[GN] Add JSON project writer

Output is a JSON file containing information about targets. The generator
can also optionally invoke a python script on generated file.

Example:
gn gen --ide=json ./out-json --json-ide-script=//scripts/custom-ide-generator.py \
    --ison-ide-script-args="additional script arguments"

Also implements --format=json for gn desc as described in https://bugs.chromium.org/p/chromium/issues/detail?id=620132

BUG=

Review-Url: https://codereview.chromium.org/2064533002
Cr-Commit-Position: refs/heads/master@{#406064}

AUTHORS

@@ -409,6 +409,7 @@ Martin Bednorz <m.s.bednorz@gmail.com>
 Martina Kollarova <martina.kollarova@intel.com>
 Masahiro Yado <yado.masa@gmail.com>
 Masaru Nishida <msr.i386@gmail.com>
+Matej Knopp <matej.knopp@gmail.com>
 Matheus Bratfisch <matheusbrat@gmail.com>
 Mathias Bynens <mathias@qiwi.be>
 Mathieu Meisser <mmeisser@logitech.com>

tools/gn/BUILD.gn

@@ -58,6 +58,8 @@ static_library("gn_lib") {
     "create_bundle_target_generator.h",
     "deps_iterator.cc",
     "deps_iterator.h",
+    "desc_builder.cc",
+    "desc_builder.h",
     "eclipse_writer.cc",
     "eclipse_writer.h",
     "err.cc",
@@ -101,6 +103,8 @@ static_library("gn_lib") {
     "input_file_manager.h",
     "item.cc",
     "item.h",
+    "json_project_writer.cc",
+    "json_project_writer.h",
     "label.cc",
     "label.h",
     "label_pattern.cc",

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 kSwitchJsonFileName[] = "json-file-name";
+const char kSwitchJsonIdeScript[] = "json-ide-script";
+const char kSwitchJsonIdeScriptArgs[] = "json-ide-script-args";
 
 // Called on worker thread to write the ninja file.
 void BackgroundDoWrite(const Target* target) {
@@ -166,11 +171,12 @@ bool RunIdeWriter(const std::string& ide,
                   Err* err) {
   const base::CommandLine* command_line =
       base::CommandLine::ForCurrentProcess();
+  bool quiet = command_line->HasSwitch(switches::kQuiet);
   base::ElapsedTimer timer;
 
