Black as a plugin

CHANGES.rst

@@ -15,6 +15,10 @@ Added
 - Prevent Pylint from updating beyond version 3.2.7 due to dropped Python 3.8 support.
 - The ``--formatter=black`` option (the default) has been added in preparation for
  future formatters.
+- Invoking Black is now implemented as a plugin. This allows for easier integration of
+ other formatters in the future. There's also a dummy ``none`` formatter plugin.
+- ``--formatter=none`` now skips running Black. This is useful when you only want to run
+ Isort or Flynt.
 
 Removed
 -------

README.rst

@@ -371,7 +371,7 @@ The following `command line arguments`_ can also be used to modify the defaults:
  versions that should be supported by Black's output. [default: per-file auto-
  detection]
 --formatter FORMATTER
- Formatter to use for reformatting code
+ [black\|none] Formatter to use for reformatting code. [default: black]
 
 To change default values for these options for a given project,
 add a ``[tool.darker]`` section to ``pyproject.toml`` in the project's root directory,

setup.cfg

@@ -45,6 +45,9 @@ darker =
  .pyi
 
 [options.entry_points]
+darker.formatter =
+ black = darker.formatters.black_formatter:BlackFormatter
+ none = darker.formatters.none_formatter:NoneFormatter
 console_scripts =
  darker = darker.__main__:main_with_error_handling
 

src/darker/__main__.py

@@ -1,4 +1,4 @@
-"""Darker - apply black reformatting to only areas edited since the last commit"""
+"""Darker - re-format only code areas edited since the last commit."""
 
 import concurrent.futures
 import logging
@@ -10,18 +10,16 @@
 from pathlib import Path
 from typing import Collection, Generator, List, Optional, Tuple
 
-from darker.black_diff import (
- BlackConfig,
- filter_python_files,
- read_black_config,
- run_black,
-)
 from darker.chooser import choose_lines
 from darker.command_line import parse_command_line
 from darker.concurrency import get_executor
 from darker.config import Exclusions, OutputMode, validate_config_output_mode
 from darker.diff import diff_chunks
 from darker.exceptions import DependencyError, MissingPackageError
+from darker.files import filter_python_files
+from darker.formatters import create_formatter
+from darker.formatters.base_formatter import BaseFormatter
+from darker.formatters.none_formatter import NoneFormatter
 from darker.fstring import apply_flynt, flynt
 from darker.git import (
  EditedLinenumsDiffer,
@@ -60,12 +58,12 @@
 ProcessedDocument = Tuple[Path, TextDocument, TextDocument]
 
 
-def format_edited_parts( # pylint: disable=too-many-arguments
+def format_edited_parts( # noqa: PLR0913 # pylint: disable=too-many-arguments
  root: Path,
- changed_files: Collection[Path], # pylint: disable=unsubscriptable-object
+ changed_files: Collection[Path],
  exclude: Exclusions,
  revrange: RevisionRange,
- black_config: BlackConfig,
+ formatter: BaseFormatter,
  report_unmodified: bool,
  workers: int = 1,
 ) -> Generator[ProcessedDocument, None, None]:
@@ -82,7 +80,7 @@ def format_edited_parts( # pylint: disable=too-many-arguments
  modified in the repository between the given Git revisions
  :param exclude: Files to exclude when running Black,``isort`` or ``flynt``
  :param revrange: The Git revisions to compare
- :param black_config: Configuration to use for running Black
+ :param formatter: The code re-formatter to use
  :param report_unmodified: ``True`` to yield also files which weren't modified
  :param workers: number of cpu processes to use (0 - autodetect)
  :return: A generator which yields details about changes for each file which should
@@ -101,7 +99,7 @@ def format_edited_parts( # pylint: disable=too-many-arguments
  edited_linenums_differ,
  exclude,
  revrange,
- black_config,
+ formatter,
  )
  futures.append(future)
 
@@ -115,21 +113,22 @@ def format_edited_parts( # pylint: disable=too-many-arguments
  yield (absolute_path_in_rev2, rev2_content, content_after_reformatting)
 
