[GN] Add JSON project writer

tools/gn/command_desc.cc

Index: tools/gn/command_desc.cc
diff --git a/tools/gn/command_desc.cc b/tools/gn/command_desc.cc
index d1edfe487b42baadd4e1cdfac511125b1a582a93..1679df92a4cad6a93439dee225924bf073a1313b 100644
--- a/tools/gn/command_desc.cc
+++ b/tools/gn/command_desc.cc
@@ -9,18 +9,13 @@
 #include <sstream>
 
 #include "base/command_line.h"
-#include "build/build_config.h"
+#include "base/json/json_writer.h"
+#include "base/memory/ptr_util.h"
 #include "tools/gn/commands.h"
 #include "tools/gn/config.h"
-#include "tools/gn/config_values_extractors.h"
-#include "tools/gn/deps_iterator.h"
-#include "tools/gn/filesystem_utils.h"
-#include "tools/gn/item.h"
-#include "tools/gn/label.h"
-#include "tools/gn/runtime_deps.h"
+#include "tools/gn/desc_builder.h"
 #include "tools/gn/setup.h"
 #include "tools/gn/standard_out.h"
-#include "tools/gn/substitution_writer.h"
 #include "tools/gn/switches.h"
 #include "tools/gn/target.h"
 #include "tools/gn/variables.h"
@@ -32,712 +27,266 @@ namespace {
 // Desc-specific command line switches.
 const char kBlame[] = "blame";
 const char kTree[] = "tree";
-
-// Prints the given directory in a nice way for the user to view.
-std::string FormatSourceDir(const SourceDir& dir) {
-#if defined(OS_WIN)
-  // On Windows we fix up system absolute paths to look like native ones.
-  // Internally, they'll look like "/C:\foo\bar/"
-  if (dir.is_system_absolute()) {
-    std::string buf = dir.value();
-    if (buf.size() > 3 && buf[2] == ':') {
-      buf.erase(buf.begin());  // Erase beginning slash.
-      return buf;
+const char kAll[] = "all";
+
+// Prints value with specified indentation level
+void PrintValue(const base::Value* value, int indentLevel) {
+  std::string indent(indentLevel * 2, ' ');
+  const base::ListValue* list = nullptr;
+  const base::DictionaryValue* dict = nullptr;
+  std::string string;
+  bool b(false);

[brettw, 2016/07/01 23:34:17]

Can you do
  bool bool_value = false;
(the paren-style init looks very strange in this case, and "b" is a confusing
name). For consistency, the list and dict above should probably be named
similarly (i.e. list_value, dict_value).

+  if (value->GetAsList(&list)) {
+    for (const auto& v : *list) {
+      PrintValue(v.get(), indentLevel);
+    }
+  } else if (value->GetAsString(&string)) {
+    OutputString(indent);
+    OutputString(string);
+    OutputString("\n");
+  } else if (value->GetAsBoolean(&b)) {
+    OutputString(indent);
+    OutputString(b ? "true" : "false");
+    OutputString("\n");
+  } else if (value->GetAsDictionary(&dict)) {
+    base::DictionaryValue::Iterator iter(*dict);
+    while (!iter.IsAtEnd()) {
+      OutputString(indent + iter.key() + "\n");
+      PrintValue(&iter.value(), indentLevel + 1);
+      iter.Advance();
     }
+  } else if (value->IsType(base::Value::TYPE_NULL)) {
+    OutputString(indent + "<null>\n");
   }
-#endif
-  return dir.value();
-}
-
-void RecursiveCollectChildDeps(const Target* target,
-                               std::set<const Target*>* result);
-
-void RecursiveCollectDeps(const Target* target,
-                          std::set<const Target*>* result) {
-  if (result->find(target) != result->end())
-    return;  // Already did this target.
-  result->insert(target);
-
-  RecursiveCollectChildDeps(target, result);
 }
 
-void RecursiveCollectChildDeps(const Target* target,
-                               std::set<const Target*>* result) {
-  for (const auto& pair : target->GetDeps(Target::DEPS_ALL))
-    RecursiveCollectDeps(pair.ptr, result);
+// Default handler for property
+void DefaultHandler(const std::string& name, const base::Value* value) {
+  OutputString("\n");
+  OutputString(name);
+  OutputString("\n");
+  PrintValue(value, 1);
 }
 
-// Prints dependencies of the given target (not the target itself). If the
-// set is non-null, new targets encountered will be added to the set, and if
-// a dependency is in the set already, it will not be recused into. When the
-// set is null, all dependencies will be printed.
-void RecursivePrintDeps(const Target* target,
-                        const Label& default_toolchain,
-                        std::set<const Target*>* seen_targets,
-                        int indent_level) {
-  // Combine all deps into one sorted list.
-  std::vector<LabelTargetPair> sorted_deps;
-  for (const auto& pair : target->GetDeps(Target::DEPS_ALL))
-    sorted_deps.push_back(pair);
-  std::sort(sorted_deps.begin(), sorted_deps.end(),
-            LabelPtrLabelLess<Target>());
-
-  std::string indent(indent_level * 2, ' ');
-  for (const auto& pair : sorted_deps) {
-    const Target* cur_dep = pair.ptr;
-
-    OutputString(indent +
-        cur_dep->label().GetUserVisibleName(default_toolchain));
-    bool print_children = true;
-    if (seen_targets) {
-      if (seen_targets->find(cur_dep) == seen_targets->end()) {
-        // New target, mark it visited.
-        seen_targets->insert(cur_dep);
-      } else {
-        // Already seen.
-        print_children = false;
-        // Only print "..." if something is actually elided, which means that
-        // the current target has children.
-        if (!cur_dep->public_deps().empty() ||
-            !cur_dep->private_deps().empty() ||
-            !cur_dep->data_deps().empty())
-          OutputString("...");
-      }
-    }
+// Specific handler for properties that needs different treatment
 
