[gn] Consolidate exec_script calls to speed up generation

tools/gypi_to_gn.py

 #!/usr/bin/env python
 # Copyright 2014 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.
 
-"""Converts a given gypi file to a python scope and writes the result to stdout.
+"""Converts given gypi files to a python scope and writes the result to stdout.
 
-It is assumed that the file contains a toplevel dictionary, and this script
+It is assumed that the files contain a toplevel dictionary, and this script
 will return that dictionary as a GN "scope" (see example below). This script
 does not know anything about GYP and it will not expand variables or execute
 conditions.
 
 It will strip conditions blocks.
 
 A variables block at the top level will be flattened so that the variables
 appear in the root dictionary. This way they can be returned to the GN code.
 
 Say your_file.gypi looked like this:
   {
      'sources': [ 'a.cc', 'b.cc' ],
      'defines': [ 'ENABLE_DOOM_MELON' ],
   }
 
 You would call it like this:
+  gypi_files = [ "your_file.gypi", "your_other_file.gypi" ]
   gypi_values = exec_script("//build/gypi_to_gn.py",
-                            [ rebase_path("your_file.gypi") ],
+                            [ rebase_path(gypi_files) ],
                             "scope",
-                            [ "your_file.gypi" ])
+                            [ gypi_files ])
 
 Notes:
  - The rebase_path call converts the gypi file from being relative to the
    current build file to being system absolute for calling the script, which
    will have a different current directory than this file.
 
  - The "scope" parameter tells GN to interpret the result as a series of GN
    variable assignments.
 
  - The last file argument to exec_script tells GN that the given file is a
    dependency of the build so Ninja can automatically re-run GN if the file
    changes.
 
 Read the values into a target like this:
   component("mycomponent") {
-    sources = gypi_values.sources
-    defines = gypi_values.defines
+    sources = gypi_values.your_file_sources
+    defines = gypi_values.your_file_defines
   }
 
 Sometimes your .gypi file will include paths relative to a different
 directory than the current .gn file. In this case, you can rebase them to
 be relative to the current directory.
-  sources = rebase_path(gypi_values.sources, ".",
+  sources = rebase_path(gypi_values.your_files_sources, ".",
                         "//path/gypi/input/values/are/relative/to")
 
 This script will tolerate a 'variables' in the toplevel dictionary or not. If
 the toplevel dictionary just contains one item called 'variables', it will be
 collapsed away and the result will be the contents of that dictinoary. Some
 .gypi files are written with or without this, depending on how they expect to
 be embedded into a .gyp file.
 
 This script also has the ability to replace certain substrings in the input.
 Generally this is used to emulate GYP variable expansion. If you passed the
 argument "--replace=<(foo)=bar" then all instances of "<(foo)" in strings in
 the input will be replaced with "bar":
 
   gypi_values = exec_script("//build/gypi_to_gn.py",
                             [ rebase_path("your_file.gypi"),
                               "--replace=<(foo)=bar"],
                             "scope",
                             [ "your_file.gypi" ])
 
 """
 
 import gn_helpers
 from optparse import OptionParser
 import sys
+import os.path
 
 def LoadPythonDictionary(path):
   file_string = open(path).read()
   try:
     file_data = eval(file_string, {'__builtins__': None}, None)
   except SyntaxError, e:
     e.filename = path
     raise
   except Exception, e:
     raise Exception("Unexpected error while reading %s: %s" % (path, str(e)))
@@ skipping 12 matching lines @@
     del file_data['target_conditions']
 
   # Strip targets in the toplevel, since some files define these and we can't
   # slurp them in.
   if 'targets' in file_data:
     del file_data['targets']
 
   return file_data
 
 
-def ReplaceSubstrings(values, search_for, replace_with):
-  """Recursively replaces substrings in a value.
-
-  Replaces all substrings of the "search_for" with "repace_with" for all
-  strings occurring in "values". This is done by recursively iterating into
-  lists as well as the keys and values of dictionaries."""
-  if isinstance(values, str):
-    return values.replace(search_for, replace_with)
-
-  if isinstance(values, list):
-    return [ReplaceSubstrings(v, search_for, replace_with) for v in values]
-
-  if isinstance(values, dict):
-    # For dictionaries, do the search for both the key and values.
-    result = {}
-    for key, value in values.items():
-      new_key = ReplaceSubstrings(key, search_for, replace_with)
-      new_value = ReplaceSubstrings(value, search_for, replace_with)
-      result[new_key] = new_value
-    return result
-
-  # Assume everything else is unchanged.
-  return values
-
 def KeepOnly(values, filters):
   """Recursively filters out strings not ending in "f" from "values"""
 
   if isinstance(values, list):
     return [v for v in values if v.endswith(tuple(filters))]
 
   if isinstance(values, dict):
     result = {}
     for key, value in values.items():
       new_key = KeepOnly(key, filters)
       new_value = KeepOnly(value, filters)
       result[new_key] = new_value
     return result
 
   return values
 
 def main():
   parser = OptionParser()
-  parser.add_option("-r", "--replace", action="append",
-    help="Replaces substrings. If passed a=b, replaces all substrs a with b.")
   parser.add_option("-k", "--keep_only", default = [], action="append",
     help="Keeps only files ending with the listed strings.")
+  parser.add_option("--prefix", action="store_true",
+    help="Prefix variables with base name")
   (options, args) = parser.parse_args()
 
-  if len(args) != 1:
-    raise Exception("Need one argument which is the .gypi file to read.")
+  if len(args) < 1:
+    raise Exception("Need at least one .gypi file to read.")
 
-  data = LoadPythonDictionary(args[0])
-  if options.replace:
-    # Do replacements for all specified patterns.
-    for replace in options.replace:
-      split = replace.split('=')
-      # Allow "foo=" to replace with nothing.
-      if len(split) == 1:
-        split.append('')
-      assert len(split) == 2, "Replacement must be of the form 'key=value'."
-      data = ReplaceSubstrings(data, split[0], split[1])
+  data = {}
 
-  if options.keep_only != []:
-    data = KeepOnly(data, options.keep_only)
+  for gypi in args:
+    gypi_data = LoadPythonDictionary(gypi)
 
-  # Sometimes .gypi files use the GYP syntax with percents at the end of the
-  # variable name (to indicate not to overwrite a previously-defined value):
-  #   'foo%': 'bar',
-  # Convert these to regular variables.
-  for key in data:
-    if len(key) > 1 and key[len(key) - 1] == '%':
-      data[key[:-1]] = data[key]
-      del data[key]
+    if options.keep_only != []:
+      gypi_data = KeepOnly(gypi_data, options.keep_only)
+
+    # Sometimes .gypi files use the GYP syntax with percents at the end of the
+    # variable name (to indicate not to overwrite a previously-defined value):
+    #   'foo%': 'bar',
+    # Convert these to regular variables.
+    for key in gypi_data:
+      if len(key) > 1 and key[len(key) - 1] == '%':
+        gypi_data[key[:-1]] = gypi_data[key]
+        del gypi_data[key]
+    gypi_name = os.path.basename(gypi)[:-len(".gypi")]
+    for key in gypi_data:
+      if options.prefix:
+        # Prefix all variables from this gypi file with the name to disambiguate
+        data[gypi_name + "_" + key] = gypi_data[key]
+      elif key in data:
+        for entry in gypi_data[key]:
+            data[key].append(entry)
+      else:
+        data[key] = gypi_data[key]
 
   print gn_helpers.ToGNString(data)
 
 if __name__ == '__main__':
   try:
     main()
   except Exception, e:
     print str(e)
     sys.exit(1)