   if (ide == kSwitchIdeValueEclipse) {
     bool res = EclipseWriter::RunAndWriteFile(build_settings, builder, err);
-    if (res && !command_line->HasSwitch(switches::kQuiet)) {
+    if (res && !quiet) {
       OutputString("Generating Eclipse settings took " +
                    base::Int64ToString(timer.Elapsed().InMilliseconds()) +
                    "ms\n");
@@ -189,7 +195,7 @@ bool RunIdeWriter(const std::string& ide,
       filters = command_line->GetSwitchValueASCII(kSwitchFilters);
     bool res = VisualStudioWriter::RunAndWriteFiles(
         build_settings, builder, version, sln_name, filters, err);
-    if (res && !command_line->HasSwitch(switches::kQuiet)) {
+    if (res && !quiet) {
       OutputString("Generating Visual Studio projects took " +
                    base::Int64ToString(timer.Elapsed().InMilliseconds()) +
                    "ms\n");
@@ -202,7 +208,7 @@ bool RunIdeWriter(const std::string& ide,
         command_line->GetSwitchValueASCII(kSwitchNinjaExtraArgs),
         command_line->GetSwitchValueASCII(kSwitchFilters), build_settings,
         builder, err);
-    if (res && !command_line->HasSwitch(switches::kQuiet)) {
+    if (res && !quiet) {
       OutputString("Generating Xcode projects took " +
                    base::Int64ToString(timer.Elapsed().InMilliseconds()) +
                    "ms\n");
@@ -214,12 +220,32 @@ bool RunIdeWriter(const std::string& ide,
       root_target = command_line->GetSwitchValueASCII(kSwitchRootTarget);
     bool res = QtCreatorWriter::RunAndWriteFile(build_settings, builder, err,
                                                 root_target);
-    if (res && !command_line->HasSwitch(switches::kQuiet)) {
+    if (res && !quiet) {
       OutputString("Generating QtCreator projects took " +
                    base::Int64ToString(timer.Elapsed().InMilliseconds()) +
                    "ms\n");
     }
     return res;
+  } else if (ide == kSwitchIdeValueJson) {
+    std::string file_name =
+        command_line->GetSwitchValueASCII(kSwitchJsonFileName);
+    if (file_name.empty())
+      file_name = "project.json";
+    std::string exec_script =
+        command_line->GetSwitchValueASCII(kSwitchJsonIdeScript);
+    std::string exec_script_extra_args =
+        command_line->GetSwitchValueASCII(kSwitchJsonIdeScriptArgs);
+    std::string filters = command_line->GetSwitchValueASCII(kSwitchFilters);
+
+    bool res = JSONProjectWriter::RunAndWriteFiles(
+        build_settings, builder, file_name, exec_script, exec_script_extra_args,
+        filters, 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 +255,7 @@ 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"
@@ -259,12 +284,13 @@ 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"
     "      of generated projects (see \"gn help label_pattern\"). Only\n"
     "      matching targets and their dependencies will be included in the\n"
-    "      solution. Only used for Visual Studio and Xcode.\n"
+    "      solution. Only used for Visual Studio, Xcode and JSON.\n"
     "\n"
     "Visual Studio Flags\n"
     "\n"
@@ -305,7 +331,27 @@ 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 python\n"
+    "  script on generated file. \n"
+    "  See comments at the beginning of json_project_writer.cc and\n"
+    "  desc_builder.cc for overview of JSON file format.\n"
+    "\n"
+    "  --json-file-name=<json_file_name>\n"
+    "      Overrides default file name (project.json) of generated JSON file.\n"
+    "\n"
+    "  --json-ide-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"
+    "  --json-ide-script-args=<argument>\n"
+    "      Optional second argument that will passed to executed script.\n";
 
 int RunGen(const std::vector<std::string>& args) {
   base::ElapsedTimer timer;

tools/gn/commands.cc

@@ -6,6 +6,7 @@
 
 #include "base/command_line.h"
 #include "base/strings/string_split.h"
+#include "base/values.h"
 #include "tools/gn/builder.h"
 #include "tools/gn/filesystem_utils.h"
 #include "tools/gn/item.h"
@@ -280,22 +281,20 @@ base::FilePath BuildFileForItem(const Item* item) {
   return item->defined_from()->GetRange().begin().file()->physical_name();
 }
 
-void PrintTargetsAsBuildfiles(bool indent,
-                              const std::vector<const Target*>& targets) {
+void PrintTargetsAsBuildfiles(const std::vector<const Target*>& targets,
+                              base::ListValue* out) {
   // Output the set of unique source files.
   std::set<std::string> unique_files;
   for (const Target* target : targets)
     unique_files.insert(FilePathToUTF8(BuildFileForItem(target)));
 
   for (const std::string& file : unique_files) {
-    if (indent)
-      OutputString("  ");
-    OutputString(file + "\n");
+    out->AppendString(file);
   }
 }
 
-void PrintTargetsAsLabels(bool indent,
-                          const std::vector<const Target*>& targets) {
+void PrintTargetsAsLabels(const std::vector<const Target*>& targets,
+                          base::ListValue* out) {
   // Putting the labels into a set automatically sorts them for us.
   std::set<Label> unique_labels;
   for (auto* target : targets)
@@ -307,16 +306,13 @@ void PrintTargetsAsLabels(bool indent,
 
   for (const Label& label : unique_labels) {
     // Print toolchain only for ones not in the default toolchain.
-    if (indent)
-      OutputString("  ");
-    OutputString(label.GetUserVisibleName(
-        label.GetToolchainLabel() != default_tc_label));
-    OutputString("\n");
+    out->AppendString(label.GetUserVisibleName(label.GetToolchainLabel() !=
+                                               default_tc_label));
   }
 }
 