+void TypeHandler(const std::string& name, const base::Value* value) {
+  std::string type;
+  if (value->GetAsString(&type)) {
+    auto t = DescBuilder::GetOutputTypeForString(type);
+    OutputString("Type: ", DECORATION_YELLOW);
+    OutputString(Target::GetStringForOutputType(t));
     OutputString("\n");
-    if (print_children) {
-      RecursivePrintDeps(cur_dep, default_toolchain, seen_targets,
-                         indent_level + 1);
-    }
   }
 }
 
-void PrintDeps(const Target* target, bool display_header) {
-  const base::CommandLine* cmdline = base::CommandLine::ForCurrentProcess();
-  Label toolchain_label = target->label().GetToolchainLabel();
-
-  // Tree mode is separate.
-  if (cmdline->HasSwitch(kTree)) {
-    if (display_header)
-      OutputString("\nDependency tree\n");
-
-    if (cmdline->HasSwitch("all")) {
-      // Show all tree deps with no eliding.
-      RecursivePrintDeps(target, toolchain_label, nullptr, 1);
-    } else {
-      // Don't recurse into duplicates.
-      std::set<const Target*> seen_targets;
-      RecursivePrintDeps(target, toolchain_label, &seen_targets, 1);
-    }
-    return;
+void ToolchainHandler(const std::string& name, const base::Value* value) {
+  std::string toolchain;
+  if (value->GetAsString(&toolchain)) {
+    OutputString("Toolchain: ", DECORATION_YELLOW);
+    OutputString(toolchain + "\n");
   }
+}
 
-  // Collect the deps to display.
-  if (cmdline->HasSwitch("all")) {
-    // Show all dependencies.
-    if (display_header)
-      OutputString("\nAll recursive dependencies\n");
-
-    std::set<const Target*> all_deps;
-    RecursiveCollectChildDeps(target, &all_deps);
-    FilterAndPrintTargetSet(display_header, all_deps);
-  } else {
-    std::vector<const Target*> deps;
-    // Show direct dependencies only.
-    if (display_header) {
-      OutputString(
-          "\nDirect dependencies "
-          "(try also \"--all\", \"--tree\", or even \"--all --tree\")\n");
+void VisibilityHandler(const std::string& name, const base::Value* value) {
+  const base::ListValue* list;
+  if (value->GetAsList(&list)) {
+    if (list->empty()) {
+      base::StringValue str("(no visibility)");
+      DefaultHandler(name, &str);
+    } else {
+      DefaultHandler(name, value);
     }
-    for (const auto& pair : target->GetDeps(Target::DEPS_ALL))
-      deps.push_back(pair.ptr);
-    std::sort(deps.begin(), deps.end());
-    FilterAndPrintTargets(display_header, &deps);
   }
 }
 
-// libs and lib_dirs are special in that they're inherited. We don't currently
-// implement a blame feature for this since the bottom-up inheritance makes
-// this difficult.
-void PrintLibDirs(const Target* target, bool display_header) {
-  const OrderedSet<SourceDir>& lib_dirs = target->all_lib_dirs();
-  if (lib_dirs.empty())
-    return;
-
-  if (display_header)
-    OutputString("\nlib_dirs\n");
-
-  for (size_t i = 0; i < lib_dirs.size(); i++)
-    OutputString("    " + FormatSourceDir(lib_dirs[i]) + "\n");
-}
-
-void PrintLibs(const Target* target, bool display_header) {
-  const OrderedSet<LibFile>& libs = target->all_libs();
-  if (libs.empty())
-    return;
-
-  if (display_header)
-    OutputString("\nlibs\n");
-
-  for (size_t i = 0; i < libs.size(); i++)
-    OutputString("    " + libs[i].value() + "\n");
-}
-
-void PrintPublic(const Target* target, bool display_header) {
-  if (display_header)
-    OutputString("\npublic\n");
-
-  if (target->all_headers_public()) {
-    OutputString("  [All headers listed in the sources are public.]\n");
-    return;
+void PublicHandler(const std::string& name, const base::Value* value) {
+  std::string p;
+  if (value->GetAsString(&p)) {
+    if (p == "*") {
+      base::StringValue str("[All headers listed in the sources are public.]");
+      DefaultHandler(name, &str);
+      return;
+    }
   }
-
-  Target::FileList public_headers = target->public_headers();
-  std::sort(public_headers.begin(), public_headers.end());
-  for (const auto& hdr : public_headers)
-    OutputString("  " + hdr.value() + "\n");
+  DefaultHandler(name, value);
 }
 
