping: {'a' == 'b'} {desc['ms_name']} {money=} {dte=} {pos_share=} {desc['status']} {desc['exposure_max']}"""
+    f"""Skipping: {"a" == "b"} {desc["ms_name"]} {money=} {dte=} {pos_share=} {desc["status"]} {desc["exposure_max"]}"""
 )
 ```
 
diff --git a/crates/ruff_python_formatter/tests/snapshots/black_compatibility@cases__preview_long_strings__regression.py.snap b/crates/ruff_python_formatter/tests/snapshots/black_compatibility@cases__preview_long_strings__regression.py.snap
index 762af6aa16c7ee..3d7e731a3659ba 100644
--- a/crates/ruff_python_formatter/tests/snapshots/black_compatibility@cases__preview_long_strings__regression.py.snap
+++ b/crates/ruff_python_formatter/tests/snapshots/black_compatibility@cases__preview_long_strings__regression.py.snap
@@ -832,7 +832,7 @@ s = f'Lorem Ipsum is simply dummy text of the printing and typesetting industry:
  
  some_commented_string = (  # This comment stays at the top.
      "This string is long but not so long that it needs hahahah toooooo be so greatttt"
-@@ -279,36 +280,25 @@
+@@ -279,37 +280,26 @@
  )
  
  lpar_and_rpar_have_comments = func_call(  # LPAR Comment
@@ -852,31 +852,32 @@ s = f'Lorem Ipsum is simply dummy text of the printing and typesetting industry:
 -    f" {'' if ID is None else ID} | perl -nE 'print if /^{field}:/'"
 -)
 +cmd_fstring = f"sudo -E deluge-console info --detailed --sort-reverse=time_added {'' if ID is None else ID} | perl -nE 'print if /^{field}:/'"
++
++cmd_fstring = f"sudo -E deluge-console info --detailed --sort-reverse=time_added {'{{}}' if ID is None else ID} | perl -nE 'print if /^{field}:/'"
  
 -cmd_fstring = (
 -    "sudo -E deluge-console info --detailed --sort-reverse=time_added"
 -    f" {'{{}}' if ID is None else ID} | perl -nE 'print if /^{field}:/'"
 -)
-+cmd_fstring = f"sudo -E deluge-console info --detailed --sort-reverse=time_added {'{{}}' if ID is None else ID} | perl -nE 'print if /^{field}:/'"
++cmd_fstring = f"sudo -E deluge-console info --detailed --sort-reverse=time_added {{'' if ID is None else ID}} | perl -nE 'print if /^{field}:/'"
  
 -cmd_fstring = (
 -    "sudo -E deluge-console info --detailed --sort-reverse=time_added {'' if ID is"
 -    f" None else ID}} | perl -nE 'print if /^{field}:/'"
 -)
-+cmd_fstring = f"sudo -E deluge-console info --detailed --sort-reverse=time_added {{'' if ID is None else ID}} | perl -nE 'print if /^{field}:/'"
- 
 +fstring = f"This string really doesn't need to be an {{{{fstring}}}}, but this one most certainly, absolutely {does}."
-+
+ 
  fstring = (
 -    "This string really doesn't need to be an {{fstring}}, but this one most"
 -    f" certainly, absolutely {does}."
 +    f"We have to remember to escape {braces}." " Like {these}." f" But not {this}."
  )
--
--fstring = f"We have to remember to escape {braces}. Like {{these}}. But not {this}."
  
+-fstring = f"We have to remember to escape {braces}. Like {{these}}. But not {this}."
+-
  
  class A:
+     class B:
 @@ -364,10 +354,7 @@
          def foo():
              if not hasattr(module, name):
@@ -979,7 +980,13 @@ s = f'Lorem Ipsum is simply dummy text of the printing and typesetting industry:
  )
  
  # The parens should NOT be removed in this case.
-@@ -518,88 +494,78 @@
+@@ -513,93 +489,83 @@
+ 
+ 
+ temp_msg = (
+-    f"{f'{humanize_number(pos)}.': <{pound_len+2}} "
++    f"{f'{humanize_number(pos)}.': <{pound_len + 2}} "
+     f"{balance: <{bal_len + 5}} "
      f"<<{author.display_name}>>\n"
  )
  
@@ -1103,7 +1110,13 @@ s = f'Lorem Ipsum is simply dummy text of the printing and typesetting industry:
      "6. Click on Create Credential at the top."
      '7. At the top click the link for "API key".'
      "8. No application restrictions are needed. Click Create at the bottom."
-@@ -613,55 +579,40 @@
+@@ -608,60 +574,45 @@
+ 
+ # It shouldn't matter if the string prefixes are capitalized.
