GN: Make file/dir resolving return errors.

tools/gn/action_target_generator.cc

 // Copyright (c) 2013 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.
 
 #include "tools/gn/action_target_generator.h"
 
 #include "tools/gn/build_settings.h"
 #include "tools/gn/err.h"
 #include "tools/gn/filesystem_utils.h"
 #include "tools/gn/parse_tree.h"
@@ skipping 58 matching lines @@
   // if it doesn't have one.
   const Value* value = scope_->GetValue(variables::kScript, true);
   if (!value) {
     *err_ = Err(function_call_, "This target type requires a \"script\".");
     return false;
   }
   if (!value->VerifyTypeIs(Value::STRING, err_))
     return false;
 
   SourceFile script_file =
-      scope_->GetSourceDir().ResolveRelativeFile(value->string_value(),
+      scope_->GetSourceDir().ResolveRelativeFile(
+          *value, err_,
           scope_->settings()->build_settings()->root_path_utf8());
-  if (script_file.value().empty()) {
-    *err_ = Err(*value, "script name is empty");
+  if (script_file.value().empty())

[scottmg, 2015/06/03 21:01:58]

should this be err_.has_error()?

     return false;
-  }
   target_->action_values().set_script(script_file);
   return true;
 }
 
 bool ActionTargetGenerator::FillScriptArgs() {
   const Value* value = scope_->GetValue(variables::kArgs, true);
   if (!value)
     return true;
   return target_->action_values().args().Parse(*value, err_);
 }
@@ skipping 36 matching lines @@
       *err_ = Err(function_call_,
           "action_foreach should have a pattern in the output.",
           "An action_foreach target should have a source expansion pattern in\n"
           "it to map source file to unique output file name. Otherwise, the\n"
           "build system can't determine when your script needs to be run.");
       return false;
     }
   }
   return true;
 }