Implemented support for automatic redundant alias removal (issue #1281).

CHANGELOG.md

@@ -5,8 +5,10 @@ NOTE: isort follows the [semver](https://semver.org/) versioning standard.
 
 ### 5.1.0 July TBD, 2020
   - isort now throws an exception if an invalid settings path is given (issue #1174).
+  - Implemented support for automatic redundant alias removal (issue #1281).
   - Fixed #1178: support for semicolons in decorators.
   - Fixed #1315: Extra newline before comment with -n + --fss.
+
 **Formatting changes implied:**
   - Fixed #1280: rewrite of as imports changes the behavior of the imports.
 

isort/hooks.py

@@ -62,13 +62,13 @@ def git_hook(strict: bool = False, modify: bool = False) -> int:
             staged_contents = get_output(staged_cmd)
 
             try:
-                if not api.check_code_string(staged_contents,
-                                             file_path=Path(filename),
-                                             config=config):
+                if not api.check_code_string(
+                    staged_contents, file_path=Path(filename), config=config
+                ):
                     errors += 1
                     if modify:
                         api.sort_file(filename, config=config)
-            except exceptions.FileSkipComment:
+            except exceptions.FileSkipped:  # pragma: no cover
                 pass
 
     return errors if strict else 0

isort/main.py

@@ -585,6 +585,16 @@ def _build_arg_parser() -> argparse.ArgumentParser:
         action="store_true",
         help="Tells isort to honor noqa comments to enforce skipping those comments.",
     )
+    parser.add_argument(
+        "--remove-redundant-aliases",
+        dest="remove_redundant_aliases",
+        action="store_true",
+        help=(
+            "Tells isort to remove redundant aliases from imports, such as import os as os."
+            " This defaults to false simply because some projects use these seemingly useless alias"
+            " to signify intent and change behaviour."
+        ),
+    )
 
     # deprecated options
     parser.add_argument(

isort/parse.py

@@ -319,14 +319,19 @@ def file_contents(contents: str, config: Config = DEFAULT_CONFIG) -> ParsedConte
                 while "as" in just_imports:
                     as_index = just_imports.index("as")
                     if type_of_import == "from":
-                        module = just_imports[0] + "." + just_imports[as_index - 1]
+                        nested_module = just_imports[as_index - 1]
+                        module = just_imports[0] + "." + nested_module
                         as_name = just_imports[as_index + 1]
-                        if as_name not in as_map["from"][module]:
+                        if nested_module == as_name and config.remove_redundant_aliases:
+                            pass
+                        elif as_name not in as_map["from"][module]:
                             as_map["from"][module].append(as_name)
                     else:
                         module = just_imports[as_index - 1]
                         as_name = just_imports[as_index + 1]
-                        if as_name not in as_map["straight"][module]:
+                        if module == as_name and config.remove_redundant_aliases:
+                            pass
+                        elif as_name not in as_map["straight"][module]:
                             as_map["straight"][module].append(as_name)
                     if not config.combine_as_imports:
                         categorized_comments["straight"][module] = comments

isort/settings.py

@@ -166,6 +166,7 @@ class _Config:
     honor_noqa: bool = False
     src_paths: FrozenSet[Path] = frozenset()
     old_finders: bool = False
+    remove_redundant_aliases: bool = False
 
     def __post_init__(self):
         py_version = self.py_version

tests/test_hooks.py

@@ -2,7 +2,7 @@
 from io import BytesIO
 from unittest.mock import MagicMock, patch
 
-from isort import hooks
+from isort import exceptions, hooks
 
 
 def test_git_hook(src_dir):
@@ -26,3 +26,15 @@ class FakeProcessResponse(object):
         with patch("subprocess.run", MagicMock(return_value=FakeProcessResponse())) as run_mock:
             with patch("isort.api", MagicMock(return_value=False)):
                 hooks.git_hook(modify=True)
+
+    # Test with skipped file returned from git
+    with patch(
+        "isort.hooks.get_lines", MagicMock(return_value=[os.path.join(src_dir, "main.py")])
+    ) as run_mock:
+
+        class FakeProcessResponse(object):
+            stdout = b"# isort: skip-file\nimport b\nimport a\n"
+
+        with patch("subprocess.run", MagicMock(return_value=FakeProcessResponse())) as run_mock:
+            with patch("isort.api", MagicMock(side_effect=exceptions.FileSkipped("", ""))):
+                hooks.git_hook(modify=True)

tests/test_ticketed_features.py

@@ -19,3 +19,16 @@ def test_thing(): pass
 """,
         show_diff=True,
     )
+
+
+def test_isort_automatically_removes_duplicate_aliases_issue_1193():
+    """Test to ensure isort can automatically remove duplicate aliases.
+    See: https://github.com/timothycrosley/isort/issues/1281
+    """
+    assert isort.check_code("from urllib import parse as parse\n", show_diff=True)
+    assert (
+        isort.code("from urllib import parse as parse", remove_redundant_aliases=True)
+        == "from urllib import parse\n"
+    )
+    assert isort.check_code("import os as os\n", show_diff=True)
+    assert isort.code("import os as os", remove_redundant_aliases=True) == "import os\n"