Prepare release 23.9.0 (#3863)

[etc/vim.git] / docs / usage_and_configuration / the_basics.md

diff --git a/docs/usage_and_configuration/the_basics.md b/docs/usage_and_configuration/the_basics.md
index 0b2cd3b354406f212ee824755defbe85ae68558e..6ae9441fb69dc38e3d6b455ad6fb67c95b0db961 100644 (file)
--- a/docs/usage_and_configuration/the_basics.md
+++ b/docs/usage_and_configuration/the_basics.md
@@ -4,11 +4,11 @@ Foundational knowledge on using and configuring Black.
 
 _Black_ is a well-behaved Unix-style command-line tool:
 
 
 _Black_ is a well-behaved Unix-style command-line tool:
 

-- it does nothing if no sources are passed to it;
+- it does nothing if it finds no sources to format;

 - it will read from standard input and write to standard output if `-` is used as the
   filename;
 - it only outputs messages to users on standard error;
 - it will read from standard input and write to standard output if `-` is used as the
   filename;
 - it only outputs messages to users on standard error;

-- exits with code 0 unless an internal error occurred (or `--check` was used).
+- exits with code 0 unless an internal error occurred or a CLI option prompted it.

 
 ## Usage
 
 
 ## Usage
 


@@ -26,64 +26,106 @@ python -m black {source_file_or_directory}
 
 ### Command line options
 
 
 ### Command line options
 

-_Black_ has quite a few knobs these days, although _Black_ is opinionated so style
-configuration options are deliberately limited and rarely added. You can list them by
-running `black --help`.
+The CLI options of _Black_ can be displayed by running `black --help`. All options are
+also covered in more detail below.

 
 

-<details>
+While _Black_ has quite a few knobs these days, it is still opinionated so style options
+are deliberately limited and rarely added.
+
+Note that all command-line options listed above can also be configured using a
+`pyproject.toml` file (more on that below).

 
 

-<summary>Help output</summary>
+#### `-c`, `--code`

 
 

-```{program-output} black --help
+Format the code passed in as a string.

 
 

+```console
+$ black --code "print ( 'hello, world' )"
+print("hello, world")

 ```
 
 ```
 

-</details>
+#### `-l`, `--line-length`

 
 

-### Code input alternatives
+How many characters per line to allow. The default is 88.

 
 

-#### Standard Input
+See also [the style documentation](labels/line-length).

 
 

-_Black_ supports formatting code via stdin, with the result being printed to stdout.
-Just let _Black_ know with `-` as the path.
+#### `-t`, `--target-version`
+
+Python versions that should be supported by Black's output. You should include all
+versions that your code supports. If you support Python 3.7 through 3.10, you should
+write:

 
 ```console
 
 ```console

-$ echo "print ( 'hello, world' )" | black -
-print("hello, world")
-reformatted -
-All done! ✨ 🍰 ✨
-1 file reformatted.
+$ black -t py37 -t py38 -t py39 -t py310

 ```
 
 ```
 

-**Tip:** if you need _Black_ to treat stdin input as a file passed directly via the CLI,
-use `--stdin-filename`. Useful to make sure _Black_ will respect the `--force-exclude`
-option on some editors that rely on using stdin.
+In a [configuration file](#configuration-via-a-file), you can write:

 
 

-#### As a string
+```toml
+target-version = ["py37", "py38", "py39", "py310"]
+```

 
 

-You can also pass code as a string using the `-c` / `--code` option.
+_Black_ uses this option to decide what grammar to use to parse your code. In addition,
+it may use it to decide what style to use. For example, support for a trailing comma
+after `*args` in a function call was added in Python 3.5, so _Black_ will add this comma
+only if the target versions are all Python 3.5 or higher:

 
 ```console
 
 ```console

-$ black --code "print ( 'hello, world' )"
-print("hello, world")
+$ black --line-length=10 --target-version=py35 -c 'f(a, *args)'
+f(
+    a,
+    *args,
+)
+$ black --line-length=10 --target-version=py34 -c 'f(a, *args)'
+f(
+    a,
+    *args
+)
+$ black --line-length=10 --target-version=py34 --target-version=py35 -c 'f(a, *args)'
+f(
+    a,
+    *args
+)

 ```
 
 ```
 

-```{warning}
---check, --diff, and --safe / --fast have no effect when using -c / --code. Safety
-checks normally turned on by default that verify _Black_'s output are disabled as well.
-This is a bug which we intend to fix eventually. More details can be found in this [bug
-report](https://github.com/psf/black/issues/2104).
-```
+#### `--pyi`

 
 

-### Writeback and reporting
+Format all input files like typing stubs regardless of file extension. This is useful
+when piping source on standard input.