-void PrintCheckIncludes(const Target* target, bool display_header) {
-  if (display_header)
-    OutputString("\ncheck_includes\n");
-
-  if (target->check_includes())
-    OutputString("  true\n");
-  else
-    OutputString("  false\n");
-}
-
-void PrintAllowCircularIncludesFrom(const Target* target, bool display_header) {
-  if (display_header)
-    OutputString("\nallow_circular_includes_from\n");
-
-  Label toolchain_label = target->label().GetToolchainLabel();
-  for (const auto& cur : target->allow_circular_includes_from())
-    OutputString("  " + cur.GetUserVisibleName(toolchain_label) + "\n");
-}
-
-void PrintVisibility(const Target* target, bool display_header) {
-  if (display_header)
-    OutputString("\nvisibility\n");
-
-  OutputString(target->visibility().Describe(2, false));
-}
-
-void PrintTestonly(const Target* target, bool display_header) {
-  if (display_header)
-    OutputString("\ntestonly\n");
-
-  if (target->testonly())
-    OutputString("  true\n");
+void ConfigsHandler(const std::string& name, const base::Value* value) {
+  bool tree = base::CommandLine::ForCurrentProcess()->HasSwitch(kTree);
+  if (tree)
+    DefaultHandler(name + " tree (in order applying)", value);
   else
-    OutputString("  false\n");
-}
-
-// Recursively prints subconfigs of a config.
-void PrintSubConfigs(const Config* config, int indent_level) {
-  if (config->configs().empty())
-    return;
-
-  std::string indent(indent_level * 2, ' ');
-  Label toolchain_label = config->label().GetToolchainLabel();
-  for (const auto& pair : config->configs()) {
-    OutputString(
-        indent + pair.label.GetUserVisibleName(toolchain_label) + "\n");
-    PrintSubConfigs(pair.ptr, indent_level + 1);
-  }
+    DefaultHandler(name + " (in order applying, try also --tree)", value);
 }
 
