1 # Copyright 2014 The Chromium Authors. All rights reserved. 2 # Use of this source code is governed by a BSD-style license that can be 3 # found in the LICENSE file. 4 5 """Converts a given gypi file to a python scope and writes the result to stdout. 6 7 USING THIS SCRIPT IN CHROMIUM 8 9 Forking Python to run this script in the middle of GN is slow, especially on 10 Windows, and it makes both the GYP and GN files harder to follow. You can't 11 use "git grep" to find files in the GN build any more, and tracking everything 12 in GYP down requires a level of indirection. Any calls will have to be removed 13 and cleaned up once the GYP-to-GN transition is complete. 14 15 As a result, we only use this script when the list of files is large and 16 frequently-changing. In these cases, having one canonical list outweights the 17 downsides. 18 19 As of this writing, the GN build is basically complete. It's likely that all 20 large and frequently changing targets where this is appropriate use this 21 mechanism already. And since we hope to turn down the GYP build soon, the time 22 horizon is also relatively short. As a result, it is likely that no additional 23 uses of this script should every be added to the build. During this later part 24 of the transition period, we should be focusing more and more on the absolute 25 readability of the GN build. 26 27 28 HOW TO USE 29 30 It is assumed that the file contains a toplevel dictionary, and this script 31 will return that dictionary as a GN "scope" (see example below). This script 32 does not know anything about GYP and it will not expand variables or execute 33 conditions. 34 35 It will strip conditions blocks. 36 37 A variables block at the top level will be flattened so that the variables 38 appear in the root dictionary. This way they can be returned to the GN code. 39 40 Say your_file.gypi looked like this: 41 { 42 'sources': [ 'a.cc', 'b.cc' ], 43 'defines': [ 'ENABLE_DOOM_MELON' ], 44 } 45 46 You would call it like this: 47 gypi_values = exec_script("//build/gypi_to_gn.py", 48 [ rebase_path("your_file.gypi") ], 49 "scope", 50 [ "your_file.gypi" ]) 51 52 Notes: 53 - The rebase_path call converts the gypi file from being relative to the 54 current build file to being system absolute for calling the script, which 55 will have a different current directory than this file. 56 57 - The "scope" parameter tells GN to interpret the result as a series of GN 58 variable assignments. 59 60 - The last file argument to exec_script tells GN that the given file is a 61 dependency of the build so Ninja can automatically re-run GN if the file 62 changes. 63 64 Read the values into a target like this: 65 component("mycomponent") { 66 sources = gypi_values.sources 67 defines = gypi_values.defines 68 } 69 70 Sometimes your .gypi file will include paths relative to a different 71 directory than the current .gn file. In this case, you can rebase them to 72 be relative to the current directory. 73 sources = rebase_path(gypi_values.sources, ".", 74 "//path/gypi/input/values/are/relative/to") 75 76 This script will tolerate a 'variables' in the toplevel dictionary or not. If 77 the toplevel dictionary just contains one item called 'variables', it will be 78 collapsed away and the result will be the contents of that dictinoary. Some 79 .gypi files are written with or without this, depending on how they expect to 80 be embedded into a .gyp file. 81 82 This script also has the ability to replace certain substrings in the input. 83 Generally this is used to emulate GYP variable expansion. If you passed the 84 argument "--replace=<(foo)=bar" then all instances of "<(foo)" in strings in 85 the input will be replaced with "bar": 86 87 gypi_values = exec_script("//build/gypi_to_gn.py", 88 [ rebase_path("your_file.gypi"), 89 "--replace=<(foo)=bar"], 90 "scope", 91 [ "your_file.gypi" ]) 92 93 """ 94 95 import gn_helpers 96 from optparse import OptionParser 97 import sys 98 99 def LoadPythonDictionary(path): 100 file_string = open(path).read() 101 try: 102 file_data = eval(file_string, {'__builtins__': None}, None) 103 except SyntaxError, e: 104 e.filename = path 105 raise 106 except Exception, e: 107 raise Exception("Unexpected error while reading %s: %s" % (path, str(e))) 108 109 assert isinstance(file_data, dict), "%s does not eval to a dictionary" % path 110 111 # Flatten any variables to the top level. 112 if 'variables' in file_data: 113 file_data.update(file_data['variables']) 114 del file_data['variables'] 115 116 # Strip all elements that this script can't process. 117 elements_to_strip = [ 118 'conditions', 119 'target_conditions', 120 'targets', 121 'includes', 122 'actions', 123 ] 124 for element in elements_to_strip: 125 if element in file_data: 126 del file_data[element] 127 128 return file_data 129 130 131 def ReplaceSubstrings(values, search_for, replace_with): 132 """Recursively replaces substrings in a value. 133 134 Replaces all substrings of the "search_for" with "repace_with" for all 135 strings occurring in "values". This is done by recursively iterating into 136 lists as well as the keys and values of dictionaries.""" 137 if isinstance(values, str): 138 return values.replace(search_for, replace_with) 139 140 if isinstance(values, list): 141 return [ReplaceSubstrings(v, search_for, replace_with) for v in values] 142 143 if isinstance(values, dict): 144 # For dictionaries, do the search for both the key and values. 145 result = {} 146 for key, value in values.items(): 147 new_key = ReplaceSubstrings(key, search_for, replace_with) 148 new_value = ReplaceSubstrings(value, search_for, replace_with) 149 result[new_key] = new_value 150 return result 151 152 # Assume everything else is unchanged. 153 return values 154 155 def main(): 156 parser = OptionParser() 157 parser.add_option("-r", "--replace", action="append", 158 help="Replaces substrings. If passed a=b, replaces all substrs a with b.") 159 (options, args) = parser.parse_args() 160 161 if len(args) != 1: 162 raise Exception("Need one argument which is the .gypi file to read.") 163 164 data = LoadPythonDictionary(args[0]) 165 if options.replace: 166 # Do replacements for all specified patterns. 167 for replace in options.replace: 168 split = replace.split('=') 169 # Allow "foo=" to replace with nothing. 170 if len(split) == 1: 171 split.append('') 172 assert len(split) == 2, "Replacement must be of the form 'key=value'." 173 data = ReplaceSubstrings(data, split[0], split[1]) 174 175 # Sometimes .gypi files use the GYP syntax with percents at the end of the 176 # variable name (to indicate not to overwrite a previously-defined value): 177 # 'foo%': 'bar', 178 # Convert these to regular variables. 179 for key in data: 180 if len(key) > 1 and key[len(key) - 1] == '%': 181 data[key[:-1]] = data[key] 182 del data[key] 183 184 print gn_helpers.ToGNString(data) 185 186 if __name__ == '__main__': 187 try: 188 main() 189 except Exception, e: 190 print str(e) 191 sys.exit(1) 192