+ temp_msg = (
+-    f"{F'{humanize_number(pos)}.': <{pound_len+2}} "
++    f"{f'{humanize_number(pos)}.': <{pound_len + 2}} "
+     f"{balance: <{bal_len + 5}} "
      f"<<{author.display_name}>>\n"
  )
  
@@ -1688,7 +1701,7 @@ class X:
 
 
 temp_msg = (
-    f"{f'{humanize_number(pos)}.': <{pound_len+2}} "
+    f"{f'{humanize_number(pos)}.': <{pound_len + 2}} "
     f"{balance: <{bal_len + 5}} "
     f"<<{author.display_name}>>\n"
 )
@@ -1773,7 +1786,7 @@ message = (
 
 # It shouldn't matter if the string prefixes are capitalized.
 temp_msg = (
-    f"{F'{humanize_number(pos)}.': <{pound_len+2}} "
+    f"{f'{humanize_number(pos)}.': <{pound_len + 2}} "
     f"{balance: <{bal_len + 5}} "
     f"<<{author.display_name}>>\n"
 )
diff --git a/crates/ruff_python_formatter/tests/snapshots/format@expression__fstring.py.snap b/crates/ruff_python_formatter/tests/snapshots/format@expression__fstring.py.snap
index d9bc028763812d..31b1ca8c35808d 100644
--- a/crates/ruff_python_formatter/tests/snapshots/format@expression__fstring.py.snap
+++ b/crates/ruff_python_formatter/tests/snapshots/format@expression__fstring.py.snap
@@ -68,9 +68,398 @@ result_f = (
 x = f'''a{""}b'''
 y = f'''c{1}d"""e'''
 z = f'''a{""}b''' f'''c{1}d"""e'''
+
+# F-String formatting test cases (Preview)
+
+# Simple expression with a mix of debug expression and comments.
+x = f"{a}"
+x = f"{
+    a = }"
+x = f"{ # comment
+    a }"
+x = f"{   # comment
+    a = }"
+
+# Remove the parentheses as adding them doesn't make then fit within the line length limit.
+# This is similar to how we format it before f-string formatting.
+aaaaaaaaaaa = (
+    f"asaaaaaaaaaaaaaaaa { aaaaaaaaaaaa + bbbbbbbbbbbb + ccccccccccccccc + dddddddd } cccccccccc"
+)
+# Here, we would use the best fit layout to put the f-string indented on the next line
+# similar to the next example.
+aaaaaaaaaaa = f"asaaaaaaaaaaaaaaaa { aaaaaaaaaaaa + bbbbbbbbbbbb + ccccccccccccccc } cccccccccc"
+aaaaaaaaaaa = (
+    f"asaaaaaaaaaaaaaaaa { aaaaaaaaaaaa + bbbbbbbbbbbb + ccccccccccccccc } cccccccccc"
+)
+
+# This should never add the optional parentheses because even after adding them, the
+# f-string exceeds the line length limit.
+x = f"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa { "bbbbbbbbbbbbbbbbbbbbbbbbbbbbb" } ccccccccccccccc"
+x = f"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa { "bbbbbbbbbbbbbbbbbbbbbbbbbbbbb" = } ccccccccccccccc"
+x = f"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa { # comment
+                                             "bbbbbbbbbbbbbbbbbbbbbbbbbbbbb" } ccccccccccccccc"
+x = f"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa { # comment
+                                             "bbbbbbbbbbbbbbbbbbbbbbbbbbbbb" = } ccccccccccccccc"
+
+# Multiple larger expressions which exceeds the line length limit. Here, we need to decide
+# whether to split at the first or second expression. This should work similarly to the
+# assignment statement formatting where we split from right to left in preview mode.
+x = f"aaaaaaaaaaaa { bbbbbbbbbbbbbb } cccccccccccccccccccc { ddddddddddddddd } eeeeeeeeeeeeee"
+
+# The above example won't split but when we start introducing line breaks:
+x = f"aaaaaaaaaaaa {
+        bbbbbbbbbbbbbb } cccccccccccccccccccc { ddddddddddddddd } eeeeeeeeeeeeee"
+x = f"aaaaaaaaaaaa { bbbbbbbbbbbbbb
+                    } cccccccccccccccccccc { ddddddddddddddd } eeeeeeeeeeeeee"
+x = f"aaaaaaaaaaaa { bbbbbbbbbbbbbb } cccccccccccccccccccc {
+        ddddddddddddddd } eeeeeeeeeeeeee"
+x = f"aaaaaaaaaaaa { bbbbbbbbbbbbbb } cccccccccccccccccccc { ddddddddddddddd
+                                                            } eeeeeeeeeeeeee"
+
+# But, in case comments are present, we would split at the expression containing the
+# comments:
+x = f"aaaaaaaaaaaa { bbbbbbbbbbbbbb # comment
+                    } cccccccccccccccccccc { ddddddddddddddd } eeeeeeeeeeeeee"
+x = f"aaaaaaaaaaaa { bbbbbbbbbbbbbb
+                    } cccccccccccccccccccc { # comment
+                                            ddddddddddddddd } eeeeeeeeeeeeee"
+
+# Here, the expression part itself starts with a curly brace so we need to add an extra
+# space between the opening curly brace and the expression.