-// This allows configs stored as either std::vector<LabelConfigPair> or
-// UniqueVector<LabelConfigPair> to be printed.
-template <class VectorType>
-void PrintConfigsVector(const Item* item,
-                        const VectorType& configs,
-                        const std::string& heading,
-                        bool display_header) {
-  if (configs.empty())
-    return;
-
+void DepsHandler(const std::string& name, const base::Value* value) {
   bool tree = base::CommandLine::ForCurrentProcess()->HasSwitch(kTree);
-
-  // Don't sort since the order determines how things are processed.
-  if (display_header) {
-    if (tree)
-      OutputString("\n" + heading + " tree (in order applying)\n");
-    else
-      OutputString("\n" + heading + " (in order applying, try also --tree)\n");
-  }
-
-  Label toolchain_label = item->label().GetToolchainLabel();
-  for (const auto& config : configs) {
-    OutputString("  " + config.label.GetUserVisibleName(toolchain_label) +
-                 "\n");
-    if (tree)
-      PrintSubConfigs(config.ptr, 2);  // 2 = start with double-indent.
-  }
-}
-
-void PrintConfigs(const Target* target, bool display_header) {
-  PrintConfigsVector(target, target->configs().vector(), "configs",
-                     display_header);
-}
-
-void PrintConfigs(const Config* config, bool display_header) {
-  PrintConfigsVector(config, config->configs().vector(), "configs",
-                     display_header);
-}
-
-void PrintPublicConfigs(const Target* target, bool display_header) {
-  PrintConfigsVector(target, target->public_configs(),
-                     "public_configs", display_header);
-}
-
-void PrintAllDependentConfigs(const Target* target, bool display_header) {
-  PrintConfigsVector(target, target->all_dependent_configs(),
-                     "all_dependent_configs", display_header);
-}
-
-void PrintFileList(const Target::FileList& files,
-                   const std::string& header,
-                   bool indent_extra,
-                   bool display_header) {
-  if (files.empty())
-    return;
-
-  if (display_header)
-    OutputString("\n" + header + "\n");
-
-  std::string indent = indent_extra ? "    " : "  ";
-
-  Target::FileList sorted = files;
-  std::sort(sorted.begin(), sorted.end());
-  for (const auto& elem : sorted)
-    OutputString(indent + elem.value() + "\n");
-}
-
-void PrintSources(const Target* target, bool display_header) {
-  PrintFileList(target->sources(), "sources", false, display_header);
-}
-
-void PrintInputs(const Target* target, bool display_header) {
-  PrintFileList(target->inputs(), "inputs", false, display_header);
-}
-
-void PrintOutputs(const Target* target, bool display_header) {
-  if (display_header)
-    OutputString("\noutputs\n");
-
-  if (target->output_type() == Target::ACTION) {
-    // Action, print out outputs, don't apply sources to it.
-    for (const auto& elem : target->action_values().outputs().list()) {
-      OutputString("  " + elem.AsString() + "\n");
-    }
-  } else if (target->output_type() == Target::CREATE_BUNDLE) {
-    std::vector<SourceFile> output_files;
-    target->bundle_data().GetOutputsAsSourceFiles(target->settings(),
-                                                  &output_files);
-    PrintFileList(output_files, std::string(), true, false);
+  bool all = base::CommandLine::ForCurrentProcess()->HasSwitch(kTree);
+  if (tree) {
+    DefaultHandler("Dependency tree", value);
   } else {
-    const SubstitutionList& outputs = target->action_values().outputs();
-    if (!outputs.required_types().empty()) {
-      // Display the pattern and resolved pattern separately, since there are
-      // subtitutions used.
-      OutputString("  Output pattern\n");
-      for (const auto& elem : outputs.list())
-        OutputString("    " + elem.AsString() + "\n");
-
-      // Now display what that resolves to given the sources.
-      OutputString("\n  Resolved output file list\n");
-    }
-
-    // Resolved output list.
-    std::vector<SourceFile> output_files;
-    SubstitutionWriter::ApplyListToSources(target->settings(), outputs,
-                                           target->sources(), &output_files);
-    PrintFileList(output_files, std::string(), true, false);
-  }
-}
-
-void PrintScript(const Target* target, bool display_header) {
-  if (display_header)
-    OutputString("\nscript\n");
-  OutputString("  " + target->action_values().script().value() + "\n");
-}
-
-void PrintArgs(const Target* target, bool display_header) {
-  if (display_header)
-    OutputString("\nargs\n");
-  for (const auto& elem : target->action_values().args().list()) {
-    OutputString("  " + elem.AsString() + "\n");
-  }
-}
-
-void PrintDepfile(const Target* target, bool display_header) {
-  if (target->action_values().depfile().empty())
-    return;
-  if (display_header)
-    OutputString("\ndepfile\n");
-  OutputString("  " + target->action_values().depfile().AsString() + "\n");
-}
-
-// Attribute the origin for attributing from where a target came from. Does
-// nothing if the input is null or it does not have a location.
-void OutputSourceOfDep(const ParseNode* origin, std::ostream& out) {
-  if (!origin)
-    return;
-  Location location = origin->GetRange().begin();
-  out << "       (Added by " + location.file()->name().value() << ":"
-      << location.line_number() << ")\n";
-}
-
-// Templatized writer for writing out different config value types.
-template<typename T> struct DescValueWriter {};
-template<> struct DescValueWriter<std::string> {
-  void operator()(const std::string& str, std::ostream& out) const {
-    out << "    " << str << "\n";
-  }
-};
-
-template<> struct DescValueWriter<SourceDir> {
-  void operator()(const SourceDir& dir, std::ostream& out) const {
-    out << "    " << FormatSourceDir(dir) << "\n";
-  }
-};
-
-template<> struct DescValueWriter<LibFile> {
-  void operator()(const LibFile& lib, std::ostream& out) const {
-    if (lib.is_source_file())
-      out << "    " << lib.source_file().value() << "\n";
-    else
-      out << "    " << lib.value() << "\n";
-  }
-};
-
-// Writes a given config value type to the string, optionally with attribution.
-// This should match RecursiveTargetConfigToStream in the order it traverses.
-template<typename T> void OutputRecursiveTargetConfig(
-    const Target* target,
-    const char* header_name,
-    const std::vector<T>& (ConfigValues::* getter)() const) {
-  bool display_blame =
-      base::CommandLine::ForCurrentProcess()->HasSwitch(kBlame);
-
-  DescValueWriter<T> writer;
-  std::ostringstream out;
-
-  for (ConfigValuesIterator iter(target); !iter.done(); iter.Next()) {
-    if ((iter.cur().*getter)().empty())
-      continue;
-
-    // Optional blame sub-head.
-    if (display_blame) {
-      const Config* config = iter.GetCurrentConfig();
-      if (config) {
-        // Source of this value is a config.
-        out << "  From " << config->label().GetUserVisibleName(false) << "\n";
-        OutputSourceOfDep(iter.origin(), out);
-      } else {
-        // Source of this value is the target itself.
-        out << "  From " << target->label().GetUserVisibleName(false) << "\n";
-      }
+    if (!all) {
+      DefaultHandler(
+          "Direct dependencies "
+          "(try also \"--all\", \"--tree\", or even \"--all --tree\")",
+          value);
+    } else {
+      DefaultHandler("All recursive dependencies", value);
     }
-
-    // Actual values.
-    ConfigValuesToStream(iter.cur(), getter, writer, out);
-  }
-
-  std::string out_str = out.str();
-  if (!out_str.empty()) {
-    if (header_name)
-      OutputString("\n" + std::string(header_name) + "\n");
-    OutputString(out_str);
   }
 }
 
-template<typename T> void OutputConfigValueArray(
-    const ConfigValues& values,
-    const char* header_name,
-    const std::vector<T>& (ConfigValues::* getter)() const) {
-  std::ostringstream out;
-
-  DescValueWriter<T> writer;
-  for (const T& cur : (values.*getter)())
-    writer(cur, out);
-
-  std::string out_str = out.str();
-  if (!out_str.empty()) {
-    if (header_name)
-      OutputString("\n" + std::string(header_name) + "\n");
-    OutputString(out_str);
-  }
-}
+// Outputs need special processing when output patterns are present
+void ProcessOutputs(base::DictionaryValue* target) {
+  base::ListValue* patterns = nullptr;
+  base::ListValue* outputs = nullptr;
+  target->GetList("output_patterns", &patterns);
+  target->GetList(variables::kOutputs, &outputs);
 
