Path evaluation to protobuf plugin.

third_party/protobuf/proto_library.gni

Index: third_party/protobuf/proto_library.gni
diff --git a/third_party/protobuf/proto_library.gni b/third_party/protobuf/proto_library.gni
index a3b0b762332bd62fccd4494354ded74f91ab009c..db75e1b1b3e3e3602c8ec9ac06025adbb0727b19 100644
--- a/third_party/protobuf/proto_library.gni
+++ b/third_party/protobuf/proto_library.gni
@@ -32,11 +32,10 @@
 #       macro to work (see cc_include) and set
 #       component_build_force_source_set = true.
 #
-#   generator_plugin (optional)
-#       Name of plugin executable which generates custom cc stubs.
-#       Plugin itself should be dependency of the invoker.
+#   generator_plugin_label (optional)
+#       GN label for plugin executable which generates custom cc stubs.
 #
-#   generator_plugin_suffix (required if generator_plugin set)
+#   generator_plugin_suffix (required if generator_plugin_label set)
 #       Suffix (before extension) for generated .cc and .h files.
 #
 #   generator_plugin_options (optional)
@@ -166,8 +165,8 @@ template("proto_library") {
       ]
     }
 
-    if (defined(invoker.generator_plugin)) {
-      generator_plugin = invoker.generator_plugin
+    if (defined(invoker.generator_plugin_label)) {
+      generator_plugin_label = invoker.generator_plugin_label
       generator_plugin_suffix = invoker.generator_plugin_suffix
       if (defined(invoker.generator_plugin_options)) {
         generator_plugin_options = invoker.generator_plugin_options
@@ -178,9 +177,22 @@ template("proto_library") {
         "$out_dir/{{source_name_part}}$generator_plugin_suffix.cc",
         "$out_dir/{{source_name_part}}$generator_plugin_suffix.h",
       ]
+
+      # Straightforward way to get the name of executable doesn't work because
+      # root_out_dir and root_build_dir may differ in cross-compilation and
+      # also Windows executables have .exe at the end.
+
+      plugin_host_label = generator_plugin_label + "($host_toolchain)"
+      generator_plugin_executable =
+          rebase_path(get_label_info(plugin_host_label, "root_out_dir") + "/" +
+                          get_label_info(plugin_host_label, "name"),
+                      root_build_dir)
+      if (is_win) {

[Nico, 2016/08/02 17:38:27]

This is likely wrong (also in the old place). I'm guessing that
$generator_plugin is a host executable, so you need to check the host os. is_win
checks the target os. If cross-compiling chrome/win on linux, this here
currently does the wrong thing. (cross-compiling chrome/win on windows isn't
fully working yet, but it's also not super far away, see
https://codereview.chromium.org/1183633003/)


See
https://cs.chromium.org/chromium/src/chrome/test/base/js2gtest.gni?rcl=0&l=42
for an example. The get_labelinfo() call there also looks a bit simpler than
what you have.

[kraynov, 2016/08/02 19:28:50]

Done.

+        generator_plugin_executable += ".exe"
+      }
       args += [
         "--plugin",
-        "protoc-gen-plugin=./$generator_plugin",
+        "protoc-gen-plugin=./$generator_plugin_executable",
         "--plugin_out",
         "$generator_plugin_options$rel_out_dir",  # Separated by colon.
       ]
@@ -189,6 +201,9 @@ template("proto_library") {
     deps = [
       protoc_label,
     ]
+    if (defined(plugin_host_label)) {
+      deps += [ plugin_host_label ]
+    }
 
     # The deps may have steps that have to run before running protobuf.
     if (defined(invoker.deps)) {