GN: Make file/dir resolving return errors.

tools/gn/commands.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/commands.h"
 
 #include "base/command_line.h"
 #include "tools/gn/builder.h"
 #include "tools/gn/filesystem_utils.h"
 #include "tools/gn/item.h"
@@ skipping 72 matching lines @@
     return true;
   }
 
   // Try to figure out what this thing is.
   Err err;
   Label label = Label::Resolve(current_dir,
                                setup->loader()->default_toolchain_label(),
                                Value(nullptr, input), &err);
   if (err.has_error()) {
     // Not a valid label, assume this must be a file.
+    err = Err();
     file_matches->push_back(current_dir.ResolveRelativeFile(
-        input, setup->build_settings().root_path_utf8()));
+        Value(nullptr, input), &err, setup->build_settings().root_path_utf8()));
+    if (err.has_error()) {
+      err.PrintToStdout();
+      return false;
+    }
     return true;
   }
 
   const Item* item = setup->builder()->GetItem(label);
   if (item) {
     if (const Config* as_config = item->AsConfig())
       config_matches->push_back(as_config);
     else if (const Target* as_target = item->AsTarget())
       target_matches->push_back(as_target);
     else if (const Toolchain* as_toolchain = item->AsToolchain())
       toolchain_matches->push_back(as_toolchain);
   } else {
     // Not an item, assume this must be a file.
     file_matches->push_back(current_dir.ResolveRelativeFile(
-        input, setup->build_settings().root_path_utf8()));
+        Value(nullptr, input), &err, setup->build_settings().root_path_utf8()));
+    if (err.has_error()) {
+      err.PrintToStdout();
+      return false;
+    }
   }
 
   return true;
 }
 
 enum TargetPrintingMode {
   TARGET_PRINT_BUILDFILE,
   TARGET_PRINT_LABEL,
   TARGET_PRINT_OUTPUT,
 };
@@ skipping 361 matching lines @@
   }
 }
 
 void FilterAndPrintTargetSet(bool indent,
                              const std::set<const Target*>& targets) {
   std::vector<const Target*> target_vector(targets.begin(), targets.end());
   FilterAndPrintTargets(indent, &target_vector);
 }
 
 }  // namespace commands