+x = f"{ {'x': 1, 'y': 2} }"
+# Although the extra space isn't required before the ending curly brace, we add it for
+# consistency.
+x = f"{ {'x': 1, 'y': 2}}"
+x = f"{ {'x': 1, 'y': 2} = }"
+x = f"{  # comment
+    {'x': 1, 'y': 2} }"
+x = f"{    # comment
+    {'x': 1, 'y': 2} = }"
+
+# But, in this case, we would split the expression itself because it exceeds the line
+# length limit so we need not add the extra space.
+xxxxxxx = f"{
+    {'aaaaaaaaaaaaaaaaaaa', 'bbbbbbbbbbbbbbbbbbbbbb', 'ccccccccccccccccccccc'}
+}"
+# And, split the expression itself because it exceeds the line length.
+xxxxxxx = f"{
+    {'aaaaaaaaaaaaaaaaaaaaaaaaa', 'bbbbbbbbbbbbbbbbbbbbbbbbbbb', 'cccccccccccccccccccccccccc'}
+}"
+
+# Triple-quoted strings
+# It's ok to use the same quote char for the inner string if it's single-quoted.
+f"""test {'inner'}"""
+f"""test {"inner"}"""
+# But if the inner string is also triple-quoted then we should preserve the existing quotes.
+f"""test {'''inner'''}"""
+
+# Comments
+
+# No comments should be dropped!
+f"{ # comment 1
+    # comment 2
+    foo # comment 3
+    # comment 4
+}"  # comment 5
+# comment 6
+
+# Conversion flags
+#
+# This is not a valid Python code because of the additional whitespace between the `!`
+# and conversion type. But, our parser isn't strict about this. This should probably be
+# removed once we have a strict parser.
+x = f"aaaaaaaaa { x !  r }"
+
+# Even in the case of debug expresions, we only need to preserve the whitespace within
+# the expression part of the replacement field.
+x = f"aaaaaaaaa { x   = !  r  }"
+
+# Combine conversion flags with format specifiers
+x = f"{x   =   !  s
+         :>0
+
+         }"
+# This is interesting. There can be a comment after the format specifier but only if it's
+# on it's own line. Refer to https://github.com/astral-sh/ruff/pull/7787 for more details.
+# We'll format is as trailing comments.
+x = f"{x  !s
+         :>0
+         # comment
+         }"
+
+x = f"""
+{              # dangling comment 1
+ x =   :.0{y # dangling comment 2
+           }f}"""
+
+# Here, the debug expression is in a nested f-string so we should start preserving
+# whitespaces from that point onwards. This means we should format the outer f-string.
+x = f"""{"foo " +    # comment 1
+    f"{   x =
+
+       }"    # comment 2
+ }
+        """
+
+# Mix of various features.
+f"{  # dangling comment 1
+    foo # after foo
+   :>{
+          x # after x
+          }
+    # dangling comment 2
+    # dangling comment 3
+} woah {x}"
+```
+
+## Outputs
+### Output 1
+```
+indent-style               = space
+line-width                 = 88
+indent-width               = 4
+quote-style                = Double
+line-ending                = LineFeed
+magic-trailing-comma       = Respect
+docstring-code             = Disabled
+docstring-code-line-width  = "dynamic"
+preview                    = Enabled
+target_version             = Py38
+source_type                = Python
+```
+
+```python
+(f"{one}" f"{two}")
+
+
+rf"Not-so-tricky \"quote"
+
+# Regression test for fstrings dropping comments
+result_f = (
+    "Traceback (most recent call last):\n"
+    f'  File "{__file__}", line {lineno_f + 5}, in _check_recursive_traceback_display\n'
+    "    f()\n"
+    f'  File "{__file__}", line {lineno_f + 1}, in f\n'
+    "    f()\n"
+    f'  File "{__file__}", line {lineno_f + 1}, in f\n'
+    "    f()\n"
+    f'  File "{__file__}", line {lineno_f + 1}, in f\n'
+    "    f()\n"
+    # XXX: The following line changes depending on whether the tests
+    # are run through the interactive interpreter or with -m
+    # It also varies depending on the platform (stack size)
+    # Fortunately, we don't care about exactness here, so we use regex
+    r"  \[Previous line repeated (\d+) more times\]"
+    "\n"
+    "RecursionError: maximum recursion depth exceeded\n"
+)
+
+
+# Regression for fstring dropping comments that were accidentally attached to
+# an expression inside a formatted value
+(
+    f"{1}"
+    # comment
+    ""
+)
+
+(
+    f"{1}"  # comment
+    f"{2}"
+)
+
+(
+    f"{1}" f"{2}"  # comment
+)
+
+(
+    1,
+    (  # comment
+        f"{2}"
+    ),
+)
+
+(
+    (
+        f"{1}"
+        # comment
+    ),
+    2,
+)
+
+# https://github.com/astral-sh/ruff/issues/6841
+x = f"""a{""}b"""
+y = f'''c{1}d"""e'''
+z = f"""a{""}b""" f'''c{1}d"""e'''
+
+# F-String formatting test cases (Preview)
+
+# Simple expression with a mix of debug expression and comments.
