Update third_party license checking (flutter#3844)

In preparation for enabling license checks in flutter/packages, update
the allowed licenses:
- Allow our license, for cases where we've locally added files
- Allow the license used by the bsdiff package

Author: stuartmorgan-g

script/tool/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.1.1
+
+- Update the allowed third-party licenses for flutter/packages.
+
 ## 0.1.0+1
 
 - Re-add the bin/ directory.

script/tool/lib/src/license_check_command.dart

@@ -52,10 +52,14 @@ const Set<String> _ignoredFullBasenameList = <String>{
 final List<RegExp> _thirdPartyLicenseBlockRegexes = <RegExp>[
 // Third-party code used in url_launcher_web.
   RegExp(
-      r'^// Copyright 2017 Workiva Inc..*'
-      '^// Licensed under the Apache License, Version 2.0',
+      r'^// Copyright 2017 Workiva Inc\..*'
+      r'^// Licensed under the Apache License, Version 2\.0',
       multiLine: true,
       dotAll: true),
+  // bsdiff in flutter/packages.
+  RegExp(r'// Copyright 2003-2005 Colin Percival\. All rights reserved\.\n'
+      r'// Use of this source code is governed by a BSD-style license that can be\n'
+      r'// found in the LICENSE file\.\n'),
 ];
 
 // The exact format of the BSD license that our license files should contain.
@@ -158,16 +162,19 @@ class LicenseCheckCommand extends PluginCommand {
       _print('Checking ${file.path}');
       final String content = await file.readAsString();
 
+      final String firstParyLicense =
+          firstPartyLicenseBlockByExtension[p.extension(file.path)] ??
+              defaultFirstParyLicenseBlock;
       if (_isThirdParty(file)) {
+        // Third-party directories allow either known third-party licenses, our
+        // the first-party license, as there may be local additions.
         if (!_thirdPartyLicenseBlockRegexes
-            .any((RegExp regex) => regex.hasMatch(content))) {
+                .any((RegExp regex) => regex.hasMatch(content)) &&
+            !content.contains(firstParyLicense)) {
           unrecognizedThirdPartyFiles.add(file);
         }
       } else {
-        final String license =
-            firstPartyLicenseBlockByExtension[p.extension(file.path)] ??
-                defaultFirstParyLicenseBlock;
-        if (!content.contains(license)) {
+        if (!content.contains(firstParyLicense)) {
           incorrectFirstPartyFiles.add(file);
         }
       }

script/tool/pubspec.yaml

@@ -1,7 +1,7 @@
 name: flutter_plugin_tools
 description: Productivity utils for flutter/plugins and flutter/packages
 repository: https://github.com/flutter/plugins/tree/master/script/tool
-version: 0.1.0+1
+version: 0.1.1
 
 dependencies:
   args: "^1.4.3"

script/tool/test/license_check_command_test.dart

@@ -269,6 +269,24 @@ void main() {
       expect(printedMessages, contains('All source files passed validation!'));
     });
 
+    test('allows first-party code in a third_party directory', () async {
+      final File firstPartyFileInThirdParty = root
+          .childDirectory('a_plugin')
+          .childDirectory('lib')
+          .childDirectory('src')
+          .childDirectory('third_party')
+          .childFile('first_party.cc');
+      firstPartyFileInThirdParty.createSync(recursive: true);
+      _writeLicense(firstPartyFileInThirdParty);
+
+      await runner.run(<String>['license-check']);
+
+      // Sanity check that the test did actually check the file.
+      expect(printedMessages,
+          contains('Checking a_plugin/lib/src/third_party/first_party.cc'));
+      expect(printedMessages, contains('All source files passed validation!'));
+    });
+
     test('fails for licenses that the tool does not expect', () async {
       final File good = root.childFile('good.cc');
       good.createSync();