[GN] Add JSON project writer

tools/gn/command_gen.cc

Index: tools/gn/command_gen.cc
diff --git a/tools/gn/command_gen.cc b/tools/gn/command_gen.cc
index 3d442745c393970e383074971a14c0f1e33db26d..185ba72fff6bfa6afa997fac26a86f0eae1fe864 100644
--- a/tools/gn/command_gen.cc
+++ b/tools/gn/command_gen.cc
@@ -11,6 +11,7 @@
 #include "tools/gn/build_settings.h"
 #include "tools/gn/commands.h"
 #include "tools/gn/eclipse_writer.h"
+#include "tools/gn/json_project_writer.h"
 #include "tools/gn/ninja_target_writer.h"
 #include "tools/gn/ninja_writer.h"
 #include "tools/gn/qt_creator_writer.h"
@@ -36,10 +37,14 @@ const char kSwitchIdeValueVs[] = "vs";
 const char kSwitchIdeValueVs2013[] = "vs2013";
 const char kSwitchIdeValueVs2015[] = "vs2015";
 const char kSwitchIdeValueXcode[] = "xcode";
+const char kSwitchIdeValueJSON[] = "json";
 const char kSwitchNinjaExtraArgs[] = "ninja-extra-args";
 const char kSwitchRootTarget[] = "root-target";
 const char kSwitchSln[] = "sln";
 const char kSwitchWorkspace[] = "workspace";
+const char kSwitchFileName[] = "file-name";
+const char kSwitchExecScript[] = "exec-script";
+const char kSwitchExecScriptExtraArgs[] = "exec-script-extra-args";
 
 // Called on worker thread to write the ninja file.
 void BackgroundDoWrite(const Target* target) {
@@ -113,7 +118,7 @@ void PrintInvalidGeneratedInput(const Builder* builder,
 
   if (generator) {
     err += "but this file was not generated by any dependencies of the " +
-        target_str + ". The target\nthat generates the file is:\n  ";
+           target_str + ". The target\nthat generates the file is:\n  ";
     err += generator->label().GetUserVisibleName(show_toolchains);
   } else {
     err += "but no targets in the build generate that file.";
@@ -220,6 +225,25 @@ bool RunIdeWriter(const std::string& ide,
                    "ms\n");
     }
     return res;
+  } else if (ide == kSwitchIdeValueJSON) {
+    std::string file_name = command_line->GetSwitchValueASCII(kSwitchFileName);
+    if (file_name.empty())
+      file_name = "project.json";
+    std::string exec_script =
+        command_line->GetSwitchValueASCII(kSwitchExecScript);
+    std::string exec_script_extra_args =
+        command_line->GetSwitchValueASCII(kSwitchExecScriptExtraArgs);
+
+    bool quiet = command_line->HasSwitch(switches::kQuiet);
+    bool res = JSONProjectWriter::RunAndWriteFiles(
+        build_settings, builder, file_name, exec_script, exec_script_extra_args,
+        quiet, err);
+    if (res && !quiet) {
+      OutputString("Generating JSON projects took " +
+                   base::Int64ToString(timer.Elapsed().InMilliseconds()) +
+                   "ms\n");
+    }
+    return res;
   }
 
   *err = Err(Location(), "Unknown IDE: " + ide);
@@ -229,8 +253,7 @@ bool RunIdeWriter(const std::string& ide,
 }  // namespace
 
 const char kGen[] = "gen";
-const char kGen_HelpShort[] =
-    "gen: Generate ninja files.";
+const char kGen_HelpShort[] = "gen: Generate ninja files.";
 const char kGen_Help[] =
     "gn gen: Generate ninja files.\n"
     "\n"
@@ -259,6 +282,7 @@ const char kGen_Help[] =
     "      \"vs2015\" - Visual Studio 2015 project/solution files.\n"
     "      \"xcode\" - Xcode workspace/solution files.\n"
     "      \"qtcreator\" - QtCreator project files.\n"
+    "      \"json\" - JSON file containing target information\n"
     "\n"
     "  --filters=<path_prefixes>\n"
     "      Semicolon-separated list of label patterns used to limit the set\n"
@@ -305,7 +329,25 @@ const char kGen_Help[] =
     "  properly define includes/defines for each file individually.\n"
     "  Instead, one set of includes/defines is generated for the entire\n"
     "  project. This works fairly well but may still result in a few indexer\n"
-    "  issues here and there.\n";
+    "  issues here and there.\n"
+    "\n"
+    "Generic JSON Output\n"
+    "\n"
+    "  Dumps target information to JSON file and optionally invokes a python\n"
+    "  script.\n"
+    "\n"
+    "  --file_name=<json_file_name>\n"
+    "      Overrides default file name of generated JSON file.\n"
+    "\n"
+    "  --exec-script=<path_to_python_script>\n"
+    "      Executes python script after the JSON file is generated.\n"
+    "      Path can be project absolute (//), system absolute (/) or\n"
+    "      relative, in which case the output directory will be base.\n"
+    "      Path to generated JSON file will be first argument when invoking\n"
+    "      script.\n"
+    "\n"
+    "  --exec-script-extra-args=<argument>\n"
+    "      Optional second argument that will passed to executed-script.\n";
 
 int RunGen(const std::vector<std::string>& args) {
   base::ElapsedTimer timer;