Add presubmit check to prevent anonymous namespace usage in headers

Bug: 391905435
Change-Id: I928d282bc3b626addc564889338cb7426e7cbe4c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6192789
Commit-Queue: Aaron Selya <selya@google.com>
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1411842}

PRESUBMIT.py

@@ -7806,3 +7806,33 @@ def CheckTodoBugReferences(input_api, output_api):
         ]
     else:
         return []
+
+def CheckForAnonymousNamespaceInHeader(input_api,
+                                   output_api,
+                                   allowlist=_HEADER_EXTENSIONS,
+                                   denylist=None):
+    denylist = tuple(denylist or input_api.DEFAULT_FILES_TO_SKIP)
+    source_file_filter = lambda x: input_api.FilterSourceFile(
+        x, allowlist, denylist)
+
+    def headers(f):
+          return input_api.FilterSourceFile(
+              f, files_to_check=(r'.+%s' % _HEADER_EXTENSIONS, ))
+
+    header_using_anon_namespace_files = []
+
+    for f in input_api.AffectedSourceFiles(headers):
+        contents = input_api.ReadFile(f, 'rb')
+        if input_api.re.search(r"namespace {", contents):
+            header_using_anon_namespace_files.append(f.LocalPath())
+
+    result = []
+    if header_using_anon_namespace_files:
+        result.append(
+            output_api.PresubmitError(
+                'These files have an anonymous namespace which is not '
+                'permitted in header files, for more information see ('
+                'https://google.github.io/styleguide/cppguide.html#Internal_Linkage'
+                '): ',
+                items=header_using_anon_namespace_files))
+    return result

PRESUBMIT_test.py

@@ -5705,6 +5705,30 @@ class CheckDeprecatedSyncConsentFunctionsTest(unittest.TestCase):
         self.assertTrue('chrome/foo/file4.java' in results[0].message),
         self.assertTrue('chrome/foo/file5.java' in results[0].message),
 
+class CheckAnonymousNamespacesInHeaderFilesTest(unittest.TestCase):
+    """Test the presubmit checking for anonymous namespaces in header files."""
+
+    def testAnonymousNamespaceInHeader(self):
+        file_types = ['src/helpers.h', 'src/helpers.hpp', 'src/helpers.hxx']
+        for header_file in file_types:
+            input_api = MockInputApi()
+            input_api.files = [
+              MockAffectedFile(header_file,
+                            ['namespace {}'])]
+            error = PRESUBMIT.CheckForAnonymousNamespaceInHeader(
+            input_api, MockOutputApi())
+            self.assertEqual(1, len(error))
+
+    def testValidNamespaceInHeader(self):
+        file_types = ['src/helpers.h', 'src/helpers.hpp', 'src/helpers.hxx']
+        for header_file in file_types:
+            input_api = MockInputApi()
+            input_api.files = [
+              MockAffectedFile(header_file,
+                            ['namespace test {}'])]
+            error = PRESUBMIT.CheckForAnonymousNamespaceInHeader(
+            input_api, MockOutputApi())
+            self.assertEqual(0, len(error))
 
 if __name__ == '__main__':
     unittest.main()