X-Git-Url: https://git.madduck.net/etc/vim.git/blobdiff_plain/4bb7bf2bdc95a8035ccf167023a7044e5f8e5ef6..3a9d6f0a5f9013b97676f3d24246bd34d93fce4c:/docs/the_black_code_style/future_style.md diff --git a/docs/the_black_code_style/future_style.md b/docs/the_black_code_style/future_style.md index 8d159e9..f5fc364 100644 --- a/docs/the_black_code_style/future_style.md +++ b/docs/the_black_code_style/future_style.md @@ -19,26 +19,39 @@ with make_context_manager1() as cm1, make_context_manager2() as cm2, make_contex ... # nothing to split on - line too long ``` -So _Black_ will eventually format it like this: +So _Black_ will, when we implement this, format it like this: ```py3 with \ - make_context_manager(1) as cm1, \ - make_context_manager(2) as cm2, \ - make_context_manager(3) as cm3, \ - make_context_manager(4) as cm4 \ + make_context_manager1() as cm1, \ + make_context_manager2() as cm2, \ + make_context_manager3() as cm3, \ + make_context_manager4() as cm4 \ : ... # backslashes and an ugly stranded colon ``` -Although when the target version is Python 3.9 or higher, _Black_ will use parentheses -instead since they're allowed in Python 3.9 and higher. +Although when the target version is Python 3.9 or higher, _Black_ uses parentheses +instead in `--preview` mode (see below) since they're allowed in Python 3.9 and higher. + +An alternative to consider if the backslashes in the above formatting are undesirable is +to use {external:py:obj}`contextlib.ExitStack` to combine context managers in the +following way: + +```python +with contextlib.ExitStack() as exit_stack: + cm1 = exit_stack.enter_context(make_context_manager1()) + cm2 = exit_stack.enter_context(make_context_manager2()) + cm3 = exit_stack.enter_context(make_context_manager3()) + cm4 = exit_stack.enter_context(make_context_manager4()) + ... +``` ## Preview style Experimental, potentially disruptive style changes are gathered under the `--preview` CLI flag. At the end of each year, these changes may be adopted into the default style, -as described in [The Black Code Style](./index.rst). Because the functionality is +as described in [The Black Code Style](index.md). Because the functionality is experimental, feedback and issue reports are highly encouraged! ### Improved string processing @@ -50,27 +63,99 @@ limit. Line continuation backslashes are converted into parenthesized strings. Unnecessary parentheses are stripped. The stability and status of this feature is tracked in [this issue](https://github.com/psf/black/issues/2188). -### Removing trailing newlines after code block open +### Improved line breaks -_Black_ will remove trailing newlines after code block openings. That means that the -following code: +For assignment expressions, _Black_ now prefers to split and wrap the right side of the +assignment instead of left side. For example: ```python -def my_func(): +some_dict[ + "with_a_long_key" +] = some_looooooooong_module.some_looooooooooooooong_function_name( + first_argument, second_argument, third_argument +) +``` - print("The line above me will be deleted!") +will be changed to: - print("But the line above me won't!") +```python +some_dict["with_a_long_key"] = ( + some_looooooooong_module.some_looooooooooooooong_function_name( + first_argument, second_argument, third_argument + ) +) ``` -Will be changed to: +### Improved parentheses management + +For dict literals with long values, they are now wrapped in parentheses. Unnecessary +parentheses are now removed. For example: ```python -def my_func(): - print("The line above me will be deleted!") +my_dict = { + my_dict = { + "a key in my dict": a_very_long_variable + * and_a_very_long_function_call() + / 100000.0, + "another key": (short_value), +} +``` + +will be changed to: - print("But the line above me won't!") +```python +my_dict = { + "a key in my dict": ( + a_very_long_variable * and_a_very_long_function_call() / 100000.0 + ), + "another key": short_value, +} ``` -This new feature will be applied to **all code blocks**: `def`, `class`, `if`, `for`, -`while`, `with`, `case` and `match`. +### Improved multiline string handling + +_Black_ is smarter when formatting multiline strings, especially in function arguments, +to avoid introducing extra line breaks. Previously, it would always consider multiline +strings as not fitting on a single line. With this new feature, _Black_ looks at the +context around the multiline string to decide if it should be inlined or split to a +separate line. For example, when a multiline string is passed to a function, _Black_ +will only split the multiline string if a line is too long or if multiple arguments are +being passed. + +For example, _Black_ will reformat + +```python +textwrap.dedent( + """\ + This is a + multiline string +""" +) +``` + +to: + +```python +textwrap.dedent("""\ + This is a + multiline string +""") +``` + +And: + +```python +MULTILINE = """ +foobar +""".replace( + "\n", "" +) +``` + +to: + +```python +MULTILINE = """ +foobar +""".replace("\n", "") +```