Add Brave license header checker.

PRESUBMIT.py

@@ -1,7 +1,7 @@
 # Copyright (c) 2022 The Brave Authors. All rights reserved.
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this file,
-# You can obtain one at http://mozilla.org/MPL/2.0/. */
+# You can obtain one at https://mozilla.org/MPL/2.0/.
 
 import os
 import sys
@@ -9,6 +9,8 @@ import sys
 USE_PYTHON3 = True
 PRESUBMIT_VERSION = '2.0.0'
 
+# pylint: disable=line-too-long
+
 
 def CheckChangeLintsClean(input_api, output_api):
     return input_api.canned_checks.CheckChangeLintsClean(input_api,
@@ -26,3 +28,85 @@ def CheckPylint(input_api, output_api):
                                         '.pylintrc'),
         extra_paths_list=extra_paths_list,
         version='2.7')
+
+
+def CheckLicense(input_api, output_api):
+    """Verifies the Brave license header."""
+
+    files_to_check = input_api.DEFAULT_FILES_TO_CHECK + (r'.+\.gni?$', )
+    files_to_skip = input_api.DEFAULT_FILES_TO_SKIP + (
+        r"\.storybook/",
+        r"ios/browser/api/ledger/legacy_database/core_data_models/",
+        r'win_build_output/',
+    )
+
+    current_year = int(input_api.time.strftime('%Y'))
+    allowed_years = (str(s) for s in reversed(range(2015, current_year + 1)))
+    years_re = '(' + '|'.join(allowed_years) + ')'
+
+    # License regexp to match in NEW and MOVED files, it doesn't allow variance.
+    # Note: presubmit machinery cannot distinguish between NEW and MOVED files,
+    # that's why we cannot force this regexp to have a precise year, also
+    # uplifts may fail during year change period, so the year check is relaxed.
+    new_file_license_re = input_api.re.compile((
+        r'.*? Copyright \(c\) %(year)s The Brave Authors\. All rights reserved\.\n'
+        r'.*? This Source Code Form is subject to the terms of the Mozilla Public\n'
+        r'.*? License, v\. 2\.0\. If a copy of the MPL was not distributed with this file,\n'
+        r'.*? You can obtain one at https://mozilla.org/MPL/2\.0/\.(?: \*/)?\n'
+    ) % {'year': years_re}, input_api.re.MULTILINE)
+
+    # License regexp to match in EXISTING files, it allows some variance.
+    existing_file_license_re = input_api.re.compile((
+        r'.*? Copyright \(c\) %(year)s The Brave Authors\. All rights reserved\.\n'
+        r'.*? This Source Code Form is subject to the terms of the Mozilla Public\n'
+        r'.*? License, v\. 2\.0\. If a copy of the MPL was not distributed with this(\n.*?)? file,\n?'
+        r'.*? (y|Y)ou can obtain one at https?://mozilla.org/MPL/2\.0/\.(?: \*/)?\n'
+    ) % {'year': years_re}, input_api.re.MULTILINE)
+
+    # License template for new files. Includes current year.
+    expected_license_template = (
+        '%(comment)s Copyright (c) %(year)s The Brave Authors. All rights reserved.\n'
+        '%(comment)s This Source Code Form is subject to the terms of the Mozilla Public\n'
+        '%(comment)s License, v. 2.0. If a copy of the MPL was not distributed with this file,\n'
+        '%(comment)s You can obtain one at https://mozilla.org/MPL/2.0/.\n'
+    ) % {
+        'comment': '#',
+        'year': current_year,
+    }
+
+    assert new_file_license_re.search(expected_license_template)
+    assert existing_file_license_re.search(expected_license_template)
+
+    bad_new_files = []
+    bad_files = []
+    sources = lambda affected_file: input_api.FilterSourceFile(
+        affected_file,
+        files_to_check=files_to_check,
+        files_to_skip=files_to_skip)
+    for f in input_api.AffectedSourceFiles(sources):
+        contents = input_api.ReadFile(f, 'r')[:1000].replace('\r\n', '\n')
+        if not contents:
+            continue
+        if f.Action() == 'A':  # 'A' means "Added", also includes moved files.
+            if not new_file_license_re.search(contents):
+                bad_new_files.append(f.LocalPath())
+        else:
+            if not existing_file_license_re.search(contents):
+                bad_files.append(f.LocalPath())
+
+    # Show this to simplify copy-paste when an invalid license is found.
+    expected_license_message = (
+        f'Expected one of license headers:\n'
+        f'{expected_license_template.replace("#", "//")}\n'
+        f'{expected_license_template}')
+
+    result = []
+    if bad_new_files:
+        result.append(
+            output_api.PresubmitError(expected_license_message,
+                                      items=bad_new_files))
+    if bad_files:
+        result.append(
+            output_api.PresubmitPromptWarning(expected_license_message,
+                                              items=bad_files))
+    return result