-void PrintTargetsAsOutputs(bool indent,
-                           const std::vector<const Target*>& targets) {
+void PrintTargetsAsOutputs(const std::vector<const Target*>& targets,
+                           base::ListValue* out) {
   if (targets.empty())
     return;
 
@@ -336,10 +332,7 @@ void PrintTargetsAsOutputs(bool indent,
     std::string result = RebasePath(output_as_source.value(),
                                     build_settings->build_dir(),
                                     build_settings->root_path_utf8());
-    if (indent)
-      OutputString("  ");
-    OutputString(result);
-    OutputString("\n");
+    out->AppendString(result);
   }
 }
 
@@ -490,7 +483,8 @@ bool FilterPatternsFromString(const BuildSettings* build_settings,
   return true;
 }
 
-void FilterAndPrintTargets(bool indent, std::vector<const Target*>* targets) {
+void FilterAndPrintTargets(std::vector<const Target*>* targets,
+                           base::ListValue* out) {
   if (targets->empty())
     return;
 
@@ -504,21 +498,40 @@ void FilterAndPrintTargets(bool indent, std::vector<const Target*>* targets) {
     return;
   switch (printing_mode) {
     case TARGET_PRINT_BUILDFILE:
-      PrintTargetsAsBuildfiles(indent, *targets);
+      PrintTargetsAsBuildfiles(*targets, out);
       break;
     case TARGET_PRINT_LABEL:
-      PrintTargetsAsLabels(indent, *targets);
+      PrintTargetsAsLabels(*targets, out);
       break;
     case TARGET_PRINT_OUTPUT:
-      PrintTargetsAsOutputs(indent, *targets);
+      PrintTargetsAsOutputs(*targets, out);
       break;
   }
 }
 
+void FilterAndPrintTargets(bool indent, std::vector<const Target*>* targets) {
+  base::ListValue tmp;
+  FilterAndPrintTargets(targets, &tmp);
+  for (const auto& value : tmp) {
+    std::string string;
+    value->GetAsString(&string);
+    if (indent)
+      OutputString("  ");
+    OutputString(string);
+    OutputString("\n");
+  }
+}
+
 void FilterAndPrintTargetSet(bool indent,
                              const std::set<const Target*>& targets) {
   std::vector<const Target*> target_vector(targets.begin(), targets.end());
   FilterAndPrintTargets(indent, &target_vector);
 }
 
+void FilterAndPrintTargetSet(const std::set<const Target*>& targets,
+                             base::ListValue* out) {
+  std::vector<const Target*> target_vector(targets.begin(), targets.end());
+  FilterAndPrintTargets(&target_vector, out);
+}
+
 }  // namespace commands

tools/gn/commands.h

@@ -11,6 +11,7 @@
 #include <vector>
 
 #include "base/strings/string_piece.h"
+#include "base/values.h"
 #include "tools/gn/target.h"
 #include "tools/gn/unique_vector.h"
 
@@ -179,8 +180,13 @@ bool FilterPatternsFromString(const BuildSettings* build_settings,
 //
 // The vector will be modified so that only the printed targets will remain.
 void FilterAndPrintTargets(bool indent, std::vector<const Target*>* targets);
+void FilterAndPrintTargets(std::vector<const Target*>* targets,
+                           base::ListValue* out);
+
 void FilterAndPrintTargetSet(bool indent,
                              const std::set<const Target*>& targets);
+void FilterAndPrintTargetSet(const std::set<const Target*>& targets,
+                             base::ListValue* out);
 