 
 

-By default _Black_ reformats the files given and/or found in place. Sometimes you need
-_Black_ to just tell you what it _would_ do without actually rewriting the Python files.
+#### `--ipynb`

 
 

-There's two variations to this mode that are independently enabled by their respective
-flags. Both variations can be enabled at once.
+Format all input files like Jupyter Notebooks regardless of file extension. This is
+useful when piping source on standard input.
+
+#### `--python-cell-magics`
+
+When processing Jupyter Notebooks, add the given magic to the list of known python-
+magics. Useful for formatting cells with custom python magics.
+
+#### `-S, --skip-string-normalization`
+
+By default, _Black_ uses double quotes for all strings and normalizes string prefixes,
+as described in [the style documentation](labels/strings). If this option is given,
+strings are left unchanged instead.
+
+#### `-C, --skip-magic-trailing-comma`
+
+By default, _Black_ uses existing trailing commas as an indication that short lines
+should be left separate, as described in
+[the style documentation](labels/magic-trailing-comma). If this option is given, the
+magic trailing comma is ignored.

 
 

-#### Exit code
+#### `--preview`
+
+Enable potentially disruptive style changes that may be added to Black's main
+functionality in the next major release. Read more about
+[our preview style](labels/preview-style).
+
+(labels/exit-code)=
+
+#### `--check`

 
 Passing `--check` will make _Black_ exit with:
 
 
 Passing `--check` will make _Black_ exit with:
 


@@ -113,17 +155,17 @@ $ echo $?
 123
 ```
 
 123
 ```
 

-#### Diffs
+#### `--diff`

 
 Passing `--diff` will make _Black_ print out diffs that indicate what changes _Black_
 would've made. They are printed to stdout so capturing them is simple.
 
 
 Passing `--diff` will make _Black_ print out diffs that indicate what changes _Black_
 would've made. They are printed to stdout so capturing them is simple.
 

-If you'd like colored diffs, you can enable them with the `--color`.
+If you'd like colored diffs, you can enable them with `--color`.

 
 ```console
 $ black test.py --diff
 
 ```console
 $ black test.py --diff

---- test.py     2021-03-08 22:23:40.848954 +0000
-+++ test.py     2021-03-08 22:23:47.126319 +0000
+--- test.py     2021-03-08 22:23:40.848954+00:00
++++ test.py     2021-03-08 22:23:47.126319+00:00

 @@ -1 +1 @@
 -print ( 'hello, world' )
 +print("hello, world")
 @@ -1 +1 @@
 -print ( 'hello, world' )
 +print("hello, world")


@@ -132,22 +174,93 @@ All done! ✨ 🍰 ✨
 1 file would be reformatted.
 ```
 
 1 file would be reformatted.
 ```
 

-### Output verbosity
+#### `--color` / `--no-color`

 
 

-_Black_ in general tries to produce the right amount of output, balancing between
-usefulness and conciseness. By default, _Black_ emits files modified and error messages,
-plus a short summary.
+Show (or do not show) colored diff. Only applies when `--diff` is given.
+
+#### `--fast` / `--safe`
+
+By default, _Black_ performs [an AST safety check](labels/ast-changes) after formatting
+your code. The `--fast` flag turns off this check and the `--safe` flag explicitly
+enables it.
+
+#### `--required-version`
+
+Require a specific version of _Black_ to be running. This is useful for ensuring that
+all contributors to your project are using the same version, because different versions
+of _Black_ may format code a little differently. This option can be set in a
+configuration file for consistent results across environments.

