src/gn/command_help.cc - third_party/gn - Git at Google

 // 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 "base/command_line.h"
 #include "gn/args.h"
 #include "gn/commands.h"
 #include "gn/err.h"
 #include "gn/functions.h"
 #include "gn/input_conversion.h"
 #include "gn/label.h"
 #include "gn/label_pattern.h"
 #include "gn/metadata.h"
 #include "gn/ninja_build_writer.h"
 #include "gn/output_conversion.h"
 #include "gn/parser.h"
 #include "gn/runtime_deps.h"
 #include "gn/setup.h"
 #include "gn/standard_out.h"
 #include "gn/string_utils.h"
 #include "gn/substitution_writer.h"
 #include "gn/switches.h"
 #include "gn/target.h"
 #include "gn/variables.h"

 namespace commands {

 namespace {

 // Some names exist in multiple sections, these prefixes are used for the
 // internal links to disambiguate when writing markdown.
 const char kCommandLinkPrefix[] = "cmd_";
 const char kFunctionLinkPrefix[] = "func_";
 const char kVariableLinkPrefix[] = "var_";

 void PrintToplevelHelp() {
   PrintSectionHelp("Commands", "<command>", "commands");
   for (const auto& cmd : commands::GetCommands())
     PrintShortHelp(cmd.second.help_short, kCommandLinkPrefix + cmd.first);

   // Target declarations.
   PrintSectionHelp("Target declarations", "<function>", "targets");
   for (const auto& func : functions::GetFunctions()) {
     if (func.second.is_target)
       PrintShortHelp(func.second.help_short, kFunctionLinkPrefix + func.first);
   }

   // Functions.
   PrintSectionHelp("Buildfile functions", "<function>", "functions");
   for (const auto& func : functions::GetFunctions()) {
     if (!func.second.is_target)
       PrintShortHelp(func.second.help_short, kFunctionLinkPrefix + func.first);
   }

   // Built-in variables.
   PrintSectionHelp("Built-in predefined variables", "<variable>",
                    "predefined_variables");
   for (const auto& builtin : variables::GetBuiltinVariables()) {
     PrintShortHelp(builtin.second.help_short,
                    kVariableLinkPrefix + builtin.first);
   }

   // Target variables.
   PrintSectionHelp("Variables you set in targets", "<variable>",
                    "target_variables");
   for (const auto& target : variables::GetTargetVariables()) {
     PrintShortHelp(target.second.help_short,
                    kVariableLinkPrefix + target.first);
   }

   PrintSectionHelp("Other help topics", "", "other");
   PrintShortHelp("all: Print all the help at once");
   PrintShortHelp("buildargs: How build arguments work.", "buildargs");
   PrintShortHelp("dotfile: Info about the toplevel .gn file.", "dotfile");
   PrintShortHelp("execution: Build graph and execution overview.", "execution");
   PrintShortHelp("grammar: Language and grammar for GN build files.",
                  "grammar");
   PrintShortHelp(
       "input_conversion: Processing input from exec_script and read_file.",
       "io_conversion");
   PrintShortHelp("label_pattern: Matching more than one label.",
                  "label_pattern");
   PrintShortHelp("labels: About labels.", "labels");
   PrintShortHelp("metadata_collection: About metadata and its collection.",
                  "metadata_collection");
   PrintShortHelp("ninja_rules: How Ninja build rules are named.",
                  "ninja_rules");
   PrintShortHelp("nogncheck: Annotating includes for checking.", "nogncheck");
   PrintShortHelp(
       "output_conversion: Specifies how to transform a value to output.",
       "io_conversion");
   PrintShortHelp("runtime_deps: How runtime dependency computation works.",
                  "runtime_deps");
   PrintShortHelp("source_expansion: Map sources to outputs for scripts.",
                  "source_expansion");
   PrintShortHelp("switches: Show available command-line switches.",
                  "switch_list");
 }

 void PrintSwitchHelp() {
   const base::CommandLine* cmdline = base::CommandLine::ForCurrentProcess();
   bool is_markdown = cmdline->HasSwitch(switches::kMarkdown);