 
-def _modify_and_reformat_single_file( # pylint: disable=too-many-arguments
+def _modify_and_reformat_single_file( # noqa: PLR0913
  root: Path,
  relative_path_in_rev2: Path,
  edited_linenums_differ: EditedLinenumsDiffer,
  exclude: Exclusions,
  revrange: RevisionRange,
- black_config: BlackConfig,
+ formatter: BaseFormatter,
 ) -> ProcessedDocument:
+ # pylint: disable=too-many-arguments
  """Black, isort and/or flynt formatting for modified chunks in a single file
 
  :param root: Root directory for the relative path
  :param relative_path_in_rev2: Relative path to a Python source code file
  :param exclude: Files to exclude when running Black, ``isort`` or ``flynt``
  :param revrange: The Git revisions to compare
- :param black_config: Configuration to use for running Black
+ :param formatter: The code re-formatter to use
  :return: Details about changes for the file
 
  """
@@ -148,13 +147,14 @@ def _modify_and_reformat_single_file( # pylint: disable=too-many-arguments
  relative_path_in_rev2,
  exclude.isort,
  edited_linenums_differ,
- black_config.get("config"),
- black_config.get("line_length"),
+ formatter.get_config_path(),
+ formatter.get_line_length(),
  )
  has_isort_changes = rev2_isorted != rev2_content
  # 2. run flynt (optional) on the isorted contents of each edited to-file
- # 3. run black on the isorted and fstringified contents of each edited to-file
- content_after_reformatting = _blacken_and_flynt_single_file(
+ # 3. run a re-formatter on the isorted and fstringified contents of each edited
+ # to-file
+ content_after_reformatting = _reformat_and_flynt_single_file(
  root,
  relative_path_in_rev2,
  get_path_in_repo(relative_path_in_rev2),
@@ -163,13 +163,12 @@ def _modify_and_reformat_single_file( # pylint: disable=too-many-arguments
  rev2_content,
  rev2_isorted,
  has_isort_changes,
- black_config,
+ formatter,
  )
  return absolute_path_in_rev2, rev2_content, content_after_reformatting
 
 
-def _blacken_and_flynt_single_file(
- # pylint: disable=too-many-arguments,too-many-locals
+def _reformat_and_flynt_single_file( # noqa: PLR0913
  root: Path,
  relative_path_in_rev2: Path,
  relative_path_in_repo: Path,
@@ -178,8 +177,9 @@ def _blacken_and_flynt_single_file(
  rev2_content: TextDocument,
  rev2_isorted: TextDocument,
  has_isort_changes: bool,
- black_config: BlackConfig,
+ formatter: BaseFormatter,
 ) -> TextDocument:
+ # pylint: disable=too-many-arguments
  """In a Python file, reformat chunks with edits since the last commit using Black
 
  :param root: The common root of all files to reformat
@@ -192,7 +192,7 @@ def _blacken_and_flynt_single_file(
  :param rev2_content: Contents of the file at ``revrange.rev2``
  :param rev2_isorted: Contents of the file after optional import sorting
  :param has_isort_changes: ``True`` if ``isort`` was run and modified the file
- :param black_config: Configuration to use for running Black
+ :param formatter: The code re-formatter to use
  :return: Contents of the file after reformatting
  :raise: NotEquivalentError
 
@@ -214,14 +214,18 @@ def _blacken_and_flynt_single_file(
  len(fstringified.lines),
  "some" if has_fstring_changes else "no",
  )
- # 3. run black on the isorted and fstringified contents of each edited to-file
- formatted = _maybe_blacken_single_file(
- relative_path_in_rev2, exclude.black, fstringified, black_config
+ # 3. run the code re-formatter on the isorted and fstringified contents of each
+ # edited to-file
+ formatted = _maybe_reformat_single_file(
+ relative_path_in_rev2, exclude.formatter, fstringified, formatter
  )
  logger.debug(
- "Black reformat resulted in %s lines, with %s changes from reformatting",
- len(formatted.lines),
+ "Running %r by %s.%s resulted in %s changed lines within a total of %s lines",
+ formatter.name,
+ formatter.__module__,
+ type(formatter).__name__,
  "no" if formatted == fstringified else "some",
+ len(formatted.lines),
  )
 
  # 4. get a diff between the edited to-file and the processed content
@@ -270,26 +274,26 @@ def _maybe_flynt_single_file(
  return apply_flynt(rev2_isorted, relpath_in_rev2, edited_linenums_differ)
 
 
-def _maybe_blacken_single_file(
+def _maybe_reformat_single_file(
  relpath_in_rev2: Path,
  exclude: Collection[str],
  fstringified: TextDocument,
- black_config: BlackConfig,
+ formatter: BaseFormatter,
 ) -> TextDocument:
- """Format Python source code with Black if the source code file path isn't excluded
+ """Re-format Python source code if the source code file path isn't excluded.
 