-void PrintRuntimeDeps(const Target* target) {
-  bool display_blame =
-      base::CommandLine::ForCurrentProcess()->HasSwitch(kBlame);
-  Label toolchain = target->label().GetToolchainLabel();
-
-  const Target* previous_from = NULL;
-  for (const auto& pair : ComputeRuntimeDeps(target)) {
-    if (display_blame) {
-      // Generally a target's runtime deps will be listed sequentially, so
-      // group them and don't duplicate the "from" label for two in a row.
-      if (previous_from == pair.second) {
-        OutputString("  ");  // Just indent.
-      } else {
-        previous_from = pair.second;
-        OutputString("From ");
-        OutputString(pair.second->label().GetUserVisibleName(toolchain));
-        OutputString("\n  ");  // Make the file name indented.
-      }
+  if (outputs || patterns) {
+    OutputString("\noutputs\n");
+    int indent = 1;
+    if (patterns) {
+      OutputString("  Output patterns\n");
+      indent = 2;
+      PrintValue(patterns, indent);
+      OutputString("\n  Resolved output file list\n");
     }
-    OutputString(pair.first.value());
-    OutputString("\n");
-  }
-}
+    if (outputs)
+      PrintValue(outputs, indent);
 
-// If "what" is empty, prints all PCH info. If "what" is nonempty, prints only
-// the things that match (if any). Returns true if anything was printed.
-bool PrintPrecompiledHeaderInfo(const ConfigValues& values,
-                                const std::string& what,
-                                bool display_headers) {
-  bool found_match = false;
-  if (what == variables::kPrecompiledHeader || what.empty()) {
-    if (!values.precompiled_header().empty()) {
-      if (display_headers)
-        OutputString("\nprecompiled_header\n");
-      OutputString(values.precompiled_header() + "\n");
-    }
-    found_match = true;
+    target->Remove("output_patterns", nullptr);
+    target->Remove(variables::kOutputs, nullptr);
   }
-  if (what == variables::kPrecompiledSource || what.empty()) {
-    if (!values.precompiled_source().is_null()) {
-      if (display_headers)
-        OutputString("\nprecompiled_source\n");
-      OutputString(values.precompiled_source().value() + "\n");
-    }
-    found_match = true;
-  }
-  return found_match;
 }
 