   // This uses "switch_list" for the tag because Markdown seems to generate
   // implicit tags for headings that match the strings, and some headings are
   // labeled "switches".
   PrintLongHelp(R"(Available global switches

   Do "gn help --the_switch_you_want_help_on" for more. Individual commands may
   take command-specific switches not listed here. See the help on your specific
   command for more.
 )",
                 "switch_list");

   if (is_markdown)
     OutputString("```\n", DECORATION_NONE);

   for (const auto& s : switches::GetSwitches())
     PrintShortHelp(s.second.short_help);

   if (is_markdown)
     OutputString("```\n", DECORATION_NONE);

   OutputString("\n");
 }

 void PrintAllHelp() {
   const base::CommandLine* cmdline = base::CommandLine::ForCurrentProcess();
   bool is_markdown = cmdline->HasSwitch(switches::kMarkdown);

   if (is_markdown) {
     OutputString("# GN Reference\n\n");
     OutputString(
         "*This page is automatically generated from* "
         "`gn help --markdown all`.\n\n");

     // Generate our own table of contents so that we have more control
     // over what's in and out.
     OutputString("## Contents\n\n");
   }

   PrintToplevelHelp();

   OutputString("\n");

   if (is_markdown) {
     OutputString("## <a name=\"commands\"></a>Commands\n\n", DECORATION_NONE,
                  NO_ESCAPING);
   }
   for (const auto& c : commands::GetCommands())
     PrintLongHelp(c.second.help, kCommandLinkPrefix + c.first);

   if (is_markdown) {
     OutputString("## <a name=\"targets\"></a>Target declarations\n\n",
                  DECORATION_NONE, NO_ESCAPING);
   }
   for (const auto& f : functions::GetFunctions()) {
     if (f.second.is_target)
       PrintLongHelp(f.second.help, kFunctionLinkPrefix + f.first);
   }

   if (is_markdown) {
     OutputString("## <a name=\"functions\"></a>Buildfile functions\n\n",
                  DECORATION_NONE, NO_ESCAPING);
   }
   for (const auto& f : functions::GetFunctions()) {
     if (!f.second.is_target)
       PrintLongHelp(f.second.help, kFunctionLinkPrefix + f.first);
   }

   if (is_markdown) {
     OutputString(
         "## <a name=\"predefined_variables\"></a>"
         "Built-in predefined variables\n\n",
         DECORATION_NONE, NO_ESCAPING);
   }
   for (const auto& v : variables::GetBuiltinVariables())
     PrintLongHelp(v.second.help, kVariableLinkPrefix + v.first);

   if (is_markdown) {
     OutputString(
         "## <a name=\"target_variables\"></a>"
         "Variables you set in targets\n\n",
         DECORATION_NONE, NO_ESCAPING);
   }
   for (const auto& v : variables::GetTargetVariables())
     PrintLongHelp(v.second.help, kVariableLinkPrefix + v.first);

   if (is_markdown) {
     OutputString("## <a name=\"other\"></a>Other help topics\n\n",
                  DECORATION_NONE, NO_ESCAPING);
   }
   PrintLongHelp(kBuildArgs_Help, "buildargs");
   PrintLongHelp(kDotfile_Help, "dotfile");
   PrintLongHelp(kExecution_Help, "execution");
   PrintLongHelp(kGrammar_Help, "grammar");
   PrintLongHelp(kInputOutputConversion_Help, "io_conversion");
   PrintLongHelp(kLabelPattern_Help, "label_pattern");
   PrintLongHelp(kLabels_Help, "labels");
   PrintLongHelp(kMetadata_Help, "metadata_collection");
   PrintLongHelp(kNinjaRules_Help, "ninja_rules");
   PrintLongHelp(kNoGnCheck_Help, "nogncheck");
   PrintLongHelp(kRuntimeDeps_Help, "runtime_deps");
   PrintLongHelp(kSourceExpansion_Help, "source_expansion");