+x = f"{a}"
+x = f"{
+    a = }"
+x = f"{  # comment
+    a
+}"
+x = f"{   # comment
+    a = }"
+
+# Remove the parentheses as adding them doesn't make then fit within the line length limit.
+# This is similar to how we format it before f-string formatting.
+aaaaaaaaaaa = f"asaaaaaaaaaaaaaaaa {aaaaaaaaaaaa + bbbbbbbbbbbb + ccccccccccccccc + dddddddd} cccccccccc"
+# Here, we would use the best fit layout to put the f-string indented on the next line
+# similar to the next example.
+aaaaaaaaaaa = (
+    f"asaaaaaaaaaaaaaaaa {aaaaaaaaaaaa + bbbbbbbbbbbb + ccccccccccccccc} cccccccccc"
+)
+aaaaaaaaaaa = (
+    f"asaaaaaaaaaaaaaaaa {aaaaaaaaaaaa + bbbbbbbbbbbb + ccccccccccccccc} cccccccccc"
+)
+
+# This should never add the optional parentheses because even after adding them, the
+# f-string exceeds the line length limit.
+x = f"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa {"bbbbbbbbbbbbbbbbbbbbbbbbbbbbb"} ccccccccccccccc"
+x = f"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa { "bbbbbbbbbbbbbbbbbbbbbbbbbbbbb" = } ccccccccccccccc"
+x = f"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa {  # comment
+    "bbbbbbbbbbbbbbbbbbbbbbbbbbbbb"
+} ccccccccccccccc"
+x = f"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa { # comment
+                                             "bbbbbbbbbbbbbbbbbbbbbbbbbbbbb" = } ccccccccccccccc"
+
+# Multiple larger expressions which exceeds the line length limit. Here, we need to decide
+# whether to split at the first or second expression. This should work similarly to the
+# assignment statement formatting where we split from right to left in preview mode.
+x = f"aaaaaaaaaaaa {bbbbbbbbbbbbbb} cccccccccccccccccccc {ddddddddddddddd} eeeeeeeeeeeeee"
+
+# The above example won't split but when we start introducing line breaks:
+x = f"aaaaaaaaaaaa {bbbbbbbbbbbbbb} cccccccccccccccccccc {
+    ddddddddddddddd
+} eeeeeeeeeeeeee"
+x = f"aaaaaaaaaaaa {bbbbbbbbbbbbbb} cccccccccccccccccccc {
+    ddddddddddddddd
+} eeeeeeeeeeeeee"
+x = f"aaaaaaaaaaaa {bbbbbbbbbbbbbb} cccccccccccccccccccc {
+    ddddddddddddddd
+} eeeeeeeeeeeeee"
+x = f"aaaaaaaaaaaa {bbbbbbbbbbbbbb} cccccccccccccccccccc {
+    ddddddddddddddd
+} eeeeeeeeeeeeee"
+
+# But, in case comments are present, we would split at the expression containing the
+# comments:
+x = f"aaaaaaaaaaaa {
+    bbbbbbbbbbbbbb  # comment
+} cccccccccccccccccccc {ddddddddddddddd} eeeeeeeeeeeeee"
+x = f"aaaaaaaaaaaa {bbbbbbbbbbbbbb} cccccccccccccccccccc {  # comment
+    ddddddddddddddd
+} eeeeeeeeeeeeee"
+
+# Here, the expression part itself starts with a curly brace so we need to add an extra
+# space between the opening curly brace and the expression.
+x = f"{ {'x': 1, 'y': 2} }"
+# Although the extra space isn't required before the ending curly brace, we add it for
+# consistency.
+x = f"{ {'x': 1, 'y': 2} }"
+x = f"{ {'x': 1, 'y': 2} = }"
+x = f"{  # comment
+    {'x': 1, 'y': 2}
+}"
+x = f"{    # comment
+    {'x': 1, 'y': 2} = }"
+
+# But, in this case, we would split the expression itself because it exceeds the line
+# length limit so we need not add the extra space.
+xxxxxxx = f"{
+    {'aaaaaaaaaaaaaaaaaaa', 'bbbbbbbbbbbbbbbbbbbbbb', 'ccccccccccccccccccccc'}
+}"
+# And, split the expression itself because it exceeds the line length.
+xxxxxxx = f"{
+    {
+        'aaaaaaaaaaaaaaaaaaaaaaaaa',
+        'bbbbbbbbbbbbbbbbbbbbbbbbbbb',
+        'cccccccccccccccccccccccccc',
+    }
+}"
+
+# Triple-quoted strings
+# It's ok to use the same quote char for the inner string if it's single-quoted.
