[Cronet] Enforce implementation does not call through API classes

components/cronet/tools/api_static_checks_unittest.py

Index: components/cronet/tools/api_static_checks_unittest.py
diff --git a/components/cronet/tools/api_static_checks_unittest.py b/components/cronet/tools/api_static_checks_unittest.py
new file mode 100755
index 0000000000000000000000000000000000000000..a6907e6dabbb43f1c7d46235a7853e5a3c6a4f95
--- /dev/null
+++ b/components/cronet/tools/api_static_checks_unittest.py
@@ -0,0 +1,95 @@
+#!/usr/bin/python
+# Copyright 2016 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""api_static_checks_unittest.py - Unittests for api_static_checks.py"""
+
+
+import contextlib
+from cStringIO import StringIO
+import os
+import shutil
+import sys
+import tempfile
+import unittest
+
+from tools import api_static_checks
+
+
+ERROR_PREFIX = (
+"""ERROR: Found the following calls from implementation classes through
+       API classes.  These could fail if older API is used that
+       does not contain newer methods.  Please call through a
+       wrapper class from VersionSafeCallbacks.
+""")
+
+
+@contextlib.contextmanager
+def capture_output():
+  # A contextmanger that collects the stdout and stderr of wrapped code
+
+  oldout,olderr = sys.stdout, sys.stderr
+  try:
+    out=[StringIO(), StringIO()]
+    sys.stdout,sys.stderr = out
+    yield out
+  finally:
+    sys.stdout,sys.stderr = oldout, olderr
+    out[0] = out[0].getvalue()
+    out[1] = out[1].getvalue()
+
+
+class ApiStaticCheckUnitTest(unittest.TestCase):
+  def setUp(self):
+    self.temp_dir = tempfile.mkdtemp()
+    os.chdir(self.temp_dir)
+
+
+  def tearDown(self):
+    shutil.rmtree(self.temp_dir)
+
+
+  def make_jar(self, java, class_name):
+    # Compile |java| wrapped in a class named |class_name| to a jar file and
+    # return jar filename.
+
+    java_filename = class_name + '.java'
+    class_filename = class_name + '.class'
+    jar_filename = class_name + '.jar'
+
+    with open(java_filename, 'w') as java_file:
+      java_file.write('public class %s {' % class_name)
+      java_file.write(java)
+      java_file.write('}')
+    os.system('javac %s' % java_filename)
+    os.system('jar cf %s %s' % (jar_filename, class_filename))
+    return jar_filename
+
+
+  def run_test(self, api_java, impl_java):
+    api_jar = self.make_jar(api_java, 'Api')
+    impl_jar = self.make_jar(impl_java, 'Impl')
+    with capture_output() as return_output:
+      return_code = api_static_checks.main(
+          ['--api_jar', api_jar, '--impl_jar', impl_jar])
+    return [return_code, return_output[0]]
+
+
+  def test_success(self):
+    # Test simple classes with functions
+    self.assertEqual(self.run_test('void a(){}', 'void b(){}'), [True, ''])
+    # Test simple classes with functions calling themselves
+    self.assertEqual(self.run_test(
+        'void a(){} void b(){a();}', 'void c(){} void d(){c();}'), [True, ''])
+
+
+  def test_failure(self):
+    # Test static call
+    self.assertEqual(self.run_test(
+        'public static void a(){}', 'void b(){Api.a();}'),
+        [False, ERROR_PREFIX + 'Impl/b -> Api/a:()V\n'])
+    # Test virtual call
+    self.assertEqual(self.run_test(
+        'public void a(){}', 'void b(){new Api().a();}'),
+        [False, ERROR_PREFIX + 'Impl/b -> Api/a:()V\n'])