Warn when exclude pattern is not matched

pre_commit/commands/run.py

@@ -38,14 +38,15 @@ def _hook_msg_start(hook, verbose):
 
 def _filter_by_include_exclude(filenames, include, exclude):
     include_re, exclude_re = re.compile(include), re.compile(exclude)
-    return {
+    filtered = set()
-        filename for filename in filenames
+    exclude_matched = False
-        if (
+    for filename in filenames:
-            include_re.search(filename) and
+        if include_re.search(filename):
-            not exclude_re.search(filename) and
+            if exclude_re.search(filename):
-            os.path.lexists(filename)
+                exclude_matched = True
-        )
+            elif os.path.lexists(filename):
-    }
+                filtered.add(filename)
+    return filtered, exclude_matched
 
 
 def _filter_by_types(filenames, types, exclude_types):
@@ -64,7 +65,13 @@ NO_FILES = '(no files to check)'
 
 def _run_single_hook(filenames, hook, repo, args, skips, cols):
     include, exclude = hook['files'], hook['exclude']
-    filenames = _filter_by_include_exclude(filenames, include, exclude)
+    filenames, excluded = _filter_by_include_exclude(
+        filenames, include, exclude,
+    )
+    if args.all_files and exclude != '^$' and not excluded:
+        logger.warning('The exclude pattern for {} did not match any files'
+                       .format(_hook_msg_start(hook, args.verbose)))
+
     types, exclude_types = hook['types'], hook['exclude_types']
     filenames = _filter_by_types(filenames, types, exclude_types)
     if hook['id'] in skips:
@@ -181,7 +188,12 @@ def _run_hooks(config, repo_hooks, args, environ):
     skips = _get_skips(environ)
     cols = _compute_cols([hook for _, hook in repo_hooks], args.verbose)
     filenames = _all_filenames(args)
-    filenames = _filter_by_include_exclude(filenames, '', config['exclude'])
+    filenames, excluded = _filter_by_include_exclude(
+        filenames, '', config['exclude'],
+    )
+    if args.all_files and config['exclude'] != '^$' and not excluded:
+        logger.warning('The global exclude pattern did not match any files')
+
     retval = 0
     for repo, hook in repo_hooks:
         retval |= _run_single_hook(filenames, hook, repo, args, skips, cols)

tests/commands/run_test.py

@@ -170,6 +170,34 @@ def test_global_exclude(cap_out, tempdir_factory, mock_out_store_directory):
         assert printed.endswith(expected)
 
 
+def test_global_exclude_no_match(
+        cap_out, tempdir_factory, mock_out_store_directory,
+):
+    git_path = make_consuming_repo(tempdir_factory, 'script_hooks_repo')
+    with cwd(git_path):
+        with modify_config() as config:
+            config['exclude'] = '^test$'
+        ret, printed = _do_run(cap_out, git_path, run_opts(all_files=True))
+        assert ret == 0
+        expected = b'The global exclude pattern did not match any files\n'
+        assert expected in printed
+
+
+def test_hook_exclude_no_match(
+        cap_out, tempdir_factory, mock_out_store_directory,
+):
+    git_path = make_consuming_repo(tempdir_factory, 'script_hooks_repo')
+    with cwd(git_path):
+        with modify_config() as config:
+            config['repos'][0]['hooks'][0]['exclude'] = '^test$'
+            print(config['repos'][0]['hooks'])
+        ret, printed = _do_run(cap_out, git_path, run_opts(all_files=True))
+        assert ret == 0
+        expected = b'The exclude pattern for Bash hook ' \
+                   b'did not match any files\n'
+        assert expected in printed
+
+
 def test_show_diff_on_failure(
         capfd, cap_out, tempdir_factory, mock_out_store_directory,
 ):
@@ -746,7 +774,7 @@ def some_filenames():
 
 
 def test_include_exclude_base_case(some_filenames):
-    ret = _filter_by_include_exclude(some_filenames, '', '^$')
+    ret, _ = _filter_by_include_exclude(some_filenames, '', '^$')
     assert ret == {
         '.pre-commit-hooks.yaml',
         'pre_commit/main.py',
@@ -758,20 +786,36 @@ def test_include_exclude_base_case(some_filenames):
 def test_matches_broken_symlink(tmpdir):  # pramga: no cover (non-windows)
     with tmpdir.as_cwd():
         os.symlink('does-not-exist', 'link')
-        ret = _filter_by_include_exclude({'link'}, '', '^$')
+        ret, _ = _filter_by_include_exclude({'link'}, '', '^$')
         assert ret == {'link'}
 
 
 def test_include_exclude_total_match(some_filenames):
-    ret = _filter_by_include_exclude(some_filenames, r'^.*\.py$', '^$')
+    ret, _ = _filter_by_include_exclude(some_filenames, r'^.*\.py$', '^$')
     assert ret == {'pre_commit/main.py', 'pre_commit/git.py'}
 
 
 def test_include_exclude_does_search_instead_of_match(some_filenames):
-    ret = _filter_by_include_exclude(some_filenames, r'\.yaml$', '^$')
+    ret, _ = _filter_by_include_exclude(some_filenames, r'\.yaml$', '^$')
     assert ret == {'.pre-commit-hooks.yaml'}
 
 
 def test_include_exclude_exclude_removes_files(some_filenames):
-    ret = _filter_by_include_exclude(some_filenames, '', r'\.py$')
+    ret, _ = _filter_by_include_exclude(some_filenames, '', r'\.py$')
     assert ret == {'.pre-commit-hooks.yaml'}
+
+
+def test_include_exclude_exclude_matches(some_filenames):
+    ret, matched = _filter_by_include_exclude(some_filenames, '', r'\.py$')
+    assert ret == {'.pre-commit-hooks.yaml'}
+    assert matched is True
+
+
+def test_include_exclude_exclude_no_matches(some_filenames):
+    ret, matched = _filter_by_include_exclude(some_filenames, '', r'^$')
+    assert ret == {
+        '.pre-commit-hooks.yaml',
+        'pre_commit/main.py',
+        'pre_commit/git.py',
+    }
+    assert matched is False