Json ide script for gn to output cmake.

Can be run like

gn gen out/debug --ide=json --json-ide-script=../../gn/gn_to_cmake.py

or

gn gen out/debug --ide=json
python gn/gn_to_cmake.py out/debug/project.json

This first pass creates CMakeLists.txt with just enough information for an
ide. Each target is just a static library with sources, include
directories, and defines.

NOTRY=true
This isn't automatically tested.

Review-Url: https://codereview.chromium.org/2363873002

gn/gn_to_cmake.py

@@ -0,0 +1,110 @@
+#!/usr/bin/env python
+#
+# Copyright 2016 Google Inc.
+#
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""
+Usage: gn_to_cmake.py <json_file_name>
+
+gn gen out/config --ide=json --json-ide-script=../../gn/gn_to_cmake.py
+
+or
+
+gn gen out/config --ide=json
+python gn/gn_to_cmake.py out/config/project.json
+"""
+
+import json
+import posixpath
+import os
+import sys
+
+def write_project(project):
+
+  def get_base_name(target_name):
+    base_name = posixpath.basename(target_name)
+    sep = base_name.rfind(":")
+    if sep != -1:
+      base_name = base_name[sep+1:]
+    return base_name
+
+  def get_output_name(target_name, target_properties):
+    output_name = target_properties.get("output_name", None)
+    if output_name is None:
+      output_name = get_base_name(target_name)
+
+    output_extension = target_properties.get("output_extension", None)
+    if output_extension is not None:
+      output_name = posixpath.splitext(output_name)[0]
+      if len(output_extension):
+        output_name += "." + output_extension
+
+    return output_name
+
+  def get_absolute_path(root_path, path):
+    if path.startswith("//"):
+      return root_path + "/" + path[2:]
+    else:
+      return path
+
+  build_settings = project['build_settings']
+  root_path = build_settings['root_path']
+  build_path = os.path.join(root_path, build_settings['build_dir'][2:])
+
+  out = open(os.path.join(build_path, 'CMakeLists.txt'), 'w+')
+  out.write('cmake_minimum_required(VERSION 2.8.8 FATAL_ERROR)\n')
+  out.write('cmake_policy(VERSION 2.8.8)\n')
+
+  for target_name, target_properties in project['targets'].items():
+    sources = target_properties.get('sources', [])
+    if not sources:
+      continue
+
+    target_output_name = get_output_name(target_name, target_properties)
+    out.write('\n')
+    out.write('add_library(')
+    out.write(target_output_name)
+    out.write(' STATIC\n')
+    for source in sources:
+      out.write('    "')
+      out.write(get_absolute_path(root_path, source))
+      out.write('"\n')
+    out.write(')\n')
+
+    out.write('set_target_properties(')
+    out.write(target_output_name)
+    out.write(' PROPERTIES EXCLUDE_FROM_ALL "TRUE")\n')
+
+    out.write('set_property(TARGET ')
+    out.write(target_output_name)
+    out.write(' APPEND PROPERTY INCLUDE_DIRECTORIES\n')
+    for include_dir in target_properties.get('include_dirs', []):
+      out.write('    "')
+      out.write(get_absolute_path(root_path, include_dir))
+      out.write('"\n')
+    out.write(')\n')
+
+    out.write('set_target_properties(')
+    out.write(target_output_name)
+    out.write(' PROPERTIES COMPILE_DEFINITIONS "')
+    for define in target_properties.get('defines', []):
+      out.write(define)
+      out.write(';')
+    out.write('")\n')
+
+def main():
+  if len(sys.argv) != 2:
+    print('Usage: ' + sys.argv[0] + ' <json_file_name>')
+    exit(1)
+
+  json_path = sys.argv[1]
+  project = None
+  with open(json_path, 'r') as json_file:
+    project = json.loads(json_file.read())
+
+  write_project(project)
+
+if __name__ == "__main__":
+  main()