New build flag system, convert Google Now flag

build/write_build_header.py

Index: build/write_build_header.py
diff --git a/build/write_build_header.py b/build/write_build_header.py
new file mode 100644
index 0000000000000000000000000000000000000000..d650a688ac583900c9f1fc8a724225dd2d04ee6f
--- /dev/null
+++ b/build/write_build_header.py
@@ -0,0 +1,93 @@
+# Copyright 2015 The Chromium Authors. All rights reserved.

[Mark Mentovai, 2015/11/24 14:33:33]

#!/usr/bin/env python

# Copyright 2015 …

(or whatever flavor #! line we use for Python these days.)

[Mark Mentovai, 2015/11/24 14:33:33]

This ought to be executable.

[brettw, 2015/11/24 23:36:01]

Done.

+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# This writes headers for build flags. See build_header.gni for usage of
+# this system as a whole.
+#
+# The parameters are passed in a response file so we don't have to worry
+# about command line lengths. The name of the response file is passed on the
+# command line.
+#
+# The format of the response file is:
+#    [--flags <list of one or more flag values>]
+
+import optparse
+import os
+import shlex
+import sys
+
+
+class Options:
+  def __init__(self, output, rulename, header_guard, flags):
+    self.output = output
+    self.rulename = rulename
+    self.header_guard = header_guard
+    self.flags = flags
+
+
+def GetOptions():
+  parser = optparse.OptionParser()
+  parser.add_option('--output', help="Output header name inside --gen-dir.")
+  parser.add_option('--rulename',
+                    help="Helpful name of build rule for including in the " +
+                         "comment at the top of the file.")
+  parser.add_option('--gen-dir',
+                    help="Path to root of generated file directory tree.")
+  parser.add_option('--definitions',
+                    help="Name of the response file containing the flags.")
+  cmdline_options, cmdline_flags = parser.parse_args()
+
+  # Compute header guard by replacing some chars with _ and upper-casing.
+  header_guard = cmdline_options.output.upper()
+  header_guard = \
+      header_guard.replace('/', '_').replace('\\', '_').replace('.', '_')
+  header_guard += '_'
+
+  # The actual output file is inside the gen dir.
+  output = os.path.join(cmdline_options.gen_dir, cmdline_options.output)
+
+  # Definition file in GYP is newline separated, in GN they are shell formatted.
+  # shlex can parse both of these.
+  with open(cmdline_options.definitions, 'r') as def_file:
+    defs = shlex.split(def_file.read())
+  flags_index = defs.index('--flags')
+
+  # Everything after --flags are flags. Values are 0/1/true/false.

[Mark Mentovai, 2015/11/24 14:33:33]

Revise to say that false and true are mapped to 0 and 1, and everything else is
passed straight through.

[brettw, 2015/11/24 23:36:01]

Done.

+  flags = []
+  for flag in defs[flags_index + 1 :]:
+    equals_index = flag.index('=')
+    key = flag[:equals_index]
+    value = flag[equals_index + 1:]
+
+    # Canonicalize and validate the value.
+    if value == 'true':
+      value = '1'
+    elif value == 'false':
+      value = '0'
+    flags.append((key, str(value)))
+
+  return Options(output=output,
+                 rulename=cmdline_options.rulename,
+                 header_guard=header_guard,
+                 flags=flags)
+
+
+def WriteHeader(options):
+  with open(options.output, 'w') as output_file:
+    output_file.write("// Generated by build/write_build_header.py\n")
+    if options.rulename:
+      output_file.write('// From "' + options.rulename + '"\n')
+
+    output_file.write('\n#ifndef %s\n' % options.header_guard)
+    output_file.write('#define %s\n\n' % options.header_guard)
+    output_file.write('#include "build/build_header.h"\n\n')
+
+    for pair in options.flags:
+      output_file.write('#define BUILDFLAG_INTERNAL_%s() (%s)\n' % pair)
+
+    output_file.write('\n#endif  // %s\n' % options.header_guard)
+
+
+options = GetOptions()
+WriteHeader(options)