Merge branch 'main' into main

.flake8

@@ -1,8 +1,8 @@
 [flake8]
 # B905 should be enabled when we drop support for 3.9
-ignore = E203, E266, E501, E704, W503, B905, B907
+ignore = E203, E266, E501, E701, E704, W503, B905, B907
 # line length is intentionally set to 80 here because black uses Bugbear
-# See https://black.readthedocs.io/en/stable/the_black_code_style/current_style.html#line-length for more details
+# See https://black.readthedocs.io/en/stable/guides/using_black_with_other_tools.html#bugbear for more details
 max-line-length = 80
 max-complexity = 18
 select = B,C,E,F,W,T4,B9

CHANGES.md

@@ -14,12 +14,19 @@
 
 <!-- Changes that affect Black's preview style -->
 
+- Move the `hug_parens_with_braces_and_square_brackets` feature to the unstable style
+  due to an outstanding crash and proposed formatting tweaks (#4198)
 - Checking for newline before adding one on docstring that is almost at the line limit
   (#4185)
 
 ### Configuration
 
-<!-- Changes to how Black can be configured -->
+- _Black_ now ignores `pyproject.toml` that is missing a `tool.black` section when
+  discovering project root and configuration. Since _Black_ continues to use version
+  control as an indicator of project root, this is expected to primarily change behavior
+  for users in a monorepo setup (desirably). If you wish to preserve previous behavior,
+  simply add an empty `[tool.black]` to the previously discovered `pyproject.toml`
+  (#4204)
 
 ### Packaging
 

docs/compatible_configs/flake8/.flake8

@@ -1,3 +1,3 @@
 [flake8]
 max-line-length = 88
-extend-ignore = E203
+extend-ignore = E203,E701

docs/compatible_configs/flake8/setup.cfg

@@ -1,3 +1,3 @@
 [flake8]
 max-line-length = 88
-extend-ignore = E203
+extend-ignore = E203,E701

docs/compatible_configs/flake8/tox.ini

@@ -1,3 +1,3 @@
 [flake8]
 max-line-length = 88
-extend-ignore = E203
+extend-ignore = E203,E701

docs/compatible_configs/pycodestyle/.flake8

@@ -0,0 +1,3 @@
+[pycodestyle]
+max-line-length = 88
+ignore = E203,E701

docs/compatible_configs/pycodestyle/setup.cfg

@@ -0,0 +1,3 @@
+[pycodestyle]
+max-line-length = 88
+ignore = E203,E701

docs/compatible_configs/pycodestyle/tox.ini

@@ -0,0 +1,3 @@
+[pycodestyle]
+max-line-length = 88
+ignore = E203,E701

docs/faq.md

@@ -77,13 +77,10 @@ following will not be formatted:
 - invalid syntax, as it can't be safely distinguished from automagics in the absence of
   a running `IPython` kernel.
 
-## Why are Flake8's E203 and W503 violated?
+## Why does Flake8 report warnings?
 
-Because they go against PEP 8. E203 falsely triggers on list
-[slices](the_black_code_style/current_style.md#slices), and adhering to W503 hinders
-readability because operators are misaligned. Disable W503 and enable the
-disabled-by-default counterpart W504. E203 should be disabled while changes are still
-[discussed](https://github.com/PyCQA/pycodestyle/issues/373).
+Some of Flake8's rules conflict with Black's style. We recommend disabling these rules.
+See [Using _Black_ with other tools](labels/why-pycodestyle-warnings).
 
 ## Which Python versions does Black support?
 

docs/guides/using_black_with_other_tools.md

@@ -134,78 +134,126 @@ profile = black
 
 </details>
 
-### Flake8
+### pycodestyle
 
-[Flake8](https://pypi.org/p/flake8/) is a code linter. It warns you of syntax errors,
-possible bugs, stylistic errors, etc. For the most part, Flake8 follows
+[pycodestyle](https://pycodestyle.pycqa.org/) is a code linter. It warns you of syntax
+errors, possible bugs, stylistic errors, etc. For the most part, pycodestyle follows
 [PEP 8](https://www.python.org/dev/peps/pep-0008/) when warning about stylistic errors.
 There are a few deviations that cause incompatibilities with _Black_.
 
