Refactor the python system_impl module.

third_party/cython/rules.gni

 # 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.
 
-template("python_binary_module_sources") {
+template("python_binary_source_set") {
   # Only available on linux for now.
   assert(is_linux)
-  assert(defined(invoker.sources))
+  assert(defined(invoker.cython_sources) || defined(invoker.sources))
 
-  cython_root = "//third_party/cython"
-  cython_script = "$cython_root/src/cython.py"
-  cython_output = "${target_out_dir}/${target_name}.cc"
-
-  generator_target_name = target_name + "_cython_compiler"
   config_name = target_name + "_python_config"
 
   target_visibility = [ ":$target_name" ]
 
-  action(generator_target_name) {
-    visibility = target_visibility
-    script = cython_script
-    sources = invoker.sources
-    outputs = [
-      cython_output,
-    ]
-    args = [
-             "--cplus",
-             "-I",
-             rebase_path("//", root_build_dir),
-             "-o",
-             rebase_path(cython_output, root_build_dir),
-           ] + rebase_path(sources, root_build_dir)
+  if (defined(invoker.cython_sources)) {
+    generator_target_name = target_name + "_cython_compiler"
+
+    cython_root = "//third_party/cython"
+    cython_script = "$cython_root/src/cython.py"
+    cython_output = "${target_out_dir}/${target_name}.cc"
+
+    action(generator_target_name) {
+      visibility = target_visibility
+      script = cython_script
+      sources = invoker.cython_sources
+      outputs = [
+        cython_output,
+      ]
+      args = [
+               "--cplus",
+               "-I",
+               rebase_path("//", root_build_dir),
+               "-o",
+               rebase_path(cython_output, root_build_dir),
+             ] + rebase_path(sources, root_build_dir)
+    }
   }
 
   config(config_name) {
     visibility = target_visibility
     python_flags = "//third_party/cython/python_flags.py"
     include_dirs = exec_script(python_flags, [ "--includes" ], "list lines")
     libs = exec_script(python_flags, [ "--libraries" ], "list lines")
     lib_dirs = exec_script(python_flags, [ "--library_dirs" ], "list lines")
     if (!is_win) {
       # Generated code includes static utility functions that often go unused.
       cflags = [ "-Wno-unused-function" ]
     }
   }
 
   source_set(target_name) {
-    deps = [
-      ":$generator_target_name",
-    ]
+    deps = []

[qsr, 2014/12/12 09:09:54]

Could you run gn format, I'm pretty sure deps should be the last thing in the
target.

[etiennej, 2014/12/12 10:58:25]

I do not mind moving it, but I ran gn format (both now, and as a presubmit
before sending the CL) and there's no change.

[qsr, 2014/12/12 12:27:45]

 Hum, weird. Can you take a look at
https://code.google.com/p/chromium/wiki/GNStyleGuide and make sure you follow
the syle, in particular for the ordering of the variables. Thanks.

 Also, this still should be pushed in the chromium repo and not the mojo repo.

[etiennej, 2014/12/12 13:39:46]

Made the fixes. I'll prepare a CL in chromium with the same changes.

+    if (defined(invoker.cython_sources)) {
+      deps += [ ":$generator_target_name" ]
+    }
     if (defined(invoker.visibility)) {
       visibility = invoker.visibility
     }
     if (defined(invoker.deps)) {
       deps += invoker.deps
     }
     if (defined(invoker.datadeps)) {
       datadeps = invoker.datadeps
     }
-    sources = [
-      cython_output,
-    ]
-    if (defined(invoker.additional_sources)) {
-      sources += invoker.additional_sources
+    sources = []
+    if (defined(invoker.cython_sources)) {
+      sources += [ cython_output ]
+    }
+    if (defined(invoker.sources)) {
+      sources += invoker.sources
     }
     all_dependent_configs = [ ":$config_name" ]
   }
 }
 
 template("python_binary_module") {
   # Only available on linux for now.
   assert(is_linux)
-  assert(defined(invoker.sources))
+
+  has_sources = defined(invoker.cython_sources) || defined(invoker.sources)
+
+  assert(has_sources || defined(invoker.deps))
   assert(defined(invoker.python_base_module))
 
   sources_target_name = target_name + "_cython_sources"
   shared_library_name = target_name + "_shared_library"
 
   if (is_linux) {
     shared_library_prefix = "lib"
     shared_library_suffix = ".so"
     python_module_suffix = ".so"
   }
 
   target_visibility = [
     ":$sources_target_name",
     ":$shared_library_name",
     ":$target_name",
   ]
 
-  python_binary_module_sources(sources_target_name) {
-    visibility = target_visibility
-    sources = invoker.sources
+  if (has_sources) {
+    python_binary_source_set(sources_target_name) {
+      visibility = target_visibility
+      if (defined(invoker.cython_sources)) {
+        cython_sources = invoker.cython_sources
+      }
+      if (defined(invoker.sources)) {
+        sources = invoker.sources
+      }
+      if (defined(invoker.deps)) {
+        deps = invoker.deps
+      }
+      if (defined(invoker.datadeps)) {
+        datadeps = invoker.datadeps
+      }
+      if (defined(invoker.configs)) {
+        configs = invoker.configs
+      }
+    }
   }
 
   shared_library(shared_library_name) {
     visibility = target_visibility
-    deps = [
-      ":$sources_target_name",
-    ]
+    deps = []
+    if (has_sources) {
+      deps += [ ":$sources_target_name" ]
+    }
     if (defined(invoker.deps)) {
       deps += invoker.deps
     }
     if (defined(invoker.datadeps)) {
       datadeps = invoker.datadeps
     }
-    if (defined(invoker.additional_sources)) {
-      sources = invoker.additional_sources
-    }
     if (defined(invoker.configs)) {
       configs += invoker.configs
     }
   }
 
   copy(target_name) {
     python_base_module = invoker.python_base_module
     sources = [
       "$root_out_dir/${shared_library_prefix}${shared_library_name}${shared_library_suffix}",
     ]
     outputs = [
       "$root_out_dir/python/$python_base_module/${target_name}${python_module_suffix}",
     ]
     deps = [
       ":$shared_library_name",
     ]
   }
 }