Implemented #1732: Support for custom sort functions.

CHANGELOG.md

@@ -9,6 +9,7 @@ Find out more about isort's release policy [here](https://pycqa.github.io/isort/
   - Implemented #1705: More intuitive handling of isort:skip_file comments on streams.
   - Implemented #1737: Support for using action comments to avoid adding imports to individual files.
   - Implemented #1750: Ability to customize output format lines.
+  - Implemented #1732: Support for custom sort functions.
   - Fixed (https://github.com/PyCQA/isort/pull/1695): added imports being added to doc string in some cases.
   - Fixed (https://github.com/PyCQA/isort/pull/1714): in rare cases line continuation combined with tabs can output invalid code.
   - Fixed (https://github.com/PyCQA/isort/pull/1726): isort ignores reverse_sort when force_sort_within_sections is true.

example_isort_sorting_plugin/example_isort_sorting_plugin.py

@@ -0,0 +1,6 @@
+from natsort import natsorted
+
+
+def natural_plus(*args, **kwargs) -> str:
+    """An even more natural sorting order for isort using natsort."""
+    return natsorted(*args, **kwargs)

example_isort_sorting_plugin/pyproject.toml

@@ -0,0 +1,19 @@
+[tool.poetry]
+name = "example_isort_sorting_plugin"
+version = "0.0.2"
+description = "An example plugin that modifies isorts sorting order to provide an even more natural sort by utilizing natsort."
+authors = ["Timothy Crosley <timothy.crosley@gmail.com>"]
+license = "MIT"
+
+[tool.poetry.plugins."isort.sort_function"]
+natural_plus = "example_isort_sorting_plugin:natural_plus"
+
+[tool.poetry.dependencies]
+python = "^3.6"
+natsort = "^7.1.1"
+
+[tool.poetry.dev-dependencies]
+
+[build-system]
+requires = ["poetry>=0.12"]
+build-backend = "poetry.masonry.api"

isort/exceptions.py

@@ -1,6 +1,6 @@
 """All isort specific exception classes should be defined here"""
 from pathlib import Path
-from typing import Any, Dict, Union
+from typing import Any, Dict, List, Union
 
 from .profiles import profiles
 
@@ -82,6 +82,18 @@ def __init__(self, profile: str):
         self.profile = profile
 
 
+class SortingFunctionDoesNotExist(ISortError):
+    """Raised when the specified sorting function isn't available"""
+
+    def __init__(self, sort_order: str, available_sort_orders: List[str]):
+        super().__init__(
+            f"Specified sort_order of {sort_order} does not exist. "
+            f"Available sort_orders: {','.join(available_sort_orders)}."
+        )
+        self.sort_order = sort_order
+        self.available_sort_orders = available_sort_orders
+
+
 class FormattingPluginDoesNotExist(ISortError):
     """Raised when a formatting plugin is set by the user that doesn't exist"""
 

isort/main.py

@@ -585,8 +585,8 @@ def _build_arg_parser() -> argparse.ArgumentParser:
     output_group.add_argument(
         "--sort-order",
         dest="sort_order",
-        choices=["default", "pythonic"],
-        help="Use natural language or pythonic sorting.",
+        help="Specify sorting function. Can be built in (natural[default] = force numbers "
+        "to be sequential, native = Python's built-in sorted function) or an installable plugin.",
     )
     inline_args_group.add_argument(
         "--sl",

isort/settings.py

@@ -30,13 +30,14 @@
 )
 from warnings import warn
 
-from . import stdlibs
+from . import sorting, stdlibs
 from ._future import dataclass, field
 from ._vendored import toml  # type: ignore
 from .exceptions import (
     FormattingPluginDoesNotExist,
     InvalidSettingsPath,
     ProfileDoesNotExist,
+    SortingFunctionDoesNotExist,
     UnsupportedSettings,
 )
 from .profiles import profiles
@@ -232,7 +233,7 @@ class _Config:
     git_ignore: Dict[Path, Set[Path]] = field(default_factory=dict)
     format_error: str = "{error}: {message}"
     format_success: str = "{success}: {message}"
-    sort_order: str = "default"
+    sort_order: str = "natural"
 
     def __post_init__(self) -> None:
         py_version = self.py_version
@@ -294,6 +295,7 @@ def __init__(
         self._section_comments: Optional[Tuple[str, ...]] = None
         self._skips: Optional[FrozenSet[str]] = None
         self._skip_globs: Optional[FrozenSet[str]] = None
+        self._sorting_function: Optional[Callable[..., List[str]]] = None
 
         if config:
             config_vars = vars(config).copy()
@@ -303,6 +305,7 @@ def __init__(
             config_vars.pop("_section_comments")
             config_vars.pop("_skips")
             config_vars.pop("_skip_globs")
+            config_vars.pop("_sorting_function")
             super().__init__(**config_vars)  # type: ignore
             return
 
@@ -651,6 +654,29 @@ def skip_globs(self) -> FrozenSet[str]:
         self._skip_globs = self.skip_glob.union(self.extend_skip_glob)
         return self._skip_globs
 
+    @property
+    def sorting_function(self) -> Callable[..., List[str]]:
+        if self._sorting_function is not None:
+            return self._sorting_function
+
+        if self.sort_order == "natural":
+            self._sorting_function = sorting.naturally
+        elif self.sort_order == "native":
+            self._sorting_function = sorted
+        else:
+            available_sort_orders = ["natural", "native"]
+            import pkg_resources
+
+            for sort_plugin in pkg_resources.iter_entry_points("isort.sort_function"):
+                available_sort_orders.append(sort_plugin.name)
+                if sort_plugin.name == self.sort_order:
+                    self._sorting_function = sort_plugin.load()
+                    break
+            else:
+                raise SortingFunctionDoesNotExist(self.sort_order, available_sort_orders)
+
+        return self._sorting_function
+
     def _parse_known_pattern(self, pattern: str) -> List[str]:
         """Expand pattern if identified as a directory and return found sub packages"""
         if pattern.endswith(os.path.sep):

isort/sorting.py

@@ -1,7 +1,10 @@
 import re
-from typing import Any, Callable, Iterable, List, Optional
+from typing import TYPE_CHECKING, Any, Callable, Iterable, List, Optional
 
-from .settings import Config
+if TYPE_CHECKING:
+    from .settings import Config
+else:
+    Config = Any
 
 _import_line_intro_re = re.compile("^(?:from|import) ")
 _import_line_midline_import_re = re.compile(" import ")
@@ -102,10 +105,7 @@ def sort(
     key: Optional[Callable[[str], Any]] = None,
     reverse: bool = False,
 ) -> List[str]:
-    sorting_func: Callable[..., List[str]] = naturally
-    if config.sort_order == "pythonic":
-        sorting_func = sorted
-    return sorting_func(to_sort, key=key, reverse=reverse)
+    return config.sorting_function(to_sort, key=key, reverse=reverse)
 
 
 def naturally(