 #### Configuration
 
 ```
 max-line-length = 88
-extend-ignore = E203, E704
+ignore = E203,E701
 ```
 
+(labels/why-pycodestyle-warnings)=
+
 #### Why those options above?
 
+##### `max-line-length`
+
+As with isort, pycodestyle should be configured to allow lines up to the length limit of
+`88`, _Black_'s default.
+
+##### `E203`
+
 In some cases, as determined by PEP 8, _Black_ will enforce an equal amount of
-whitespace around slice operators. Due to this, Flake8 will raise
-`E203 whitespace before ':'` warnings. Since this warning is not PEP 8 compliant, Flake8
-should be configured to ignore it via `extend-ignore = E203`.
+whitespace around slice operators. Due to this, pycodestyle will raise
+`E203 whitespace before ':'` warnings. Since this warning is not PEP 8 compliant, it
+should be disabled.
+
+##### `E701` / `E704`
+
+_Black_ will collapse implementations of classes and functions consisting solely of `..`
+to a single line. This matches how such examples are formatted in PEP 8. It remains true
+that in all other cases Black will prevent multiple statements on the same line, in
+accordance with PEP 8 generally discouraging this.
+
+However, `pycodestyle` does not mirror this logic and may raise
+`E701 multiple statements on one line (colon)` in this situation. Its
+disabled-by-default `E704 multiple statements on one line (def)` rule may also raise
+warnings and should not be enabled.
+
+##### `W503`
 
 When breaking a line, _Black_ will break it before a binary operator. This is compliant
 with PEP 8 as of
 [April 2016](https://github.com/python/peps/commit/c59c4376ad233a62ca4b3a6060c81368bd21e85b#diff-64ec08cc46db7540f18f2af46037f599).
 There's a disabled-by-default warning in Flake8 which goes against this PEP 8
 recommendation called `W503 line break before binary operator`. It should not be enabled
-in your configuration.
-
-Also, as like with isort, flake8 should be configured to allow lines up to the length
-limit of `88`, _Black_'s default. This explains `max-line-length = 88`.
+in your configuration. You can use its counterpart
+`W504 line break after binary operator` instead.
 
 #### Formats
 
 <details>
-<summary>.flake8</summary>
+<summary>setup.cfg, .pycodestyle, tox.ini</summary>
 
 ```ini
-[flake8]
+[pycodestyle]
 max-line-length = 88
-extend-ignore = E203, E704
+ignore = E203,E701
 ```
 
 </details>
 
-<details>
-<summary>setup.cfg</summary>
+### Flake8
 
-```ini
+[Flake8](https://pypi.org/p/flake8/) is a wrapper around multiple linters, including
+pycodestyle. As such, it has many of the same issues.
+
+#### Bugbear
+
+It's recommended to use [the Bugbear plugin](https://github.com/PyCQA/flake8-bugbear)
+and enable
+[its B950 check](https://github.com/PyCQA/flake8-bugbear#opinionated-warnings#:~:text=you%20expect%20it.-,B950,-%3A%20Line%20too%20long)
+instead of using Flake8's E501, because it aligns with
+[Black's 10% rule](labels/line-length).
+
+Install Bugbear and use the following config:
+
+```
+[flake8]
+max-line-length = 80
+extend-select = B950
+extend-ignore = E203,E501,E701
+```
+
+#### Minimal Configuration
+
+In cases where you can't or don't want to install Bugbear, you can use this minimally
+compatible config:
+
+```
 [flake8]
 max-line-length = 88
-extend-ignore = E203, E704
+extend-ignore = E203,E701
 ```
 
-</details>
+#### Why those options above?
+
+See [the pycodestyle section](labels/why-pycodestyle-warnings) above.
+
+#### Formats
 
 <details>
-<summary>tox.ini</summary>
+<summary>.flake8, setup.cfg, tox.ini</summary>
 