  :param relpath_in_rev2: Relative path to a Python source code file. Possibly a
  VSCode ``.py.<HASH>.tmp`` file in the working tree.
- :param exclude: Files to exclude when running Black
+ :param exclude: Files to exclude when running the re-formatter
  :param fstringified: Contents of the file after optional import sorting and flynt
- :param black_config: Configuration to use for running Black
+ :param formatter: The code re-formatter to use
  :return: Python source code after reformatting
 
  """
  if glob_any(relpath_in_rev2, exclude):
  # File was excluded by Black configuration, don't reformat
  return fstringified
- return run_black(fstringified, black_config)
+ return formatter.run(fstringified)
 
 
 def _drop_changes_on_unedited_lines(
@@ -459,7 +463,8 @@ def main( # noqa: C901,PLR0912,PLR0915
 
  1. run isort on each edited file (optional)
  2. run flynt (optional) on the isorted contents of each edited to-file
- 3. run black on the isorted and fstringified contents of each edited to-file
+ 3. run a code re-formatter on the isorted and fstringified contents of each edited
+ to-file
  4. get a diff between the edited to-file and the processed content
  5. convert the diff into chunks, keeping original and reformatted content for each
  chunk
@@ -511,19 +516,8 @@ def main( # noqa: C901,PLR0912,PLR0915
  f"{get_extra_instruction('flynt')} to use the `--flynt` option."
  )
 
- black_config = read_black_config(tuple(args.src), args.config)
- if args.config:
- black_config["config"] = args.config
- if args.line_length:
- black_config["line_length"] = args.line_length
- if args.target_version:
- black_config["target_version"] = {args.target_version}
- if args.skip_string_normalization is not None:
- black_config["skip_string_normalization"] = args.skip_string_normalization
- if args.skip_magic_trailing_comma is not None:
- black_config["skip_magic_trailing_comma"] = args.skip_magic_trailing_comma
- if args.preview:
- black_config["preview"] = args.preview
+ formatter = create_formatter(args.formatter)
+ formatter.read_config(tuple(args.src), args)
 
  paths, common_root = resolve_paths(args.stdin_filename, args.src)
  # `common_root` is now the common root of given paths,
@@ -570,8 +564,8 @@ def main( # noqa: C901,PLR0912,PLR0915
  else common_root
  )
  # These paths are relative to `common_root`:
- files_to_process = filter_python_files(paths, common_root_, {})
- files_to_blacken = filter_python_files(paths, common_root_, black_config)
+ files_to_process = filter_python_files(paths, common_root_, NoneFormatter())
+ files_to_reformat = filter_python_files(paths, common_root_, formatter)
 
  # Now decide which files to reformat (Black & isort). Note that this doesn't apply
  # to linting.
@@ -580,7 +574,7 @@ def main( # noqa: C901,PLR0912,PLR0915
  # modified or not. Paths have previously been validated to contain exactly one
  # existing file.
  changed_files_to_reformat = files_to_process
- black_exclude = set()
+ formatter_exclude = set()
  else:
  # In other modes, only reformat files which have been modified.
  if git_is_repository(common_root):
@@ -595,10 +589,10 @@ def main( # noqa: C901,PLR0912,PLR0915
 
  else:
  changed_files_to_reformat = files_to_process
- black_exclude = {
+ formatter_exclude = {
  str(path)
  for path in changed_files_to_reformat
- if path not in files_to_blacken
+ if path not in files_to_reformat
  }
  use_color = should_use_color(config["color"])
  formatting_failures_on_modified_lines = False
@@ -607,12 +601,12 @@ def main( # noqa: C901,PLR0912,PLR0915
  common_root,
  changed_files_to_reformat,
  Exclusions(
- black=black_exclude,
+ formatter=formatter_exclude,
  isort=set() if args.isort else {"**/*"},
  flynt=set() if args.flynt else {"**/*"},
  ),
  revrange,
- black_config,
+ formatter,
  report_unmodified=output_mode == OutputMode.CONTENT,
  workers=config["workers"],
  ),