[flake8-use-pathlib] Catch redundant joins in PTH201 and avoid sy…

…ntax errors (#15177)

## Summary

Resolves #10453, resolves #15165.

## Test Plan

`cargo nextest run` and `cargo insta test`.

crates/ruff_linter/resources/test/fixtures/flake8_use_pathlib/PTH201.py

@@ -1,15 +1,70 @@
 from pathlib import Path, PurePath
 from pathlib import Path as pth
 
+
 # match
 _ = Path(".")
 _ = pth(".")
 _ = PurePath(".")
 _ = Path("")
 
+Path('', )
+
+Path(
+    '',
+)
+
+Path(  # Comment before argument
+    '',
+)
+
+Path(
+    '',  # EOL comment
+)
+
+Path(
+    ''  # Comment in the middle of implicitly concatenated string
+    ".",
+)
+
+Path(
+    ''  # Comment before comma
+    ,
+)
+
+Path(
+    '',
+) / "bare"
+
+Path(  # Comment before argument
+    '',
+) / ("parenthesized")
+
+Path(
+    '',  # EOL comment
+) / ( ("double parenthesized"  )   )
+
+(  Path(
+    ''  # Comment in the middle of implicitly concatenated string
+    ".",
+) )/ (("parenthesized path call")
+      # Comment between closing parentheses
+)
+
+Path(
+    ''  # Comment before comma
+    ,
+) / "multiple" / (
+    "frag"  # Comment
+    'ment'
+)
+
+
 # no match
 _ = Path()
 print(".")
 Path("file.txt")
 Path(".", "folder")
 PurePath(".", "folder")
+
+Path()

crates/ruff_linter/src/checkers/ast/analyze/expression.rs

@@ -983,7 +983,7 @@ pub(crate) fn expression(expr: &Expr, checker: &mut Checker) {
                 flake8_use_pathlib::rules::replaceable_by_pathlib(checker, call);
             }
             if checker.enabled(Rule::PathConstructorCurrentDirectory) {
-                flake8_use_pathlib::rules::path_constructor_current_directory(checker, expr, func);
+                flake8_use_pathlib::rules::path_constructor_current_directory(checker, call);
             }
             if checker.enabled(Rule::OsSepSplit) {
                 flake8_use_pathlib::rules::os_sep_split(checker, call);

crates/ruff_linter/src/rules/flake8_use_pathlib/rules/path_constructor_current_directory.rs

@@ -1,8 +1,15 @@
-use ruff_diagnostics::{AlwaysFixableViolation, Diagnostic, Edit, Fix};
+use std::ops::Range;
+
+use ruff_diagnostics::{AlwaysFixableViolation, Applicability, Diagnostic, Edit, Fix};
 use ruff_macros::{derive_message_formats, ViolationMetadata};
-use ruff_python_ast::{self as ast, Expr, ExprCall};
+use ruff_python_ast::parenthesize::parenthesized_range;
+use ruff_python_ast::{AstNode, Expr, ExprBinOp, ExprCall, Operator};
+use ruff_python_semantic::SemanticModel;
+use ruff_python_trivia::CommentRanges;
+use ruff_text_size::{Ranged, TextRange};
 
 use crate::checkers::ast::Checker;
+use crate::fix::edits::{remove_argument, Parentheses};
 
 /// ## What it does
 /// Checks for `pathlib.Path` objects that are initialized with the current
@@ -43,7 +50,17 @@ impl AlwaysFixableViolation for PathConstructorCurrentDirectory {
 }
 
 /// PTH201
-pub(crate) fn path_constructor_current_directory(checker: &mut Checker, expr: &Expr, func: &Expr) {
+pub(crate) fn path_constructor_current_directory(checker: &mut Checker, call: &ExprCall) {
+    let applicability = |range| {
+        if checker.comment_ranges().intersects(range) {
+            Applicability::Unsafe
+        } else {
+            Applicability::Safe
+        }
+    };
+
+    let (func, arguments) = (&call.func, &call.arguments);
+
     if !checker
         .semantic()
         .resolve_qualified_name(func)
@@ -54,21 +71,75 @@ pub(crate) fn path_constructor_current_directory(checker: &mut Checker, expr: &E
         return;
     }
 
-    let Expr::Call(ExprCall { arguments, .. }) = expr else {
+    if !arguments.keywords.is_empty() {
+        return;
+    }
+
+    let [Expr::StringLiteral(arg)] = &*arguments.args else {
         return;
     };
 
-    if !arguments.keywords.is_empty() {
+    if !matches!(arg.value.to_str(), "" | ".") {
         return;
     }
 
-    let [Expr::StringLiteral(ast::ExprStringLiteral { value, range })] = &*arguments.args else {
-        return;
+    let mut diagnostic = Diagnostic::new(PathConstructorCurrentDirectory, arg.range());
+
+    match parent_and_next_path_fragment_range(
+        checker.semantic(),
+        checker.comment_ranges(),
+        checker.source(),
+    ) {
+        Some((parent_range, next_fragment_range)) => {
+            let next_fragment_expr = checker.locator().slice(next_fragment_range);
+            let call_expr = checker.locator().slice(call.range());
+
+            let relative_argument_range: Range<usize> = {
+                let range = arg.range() - call.start();
+                range.start().into()..range.end().into()
+            };
+
+            let mut new_call_expr = call_expr.to_string();
+            new_call_expr.replace_range(relative_argument_range, next_fragment_expr);
+
+            let edit = Edit::range_replacement(new_call_expr, parent_range);
+
+            diagnostic.set_fix(Fix::applicable_edit(edit, applicability(parent_range)));
+        }
+        None => diagnostic.try_set_fix(|| {
+            let edit = remove_argument(arg, arguments, Parentheses::Preserve, checker.source())?;
+            Ok(Fix::applicable_edit(edit, applicability(call.range())))
+        }),
     };
 
-    if matches!(value.to_str(), "" | ".") {
-        let mut diagnostic = Diagnostic::new(PathConstructorCurrentDirectory, *range);
-        diagnostic.set_fix(Fix::safe_edit(Edit::range_deletion(*range)));
-        checker.diagnostics.push(diagnostic);
+    checker.diagnostics.push(diagnostic);
+}
+
+fn parent_and_next_path_fragment_range(
+    semantic: &SemanticModel,
+    comment_ranges: &CommentRanges,
+    source: &str,
+) -> Option<(TextRange, TextRange)> {
+    let parent = semantic.current_expression_parent()?;
+
+    let Expr::BinOp(parent @ ExprBinOp { op, right, .. }) = parent else {
+        return None;
+    };
+
+    let range = right.range();
+
+    if !matches!(op, Operator::Div) {
+        return None;
     }
+
+    Some((
+        parent.range(),
+        parenthesized_range(
+            right.into(),
+            parent.as_any_node_ref(),
+            comment_ranges,
+            source,
+        )
+        .unwrap_or(range),
+    ))
 }