   PrintSwitchHelp();
 }

 // Prints help on the given switch. There should be no leading hyphens. Returns
 // true if the switch was found and help was printed. False means the switch is
 // unknown.
 bool PrintHelpOnSwitch(const std::string& what) {
   const switches::SwitchInfoMap& all = switches::GetSwitches();
   switches::SwitchInfoMap::const_iterator found =
       all.find(std::string_view(what));
   if (found == all.end())
     return false;
   PrintLongHelp(found->second.long_help);
   return true;
 }

 // Special-case help for ambiguous "args" case.
 void PrintArgsHelp() {
   PrintLongHelp(
       "The string \"args\" is both a command and a variable for action "
       "targets.\nShowing help for both...\n\n");
   PrintLongHelp(commands::kArgs_Help);
   PrintLongHelp(
       "\n----------------------------------------------------------------------"
       "---------\n\n");
   PrintLongHelp(variables::kArgs_Help);
 }

 }  // namespace

 const char kHelp[] = "help";
 const char kHelp_HelpShort[] = "help: Does what you think.";
 const char kHelp_Help[] =
     R"(gn help <anything>

   Yo dawg, I heard you like help on your help so I put help on the help in the
   help.

   You can also use "all" as the parameter to get all help at once.

 Switches

   --markdown
       Format output in markdown syntax.

 Example

   gn help --markdown all
       Dump all help to stdout in markdown format.
 )";

 int RunHelp(const std::vector<std::string>& args) {
   std::string what;
   if (args.size() == 0) {
     // If no argument is specified, check for switches to allow things like
     // "gn help --args" for help on the args switch.
     const base::CommandLine::SwitchMap& switches =
         base::CommandLine::ForCurrentProcess()->GetSwitches();
     if (switches.empty()) {
       // Still nothing, show help overview.
       PrintToplevelHelp();
       return 0;
     }

     // Switch help needs to be done separately. The CommandLine will strip the
     // switch separators so --args will come out as "args" which is then
     // ambiguous with the variable named "args".
     if (!PrintHelpOnSwitch(switches.begin()->first))
       PrintToplevelHelp();
     return 0;
   } else {
     what = args[0];
   }

   std::vector<std::string_view> all_help_topics;

   // Special-case ambiguous topics.
   if (what == "args") {
     PrintArgsHelp();
     return 0;
   }

   // Check commands.
   const commands::CommandInfoMap& command_map = commands::GetCommands();
   auto found_command = command_map.find(what);
   if (found_command != command_map.end()) {
     PrintLongHelp(found_command->second.help);
     return 0;
   }
   for (const auto& entry : command_map)
     all_help_topics.push_back(entry.first);

   // Check functions.
   const functions::FunctionInfoMap& function_map = functions::GetFunctions();
   auto found_function = function_map.find(what);
   if (found_function != function_map.end())
     PrintLongHelp(found_function->second.help);
   for (const auto& entry : function_map)
     all_help_topics.push_back(entry.first);

   // Builtin variables.
   const variables::VariableInfoMap& builtin_vars =
       variables::GetBuiltinVariables();
   auto found_builtin_var = builtin_vars.find(what);
   if (found_builtin_var != builtin_vars.end())
     PrintLongHelp(found_builtin_var->second.help);
   for (const auto& entry : builtin_vars)
     all_help_topics.push_back(entry.first);

   // Target variables.
   const variables::VariableInfoMap& target_vars =
       variables::GetTargetVariables();
   auto found_target_var = target_vars.find(what);
   if (found_target_var != target_vars.end())
     PrintLongHelp(found_target_var->second.help);
   for (const auto& entry : target_vars)
     all_help_topics.push_back(entry.first);

   if (found_function != function_map.end() ||
       found_builtin_var != builtin_vars.end() ||
       found_target_var != target_vars.end())
     return 0;

