Add support for data deps.

tools/gn/command_help.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 <algorithm>
 #include <iostream>
 
 #include "tools/gn/commands.h"
 #include "tools/gn/err.h"
 #include "tools/gn/functions.h"
 #include "tools/gn/input_conversion.h"
 #include "tools/gn/setup.h"
 #include "tools/gn/standard_out.h"
+#include "tools/gn/variables.h"
 
 namespace commands {
 
 namespace {
 
 // Prints a line for a command, assuming there is a colon. Everything before
 // the colon is the command (and is highlighted) and everything after it is
 // normal.
 void PrintShortHelp(const std::string& line) {
   size_t colon_offset = line.find(':');
   size_t first_normal = 0;
   if (colon_offset != std::string::npos) {
     OutputString("  " + line.substr(0, colon_offset), DECORATION_YELLOW);
     first_normal = colon_offset;
   }
   OutputString(line.substr(first_normal) + "\n");
 }
 
 void PrintToplevelHelp() {
-  std::cout <<
-      "Commands (type \"gn help <command>\" for more details):\n";
+  OutputString("Commands (type \"gn help <command>\" for more details):\n");
 
   const commands::CommandInfoMap& command_map = commands::GetCommands();
   for (commands::CommandInfoMap::const_iterator i = command_map.begin();
        i != command_map.end(); ++i)
     PrintShortHelp(i->second.help_short);
 
   OutputString(
       "\n"
       "  When run with no arguments \"gn gen\" is assumed.\n"
       "\n"
       "Common switches:\n"
       "  -q: Quiet mode, don't print anything on success.\n"
       "  --root: Specifies source root (overrides .gn file).\n"
       "  --secondary: Specifies secondary source root (overrides .gn file).\n"
-      "  -v: Verbose mode, print lots of logging.\n"
-      "\n"
-      "Buildfile functions (type \"gn help <function>\" for more details):\n");
+      "  -v: Verbose mode, print lots of logging.\n");
 
+  // Functions.
+  OutputString("\nBuildfile functions (type \"gn help <function>\" for more "
+               "details):\n");
   const functions::FunctionInfoMap& function_map = functions::GetFunctions();
   std::vector<std::string> sorted_functions;
   for (functions::FunctionInfoMap::const_iterator i = function_map.begin();
        i != function_map.end(); ++i)
     sorted_functions.push_back(i->first.as_string());
   std::sort(sorted_functions.begin(), sorted_functions.end());
   for (size_t i = 0; i < sorted_functions.size(); i++)
     OutputString("  " + sorted_functions[i] + "\n", DECORATION_YELLOW);
 
+  // Built-in variables.
+  OutputString("\nBuilt-in predefined variables (type \"gn help <variable>\" "
+               "for more details):\n");
+  const variables::VariableInfoMap& builtin_vars =
+      variables::GetBuiltinVariables();
+  for (variables::VariableInfoMap::const_iterator i = builtin_vars.begin();
+       i != builtin_vars.end(); ++i)
+    PrintShortHelp(i->second.help_short);
+
+  // Target variables.
+  OutputString("\nVariables you set in targets (type \"gn help <variable>\" "
+               "for more details):\n");
+  const variables::VariableInfoMap& target_vars =
+      variables::GetTargetVariables();
+  for (variables::VariableInfoMap::const_iterator i = target_vars.begin();
+       i != target_vars.end(); ++i)
+    PrintShortHelp(i->second.help_short);
+
   OutputString("\nOther help topics:\n");
   PrintShortHelp("dotfile: Info about the toplevel .gn file.");
   PrintShortHelp(
       "input_conversion: Processing input from exec_script and read_file.");
 }
 
 }  // namespace
 
 const char kHelp[] = "help";
 const char kHelp_HelpShort[] =
@@ skipping 20 matching lines @@
 
   // Check functions.
   const functions::FunctionInfoMap& function_map = functions::GetFunctions();
   functions::FunctionInfoMap::const_iterator found_function =
       function_map.find(args[0]);
   if (found_function != function_map.end()) {
     OutputString(found_function->second.help);
     return 0;
   }
 
+  // Builtin variables.
+  const variables::VariableInfoMap& builtin_vars =
+      variables::GetBuiltinVariables();
+  variables::VariableInfoMap::const_iterator found_builtin_var =
+      builtin_vars.find(args[0]);
+  if (found_builtin_var != builtin_vars.end()) {
+    OutputString(found_builtin_var->second.help);
+    return 0;
+  }
+
+  // Target variables.
+  const variables::VariableInfoMap& target_vars =
+      variables::GetTargetVariables();
+  variables::VariableInfoMap::const_iterator found_target_var =
+      target_vars.find(args[0]);
+  if (found_target_var != target_vars.end()) {
+    OutputString(found_target_var->second.help);
+    return 0;
+  }
+
   // Random other topics.
   if (args[0] == "input_conversion") {
     OutputString(kInputConversion_Help);
     return 0;
   } if (args[0] == "dotfile") {
     OutputString(kDotfile_Help);
     return 0;
   }
 
   // No help on this.
   Err(Location(), "No help on \"" + args[0] + "\".").PrintToStdout();
   RunHelp(std::vector<std::string>());
   return 1;
 }
 
 }  // namespace commands