 bool PrintTarget(const Target* target,
                  const std::string& what,
-                 bool display_target_header) {
-  if (display_target_header) {
-    OutputString("Target: ", DECORATION_YELLOW);
-    OutputString(target->label().GetUserVisibleName(false) + "\n");
-    OutputString("Type: ", DECORATION_YELLOW);
-    OutputString(std::string(
-        Target::GetStringForOutputType(target->output_type())) + "\n");
-    OutputString("Toolchain: ", DECORATION_YELLOW);
-    OutputString(
-        target->label().GetToolchainLabel().GetUserVisibleName(false) + "\n");
-  }
-
-  // Display headers when outputting everything.
-  bool display_headers = what.empty();
-  bool is_binary_output = target->IsBinary();
-
-  bool found_match = false;
-
-  // General target meta variables.
-  if (what.empty() || what == variables::kVisibility) {
-    PrintVisibility(target, display_headers);
-    found_match = true;
-  }
-  if (what.empty() || what == variables::kTestonly) {
-    PrintTestonly(target, display_headers);
-    found_match  = true;
-  }
-
-  // Binary target meta variables.
-  if (is_binary_output) {
-    if (what.empty() || what == variables::kCheckIncludes) {
-      PrintCheckIncludes(target, display_headers);
-      found_match = true;
-    }
-    if (what.empty() || what == variables::kAllowCircularIncludesFrom) {
-      PrintAllowCircularIncludesFrom(target, display_headers);
-      found_match = true;
-    }
-  }
-
-  // Sources and inputs.
-  if (what.empty() || what == variables::kSources) {
-    PrintSources(target, display_headers);
-    found_match = true;
-  }
-  if (what.empty() || what == variables::kPublic) {
-    PrintPublic(target, display_headers);
-    found_match = true;
-  }
-  if (what.empty() || what == variables::kInputs) {
-    PrintInputs(target, display_headers);
-    found_match = true;
-  }
-
-  // Configs. Configs set directly on a target are only relevant for binary
-  // targets
-  if (is_binary_output && (what.empty() || what == variables::kConfigs)) {
-    PrintConfigs(target, display_headers);
-    found_match = true;
-  }
-
-  // Dependent/public configs can be applied to anything.
-  if (what.empty() || what == variables::kPublicConfigs) {
-    PrintPublicConfigs(target, display_headers);
-    found_match = true;
-  }
-  if (what.empty() || what == variables::kAllDependentConfigs) {
-    PrintAllDependentConfigs(target, display_headers);
-    found_match = true;
-  }
-
-  // Action values.
-  if (target->output_type() == Target::ACTION ||
-      target->output_type() == Target::ACTION_FOREACH) {
-    if (what.empty() || what == variables::kScript) {
-      PrintScript(target, display_headers);
-      found_match = true;
-    }
-    if (what.empty() || what == variables::kArgs) {
-      PrintArgs(target, display_headers);
-      found_match = true;
-    }
-    if (what.empty() || what == variables::kDepfile) {
-      PrintDepfile(target, display_headers);
-      found_match = true;
-    }
-  }
-
-  // Outputs.
-  if (target->output_type() == Target::ACTION ||
-      target->output_type() == Target::ACTION_FOREACH ||
-      target->output_type() == Target::COPY_FILES ||
-      target->output_type() == Target::CREATE_BUNDLE) {
-    if (what.empty() || what == variables::kOutputs) {
-      PrintOutputs(target, display_headers);
-      found_match = true;
-    }
-  }
-
-  // Values from configs only apply to binary targets.
-  if (is_binary_output) {
-    #define CONFIG_VALUE_ARRAY_HANDLER(name, type) \
-      if (what.empty() || what == #name) { \
-        OutputRecursiveTargetConfig<type>( \
-            target, display_headers ? #name : nullptr, &ConfigValues::name); \
-        found_match = true; \
-      }
-
-    CONFIG_VALUE_ARRAY_HANDLER(arflags, std::string)
-    CONFIG_VALUE_ARRAY_HANDLER(asmflags, std::string)
-    CONFIG_VALUE_ARRAY_HANDLER(cflags, std::string)
-    CONFIG_VALUE_ARRAY_HANDLER(cflags_c, std::string)
-    CONFIG_VALUE_ARRAY_HANDLER(cflags_cc, std::string)
-    CONFIG_VALUE_ARRAY_HANDLER(cflags_objc, std::string)
-    CONFIG_VALUE_ARRAY_HANDLER(cflags_objcc, std::string)
-    CONFIG_VALUE_ARRAY_HANDLER(defines, std::string)
-    CONFIG_VALUE_ARRAY_HANDLER(include_dirs, SourceDir)
-    CONFIG_VALUE_ARRAY_HANDLER(ldflags, std::string)
-    // Libs and lib_dirs are handled specially below.
-
-    #undef CONFIG_VALUE_ARRAY_HANDLER
-
-    found_match |= PrintPrecompiledHeaderInfo(target->config_values(),
-                                              what, display_headers);
-  }
-
-  // Deps
-  if (what.empty() || what == "deps") {
-    PrintDeps(target, display_headers);
-    found_match = true;
-  }
-
-  // Runtime deps are special, print only when explicitly asked for and not in
-  // overview mode.
-  if (what == "runtime_deps") {
-    PrintRuntimeDeps(target);
-    found_match = true;
-  }
-
-  // Libs can be part of any target and get recursively pushed up the chain,
-  // so display them regardless of target type.
-  if (what.empty() || what == variables::kLibs) {
-    PrintLibs(target, display_headers);
-    found_match = true;
-  }
-  if (what.empty() || what == variables::kLibDirs) {
-    PrintLibDirs(target, display_headers);
-    found_match = true;
-  }
-
-  if (!found_match) {
+                 bool single_target,
+                 bool all,
+                 bool tree,
+                 bool blame) {
+  std::unique_ptr<base::DictionaryValue> dict =
+      DescBuilder::DescriptionForTarget(target, what, all, tree, blame);
+  if (!what.empty() && dict->empty()) {
     OutputString("Don't know how to display \"" + what + "\" for \"" +
-        Target::GetStringForOutputType(target->output_type()) + "\".\n");
+                 Target::GetStringForOutputType(target->output_type()) +
+                 "\".\n");
     return false;
   }
+  // Print single value, without any headers
+  if (!what.empty() && dict->size() == 1 && single_target) {
+    base::DictionaryValue::Iterator iter(*dict);
+    PrintValue(&iter.value(), 0);
+    return true;
+  }
+
+  OutputString("Target ", DECORATION_YELLOW);
+  OutputString(target->label().GetUserVisibleName(false));
+  OutputString("\n");
+
+  std::unique_ptr<base::Value> v;
+#define HANDLER(property, handler_name) \
+  if (dict->Remove(property, &v)) {     \
+    handler_name(property, v.get());    \
+  }
+
+  // Entries with DefaultHandler are present to enforce order
+  HANDLER("type", TypeHandler);
+  HANDLER("toolchain", ToolchainHandler);
+  HANDLER(variables::kVisibility, VisibilityHandler);
+  HANDLER(variables::kTestonly, DefaultHandler);
+  HANDLER(variables::kCheckIncludes, DefaultHandler);
+  HANDLER(variables::kAllowCircularIncludesFrom, DefaultHandler);
+  HANDLER(variables::kSources, DefaultHandler);
+  HANDLER(variables::kPublic, PublicHandler);
+  HANDLER(variables::kInputs, DefaultHandler);
+  HANDLER(variables::kConfigs, ConfigsHandler);
+  HANDLER(variables::kPublicConfigs, ConfigsHandler);
+  HANDLER(variables::kAllDependentConfigs, ConfigsHandler);
+  HANDLER(variables::kScript, DefaultHandler);
+  HANDLER(variables::kArgs, DefaultHandler);
+  HANDLER(variables::kDepfile, DefaultHandler);
+  ProcessOutputs(dict.get());
+  HANDLER("bundle_data", DefaultHandler);
+  HANDLER(variables::kArflags, DefaultHandler);
+  HANDLER(variables::kAsmflags, DefaultHandler);
+  HANDLER(variables::kCflags, DefaultHandler);
+  HANDLER(variables::kCflagsC, DefaultHandler);
+  HANDLER(variables::kCflagsCC, DefaultHandler);
+  HANDLER(variables::kCflagsObjC, DefaultHandler);
+  HANDLER(variables::kCflagsObjCC, DefaultHandler);
+  HANDLER(variables::kDefines, DefaultHandler);
+  HANDLER(variables::kIncludeDirs, DefaultHandler);
+  HANDLER(variables::kLdflags, DefaultHandler);
+  HANDLER(variables::kPrecompiledHeader, DefaultHandler);
+  HANDLER(variables::kPrecompiledSource, DefaultHandler);
+  HANDLER(variables::kDeps, DepsHandler);
+  HANDLER(variables::kLibs, DefaultHandler);
+  HANDLER(variables::kLibDirs, DefaultHandler);
+
+#undef HANDLER
+
+  // Process the rest (if any)
+  base::DictionaryValue::Iterator iter(*dict);
+  while (!iter.IsAtEnd()) {
+    DefaultHandler(iter.key(), &iter.value());
+    iter.Advance();
+  }
+
   return true;
 }
 