+f"""test {"inner"}"""
+f"""test {"inner"}"""
+# But if the inner string is also triple-quoted then we should preserve the existing quotes.
+f"""test {'''inner'''}"""
+
+# Comments
+
+# No comments should be dropped!
+f"{  # comment 1
+    # comment 2
+    foo  # comment 3
+    # comment 4
+}"  # comment 5
+# comment 6
+
+# Conversion flags
+#
+# This is not a valid Python code because of the additional whitespace between the `!`
+# and conversion type. But, our parser isn't strict about this. This should probably be
+# removed once we have a strict parser.
+x = f"aaaaaaaaa {x!r}"
+
+# Even in the case of debug expresions, we only need to preserve the whitespace within
+# the expression part of the replacement field.
+x = f"aaaaaaaaa { x   = !r}"
+
+# Combine conversion flags with format specifiers
+x = f"{x   =   !s:>0}"
+# This is interesting. There can be a comment after the format specifier but only if it's
+# on it's own line. Refer to https://github.com/astral-sh/ruff/pull/7787 for more details.
+# We'll format is as trailing comments.
+x = f"{
+    x!s:>0
+    # comment
+}"
+
+x = f"""
+{              # dangling comment 1
+ x =   :.0{y # dangling comment 2
+           }f}"""
+
+# Here, the debug expression is in a nested f-string so we should start preserving
+# whitespaces from that point onwards. This means we should format the outer f-string.
+x = f"""{
+    "foo "  # comment 1
+    + f"{   x =
+
+       }"  # comment 2
+}
+        """
+
+# Mix of various features.
+f"{  # dangling comment 1
+    foo:>{  # after foo
+        x  # after x
+    }
+    # dangling comment 2
+    # dangling comment 3
+} woah {x}"
+```
+
+
+### Output 2
+```
+indent-style               = space
+line-width                 = 88
+indent-width               = 4
+quote-style                = Double
+line-ending                = LineFeed
+magic-trailing-comma       = Respect
+docstring-code             = Disabled
+docstring-code-line-width  = "dynamic"
+preview                    = Disabled
+target_version             = Py38
+source_type                = Python
 ```
 
-## Output
 ```python
 (f"{one}" f"{two}")
 
@@ -134,6 +523,361 @@ result_f = (
 x = f"""a{""}b"""
 y = f'''c{1}d"""e'''
 z = f"""a{""}b""" f'''c{1}d"""e'''
+
+# F-String formatting test cases (Preview)
+
+# Simple expression with a mix of debug expression and comments.
+x = f"{a}"
+x = f"{
+    a = }"
+x = f"{ # comment
+    a }"
+x = f"{   # comment
+    a = }"
+
+# Remove the parentheses as adding them doesn't make then fit within the line length limit.
+# This is similar to how we format it before f-string formatting.
+aaaaaaaaaaa = f"asaaaaaaaaaaaaaaaa { aaaaaaaaaaaa + bbbbbbbbbbbb + ccccccccccccccc + dddddddd } cccccccccc"
+# Here, we would use the best fit layout to put the f-string indented on the next line
+# similar to the next example.
+aaaaaaaaaaa = (
+    f"asaaaaaaaaaaaaaaaa { aaaaaaaaaaaa + bbbbbbbbbbbb + ccccccccccccccc } cccccccccc"
+)
+aaaaaaaaaaa = (
+    f"asaaaaaaaaaaaaaaaa { aaaaaaaaaaaa + bbbbbbbbbbbb + ccccccccccccccc } cccccccccc"
+)
+
+# This should never add the optional parentheses because even after adding them, the
+# f-string exceeds the line length limit.
+x = f"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa { "bbbbbbbbbbbbbbbbbbbbbbbbbbbbb" } ccccccccccccccc"
+x = f"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa { "bbbbbbbbbbbbbbbbbbbbbbbbbbbbb" = } ccccccccccccccc"
+x = f"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa { # comment
+                                             "bbbbbbbbbbbbbbbbbbbbbbbbbbbbb" } ccccccccccccccc"
+x = f"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa { # comment
+                                             "bbbbbbbbbbbbbbbbbbbbbbbbbbbbb" = } ccccccccccccccc"
+
+# Multiple larger expressions which exceeds the line length limit. Here, we need to decide
+# whether to split at the first or second expression. This should work similarly to the
+# assignment statement formatting where we split from right to left in preview mode.