 
 ```console
 
 ```console

-$ black src/
+$ black --version
+black, 23.9.0 (compiled: yes)
+$ black --required-version 23.9.0 -c "format = 'this'"
+format = "this"
+$ black --required-version 31.5b2 -c "still = 'beta?!'"
+Oh no! 💥 💔 💥 The required version does not match the running version!
+```
+
+You can also pass just the major version:
+
+```console
+$ black --required-version 22 -c "format = 'this'"
+format = "this"
+$ black --required-version 31 -c "still = 'beta?!'"
+Oh no! 💥 💔 💥 The required version does not match the running version!
+```
+
+Because of our [stability policy](../the_black_code_style/index.md), this will guarantee
+stable formatting, but still allow you to take advantage of improvements that do not
+affect formatting.
+
+#### `--include`
+
+A regular expression that matches files and directories that should be included on
+recursive searches. An empty value means all files are included regardless of the name.
+Use forward slashes for directories on all platforms (Windows, too). Exclusions are
+calculated first, inclusions later.
+
+#### `--exclude`
+
+A regular expression that matches files and directories that should be excluded on
+recursive searches. An empty value means no paths are excluded. Use forward slashes for
+directories on all platforms (Windows, too). Exclusions are calculated first, inclusions
+later.
+
+#### `--extend-exclude`
+
+Like `--exclude`, but adds additional files and directories on top of the excluded ones.
+Useful if you simply want to add to the default.
+
+#### `--force-exclude`
+
+Like `--exclude`, but files and directories matching this regex will be excluded even
+when they are passed explicitly as arguments. This is useful when invoking _Black_
+programmatically on changed files, such as in a pre-commit hook or editor plugin.
+
+#### `--stdin-filename`
+
+The name of the file when passing it through stdin. Useful to make sure Black will
+respect the `--force-exclude` option on some editors that rely on using stdin.
+
+#### `-W`, `--workers`
+
+When _Black_ formats multiple files, it may use a process pool to speed up formatting.
+This option controls the number of parallel workers. This can also be specified via the
+`BLACK_NUM_WORKERS` environment variable.
+
+#### `-q`, `--quiet`
+
+Passing `-q` / `--quiet` will cause _Black_ to stop emitting all non-critical output.
+Error messages will still be emitted (which can silenced by `2>/dev/null`).
+
+```console
+$ black src/ -q

 error: cannot format src/black_primer/cli.py: Cannot parse: 5:6: mport asyncio
 error: cannot format src/black_primer/cli.py: Cannot parse: 5:6: mport asyncio

-reformatted src/black_primer/lib.py
-reformatted src/blackd/__init__.py
-reformatted src/black/__init__.py
-Oh no! 💥 💔 💥
-3 files reformatted, 2 files left unchanged, 1 file failed to reformat.

 ```
 
 ```
 

+#### `-v`, `--verbose`
+

 Passing `-v` / `--verbose` will cause _Black_ to also emit messages about files that
 were not changed or were ignored due to exclusion patterns. If _Black_ is using a
 configuration file, a blue message detailing which one it is using will be emitted.
 Passing `-v` / `--verbose` will cause _Black_ to also emit messages about files that
 were not changed or were ignored due to exclusion patterns. If _Black_ is using a
 configuration file, a blue message detailing which one it is using will be emitted.


@@ -166,23 +279,87 @@ Oh no! 💥 💔 💥
 3 files reformatted, 2 files left unchanged, 1 file failed to reformat
 ```
 
 3 files reformatted, 2 files left unchanged, 1 file failed to reformat
 ```
 

-Passing `-q` / `--quiet` will cause _Black_ to stop emitting all non-critial output.
-Error messages will still be emitted (which can silenced by `2>/dev/null`).
+#### `--version`
+
+You can check the version of _Black_ you have installed using the `--version` flag.

 
 ```console
 
 ```console

-$ black src/ -q
-error: cannot format src/black_primer/cli.py: Cannot parse: 5:6: mport asyncio
+$ black --version
+black, 23.9.0

 ```
 
 ```
 

-### Getting the version
+#### `--config`

 
 

-You can check the version of _Black_ you have installed using the `--version` flag.
+Read configuration options from a configuration file. See
+[below](#configuration-via-a-file) for more details on the configuration file.
+
+#### `-h`, `--help`
+
+Show available command-line options and exit.
+
+### Environment variable options
+
+_Black_ supports the following configuration via environment variables.
+
+#### `BLACK_CACHE_DIR`
+
+The directory where _Black_ should store its cache.
+
+#### `BLACK_NUM_WORKERS`
+
+The number of parallel workers _Black_ should use. The command line option `-W` /
+`--workers` takes precedence over this environment variable.
+
+### Code input alternatives
+
+_Black_ supports formatting code via stdin, with the result being printed to stdout.
+Just let _Black_ know with `-` as the path.