 bool PrintConfig(const Config* config,
                  const std::string& what,
-                 bool display_config_header) {
-  const ConfigValues& values = config->resolved_values();
-
-  if (display_config_header) {
-    OutputString("Config: ", DECORATION_YELLOW);
-    OutputString(config->label().GetUserVisibleName(false) + "\n");
-    OutputString("Toolchain: ", DECORATION_YELLOW);
-    OutputString(
-        config->label().GetToolchainLabel().GetUserVisibleName(false) + "\n");
-    if (what.empty() && !config->configs().empty()) {
-      OutputString(
-          "(This is a composite config, the values below are after the\n"
-          "expansion of the child configs.)\n");
-    }
+                 bool single_config) {
+  std::unique_ptr<base::DictionaryValue> dict =
+      DescBuilder::DescriptionForConfig(config, what);
+  if (!what.empty() && dict->empty()) {
+    OutputString("Don't know how to display \"" + what + "\" for a config.\n");
+    return false;
   }
-
-  // Display headers when outputting everything.
-  bool display_headers = what.empty();
-
-  if (what.empty() || what == variables::kConfigs)
-    PrintConfigs(config, display_headers);
-
-#define CONFIG_VALUE_ARRAY_HANDLER(name, type) \
-  if (what.empty() || what == #name) { \
-    OutputConfigValueArray<type>(values, display_headers ? #name : nullptr, \
-                                 &ConfigValues::name); \
-    found_match = true; \
+  // Print single value, without any headers
+  if (!what.empty() && dict->size() == 1 && single_config) {
+    base::DictionaryValue::Iterator iter(*dict);
+    PrintValue(&iter.value(), 0);
+    return true;
   }
 
-  bool found_match = false;
-
-  CONFIG_VALUE_ARRAY_HANDLER(arflags, std::string)
-  CONFIG_VALUE_ARRAY_HANDLER(asmflags, std::string)
-  CONFIG_VALUE_ARRAY_HANDLER(cflags, std::string)
-  CONFIG_VALUE_ARRAY_HANDLER(cflags_c, std::string)
-  CONFIG_VALUE_ARRAY_HANDLER(cflags_cc, std::string)
-  CONFIG_VALUE_ARRAY_HANDLER(cflags_objc, std::string)
-  CONFIG_VALUE_ARRAY_HANDLER(cflags_objcc, std::string)
-  CONFIG_VALUE_ARRAY_HANDLER(defines, std::string)
-  CONFIG_VALUE_ARRAY_HANDLER(include_dirs, SourceDir)
-  CONFIG_VALUE_ARRAY_HANDLER(ldflags, std::string)
-  CONFIG_VALUE_ARRAY_HANDLER(lib_dirs, SourceDir)
-  CONFIG_VALUE_ARRAY_HANDLER(libs, LibFile)
+  OutputString("Config: ", DECORATION_YELLOW);
+  OutputString(config->label().GetUserVisibleName(false));
+  OutputString("\n");
 
-#undef CONFIG_VALUE_ARRAY_HANDLER
+  std::unique_ptr<base::Value> v;
+#define HANDLER(property, handler_name) \
+  if (dict->Remove(property, &v)) {     \
+    handler_name(property, v.get());    \
+  }
 
