Add make-gtest-filter.py

Helper script to construct a gtest_filter.

Change-Id: I370a36c96d9f6f4e3beb450dd1ca26a65154e56f
Reviewed-on: https://chromium-review.googlesource.com/c/1265025
Commit-Queue: Dan H <harringtond@google.com>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Reviewed-by: Carlos Knippschild <carlosk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#601273}

tools/make-gtest-filter.py

+#!/usr/bin/env python
+# Copyright (c) 2018 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.
+"""Reads lines from files or stdin and identifies C++ tests.
+
+Outputs a filter that can be used with --gtest_filter to run only the tests
+identified.
+
+Usage:
+
+Outputs filter for all test fixtures in a directory. --class-only avoids an
+overly long filter string.
+> cat components/mycomp/**test.cc | make-gtest-filter.py --class-only
+
+Outputs filter for all tests in a file.
+> make-gtest-filter.py ./myfile_unittest.cc
+
+Outputs filter for only test at line 123
+> make-gtest-filter.py --line=123 ./myfile_unittest.cc
+"""
+
+import argparse
+import fileinput
+import re
+import sys
+
+parser = argparse.ArgumentParser()
+parser.add_argument('--line', type=int)
+parser.add_argument('--class-only', action='store_true')
+args, left = parser.parse_known_args()
+file_input = fileinput.input(left)
+
+if args.line:
+  # If --line is used, restrict text to a few lines around the requested
+  # line.
+  requested_line = args.line
+  selected_lines = []
+  for line in file_input:
+    if (fileinput.lineno() >= requested_line and
+        fileinput.lineno() <= requested_line + 1):
+      selected_lines.append(line)
+  txt = ''.join(selected_lines)
+else:
+  txt = ''.join(list(file_input))
+
+# This regex is not exhaustive, and should be updated as needed.
+rx = re.compile(
+    r'^(?:TYPED_)?(?:IN_PROC_BROWSER_)?TEST(_F|_P)?\(\s*(\w+)\s*,\s*(\w+)\s*\)',
+    flags=re.DOTALL | re.M)
+tests = []
+for m in rx.finditer(txt):
+  tests.append(m.group(2) + '.' + m.group(3))
+
+# Note: Test names have the following structures:
+#  * FixtureName.TestName
+#  * InstantiationName/FixtureName.TestName/##
+# Since this script doesn't parse instantiations, we generate filters to match
+# either regular tests or instantiated tests.
+if args.class_only:
+  fixtures = set([t.split('.')[0] for t in tests])
+  test_filters = [c + '.*' for c in fixtures]
+  instantiation_filters = ['*/' + c + '.*/*' for c in fixtures]
+  print ':'.join(test_filters + instantiation_filters)
+else:
+  instantiations = ['*/' + c + '/*' for c in tests]
+  print ':'.join(tests + instantiations)