+x = f"aaaaaaaaaaaa { bbbbbbbbbbbbbb } cccccccccccccccccccc { ddddddddddddddd } eeeeeeeeeeeeee"
+
+# The above example won't split but when we start introducing line breaks:
+x = f"aaaaaaaaaaaa {
+        bbbbbbbbbbbbbb } cccccccccccccccccccc { ddddddddddddddd } eeeeeeeeeeeeee"
+x = f"aaaaaaaaaaaa { bbbbbbbbbbbbbb
+                    } cccccccccccccccccccc { ddddddddddddddd } eeeeeeeeeeeeee"
+x = f"aaaaaaaaaaaa { bbbbbbbbbbbbbb } cccccccccccccccccccc {
+        ddddddddddddddd } eeeeeeeeeeeeee"
+x = f"aaaaaaaaaaaa { bbbbbbbbbbbbbb } cccccccccccccccccccc { ddddddddddddddd
+                                                            } eeeeeeeeeeeeee"
+
+# But, in case comments are present, we would split at the expression containing the
+# comments:
+x = f"aaaaaaaaaaaa { bbbbbbbbbbbbbb # comment
+                    } cccccccccccccccccccc { ddddddddddddddd } eeeeeeeeeeeeee"
+x = f"aaaaaaaaaaaa { bbbbbbbbbbbbbb
+                    } cccccccccccccccccccc { # comment
+                                            ddddddddddddddd } eeeeeeeeeeeeee"
+
+# Here, the expression part itself starts with a curly brace so we need to add an extra
+# space between the opening curly brace and the expression.
+x = f"{ {'x': 1, 'y': 2} }"
+# Although the extra space isn't required before the ending curly brace, we add it for
+# consistency.
+x = f"{ {'x': 1, 'y': 2}}"
+x = f"{ {'x': 1, 'y': 2} = }"
+x = f"{  # comment
+    {'x': 1, 'y': 2} }"
+x = f"{    # comment
+    {'x': 1, 'y': 2} = }"
+
+# But, in this case, we would split the expression itself because it exceeds the line
+# length limit so we need not add the extra space.
+xxxxxxx = f"{
+    {'aaaaaaaaaaaaaaaaaaa', 'bbbbbbbbbbbbbbbbbbbbbb', 'ccccccccccccccccccccc'}
+}"
+# And, split the expression itself because it exceeds the line length.
+xxxxxxx = f"{
+    {'aaaaaaaaaaaaaaaaaaaaaaaaa', 'bbbbbbbbbbbbbbbbbbbbbbbbbbb', 'cccccccccccccccccccccccccc'}
+}"
+
+# Triple-quoted strings
+# It's ok to use the same quote char for the inner string if it's single-quoted.
+f"""test {'inner'}"""
+f"""test {"inner"}"""
+# But if the inner string is also triple-quoted then we should preserve the existing quotes.
+f"""test {'''inner'''}"""
+
+# Comments
+
+# No comments should be dropped!
+f"{ # comment 1
+    # comment 2
+    foo # comment 3
+    # comment 4
+}"  # comment 5
+# comment 6
+
+# Conversion flags
+#
+# This is not a valid Python code because of the additional whitespace between the `!`
+# and conversion type. But, our parser isn't strict about this. This should probably be
+# removed once we have a strict parser.
+x = f"aaaaaaaaa { x !  r }"
+
+# Even in the case of debug expresions, we only need to preserve the whitespace within
+# the expression part of the replacement field.
+x = f"aaaaaaaaa { x   = !  r  }"
+
+# Combine conversion flags with format specifiers
+x = f"{x   =   !  s
+         :>0
+
+         }"
+# This is interesting. There can be a comment after the format specifier but only if it's
+# on it's own line. Refer to https://github.com/astral-sh/ruff/pull/7787 for more details.
+# We'll format is as trailing comments.
+x = f"{x  !s
+         :>0
+         # comment
+         }"
+
+x = f"""
+{              # dangling comment 1
+ x =   :.0{y # dangling comment 2
+           }f}"""
+
+# Here, the debug expression is in a nested f-string so we should start preserving
+# whitespaces from that point onwards. This means we should format the outer f-string.
+x = f"""{"foo " +    # comment 1
+    f"{   x =
+
+       }"    # comment 2
+ }
+        """
+
+# Mix of various features.
+f"{  # dangling comment 1
+    foo # after foo
+   :>{
+          x # after x
+          }
+    # dangling comment 2
+    # dangling comment 3
+} woah {x}"
+```
+
+
+#### Preview changes
+```diff
+--- Stable
++++ Preview
+@@ -6,13 +6,13 @@
+ # Regression test for fstrings dropping comments
+ result_f = (
+     "Traceback (most recent call last):\n"
+-    f'  File "{__file__}", line {lineno_f+5}, in _check_recursive_traceback_display\n'
++    f'  File "{__file__}", line {lineno_f + 5}, in _check_recursive_traceback_display\n'
+     "    f()\n"
+-    f'  File "{__file__}", line {lineno_f+1}, in f\n'
++    f'  File "{__file__}", line {lineno_f + 1}, in f\n'
+     "    f()\n"
+-    f'  File "{__file__}", line {lineno_f+1}, in f\n'
++    f'  File "{__file__}", line {lineno_f + 1}, in f\n'
+     "    f()\n"
+-    f'  File "{__file__}", line {lineno_f+1}, in f\n'
++    f'  File "{__file__}", line {lineno_f + 1}, in f\n'
+     "    f()\n"
+     # XXX: The following line changes depending on whether the tests
+     # are run through the interactive interpreter or with -m
+@@ -67,64 +67,72 @@
+ x = f"{a}"
+ x = f"{
+     a = }"
+-x = f"{ # comment
+-    a }"
++x = f"{  # comment
++    a
++}"
+ x = f"{   # comment
+     a = }"
+ 
+ # Remove the parentheses as adding them doesn't make then fit within the line length limit.
