GN: Add logging for the location of an invocation.

tools/gn/err.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/err.h"
 
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
 #include "tools/gn/filesystem_utils.h"
 #include "tools/gn/input_file.h"
@@ skipping 143 matching lines @@
 }
 
 void Err::InternalPrintToStdout(bool is_sub_err) const {
   DCHECK(has_error_);
 
   if (!is_sub_err)
     OutputString("ERROR ", DECORATION_RED);
 
   // File name and location.
   const InputFile* input_file = location_.file();
-  std::string loc_str;
-  if (input_file) {
-    std::string name;
-    if (input_file->friendly_name().empty())
-      name = input_file->name().value();
+  std::string loc_str = location_.Describe(true);
+  if (!loc_str.empty()) {
+    if (is_sub_err)
+      loc_str.insert(0, "See ");
     else
-      name = input_file->friendly_name();
-
-    if (is_sub_err)
-      loc_str = "See ";
-    else
-      loc_str = "at ";
-    loc_str += name + ": " +
-        base::IntToString(location_.line_number()) + ":" +
-        base::IntToString(location_.char_offset()) + ": ";
+      loc_str.insert(0, "at ");
+    loc_str.append(": ");
   }
   OutputString(loc_str + message_ + "\n");
 
   // Quoted line.
   if (input_file) {
     std::string line = GetNthLine(input_file->contents(),
                                   location_.line_number());
     if (!ContainsOnlyWhitespaceASCII(line)) {
       OutputString(line + "\n", DECORATION_BOLD);
       OutputHighlighedPosition(location_, ranges_, line.size());
     }
   }
 
   // Optional help text.
   if (!help_text_.empty())
     OutputString(help_text_ + "\n");
 
   // Sub errors.
   for (size_t i = 0; i < sub_errs_.size(); i++)
     sub_errs_[i].InternalPrintToStdout(true);
 }