Add a script that can discover *.isolated files in a directory.

build/find_isolated_tests.py

Index: build/find_isolated_tests.py
diff --git a/build/find_isolated_tests.py b/build/find_isolated_tests.py
new file mode 100755
index 0000000000000000000000000000000000000000..c5b3ab77a90454ceade7215d17515b8c20757e02
--- /dev/null
+++ b/build/find_isolated_tests.py
@@ -0,0 +1,78 @@
+#!/usr/bin/env python
+# Copyright 2014 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.
+
+"""Scans build output directory for .isolated files, calculates their SHA1
+hashes, stores final list in JSON document and then removes *.isolated files
+found (to ensure no stale *.isolated stay around on the next build).
+
+Used to figure out what tests were build in isolated mode to trigger these
+tests to run on swarming.
+
+For more info see:
+https://sites.google.com/a/chromium.org/dev/developers/testing/isolated-testing
+"""
+
+import glob
+import hashlib
+import json
+import optparse
+import os
+import re
+import sys
+
+
+def hash_file(filepath):
+  """Calculates the hash of a file without reading it all in memory at once."""
+  digest = hashlib.sha1()
+  with open(filepath, 'rb') as f:
+    while True:
+      chunk = f.read(1024*1024)
+      if not chunk:
+        break
+      digest.update(chunk)
+  return digest.hexdigest()
+
+
+def main():
+  parser = optparse.OptionParser(
+      usage='%prog --build-dir <path> --output-json <path>',
+      description=sys.modules[__name__].__doc__)
+  parser.add_option(
+      '--build-dir',
+      help='Path to a directory to search for *.isolated files.')
+  parser.add_option(
+      '--output-json',
+      help='File to dump JSON results into.')
+
+  options, _ = parser.parse_args()
+  if not options.build_dir:
+    parser.error('--build-dir option is required')
+  if not options.output_json:
+    parser.error('--output-json option is required')
+
+  result = {}
+
+  # Get the file hash values and output the pair.
+  pattern = os.path.join(options.build_dir, '*.isolated')
+  for filepath in sorted(glob.glob(pattern)):
+    test_name = os.path.splitext(os.path.basename(filepath))[0]
+    if re.match(r'^.+?\.\d$', test_name):
+      # It's a split .isolated file, e.g. foo.0.isolated. Ignore these.
+      continue
+
+    # TODO(csharp): Remove deletion once the isolate tracked dependencies are
+    # inputs for the isolated files.
+    sha1_hash = hash_file(filepath)
+    os.remove(filepath)
+    result[test_name] = sha1_hash
+
+  with open(options.output_json, 'wb') as f:
+    json.dump(result, f)
+
+  return 0
+
+
+if __name__ == '__main__':
+  sys.exit(main())