 // Extra help from command_check.cc
 extern const char kNoGnCheck_Help[];

tools/gn/desc_builder.h

+// Copyright (c) 2016 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.
+
+#ifndef TOOLS_GN_DESC_BUILDER_H_
+#define TOOLS_GN_DESC_BUILDER_H_
+
+#include "base/values.h"
+#include "tools/gn/target.h"
+
+class DescBuilder {
+ public:
+  // Creates Dictionary representation for given target
+  static std::unique_ptr<base::DictionaryValue> DescriptionForTarget(
+      const Target* target,
+      const std::string& what,
+      bool all,
+      bool tree,
+      bool blame);
+
+  // Creates Dictionary representation for given config
+  static std::unique_ptr<base::DictionaryValue> DescriptionForConfig(
+      const Config* config,
+      const std::string& what);
+};
+
+#endif

tools/gn/json_project_writer.cc

+// Copyright (c) 2016 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/json_project_writer.h"
+
+#include <iostream>
+
+#include "base/command_line.h"
+#include "base/json/json_writer.h"
+#include "base/memory/ptr_util.h"
+#include "base/strings/string_number_conversions.h"
+#include "tools/gn/builder.h"
+#include "tools/gn/commands.h"
+#include "tools/gn/deps_iterator.h"
+#include "tools/gn/desc_builder.h"
+#include "tools/gn/exec_process.h"
+#include "tools/gn/filesystem_utils.h"
+#include "tools/gn/settings.h"
+
+// Structure of JSON output file
+// {
+//   "build_settings" = {
+//     "root_path" : "absolute path of project root",
+//     "build_dir" : "build directory (project relative)",
+//     "default_toolchain" : "name of default toolchain"
+//   }
+//   "targets" = {
+//      "target x name" : { target x properties },
+//      "target y name" : { target y properties },
+//      ...
+//    }
+// }
+// See desc_builder.cc for overview of target properties
+
+namespace {
+
+void AddTargetDependencies(const Target* target,
+                           std::set<const Target*>* deps) {
+  for (const auto& pair : target->GetDeps(Target::DEPS_LINKED)) {
+    if (deps->find(pair.ptr) == deps->end()) {
+      deps->insert(pair.ptr);
+      AddTargetDependencies(pair.ptr, deps);
+    }
+  }
+}
+
+// Filters targets according to filter string; Will also recursively
+// add dependent targets.
+bool FilterTargets(const BuildSettings* build_settings,
+                   std::vector<const Target*>& all_targets,
+                   std::vector<const Target*>* targets,
+                   const std::string& dir_filter_string,
+                   Err* err) {
+  if (dir_filter_string.empty()) {
+    *targets = all_targets;
+  } else {
+    targets->reserve(all_targets.size());
+    std::vector<LabelPattern> filters;
+    if (!commands::FilterPatternsFromString(build_settings, dir_filter_string,
+                                            &filters, err)) {
+      return false;
+    }
+    commands::FilterTargetsByPatterns(all_targets, filters, targets);
+
+    std::set<const Target*> target_set(targets->begin(), targets->end());
+    for (const auto* target : *targets)
+      AddTargetDependencies(target, &target_set);
+
+    targets->clear();
+    targets->insert(targets->end(), target_set.begin(), target_set.end());
+  }
+
+  // Sort the list of targets per-label to get a consistent ordering of them
+  // in the generated project (and thus stability of the file generated).
+  std::sort(targets->begin(), targets->end(),
+            [](const Target* a, const Target* b) {
+              return a->label().name() < b->label().name();
+            });
+
+  return true;
+}
+
+std::string RenderJSON(const BuildSettings* build_settings,
+                       const Builder* builder,
+                       std::vector<const Target*>& all_targets) {
+  Label default_toolchain_label;
+
+  auto targets = base::WrapUnique(new base::DictionaryValue());
+  for (const auto* target : all_targets) {
+    if (default_toolchain_label.is_null())
+      default_toolchain_label = target->settings()->default_toolchain_label();
+    auto description =
+        DescBuilder::DescriptionForTarget(target, "", false, false, false);
+    // Outputs need to be asked for separately.
+    auto outputs = DescBuilder::DescriptionForTarget(target, "source_outputs",
