#!/usr/bin/env python
# Copyright 2019 The Chromium Authors
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
"""Generates the list of expired flags as a C++ source file.
This program generates a data structure representing the set of flags that
expired before or as of the current Chromium milestone. Specifically, it reads
the flag metadata JSON file and emits a structure mapping flag internal names to
expiration milestones. This data structure is then linked into the built
Chromium, to be used to decide whether to show or hide a given flag in the flags
UI.
This program can be run with no arguments to run its own unit tests.
"""
from __future__ import print_function
import flags_utils
import os
import sys
ROOT_PATH = os.path.join(os.path.dirname(__file__), '..', '..')
def get_chromium_version():
"""Parses the Chromium version out of //chrome/VERSION."""
with open(os.path.join(ROOT_PATH, 'chrome', 'VERSION'),
encoding='utf-8') as f:
for line in f.readlines():
key, value = line.strip().split('=')
if key == 'MAJOR':
return int(value)
return None
def gen_file_header(prog_name, meta_name):
"""Returns the header for the generated expiry list file.
The generated header contains at least:
* A copyright message on the first line
* A reference to this program (prog_name)
* A reference to the input metadata file
>>> 'The Chromium Authors' in gen_file_header('foo', 'bar')
True
>>> '/progname' in gen_file_header('/progname', '/dataname')
True
>>> '/dataname' in gen_file_header('/progname', '/dataname')
True
"""
return """// Copyright 2019 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// This is a generated file. Do not edit it! It was generated by:
// {prog_name}
// and it was generated from:
// {meta_name}
#include "chrome/browser/expired_flags_list.h"
namespace flags {{
const ExpiredFlag kExpiredFlags[] = {{
""".format(prog_name=prog_name, meta_name=meta_name)
def gen_file_footer():
return """
{nullptr, 0},
};
} // namespace flags"""
def gen_file_body(flags, mstone):
"""Generates the body of the flag expiration list.
Flags appear in the list only if:
* Their expiration mstone is not -1
* Either the chrome version is unknown OR
* Their expiration mstone is <= the chrome version
>>> flags = [ { 'name': 'foo', 'expiry_milestone': 1 } ]
>>> flags.append({ 'name': 'bar', 'expiry_milestone': 2 })
>>> flags.append({ 'name': 'baz', 'expiry_milestone': -1 })
>>> gen_file_body(flags, 1)
' {"foo", 1},'
>>> gen_file_body(flags, 2)
' {"foo", 1},\\n {"bar", 2},'
>>> gen_file_body(flags, None)
' {"foo", 1},\\n {"bar", 2},'
"""
if mstone != None:
flags = flags_utils.keep_expired_by(flags, mstone)
output = []
for f in flags:
if f['expiry_milestone'] != -1:
name, expiry = f['name'], f['expiry_milestone']
output.append(' {"' + name + '", ' + str(expiry) + '},')
return '\n'.join(output)
def gen_expiry_file(program_name, metadata_name):
output = gen_file_header(program_name, metadata_name)
output += gen_file_body(flags_utils.load_metadata(), get_chromium_version())
output += gen_file_footer()
return output
def write_if_changed(filename, contents):
"""Write contents into the named file if the file's content is different.
This avoids updating the mtime if the file's contents haven't changed,
which helps reduce spurious rebuilds.
"""
try:
with open(filename, 'r', encoding='utf-8') as f:
current = f.read()
except FileNotFoundError:
# If the file doesn't exist yet, we'll always need to rewrite the file.
current = None
if not current or contents != current:
with open(filename, 'w', encoding='utf-8') as f:
f.write(contents)
def main():
import doctest
doctest.testmod()
if len(sys.argv) < 3:
print('{}: only ran tests'.format(sys.argv[0]))
return
output = gen_expiry_file(sys.argv[0], sys.argv[1])
write_if_changed(sys.argv[2], output)
if __name__ == '__main__':
main()
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