 ```ini
 [flake8]
 max-line-length = 88
-extend-ignore = E203, E704
+extend-ignore = E203,E701
 ```
 
 </details>
 
 ### Pylint
 
-[Pylint](https://pypi.org/p/pylint/) is also a code linter like Flake8. It has the same
-checks as flake8 and more. In particular, it has more formatting checks regarding style
-conventions like variable naming. With so many checks, Pylint is bound to have some
-mixed feelings about _Black_'s formatting style.
+[Pylint](https://pypi.org/p/pylint/) is also a code linter like Flake8. It has many of
+the same checks as Flake8 and more. It particularly has more formatting checks regarding
+style conventions like variable naming.
 
 #### Configuration
 
@@ -252,35 +300,3 @@ max-line-length = "88"
 ```
 
 </details>
-
-### pycodestyle
-
-[pycodestyle](https://pycodestyle.pycqa.org/) is also a code linter like Flake8.
-
-#### Configuration
-
-```
-max-line-length = 88
-ignore = E203
-```
-
-#### Why those options above?
-
-pycodestyle should be configured to only complain about lines that surpass `88`
-characters via `max_line_length = 88`.
-
-See
-[Why are Flake8’s E203 and W503 violated?](https://black.readthedocs.io/en/stable/faq.html#why-are-flake8-s-e203-and-w503-violated)
-
-#### Formats
-
-<details>
-<summary>setup.cfg</summary>
-
-```cfg
-[pycodestyle]
-ignore = E203
-max_line_length = 88
-```
-
-</details>

docs/the_black_code_style/current_style.md

@@ -143,7 +143,7 @@ significantly shorter files than sticking with 80 (the most popular), or even 79
 by the standard library). In general,
 [90-ish seems like the wise choice](https://youtu.be/wf-BqAjZb8M?t=260).
 
-If you're paid by the line of code you write, you can pass `--line-length` with a lower
+If you're paid by the lines of code you write, you can pass `--line-length` with a lower
 number. _Black_ will try to respect that. However, sometimes it won't be able to without
 breaking other rules. In those rare cases, auto-formatted code will exceed your allotted
 limit.
@@ -153,35 +153,10 @@ harder to work with line lengths exceeding 100 characters. It also adversely aff
 side-by-side diff review on typical screen resolutions. Long lines also make it harder
 to present code neatly in documentation or talk slides.
 
-#### Flake8
+#### Flake8 and other linters
 
-If you use Flake8, you have a few options:
-
-1. Recommended is using [Bugbear](https://github.com/PyCQA/flake8-bugbear) and enabling
-   its B950 check instead of using Flake8's E501, because it aligns with Black's 10%
-   rule. Install Bugbear and use the following config:
-
-   ```ini
-   [flake8]
-   max-line-length = 80
-   ...
-   select = C,E,F,W,B,B950
-   extend-ignore = E203, E501, E704
-   ```
-
-   The rationale for B950 is explained in
-   [Bugbear's documentation](https://github.com/PyCQA/flake8-bugbear#opinionated-warnings).
-
-2. For a minimally compatible config:
-
-   ```ini
-   [flake8]
-   max-line-length = 88
-   extend-ignore = E203, E704
-   ```
-
-An explanation of why E203 is disabled can be found in the [Slices section](#slices) of
-this page.
+See [Using _Black_ with other tools](../guides/using_black_with_other_tools.md) about
+linter compatibility.
 
 ### Empty lines
 

docs/the_black_code_style/future_style.md

@@ -16,14 +16,14 @@ feature, it is demoted to the `--unstable` style. To avoid thrash when a feature
 demoted from the `--preview` to the `--unstable` style, users can use the
 `--enable-unstable-feature` flag to enable specific unstable features.
 
