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193 lines
6.7 KiB
193 lines
6.7 KiB
# Copyright 2014 The Chromium Authors. All rights reserved.
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# Use of this source code is governed by a BSD-style license that can be
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# found in the LICENSE file.
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"""Converts a given gypi file to a python scope and writes the result to stdout.
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USING THIS SCRIPT IN CHROMIUM
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Forking Python to run this script in the middle of GN is slow, especially on
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Windows, and it makes both the GYP and GN files harder to follow. You can't
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use "git grep" to find files in the GN build any more, and tracking everything
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in GYP down requires a level of indirection. Any calls will have to be removed
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and cleaned up once the GYP-to-GN transition is complete.
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As a result, we only use this script when the list of files is large and
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frequently-changing. In these cases, having one canonical list outweights the
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downsides.
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As of this writing, the GN build is basically complete. It's likely that all
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large and frequently changing targets where this is appropriate use this
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mechanism already. And since we hope to turn down the GYP build soon, the time
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horizon is also relatively short. As a result, it is likely that no additional
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uses of this script should every be added to the build. During this later part
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of the transition period, we should be focusing more and more on the absolute
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readability of the GN build.
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HOW TO USE
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It is assumed that the file contains a toplevel dictionary, and this script
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will return that dictionary as a GN "scope" (see example below). This script
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does not know anything about GYP and it will not expand variables or execute
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conditions.
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It will strip conditions blocks.
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A variables block at the top level will be flattened so that the variables
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appear in the root dictionary. This way they can be returned to the GN code.
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Say your_file.gypi looked like this:
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{
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'sources': [ 'a.cc', 'b.cc' ],
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'defines': [ 'ENABLE_DOOM_MELON' ],
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}
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You would call it like this:
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gypi_values = exec_script("//build/gypi_to_gn.py",
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[ rebase_path("your_file.gypi") ],
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"scope",
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[ "your_file.gypi" ])
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Notes:
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- The rebase_path call converts the gypi file from being relative to the
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current build file to being system absolute for calling the script, which
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will have a different current directory than this file.
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- The "scope" parameter tells GN to interpret the result as a series of GN
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variable assignments.
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- The last file argument to exec_script tells GN that the given file is a
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dependency of the build so Ninja can automatically re-run GN if the file
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changes.
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Read the values into a target like this:
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component("mycomponent") {
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sources = gypi_values.sources
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defines = gypi_values.defines
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}
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Sometimes your .gypi file will include paths relative to a different
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directory than the current .gn file. In this case, you can rebase them to
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be relative to the current directory.
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sources = rebase_path(gypi_values.sources, ".",
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"//path/gypi/input/values/are/relative/to")
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This script will tolerate a 'variables' in the toplevel dictionary or not. If
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the toplevel dictionary just contains one item called 'variables', it will be
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collapsed away and the result will be the contents of that dictinoary. Some
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.gypi files are written with or without this, depending on how they expect to
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be embedded into a .gyp file.
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This script also has the ability to replace certain substrings in the input.
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Generally this is used to emulate GYP variable expansion. If you passed the
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argument "--replace=<(foo)=bar" then all instances of "<(foo)" in strings in
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the input will be replaced with "bar":
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gypi_values = exec_script("//build/gypi_to_gn.py",
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[ rebase_path("your_file.gypi"),
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"--replace=<(foo)=bar"],
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"scope",
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[ "your_file.gypi" ])
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"""
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import gn_helpers
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from optparse import OptionParser
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import sys
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def LoadPythonDictionary(path):
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file_string = open(path).read()
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try:
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file_data = eval(file_string, {'__builtins__': None}, None)
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except SyntaxError, e:
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e.filename = path
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raise
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except Exception, e:
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raise Exception("Unexpected error while reading %s: %s" % (path, str(e)))
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assert isinstance(file_data, dict), "%s does not eval to a dictionary" % path
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# Flatten any variables to the top level.
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if 'variables' in file_data:
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file_data.update(file_data['variables'])
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del file_data['variables']
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# Strip all elements that this script can't process.
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elements_to_strip = [
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'conditions',
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'target_conditions',
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'target_defaults',
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'targets',
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'includes',
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'actions',
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]
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for element in elements_to_strip:
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if element in file_data:
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del file_data[element]
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return file_data
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def ReplaceSubstrings(values, search_for, replace_with):
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"""Recursively replaces substrings in a value.
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Replaces all substrings of the "search_for" with "repace_with" for all
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strings occurring in "values". This is done by recursively iterating into
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lists as well as the keys and values of dictionaries."""
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if isinstance(values, str):
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return values.replace(search_for, replace_with)
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if isinstance(values, list):
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return [ReplaceSubstrings(v, search_for, replace_with) for v in values]
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if isinstance(values, dict):
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# For dictionaries, do the search for both the key and values.
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result = {}
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for key, value in values.items():
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new_key = ReplaceSubstrings(key, search_for, replace_with)
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new_value = ReplaceSubstrings(value, search_for, replace_with)
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result[new_key] = new_value
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return result
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# Assume everything else is unchanged.
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return values
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def main():
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parser = OptionParser()
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parser.add_option("-r", "--replace", action="append",
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help="Replaces substrings. If passed a=b, replaces all substrs a with b.")
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(options, args) = parser.parse_args()
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if len(args) != 1:
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raise Exception("Need one argument which is the .gypi file to read.")
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data = LoadPythonDictionary(args[0])
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if options.replace:
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# Do replacements for all specified patterns.
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for replace in options.replace:
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split = replace.split('=')
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# Allow "foo=" to replace with nothing.
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if len(split) == 1:
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split.append('')
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assert len(split) == 2, "Replacement must be of the form 'key=value'."
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data = ReplaceSubstrings(data, split[0], split[1])
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# Sometimes .gypi files use the GYP syntax with percents at the end of the
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# variable name (to indicate not to overwrite a previously-defined value):
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# 'foo%': 'bar',
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# Convert these to regular variables.
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for key in data:
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if len(key) > 1 and key[len(key) - 1] == '%':
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data[key[:-1]] = data[key]
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del data[key]
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print gn_helpers.ToGNString(data)
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if __name__ == '__main__':
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try:
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main()
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except Exception, e:
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print str(e)
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sys.exit(1)
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