Bug 1562645 - Extend mozlint to have license check r=ahal

The goal is to have something simple and not relying on other tools.
I tried with licensecheck and licensee but, with if we use a different
wording to declare "public domain" (as example), they might not
catch it. Requiring to contribute upstream, etc

Instead, I just create a list of line of license to catch it.
From my trials, it works well enough and it is trivial python.

Differential Revision: https://phabricator.services.mozilla.com/D37082

--HG--
extra : moz-landing-system : lando

tools/lint/license.yml

@@ -0,0 +1,28 @@
+---
+license:
+    description: License Check
+    include:
+        - .
+    exclude:
+        - config/external/nspr/_pl_bld.h
+        - config/external/nspr/_pr_bld.h
+        - gfx/2d/MMIHelpers.h
+        - gfx/2d/ShadersD2D1.h
+        - gfx/layers/protobuf/LayerScopePacket.pb.cc
+        - gfx/layers/protobuf/LayerScopePacket.pb.h
+        - gfx/thebes/CJKCompatSVS.cpp
+        - js/src/builtin/intl/TimeZoneDataGenerated.h
+        - js/src/irregexp/RegExpCharacters-inl.h
+        - js/src/irregexp/RegExpCharacters.cpp
+        - media/libdav1d/vcs_version.h
+        - mozglue/android/NativeCrypto.h
+        - toolkit/components/reputationservice/chromium/chrome/common/safe_browsing/csd.pb.cc
+        - toolkit/components/reputationservice/chromium/chrome/common/safe_browsing/csd.pb.h
+        - toolkit/mozapps/update/updater/crctable.h
+        - xpcom/io/crc32c.h
+    extensions: ['.cpp', '.c', '.cc', '.h', '.m', '.mm']
+    # , 'js', 'jsm', 'jsx', 'xml', 'xul', 'html', 'xhtml', 'py', 'rs']
+    support-files:
+        - 'tools/lint/license/**'
+    type: external
+    payload: license:lint

tools/lint/license/__init__.py

@@ -0,0 +1,54 @@
+# 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/.
+
+from __future__ import absolute_import, print_function
+
+import os
+
+from mozlint import result
+from mozlint.pathutils import expand_exclusions
+
+here = os.path.abspath(os.path.dirname(__file__))
+
+results = []
+
+
+def load_valid_license():
+    """
+    Load the list of license patterns
+    """
+    license_list = os.path.join(here, 'valid-licenses.txt')
+    with open(license_list) as f:
+        return f.readlines()
+
+
+def is_valid_license(licenses, filename):
+    """
+    From a given file, check if we can find the license patterns
+    in the X first lines of the file
+    """
+    nb_lines = 10
+    with open(filename) as myfile:
+        head = myfile.readlines(nb_lines)
+        for l in licenses:
+            if l.lower().strip() in ''.join(head).lower():
+                return True
+    return False
+
+
+def lint(paths, config, fix=None, **lintargs):
+    files = list(expand_exclusions(paths, config, lintargs['root']))
+
+    licenses = load_valid_license()
+    for f in files:
+        if "/test" in f or "/gtest" in f:
+            # We don't require license for test
+            continue
+        if not is_valid_license(licenses, f):
+            res = {'path': f,
+                   'message': "No matching license strings found in tools/lint/license/valid-licenses.txt",  # noqa
+                   'level': 'error'
+                   }
+            results.append(result.from_config(config, **res))
+    return results

tools/lint/license/valid-licenses.txt

@@ -0,0 +1,18 @@
+mozilla.org/MPL/
+Licensed under the Apache License, Version 2.0
+copyright is dedicated to the Public Domain.
+Licensed under the MIT License
+Redistributions of source code must retain the above copyright
+Use of this source code is governed by a BSD-style license
+The author hereby disclaims copyright to this source code
+Use, Modification and Redistribution (including distribution of any
+author grants irrevocable permission to anyone to use, modify,
+THIS FILE IS AUTO-GENERATED
+Permission is hereby granted, free of charge, to any person obtaining
+Permission to use, copy, modify, distribute, and sell this software
+Permission to use, copy, modify, distribute and sell this software
+This file is dual licensed under the MIT
+License: Public domain. You are free to use this code however you
+You are granted a license to use, reproduce and create derivative works
+GENERATED FILE, DO NOT EDIT
+This code is governed by the BSD license