Resolve #1353: Added support for output format plugin

CHANGELOG.md

@@ -13,6 +13,7 @@ NOTE: isort follows the [semver](https://semver.org/) versioning standard.
   - Implemented #1214: Added support for git_hook lazy option (Thanks @sztamas!)
   - Implemented #941: Added an additional `multi_line_output` mode for more compact formatting (Thanks @sztamas!)
   - Implemented #1020: Option for LOCALFOLDER.
+  - Implemented #1353: Added support for output formatting plugins.
   - `# isort: split` can now be used at the end of an import line.
   - Fixed #1339: Extra indent is not preserved when isort:skip is used in nested imports.
   - Fixed #1348: `--diff` works incorrectly with files that have CRLF line endings.

example_isort_formatting_plugin/example_isort_formatting_plugin.py

@@ -0,0 +1,22 @@
+import black
+
+import isort
+
+
+def black_format_import_section(
+    contents: str, extension: str, config: isort.settings.Config
+) -> str:
+    """Formats the given import section using black."""
+    if extension.lower() not in ("pyi", "py"):
+        return contents
+
+    try:
+        return black.format_file_contents(
+            contents,
+            fast=True,
+            mode=black.FileMode(
+                is_pyi=extension.lower() == "pyi", line_length=config.line_length,
+            ),
+        )
+    except black.NothingChanged:
+        return contents

example_isort_formatting_plugin/pyproject.toml

@@ -0,0 +1,20 @@
+[tool.poetry]
+name = "example_isort_formatting_plugin"
+version = "0.0.1"
+description = "An example plugin that modifies isort formatting using black."
+authors = ["Timothy Crosley <[email protected]>"]
+license = "MIT"
+
+[tool.poetry.plugins."isort.formatters"]
+example = "example_isort_formatting_plugin:black_format_import_section"
+
+[tool.poetry.dependencies]
+python = "^3.6"
+isort = "^5.1.4"
+black = "^19.10b0"
+
+[tool.poetry.dev-dependencies]
+
+[build-system]
+requires = ["poetry>=0.12"]
+build-backend = "poetry.masonry.api"

isort/exceptions.py

@@ -77,3 +77,11 @@ def __init__(self, profile: str):
             f"Available profiles: {','.join(profiles)}."
         )
         self.profile = profile
+
+
+class FormattingPluginDoesNotExist(ISortError):
+    """Raised when a formatting plugin is set by the user that doesn't exist"""
+
+    def __init__(self, formatter: str):
+        super().__init__(f"Specified formatting plugin of {formatter} does not exist. ")
+        self.formatter = formatter

isort/main.py

@@ -625,6 +625,13 @@ def _build_arg_parser() -> argparse.ArgumentParser:
         "Still it can be a great shortcut for collecting imports every once in a while when you put"
         " them in the middle of a file.",
     )
+    parser.add_argument(
+        "--formatter",
+        dest="formatter",
+        type=str,
+        help="Specifies the name of a formatting plugin to use when producing output.",
+    )
+
     # deprecated options
     parser.add_argument(
         "--recursive",
@@ -686,6 +693,8 @@ def _preconvert(item):
         return item.name
     elif isinstance(item, Path):
         return str(item)
+    elif callable(item) and hasattr(item, "__name__"):
+        return item.__name__
     else:
         raise TypeError("Unserializable object {} of type {}".format(item, type(item)))
 

isort/output.py

@@ -171,6 +171,11 @@ def sorted_imports(
     while output and output[0].strip() == "":
         output.pop(0)
 
+    if config.formatting_function:
+        output = config.formatting_function(
+            parsed.line_separator.join(output), extension, config
+        ).splitlines()
+
     output_at = 0
     if parsed.import_index < parsed.original_line_count:
         output_at = parsed.import_index

isort/settings.py

@@ -17,7 +17,7 @@
 from . import stdlibs
 from ._future import dataclass, field
 from ._vendored import toml
-from .exceptions import InvalidSettingsPath, ProfileDoesNotExist
+from .exceptions import FormattingPluginDoesNotExist, InvalidSettingsPath, ProfileDoesNotExist
 from .profiles import profiles
 from .sections import DEFAULT as SECTION_DEFAULTS
 from .sections import FIRSTPARTY, FUTURE, LOCALFOLDER, STDLIB, THIRDPARTY
@@ -173,6 +173,8 @@ class _Config:
     remove_redundant_aliases: bool = False
     float_to_top: bool = False
     filter_files: bool = False
+    formatter: str = ""
+    formatting_function: Optional[Callable[[str, str, object], str]] = None
 
     def __post_init__(self):
         py_version = self.py_version
@@ -348,6 +350,16 @@ def __init__(
                 path_root / path for path in combined_config.get("src_paths", ())
             )
 
+        if "formatter" in combined_config:
+            import pkg_resources
+
+            for plugin in pkg_resources.iter_entry_points("isort.formatters"):
+                if plugin.name == combined_config["formatter"]:
+                    combined_config["formatting_function"] = plugin.load()
+                    break
+            else:
+                raise FormattingPluginDoesNotExist(combined_config["formatter"])
+
         # Remove any config values that are used for creating config object but
         # aren't defined in dataclass
         combined_config.pop("source", None)