+                                                     false, false, false);
+    base::DictionaryValue* outputs_value = nullptr;
+    if (outputs->GetDictionary("source_outputs", &outputs_value) &&
+        !outputs_value->empty()) {
+      description->MergeDictionary(outputs.get());
+    }
+    targets->Set(target->label().GetUserVisibleName(default_toolchain_label),
+                 std::move(description));
+  }
+
+  auto settings = base::WrapUnique(new base::DictionaryValue());
+  settings->SetString("root_path", build_settings->root_path_utf8());
+  settings->SetString("build_dir", build_settings->build_dir().value());
+  settings->SetString("default_toolchain",
+                      default_toolchain_label.GetUserVisibleName(false));
+
+  auto output = base::WrapUnique(new base::DictionaryValue());
+  output->Set("targets", std::move(targets));
+  output->Set("build_settings", std::move(settings));
+
+  std::string s;
+  base::JSONWriter::WriteWithOptions(
+      *output.get(), base::JSONWriter::OPTIONS_PRETTY_PRINT, &s);
+  return s;
+}
+
+bool InvokePython(const BuildSettings* build_settings,
+                  const base::FilePath& python_script_path,
+                  const std::string& python_script_extra_args,
+                  const base::FilePath& output_path,
+                  bool quiet,
+                  Err* err) {
+  const base::FilePath& python_path = build_settings->python_path();
+  base::CommandLine cmdline(python_path);
+  cmdline.AppendArg("--");
+  cmdline.AppendArgPath(python_script_path);
+  cmdline.AppendArgPath(output_path);
+  if (!python_script_extra_args.empty()) {
+    cmdline.AppendArg(python_script_extra_args);
+  }
+  base::FilePath startup_dir =
+      build_settings->GetFullPath(build_settings->build_dir());
+
+  std::string output;
+  std::string stderr_output;
+
+  int exit_code = 0;
+  if (!internal::ExecProcess(cmdline, startup_dir, &output, &stderr_output,
+                             &exit_code)) {
+    *err =
+        Err(Location(), "Could not execute python.",
+            "I was trying to execute \"" + FilePathToUTF8(python_path) + "\".");
+    return false;
+  }
+
+  if (!quiet) {
+    std::cout << output;
+    std::cerr << stderr_output;
+  }
+
+  if (exit_code != 0) {
+    *err = Err(Location(), "Python has quit with exit code " +
+                               base::IntToString(exit_code) + ".");
+    return false;
+  }
+
+  return true;
+}
+
+}  // namespace
+
+bool JSONProjectWriter::RunAndWriteFiles(
+    const BuildSettings* build_settings,
+    const Builder* builder,
+    const std::string& file_name,
+    const std::string& exec_script,
+    const std::string& exec_script_extra_args,
+    const std::string& dir_filter_string,
+    bool quiet,
+    Err* err) {
+  SourceFile output_file = build_settings->build_dir().ResolveRelativeFile(
+      Value(nullptr, file_name), err);
+  if (output_file.is_null()) {
+    return false;
+  }
+
+  base::FilePath output_path = build_settings->GetFullPath(output_file);
+
+  std::vector<const Target*> all_targets = builder->GetAllResolvedTargets();
+  std::vector<const Target*> targets;
+  if (!FilterTargets(build_settings, all_targets, &targets, dir_filter_string,
+                     err)) {
+    return false;
+  }
+
+  std::string json = RenderJSON(build_settings, builder, targets);
+  if (!ContentsEqual(output_path, json)) {
+    if (!WriteFileIfChanged(output_path, json, err)) {
+      return false;
+    }
+
+    if (!exec_script.empty()) {
+      SourceFile script_file;
+      if (exec_script[0] != '/') {
+        // Relative path, assume the base is in build_dir.
+        script_file = build_settings->build_dir().ResolveRelativeFile(
+            Value(nullptr, exec_script), err);
+        if (script_file.is_null()) {
+          return false;
+        }
+      } else {
+        script_file = SourceFile(exec_script);
+      }
+      base::FilePath script_path = build_settings->GetFullPath(script_file);
+      return InvokePython(build_settings, script_path, exec_script_extra_args,
+                          output_path, quiet, err);
+    }
+  }
+
+  return true;
+}