   // Random other topics.
   std::map<std::string, void (*)()> random_topics;
   random_topics["all"] = PrintAllHelp;
   random_topics["execution"] = []() { PrintLongHelp(kExecution_Help); };
   random_topics["buildargs"] = []() { PrintLongHelp(kBuildArgs_Help); };
   random_topics["dotfile"] = []() { PrintLongHelp(kDotfile_Help); };
   random_topics["grammar"] = []() { PrintLongHelp(kGrammar_Help); };
   random_topics["io_conversion"] = []() {
     PrintLongHelp(kInputOutputConversion_Help);
   };
   random_topics["label_pattern"] = []() { PrintLongHelp(kLabelPattern_Help); };
   random_topics["labels"] = []() { PrintLongHelp(kLabels_Help); };
   random_topics["metadata_collection"] = []() {
     PrintLongHelp(kMetadata_Help);
   };
   random_topics["ninja_rules"] = []() { PrintLongHelp(kNinjaRules_Help); };
   random_topics["nogncheck"] = []() { PrintLongHelp(kNoGnCheck_Help); };
   random_topics["runtime_deps"] = []() { PrintLongHelp(kRuntimeDeps_Help); };
   random_topics["source_expansion"] = []() {
     PrintLongHelp(kSourceExpansion_Help);
   };
   random_topics["switches"] = PrintSwitchHelp;
   auto found_random_topic = random_topics.find(what);
   if (found_random_topic != random_topics.end()) {
     found_random_topic->second();
     return 0;
   }
   for (const auto& entry : random_topics)
     all_help_topics.push_back(entry.first);

   // No help on this.
   Err(Location(), "No help on \"" + what + "\".").PrintToStdout();
   std::string_view suggestion = SpellcheckString(what, all_help_topics);
   if (suggestion.empty()) {
     OutputString("Run `gn help` for a list of available topics.\n",
                  DECORATION_NONE);
   } else {
     OutputString("Did you mean `gn help " + std::string(suggestion) + "`?\n",
                  DECORATION_NONE);
   }
   return 1;
 }

 }  // namespace commands
	// 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 "base/command_line.h"
	#include "gn/args.h"
	#include "gn/commands.h"
	#include "gn/err.h"
	#include "gn/functions.h"
	#include "gn/input_conversion.h"
	#include "gn/label.h"
	#include "gn/label_pattern.h"
	#include "gn/metadata.h"
	#include "gn/ninja_build_writer.h"
	#include "gn/output_conversion.h"
	#include "gn/parser.h"
	#include "gn/runtime_deps.h"
	#include "gn/setup.h"
	#include "gn/standard_out.h"
	#include "gn/string_utils.h"
	#include "gn/substitution_writer.h"
	#include "gn/switches.h"
	#include "gn/target.h"
	#include "gn/variables.h"

	namespace commands {

	namespace {

	// Some names exist in multiple sections, these prefixes are used for the
	// internal links to disambiguate when writing markdown.
	const char kCommandLinkPrefix[] = "cmd_";
	const char kFunctionLinkPrefix[] = "func_";
	const char kVariableLinkPrefix[] = "var_";

	void PrintToplevelHelp() {
	PrintSectionHelp("Commands", "<command>", "commands");
	for (const auto& cmd : commands::GetCommands())
	PrintShortHelp(cmd.second.help_short, kCommandLinkPrefix + cmd.first);

	// Target declarations.
	PrintSectionHelp("Target declarations", "<function>", "targets");
	for (const auto& func : functions::GetFunctions()) {
	if (func.second.is_target)
	PrintShortHelp(func.second.help_short, kFunctionLinkPrefix + func.first);
	}

	// Functions.
	PrintSectionHelp("Buildfile functions", "<function>", "functions");
	for (const auto& func : functions::GetFunctions()) {
	if (!func.second.is_target)
	PrintShortHelp(func.second.help_short, kFunctionLinkPrefix + func.first);
	}