+ # This is similar to how we format it before f-string formatting.
+-aaaaaaaaaaa = f"asaaaaaaaaaaaaaaaa { aaaaaaaaaaaa + bbbbbbbbbbbb + ccccccccccccccc + dddddddd } cccccccccc"
++aaaaaaaaaaa = f"asaaaaaaaaaaaaaaaa {aaaaaaaaaaaa + bbbbbbbbbbbb + ccccccccccccccc + dddddddd} cccccccccc"
+ # Here, we would use the best fit layout to put the f-string indented on the next line
+ # similar to the next example.
+ aaaaaaaaaaa = (
+-    f"asaaaaaaaaaaaaaaaa { aaaaaaaaaaaa + bbbbbbbbbbbb + ccccccccccccccc } cccccccccc"
++    f"asaaaaaaaaaaaaaaaa {aaaaaaaaaaaa + bbbbbbbbbbbb + ccccccccccccccc} cccccccccc"
+ )
+ aaaaaaaaaaa = (
+-    f"asaaaaaaaaaaaaaaaa { aaaaaaaaaaaa + bbbbbbbbbbbb + ccccccccccccccc } cccccccccc"
++    f"asaaaaaaaaaaaaaaaa {aaaaaaaaaaaa + bbbbbbbbbbbb + ccccccccccccccc} cccccccccc"
+ )
+ 
+ # This should never add the optional parentheses because even after adding them, the
+ # f-string exceeds the line length limit.
+-x = f"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa { "bbbbbbbbbbbbbbbbbbbbbbbbbbbbb" } ccccccccccccccc"
++x = f"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa {"bbbbbbbbbbbbbbbbbbbbbbbbbbbbb"} ccccccccccccccc"
+ x = f"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa { "bbbbbbbbbbbbbbbbbbbbbbbbbbbbb" = } ccccccccccccccc"
+-x = f"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa { # comment
+-                                             "bbbbbbbbbbbbbbbbbbbbbbbbbbbbb" } ccccccccccccccc"
++x = f"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa {  # comment
++    "bbbbbbbbbbbbbbbbbbbbbbbbbbbbb"
++} ccccccccccccccc"
+ x = f"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa { # comment
+                                              "bbbbbbbbbbbbbbbbbbbbbbbbbbbbb" = } ccccccccccccccc"
+ 
+ # Multiple larger expressions which exceeds the line length limit. Here, we need to decide
+ # whether to split at the first or second expression. This should work similarly to the
+ # assignment statement formatting where we split from right to left in preview mode.
+-x = f"aaaaaaaaaaaa { bbbbbbbbbbbbbb } cccccccccccccccccccc { ddddddddddddddd } eeeeeeeeeeeeee"
++x = f"aaaaaaaaaaaa {bbbbbbbbbbbbbb} cccccccccccccccccccc {ddddddddddddddd} eeeeeeeeeeeeee"
+ 
+ # The above example won't split but when we start introducing line breaks:
+-x = f"aaaaaaaaaaaa {
+-        bbbbbbbbbbbbbb } cccccccccccccccccccc { ddddddddddddddd } eeeeeeeeeeeeee"
+-x = f"aaaaaaaaaaaa { bbbbbbbbbbbbbb
+-                    } cccccccccccccccccccc { ddddddddddddddd } eeeeeeeeeeeeee"
+-x = f"aaaaaaaaaaaa { bbbbbbbbbbbbbb } cccccccccccccccccccc {
+-        ddddddddddddddd } eeeeeeeeeeeeee"
+-x = f"aaaaaaaaaaaa { bbbbbbbbbbbbbb } cccccccccccccccccccc { ddddddddddddddd
+-                                                            } eeeeeeeeeeeeee"
++x = f"aaaaaaaaaaaa {bbbbbbbbbbbbbb} cccccccccccccccccccc {
++    ddddddddddddddd
++} eeeeeeeeeeeeee"
++x = f"aaaaaaaaaaaa {bbbbbbbbbbbbbb} cccccccccccccccccccc {
++    ddddddddddddddd
++} eeeeeeeeeeeeee"
++x = f"aaaaaaaaaaaa {bbbbbbbbbbbbbb} cccccccccccccccccccc {
++    ddddddddddddddd
++} eeeeeeeeeeeeee"
++x = f"aaaaaaaaaaaa {bbbbbbbbbbbbbb} cccccccccccccccccccc {
++    ddddddddddddddd
++} eeeeeeeeeeeeee"
+ 
+ # But, in case comments are present, we would split at the expression containing the
+ # comments:
+-x = f"aaaaaaaaaaaa { bbbbbbbbbbbbbb # comment
+-                    } cccccccccccccccccccc { ddddddddddddddd } eeeeeeeeeeeeee"
+-x = f"aaaaaaaaaaaa { bbbbbbbbbbbbbb
+-                    } cccccccccccccccccccc { # comment
+-                                            ddddddddddddddd } eeeeeeeeeeeeee"
++x = f"aaaaaaaaaaaa {
++    bbbbbbbbbbbbbb  # comment
++} cccccccccccccccccccc {ddddddddddddddd} eeeeeeeeeeeeee"
++x = f"aaaaaaaaaaaa {bbbbbbbbbbbbbb} cccccccccccccccccccc {  # comment
++    ddddddddddddddd
++} eeeeeeeeeeeeee"
+ 
+ # Here, the expression part itself starts with a curly brace so we need to add an extra
+ # space between the opening curly brace and the expression.
