patch from petermayo to fix GN dependency regeneration

tools/gn/ninja_build_writer.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/ninja_build_writer.h"
 
 #include <fstream>
 #include <map>
 
 #include "base/command_line.h"
@@ skipping 59 matching lines @@
     }
   }
 
 #if defined(OS_WIN)
   return base::WideToUTF8(cmdline.GetCommandLineString());
 #else
   return cmdline.GetCommandLineString();
 #endif
 }
 
+void WriteAnotherFile(std::ostream& out, const base::FilePath& name,
+                      EscapingMode mode) {
+  EscapeOptions path_escaping;
+  path_escaping.mode = mode;
+
+  out << " ";
+  EscapeStringToStream(out, FilePathToUTF8(name), path_escaping);
+}
+
 }  // namespace
 
 NinjaBuildWriter::NinjaBuildWriter(
     const BuildSettings* build_settings,
     const std::vector<const Settings*>& all_settings,
     const Toolchain* default_toolchain,
     const std::vector<const Target*>& default_toolchain_targets,
     std::ostream& out,
     std::ostream& dep_out)
     : build_settings_(build_settings),
@@ skipping 46 matching lines @@
   }
 
   NinjaBuildWriter gen(build_settings, all_settings, default_toolchain,
                        default_toolchain_targets, file, depfile);
   return gen.Run(err);
 }
 
 void NinjaBuildWriter::WriteNinjaRules() {
   out_ << "rule gn\n";
   out_ << "  command = " << GetSelfInvocationCommand(build_settings_) << "\n";
-  out_ << "  description = Regenerating ninja files\n\n";
+  out_ << "  description = Regenerating ninja files\n";
+  out_ << "  restat = 1\n\n";
 
-  // This rule will regenerate the ninja files when any input file has changed.
-  out_ << "build build.ninja: gn\n"
+  // This rule will regenerate the ninja files when any input file has changed,
+  // or is missing.
+  out_ << "build build.ninja";
+
+  // Other files read by the build.
+  std::vector<SourceFile> written_files = g_scheduler->GetWrittenFiles();
+  for (const auto& written_file : written_files)
+    WriteAnotherFile(out_, build_settings_->GetFullPath(written_file),
+                     ESCAPE_NINJA_COMMAND);
+
+  out_ << ": gn\n"
        << "  generator = 1\n"
        << "  depfile = build.ninja.d\n";
 
   // Input build files. These go in the ".d" file. If we write them as
   // dependencies in the .ninja file itself, ninja will expect the files to
   // exist and will error if they don't. When files are listed in a depfile,
   // missing files are ignored.
   dep_out_ << "build.ninja:";
   std::vector<base::FilePath> input_files;
   g_scheduler->input_file_manager()->GetAllPhysicalInputFileNames(&input_files);
   for (const auto& input_file : input_files)
-    dep_out_ << " " << FilePathToUTF8(input_file);
+    WriteAnotherFile(dep_out_, input_file, ESCAPE_NONE);
 
   // Other files read by the build.
   std::vector<base::FilePath> other_files = g_scheduler->GetGenDependencies();
   for (const auto& other_file : other_files)
-    dep_out_ << " " << FilePathToUTF8(other_file);
+    WriteAnotherFile(dep_out_, other_file, ESCAPE_NONE);
 
   out_ << std::endl;
 }
 
 void NinjaBuildWriter::WriteLinkPool() {
   out_ << "pool link_pool\n"
        << "  depth = " << default_toolchain_->concurrent_links() << std::endl
        << std::endl;
 }
 
@@ skipping 136 matching lines @@
   EscapeOptions ninja_escape;
   ninja_escape.mode = ESCAPE_NINJA;
 
   // Escape for special chars Ninja will handle.
   std::string escaped = EscapeString(phony_name, ninja_escape, nullptr);
 
   out_ << "build " << escaped << ": phony ";
   path_output_.WriteFile(out_, target_file);
   out_ << std::endl;
 }