	// Built-in variables.
	PrintSectionHelp("Built-in predefined variables", "<variable>",
	"predefined_variables");
	for (const auto& builtin : variables::GetBuiltinVariables()) {
	PrintShortHelp(builtin.second.help_short,
	kVariableLinkPrefix + builtin.first);
	}

	// Target variables.
	PrintSectionHelp("Variables you set in targets", "<variable>",
	"target_variables");
	for (const auto& target : variables::GetTargetVariables()) {
	PrintShortHelp(target.second.help_short,
	kVariableLinkPrefix + target.first);
	}

	PrintSectionHelp("Other help topics", "", "other");
	PrintShortHelp("all: Print all the help at once");
	PrintShortHelp("buildargs: How build arguments work.", "buildargs");
	PrintShortHelp("dotfile: Info about the toplevel .gn file.", "dotfile");
	PrintShortHelp("execution: Build graph and execution overview.", "execution");
	PrintShortHelp("grammar: Language and grammar for GN build files.",
	"grammar");
	PrintShortHelp(
	"input_conversion: Processing input from exec_script and read_file.",
	"io_conversion");
	PrintShortHelp("label_pattern: Matching more than one label.",
	"label_pattern");
	PrintShortHelp("labels: About labels.", "labels");
	PrintShortHelp("metadata_collection: About metadata and its collection.",
	"metadata_collection");
	PrintShortHelp("ninja_rules: How Ninja build rules are named.",
	"ninja_rules");
	PrintShortHelp("nogncheck: Annotating includes for checking.", "nogncheck");
	PrintShortHelp(
	"output_conversion: Specifies how to transform a value to output.",
	"io_conversion");
	PrintShortHelp("runtime_deps: How runtime dependency computation works.",
	"runtime_deps");
	PrintShortHelp("source_expansion: Map sources to outputs for scripts.",
	"source_expansion");
	PrintShortHelp("switches: Show available command-line switches.",
	"switch_list");
	}

	void PrintSwitchHelp() {
	const base::CommandLine* cmdline = base::CommandLine::ForCurrentProcess();
	bool is_markdown = cmdline->HasSwitch(switches::kMarkdown);

	// This uses "switch_list" for the tag because Markdown seems to generate
	// implicit tags for headings that match the strings, and some headings are
	// labeled "switches".
	PrintLongHelp(R"(Available global switches

	Do "gn help --the_switch_you_want_help_on" for more. Individual commands may
	take command-specific switches not listed here. See the help on your specific
	command for more.
	)",
	"switch_list");

	if (is_markdown)
	OutputString("```\n", DECORATION_NONE);

	for (const auto& s : switches::GetSwitches())
	PrintShortHelp(s.second.short_help);

	if (is_markdown)
	OutputString("```\n", DECORATION_NONE);

	OutputString("\n");
	}

	void PrintAllHelp() {
	const base::CommandLine* cmdline = base::CommandLine::ForCurrentProcess();
	bool is_markdown = cmdline->HasSwitch(switches::kMarkdown);

	if (is_markdown) {
	OutputString("# GN Reference\n\n");
	OutputString(
	"This page is automatically generated from "
	"`gn help --markdown all`.\n\n");

	// Generate our own table of contents so that we have more control
	// over what's in and out.
	OutputString("## Contents\n\n");
	}

	PrintToplevelHelp();

	OutputString("\n");

	if (is_markdown) {
	OutputString("## <a name=\"commands\"></a>Commands\n\n", DECORATION_NONE,
	NO_ESCAPING);
	}
	for (const auto& c : commands::GetCommands())
	PrintLongHelp(c.second.help, kCommandLinkPrefix + c.first);

	if (is_markdown) {
	OutputString("## <a name=\"targets\"></a>Target declarations\n\n",
	DECORATION_NONE, NO_ESCAPING);
	}
	for (const auto& f : functions::GetFunctions()) {
	if (f.second.is_target)
	PrintLongHelp(f.second.help, kFunctionLinkPrefix + f.first);
	}