+ x = f"{ {'x': 1, 'y': 2} }"
+ # Although the extra space isn't required before the ending curly brace, we add it for
+ # consistency.
+-x = f"{ {'x': 1, 'y': 2}}"
++x = f"{ {'x': 1, 'y': 2} }"
+ x = f"{ {'x': 1, 'y': 2} = }"
+ x = f"{  # comment
+-    {'x': 1, 'y': 2} }"
++    {'x': 1, 'y': 2}
++}"
+ x = f"{    # comment
+     {'x': 1, 'y': 2} = }"
+ 
+@@ -135,22 +143,26 @@
+ }"
+ # And, split the expression itself because it exceeds the line length.
+ xxxxxxx = f"{
+-    {'aaaaaaaaaaaaaaaaaaaaaaaaa', 'bbbbbbbbbbbbbbbbbbbbbbbbbbb', 'cccccccccccccccccccccccccc'}
++    {
++        'aaaaaaaaaaaaaaaaaaaaaaaaa',
++        'bbbbbbbbbbbbbbbbbbbbbbbbbbb',
++        'cccccccccccccccccccccccccc',
++    }
+ }"
+ 
+ # Triple-quoted strings
+ # It's ok to use the same quote char for the inner string if it's single-quoted.
+-f"""test {'inner'}"""
+ f"""test {"inner"}"""
++f"""test {"inner"}"""
+ # But if the inner string is also triple-quoted then we should preserve the existing quotes.
+ f"""test {'''inner'''}"""
+ 
+ # Comments
+ 
+ # No comments should be dropped!
+-f"{ # comment 1
++f"{  # comment 1
+     # comment 2
+-    foo # comment 3
++    foo  # comment 3
+     # comment 4
+ }"  # comment 5
+ # comment 6
+@@ -160,24 +172,21 @@
+ # This is not a valid Python code because of the additional whitespace between the `!`
+ # and conversion type. But, our parser isn't strict about this. This should probably be
+ # removed once we have a strict parser.
+-x = f"aaaaaaaaa { x !  r }"
++x = f"aaaaaaaaa {x!r}"
+ 
+ # Even in the case of debug expresions, we only need to preserve the whitespace within
+ # the expression part of the replacement field.
+-x = f"aaaaaaaaa { x   = !  r  }"
++x = f"aaaaaaaaa { x   = !r}"
+ 
+ # Combine conversion flags with format specifiers
+-x = f"{x   =   !  s
+-         :>0
+-
+-         }"
++x = f"{x   =   !s:>0}"
+ # This is interesting. There can be a comment after the format specifier but only if it's
+ # on it's own line. Refer to https://github.com/astral-sh/ruff/pull/7787 for more details.
+ # We'll format is as trailing comments.
+-x = f"{x  !s
+-         :>0
+-         # comment
+-         }"
++x = f"{
++    x!s:>0
++    # comment
++}"
+ 
+ x = f"""
+ {              # dangling comment 1
+@@ -186,19 +195,19 @@
+ 
+ # Here, the debug expression is in a nested f-string so we should start preserving
+ # whitespaces from that point onwards. This means we should format the outer f-string.
+-x = f"""{"foo " +    # comment 1
+-    f"{   x =
++x = f"""{
++    "foo "  # comment 1
++    + f"{   x =
+ 
+-       }"    # comment 2
+- }
++       }"  # comment 2
++}
+         """
+ 
+ # Mix of various features.
+ f"{  # dangling comment 1
+-    foo # after foo
+-   :>{
+-          x # after x
+-          }
++    foo:>{  # after foo
++        x  # after x
++    }
+     # dangling comment 2
+     # dangling comment 3
+ } woah {x}"
 ```