+(labels/preview-features)=
+
 Currently, the following features are included in the preview style:
 
 - `hex_codes_in_unicode_sequences`: normalize casing of Unicode escape characters in
   strings
 - `unify_docstring_detection`: fix inconsistencies in whether certain strings are
   detected as docstrings
-- `hug_parens_with_braces_and_square_brackets`: more compact formatting of nested
-  brackets ([see below](labels/hug-parens))
 - `no_normalize_fmt_skip_whitespace`: whitespace before `# fmt: skip` comments is no
   longer normalized
 - `typed_params_trailing_comma`: consistently add trailing commas to typed function
@@ -41,6 +41,8 @@ The unstable style additionally includes the following features:
   ([see below](labels/wrap-long-dict-values))
 - `multiline_string_handling`: more compact formatting of expressions involving
   multiline strings ([see below](labels/multiline-string-handling))
+- `hug_parens_with_braces_and_square_brackets`: more compact formatting of nested
+  brackets ([see below](labels/hug-parens))
 
 (labels/hug-parens)=
 

docs/usage_and_configuration/the_basics.md

@@ -456,10 +456,11 @@ of tools like [Poetry](https://python-poetry.org/),
 
 ### Where _Black_ looks for the file
 
-By default _Black_ looks for `pyproject.toml` starting from the common base directory of
-all files and directories passed on the command line. If it's not there, it looks in
-parent directories. It stops looking when it finds the file, or a `.git` directory, or a
-`.hg` directory, or the root of the file system, whichever comes first.
+By default _Black_ looks for `pyproject.toml` containing a `[tool.black]` section
+starting from the common base directory of all files and directories passed on the
+command line. If it's not there, it looks in parent directories. It stops looking when
+it finds the file, or a `.git` directory, or a `.hg` directory, or the root of the file
+system, whichever comes first.
 
 If you're formatting standard input, _Black_ will look for configuration starting from
 the current working directory.

scripts/generate_schema.py

@@ -62,7 +62,7 @@ def main(schemastore: bool, outfile: IO[str]) -> None:
     }
 
     if schemastore:
-        schema["$id"] = ("https://json.schemastore.org/partial-black.json",)
+        schema["$id"] = "https://json.schemastore.org/partial-black.json"
         # The precise list of unstable features may change frequently, so don't
         # bother putting it in SchemaStore
         schema["properties"]["enable-unstable-feature"]["items"] = {"type": "string"}

src/black/files.py

@@ -42,6 +42,12 @@
     import colorama  # noqa: F401
 
 
+@lru_cache
+def _load_toml(path: Union[Path, str]) -> Dict[str, Any]:
+    with open(path, "rb") as f:
+        return tomllib.load(f)
+
+
 @lru_cache
 def find_project_root(
     srcs: Sequence[str], stdin_filename: Optional[str] = None
@@ -84,7 +90,9 @@ def find_project_root(
             return directory, ".hg directory"
 
         if (directory / "pyproject.toml").is_file():
-            return directory, "pyproject.toml"
+            pyproject_toml = _load_toml(directory / "pyproject.toml")
+            if "black" in pyproject_toml.get("tool", {}):
+                return directory, "pyproject.toml"
 
     return directory, "file system root"
 
@@ -117,8 +125,7 @@ def parse_pyproject_toml(path_config: str) -> Dict[str, Any]:
 
     If parsing fails, will raise a tomllib.TOMLDecodeError.
     """
-    with open(path_config, "rb") as f:
-        pyproject_toml = tomllib.load(f)
+    pyproject_toml = _load_toml(path_config)
     config: Dict[str, Any] = pyproject_toml.get("tool", {}).get("black", {})
     config = {k.replace("--", "").replace("-", "_"): v for k, v in config.items()}