	if (is_markdown) {
	OutputString("## <a name=\"functions\"></a>Buildfile functions\n\n",
	DECORATION_NONE, NO_ESCAPING);
	}
	for (const auto& f : functions::GetFunctions()) {
	if (!f.second.is_target)
	PrintLongHelp(f.second.help, kFunctionLinkPrefix + f.first);
	}

	if (is_markdown) {
	OutputString(
	"## <a name=\"predefined_variables\"></a>"
	"Built-in predefined variables\n\n",
	DECORATION_NONE, NO_ESCAPING);
	}
	for (const auto& v : variables::GetBuiltinVariables())
	PrintLongHelp(v.second.help, kVariableLinkPrefix + v.first);

	if (is_markdown) {
	OutputString(
	"## <a name=\"target_variables\"></a>"
	"Variables you set in targets\n\n",
	DECORATION_NONE, NO_ESCAPING);
	}
	for (const auto& v : variables::GetTargetVariables())
	PrintLongHelp(v.second.help, kVariableLinkPrefix + v.first);

	if (is_markdown) {
	OutputString("## <a name=\"other\"></a>Other help topics\n\n",
	DECORATION_NONE, NO_ESCAPING);
	}
	PrintLongHelp(kBuildArgs_Help, "buildargs");
	PrintLongHelp(kDotfile_Help, "dotfile");
	PrintLongHelp(kExecution_Help, "execution");
	PrintLongHelp(kGrammar_Help, "grammar");
	PrintLongHelp(kInputOutputConversion_Help, "io_conversion");
	PrintLongHelp(kLabelPattern_Help, "label_pattern");
	PrintLongHelp(kLabels_Help, "labels");
	PrintLongHelp(kMetadata_Help, "metadata_collection");
	PrintLongHelp(kNinjaRules_Help, "ninja_rules");
	PrintLongHelp(kNoGnCheck_Help, "nogncheck");
	PrintLongHelp(kRuntimeDeps_Help, "runtime_deps");
	PrintLongHelp(kSourceExpansion_Help, "source_expansion");

	PrintSwitchHelp();
	}

	// Prints help on the given switch. There should be no leading hyphens. Returns
	// true if the switch was found and help was printed. False means the switch is
	// unknown.
	bool PrintHelpOnSwitch(const std::string& what) {
	const switches::SwitchInfoMap& all = switches::GetSwitches();
	switches::SwitchInfoMap::const_iterator found =
	all.find(std::string_view(what));
	if (found == all.end())
	return false;
	PrintLongHelp(found->second.long_help);
	return true;
	}

	// Special-case help for ambiguous "args" case.
	void PrintArgsHelp() {
	PrintLongHelp(
	"The string \"args\" is both a command and a variable for action "
	"targets.\nShowing help for both...\n\n");
	PrintLongHelp(commands::kArgs_Help);
	PrintLongHelp(
	"\n----------------------------------------------------------------------"
	"---------\n\n");
	PrintLongHelp(variables::kArgs_Help);
	}

	} // namespace

	const char kHelp[] = "help";
	const char kHelp_HelpShort[] = "help: Does what you think.";
	const char kHelp_Help[] =
	R"(gn help <anything>

	Yo dawg, I heard you like help on your help so I put help on the help in the
	help.

	You can also use "all" as the parameter to get all help at once.

	Switches

	--markdown
	Format output in markdown syntax.

	Example

	gn help --markdown all
	Dump all help to stdout in markdown format.
	)";

	int RunHelp(const std::vector<std::string>& args) {
	std::string what;
	if (args.size() == 0) {
	// If no argument is specified, check for switches to allow things like
	// "gn help --args" for help on the args switch.
	const base::CommandLine::SwitchMap& switches =
	base::CommandLine::ForCurrentProcess()->GetSwitches();
	if (switches.empty()) {
	// Still nothing, show help overview.
	PrintToplevelHelp();
	return 0;
	}