 
 ```console
 
 ```console

-$ black --version
-black, version 21.5b0
+$ echo "print ( 'hello, world' )" | black -
+print("hello, world")
+reformatted -
+All done! ✨ 🍰 ✨
+1 file reformatted.
+```
+
+**Tip:** if you need _Black_ to treat stdin input as a file passed directly via the CLI,
+use `--stdin-filename`. Useful to make sure _Black_ will respect the `--force-exclude`
+option on some editors that rely on using stdin.
+
+You can also pass code as a string using the `-c` / `--code` option.
+
+### Writeback and reporting
+
+By default _Black_ reformats the files given and/or found in place. Sometimes you need
+_Black_ to just tell you what it _would_ do without actually rewriting the Python files.
+
+There's two variations to this mode that are independently enabled by their respective
+flags:
+
+- `--check` (exit with code 1 if any file would be reformatted)
+- `--diff` (print a diff instead of reformatting files)
+
+Both variations can be enabled at once.
+
+### Output verbosity
+
+_Black_ in general tries to produce the right amount of output, balancing between
+usefulness and conciseness. By default, _Black_ emits files modified and error messages,
+plus a short summary.
+
+```console
+$ black src/
+error: cannot format src/black_primer/cli.py: Cannot parse: 5:6: mport asyncio
+reformatted src/black_primer/lib.py
+reformatted src/blackd/__init__.py
+reformatted src/black/__init__.py
+Oh no! 💥 💔 💥
+3 files reformatted, 2 files left unchanged, 1 file failed to reformat.

 ```
 
 ```
 

+The `--quiet` and `--verbose` flags control output verbosity.
+

 ## Configuration via a file
 
 _Black_ is able to read project-specific default values for its command line options
 ## Configuration via a file
 
 _Black_ is able to read project-specific default values for its command line options


@@ -198,9 +375,10 @@ code in compliance with many other _Black_ formatted projects.
 
 [PEP 518](https://www.python.org/dev/peps/pep-0518/) defines `pyproject.toml` as a
 configuration file to store build system requirements for Python projects. With the help
 
 [PEP 518](https://www.python.org/dev/peps/pep-0518/) defines `pyproject.toml` as a
 configuration file to store build system requirements for Python projects. With the help

-of tools like [Poetry](https://python-poetry.org/) or
-[Flit](https://flit.readthedocs.io/en/latest/) it can fully replace the need for
-`setup.py` and `setup.cfg` files.
+of tools like [Poetry](https://python-poetry.org/),
+[Flit](https://flit.readthedocs.io/en/latest/), or
+[Hatch](https://hatch.pypa.io/latest/) it can fully replace the need for `setup.py` and
+`setup.cfg` files.

 
 ### Where _Black_ looks for the file
 
 
 ### Where _Black_ looks for the file
 


@@ -253,10 +431,14 @@ expressions by Black. Use `[ ]` to denote a significant space character.
 line-length = 88
 target-version = ['py37']
 include = '\.pyi?$'
 line-length = 88
 target-version = ['py37']
 include = '\.pyi?$'

+# 'extend-exclude' excludes files or directories in addition to the defaults

 extend-exclude = '''
 # A regex preceded with ^/ will apply only to files and directories
 # in the root of the project.
 extend-exclude = '''
 # A regex preceded with ^/ will apply only to files and directories
 # in the root of the project.

-^/foo.py  # exclude a file named foo.py in the root of the project (in addition to the defaults)
+(
+  ^/foo.py    # exclude a file named foo.py in the root of the project
+  | .*_pb2.py  # exclude autogenerated Protocol Buffer files anywhere in the project
+)

 '''
 ```
 
 '''
 ```
 


@@ -274,9 +456,6 @@ file hierarchy.
 
 ## Next steps
 
 
 ## Next steps
 

-You've probably noted that not all of the options you can pass to _Black_ have been
-covered. Don't worry, the rest will be covered in a later section.
-

 A good next step would be configuring auto-discovery so `black .` is all you need
 instead of laborously listing every file or directory. You can get started by heading
 over to [File collection and discovery](./file_collection_and_discovery.md).
 A good next step would be configuring auto-discovery so `black .` is all you need
 instead of laborously listing every file or directory. You can get started by heading
 over to [File collection and discovery](./file_collection_and_discovery.md).