Add hook for checking python modules

.pre-commit-hooks.yaml

@@ -64,6 +64,12 @@
     entry: check-merge-conflict
     language: python
     types: [text]
+-   id: check-python-modules
+    name: Check python modules
+    description: Ensure python modules have their __init__.py file.
+    entry: check-python-modules
+    language: python
+    types: [python]
 -   id: check-symlinks
     name: Check for broken symlinks
     description: Checks for symlinks which do not point to anything.

README.md

@@ -42,6 +42,7 @@ Add this to your `.pre-commit-config.yaml`
   proper shebang.
 - `check-json` - Attempts to load all json files to verify syntax.
 - `check-merge-conflict` - Check for files that contain merge conflict strings.
+- `check-python-modules` - Ensure python modules have their `__init__.py` file.
 - `check-symlinks` - Checks for symlinks which do not point to anything.
 - `check-vcs-permalinks` - Ensures that links to vcs websites are permalinks.
 - `check-xml` - Attempts to load all xml files to verify syntax.

pre_commit_hooks/check_python_modules.py

@@ -0,0 +1,50 @@
+from __future__ import absolute_import
+from __future__ import print_function
+
+import os.path
+from argparse import ArgumentParser
+from typing import Optional
+from typing import Sequence
+from typing import Set
+
+OK = 0
+ERR = 1
+
+
+class ModuleInitChecker:
+    def __init__(self):
+        # type: () -> None
+        self.seen_dirnames = set()  # type: Set[str]
+
+    def check(self, filename):
+        # type: (str) -> int
+        dirname = os.path.dirname(filename)
+        if dirname in self.seen_dirnames:
+            return OK
+
+        init_file = os.path.join(dirname, '__init__.py')
+        if dirname and not os.path.exists(init_file):
+            self.seen_dirnames.add(dirname)
+            with open(init_file, 'w'):
+                print(f'Created {init_file}')
+                return ERR
+
+        return OK
+
+
+def main(argv=None):  # type: (Optional[Sequence[str]]) -> int
+    parser = ArgumentParser()
+    parser.add_argument('filenames', nargs='*')
+
+    args = parser.parse_args(argv)
+
+    status = OK
+    checker = ModuleInitChecker()
+    for filename in args.filenames:
+        status |= checker.check(filename)
+
+    return status
+
+
+if __name__ == '__main__':
+    exit(main())

setup.py

@@ -41,6 +41,7 @@ setup(
             'check-executables-have-shebangs = pre_commit_hooks.check_executables_have_shebangs:main',  # noqa: E501
             'check-json = pre_commit_hooks.check_json:main',
             'check-merge-conflict = pre_commit_hooks.check_merge_conflict:main',  # noqa: E501
+            'check-python-modules = pre_commit_hooks.check_python_modules:main',  # noqa: E501
             'check-symlinks = pre_commit_hooks.check_symlinks:main',
             'check-vcs-permalinks = pre_commit_hooks.check_vcs_permalinks:main',  # noqa: E501
             'check-xml = pre_commit_hooks.check_xml:main',

tests/check_python_modules_test.py

@@ -0,0 +1,13 @@
+import pytest
+
+from pre_commit_hooks.check_python_modules import main
+
+
+@pytest.mark.parametrize('has_init', (True, False))
+def test_main(tmpdir, has_init):
+    if has_init:
+        tmpdir.join('__init__.py').ensure()
+    path = tmpdir.join('thing.py').ensure()
+
+    expected = 0 if has_init else 1
+    assert main((path.strpath,)) == expected