-  // Handles all PCH-related variables.
-  found_match |= PrintPrecompiledHeaderInfo(config->resolved_values(),
-                                            what, display_headers);
+  HANDLER("toolchain", ToolchainHandler);
+  if (!config->configs().empty()) {
+    OutputString(
+        "(This is a composite config, the values below are after the\n"
+        "expansion of the child configs.)\n");
+  }
+  HANDLER(variables::kArflags, DefaultHandler);
+  HANDLER(variables::kAsmflags, DefaultHandler);
+  HANDLER(variables::kCflags, DefaultHandler);
+  HANDLER(variables::kCflagsC, DefaultHandler);
+  HANDLER(variables::kCflagsCC, DefaultHandler);
+  HANDLER(variables::kCflagsObjC, DefaultHandler);
+  HANDLER(variables::kCflagsObjCC, DefaultHandler);
+  HANDLER(variables::kDefines, DefaultHandler);
+  HANDLER(variables::kIncludeDirs, DefaultHandler);
+  HANDLER(variables::kLdflags, DefaultHandler);
+  HANDLER(variables::kLibs, DefaultHandler);
+  HANDLER(variables::kLibDirs, DefaultHandler);
+  HANDLER(variables::kPrecompiledHeader, DefaultHandler);
+  HANDLER(variables::kPrecompiledSource, DefaultHandler);
+
+#undef HANDLER
 
-  if (!found_match) {
-    OutputString("Don't know how to display \"" + what + "\" for a config.\n");
-    return false;
-  }
   return true;
 }
 
@@ -749,7 +298,8 @@ const char kDesc[] = "desc";
 const char kDesc_HelpShort[] =
     "desc: Show lots of insightful information about a target or config.";
 const char kDesc_Help[] =
-    "gn desc <out_dir> <label or pattern> [<what to show>] [--blame]\n"
+    "gn desc <out_dir> <label or pattern> [<what to show>] [--blame] "
+    "[--format=json]\n"
     "\n"
     "  Displays information about a given target or config. The build\n"
     "  build parameters will be taken for the build in the given <out_dir>.\n"
@@ -819,7 +369,7 @@ const char kDesc_Help[] =
     "\n"
     "  Configs can have child configs. Specifying --tree will show the\n"
     "  hierarchy.\n"
-    "\n"
+    "\n"    
     "Printing deps\n"
     "\n"
     "  Deps will include all public, private, and data deps (TODO this could\n"
@@ -847,6 +397,10 @@ const char kDesc_Help[] =
     "\n"
     TARGET_TYPE_FILTER_COMMAND_LINE_HELP
     "\n"
+    "Format\n"
+    "\n"
+    "  Optional --format=json flag can be specified to switch output to JSON.\n"
+    "\n"
     "Note\n"
     "\n"
     "  This command will show the full name of directories and source files,\n"
@@ -903,28 +457,52 @@ int RunDesc(const std::vector<std::string>& args) {
   if (args.size() == 3)
     what_to_print = args[2];
 
-  bool multiple_outputs = (target_matches.size() + config_matches.size()) > 1;
-
-  // Display headers for each target when printing all values, or when printing
-  // multiple targets or configs.
-  bool display_item_header = multiple_outputs || what_to_print.empty();
-
-  bool printed_output = false;
-  for (const Target* target : target_matches) {
-    if (printed_output)
-      OutputString("\n\n");
-    printed_output = true;
-
-    if (!PrintTarget(target, what_to_print, display_item_header))
-      return 1;
-  }
-  for (const Config* config : config_matches) {
-    if (printed_output)
-      OutputString("\n\n");
-    printed_output = true;
+  bool json = cmdline->GetSwitchValueASCII("format") == "json";
+
+  if (json) {
+    // Convert all targets/configs to JSON, serialize and print them
+    auto res = base::WrapUnique(new base::DictionaryValue());
+    if (!target_matches.empty()) {
+      for (const auto* target : target_matches) {
+        res->Set(target->label().GetUserVisibleName(
+                     target->settings()->default_toolchain_label()),
+                 DescBuilder::DescriptionForTarget(
+                     target, what_to_print, cmdline->HasSwitch(kAll),
+                     cmdline->HasSwitch(kTree), cmdline->HasSwitch(kBlame)));
+      }
+    } else if (!config_matches.empty()) {
+      for (const auto* config : config_matches) {
+        res->Set(config->label().GetUserVisibleName(false),
+                 DescBuilder::DescriptionForConfig(config, what_to_print));
+      }
+    }
+    std::string s;
+    base::JSONWriter::WriteWithOptions(
+        *res.get(), base::JSONWriter::OPTIONS_PRETTY_PRINT, &s);
+    OutputString(s);
+  } else {
+    // Regular (non-json) formatted output
+    bool multiple_outputs = (target_matches.size() + config_matches.size()) > 1;
+
+    bool printed_output = false;
+    for (const Target* target : target_matches) {
+      if (printed_output)
+        OutputString("\n\n");
+      printed_output = true;
+
+      if (!PrintTarget(target, what_to_print, !multiple_outputs,
+                       cmdline->HasSwitch(kAll), cmdline->HasSwitch(kTree),
+                       cmdline->HasSwitch(kBlame)))
+        return 1;
+    }
+    for (const Config* config : config_matches) {
+      if (printed_output)
+        OutputString("\n\n");
+      printed_output = true;
 
-    if (!PrintConfig(config, what_to_print, display_item_header))
-      return 1;
+      if (!PrintConfig(config, what_to_print, !multiple_outputs))
+        return 1;
+    }
   }
 
   return 0;