tools/gn/json_project_writer.h

+// Copyright (c) 2016 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.
+
+#ifndef TOOLS_GN_JSON_WRITER_H_
+#define TOOLS_GN_JSON_WRITER_H_
+
+#include "tools/gn/err.h"
+#include "tools/gn/target.h"
+
+class Builder;
+class BuildSettings;
+
+class JSONProjectWriter {
+ public:
+  static bool RunAndWriteFiles(const BuildSettings* build_setting,
+                               const Builder* builder,
+                               const std::string& file_name,
+                               const std::string& exec_script,
+                               const std::string& exec_script_extra_args,
+                               const std::string& dir_filter_string,
+                               bool quiet,
+                               Err* err);
+};
+
+#endif

tools/gn/target.cc

@@ -14,6 +14,7 @@
 #include "tools/gn/config_values_extractors.h"
 #include "tools/gn/deps_iterator.h"
 #include "tools/gn/filesystem_utils.h"
+#include "tools/gn/functions.h"
 #include "tools/gn/scheduler.h"
 #include "tools/gn/source_file_type.h"
 #include "tools/gn/substitution_writer.h"
@@ -215,29 +216,29 @@ Target::~Target() {
 const char* Target::GetStringForOutputType(OutputType type) {
   switch (type) {
     case UNKNOWN:
-      return "Unknown";
+      return "unknown";
     case GROUP:
-      return "Group";
+      return functions::kGroup;
     case EXECUTABLE:
-      return "Executable";
+      return functions::kExecutable;
     case LOADABLE_MODULE:
-      return "Loadable module";
+      return functions::kLoadableModule;
     case SHARED_LIBRARY:
-      return "Shared library";
+      return functions::kSharedLibrary;
     case STATIC_LIBRARY:
-      return "Static library";
+      return functions::kStaticLibrary;
     case SOURCE_SET:
-      return "Source set";
+      return functions::kSourceSet;
     case COPY_FILES:
-      return "Copy";
+      return functions::kCopy;
     case ACTION:
-      return "Action";
+      return functions::kAction;
     case ACTION_FOREACH:
-      return "ActionForEach";
+      return functions::kActionForEach;
     case BUNDLE_DATA:
-      return "Bundle data";
+      return functions::kBundleData;
     case CREATE_BUNDLE:
-      return "Create bundle";
+      return functions::kCreateBundle;
     default:
       return "";
   }

tools/gn/visibility.cc

@@ -4,8 +4,10 @@
 
 #include "tools/gn/visibility.h"
 
+#include "base/memory/ptr_util.h"
 #include "base/strings/string_piece.h"
 #include "base/strings/string_util.h"
+#include "base/values.h"
 #include "tools/gn/err.h"
 #include "tools/gn/filesystem_utils.h"
 #include "tools/gn/item.h"
@@ -83,6 +85,14 @@ std::string Visibility::Describe(int indent, bool include_brackets) const {
   return result;
 }
 
+std::unique_ptr<base::Value> Visibility::AsValue() const {
+  auto* res = new base::ListValue();
+  for (const auto& pattern : patterns_)
+    res->AppendString(pattern.Describe());
+
+  return WrapUnique(res);
+}
+
 // static
 bool Visibility::CheckItemVisibility(const Item* from,
                                      const Item* to,

tools/gn/visibility.h

@@ -5,12 +5,17 @@
 #ifndef TOOLS_GN_VISIBILITY_H_
 #define TOOLS_GN_VISIBILITY_H_
 
+#include <memory>
 #include <vector>
 
 #include "base/macros.h"
 #include "tools/gn/label_pattern.h"
 #include "tools/gn/source_dir.h"
 
+namespace base {
+class Value;
+}
+
 class Err;
 class Item;
 class Label;
@@ -43,6 +48,9 @@ class Visibility {
   // result will end in a newline.
   std::string Describe(int indent, bool include_brackets) const;
 
+  // Returns value representation of this visibility
+  std::unique_ptr<base::Value> AsValue() const;
+
   // Helper function to check visibility between the given two items. If
   // to is invisible to from, returns false and sets the error.
   static bool CheckItemVisibility(const Item* from, const Item* to, Err* err);