	// Switch help needs to be done separately. The CommandLine will strip the
	// switch separators so --args will come out as "args" which is then
	// ambiguous with the variable named "args".
	if (!PrintHelpOnSwitch(switches.begin()->first))
	PrintToplevelHelp();
	return 0;
	} else {
	what = args[0];
	}

	std::vector<std::string_view> all_help_topics;

	// Special-case ambiguous topics.
	if (what == "args") {
	PrintArgsHelp();
	return 0;
	}

	// Check commands.
	const commands::CommandInfoMap& command_map = commands::GetCommands();
	auto found_command = command_map.find(what);
	if (found_command != command_map.end()) {
	PrintLongHelp(found_command->second.help);
	return 0;
	}
	for (const auto& entry : command_map)
	all_help_topics.push_back(entry.first);

	// Check functions.
	const functions::FunctionInfoMap& function_map = functions::GetFunctions();
	auto found_function = function_map.find(what);
	if (found_function != function_map.end())
	PrintLongHelp(found_function->second.help);
	for (const auto& entry : function_map)
	all_help_topics.push_back(entry.first);

	// Builtin variables.
	const variables::VariableInfoMap& builtin_vars =
	variables::GetBuiltinVariables();
	auto found_builtin_var = builtin_vars.find(what);
	if (found_builtin_var != builtin_vars.end())
	PrintLongHelp(found_builtin_var->second.help);
	for (const auto& entry : builtin_vars)
	all_help_topics.push_back(entry.first);

	// Target variables.
	const variables::VariableInfoMap& target_vars =
	variables::GetTargetVariables();
	auto found_target_var = target_vars.find(what);
	if (found_target_var != target_vars.end())
	PrintLongHelp(found_target_var->second.help);
	for (const auto& entry : target_vars)
	all_help_topics.push_back(entry.first);

	if (found_function != function_map.end() \|\|
	found_builtin_var != builtin_vars.end() \|\|
	found_target_var != target_vars.end())
	return 0;

	// Random other topics.
	std::map<std::string, void (*)()> random_topics;
	random_topics["all"] = PrintAllHelp;
	random_topics["execution"] = []() { PrintLongHelp(kExecution_Help); };
	random_topics["buildargs"] = []() { PrintLongHelp(kBuildArgs_Help); };
	random_topics["dotfile"] = []() { PrintLongHelp(kDotfile_Help); };
	random_topics["grammar"] = []() { PrintLongHelp(kGrammar_Help); };
	random_topics["io_conversion"] = []() {
	PrintLongHelp(kInputOutputConversion_Help);
	};
	random_topics["label_pattern"] = []() { PrintLongHelp(kLabelPattern_Help); };
	random_topics["labels"] = []() { PrintLongHelp(kLabels_Help); };
	random_topics["metadata_collection"] = []() {
	PrintLongHelp(kMetadata_Help);
	};
	random_topics["ninja_rules"] = []() { PrintLongHelp(kNinjaRules_Help); };
	random_topics["nogncheck"] = []() { PrintLongHelp(kNoGnCheck_Help); };
	random_topics["runtime_deps"] = []() { PrintLongHelp(kRuntimeDeps_Help); };
	random_topics["source_expansion"] = []() {
	PrintLongHelp(kSourceExpansion_Help);
	};
	random_topics["switches"] = PrintSwitchHelp;
	auto found_random_topic = random_topics.find(what);
	if (found_random_topic != random_topics.end()) {
	found_random_topic->second();
	return 0;
	}
	for (const auto& entry : random_topics)
	all_help_topics.push_back(entry.first);

	// No help on this.
	Err(Location(), "No help on \"" + what + "\".").PrintToStdout();
	std::string_view suggestion = SpellcheckString(what, all_help_topics);
	if (suggestion.empty()) {
	OutputString("Run `gn help` for a list of available topics.\n",
	DECORATION_NONE);
	} else {
	OutputString("Did you mean `gn help " + std::string(suggestion) + "`?\n",
	DECORATION_NONE);
	}
	return 1;
	}

	} // namespace commands