functions.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 "tools/gn/functions.h"

#include <stddef.h>
#include <iostream>
#include <utility>

#include "base/environment.h"
#include "base/strings/string_util.h"
#include "tools/gn/config.h"
#include "tools/gn/config_values_generator.h"
#include "tools/gn/err.h"
#include "tools/gn/input_file.h"
#include "tools/gn/parse_tree.h"
#include "tools/gn/scheduler.h"
#include "tools/gn/scope.h"
#include "tools/gn/settings.h"
#include "tools/gn/template.h"
#include "tools/gn/token.h"
#include "tools/gn/value.h"
#include "tools/gn/value_extractors.h"
#include "tools/gn/variables.h"

namespace {

// Some functions take a {} following them, and some don't. For the ones that
// don't, this is used to verify that the given block node is null and will
// set the error accordingly if it's not. Returns true if the block is null.
bool VerifyNoBlockForFunctionCall(const FunctionCallNode* function,
                                  const BlockNode* block,
                                  Err* err) {
  if (!block)
    return true;

  *err = Err(block, "Unexpected '{'.",
      "This function call doesn't take a {} block following it, and you\n"
      "can't have a {} block that's not connected to something like an if\n"
      "statement or a target declaration.");
  err->AppendRange(function->function().range());
  return false;
}

}  // namespace

bool EnsureNotProcessingImport(const ParseNode* node,
                               const Scope* scope,
                               Err* err) {
  if (scope->IsProcessingImport()) {
    *err = Err(node, "Not valid from an import.",
        "Imports are for defining defaults, variables, and rules. The\n"
        "appropriate place for this kind of thing is really in a normal\n"
        "BUILD file.");
    return false;
  }
  return true;
}

bool EnsureNotProcessingBuildConfig(const ParseNode* node,
                                    const Scope* scope,
                                    Err* err) {
  if (scope->IsProcessingBuildConfig()) {
    *err = Err(node, "Not valid from the build config.",
        "You can't do this kind of thing from the build config script, "
        "silly!\nPut it in a regular BUILD file.");
    return false;
  }
  return true;
}

bool FillTargetBlockScope(const Scope* scope,
                          const FunctionCallNode* function,
                          const std::string& target_type,
                          const BlockNode* block,
                          const std::vector<Value>& args,
                          Scope* block_scope,
                          Err* err) {
  if (!block) {
    FillNeedsBlockError(function, err);
    return false;
  }

  // Copy the target defaults, if any, into the scope we're going to execute
  // the block in.
  const Scope* default_scope = scope->GetTargetDefaults(target_type);
  if (default_scope) {
    Scope::MergeOptions merge_options;
    merge_options.skip_private_vars = true;
    if (!default_scope->NonRecursiveMergeTo(block_scope, merge_options,
                                            function, "target defaults", err))
      return false;
  }

  // The name is the single argument to the target function.
  if (!EnsureSingleStringArg(function, args, err))
    return false;

  // Set the target name variable to the current target, and mark it used
  // because we don't want to issue an error if the script ignores it.
  const base::StringPiece target_name("target_name");
  block_scope->SetValue(target_name, Value(function, args[0].string_value()),
                        function);
  block_scope->MarkUsed(target_name);
  return true;
}

void FillNeedsBlockError(const FunctionCallNode* function, Err* err) {
  *err = Err(function->function(), "This function call requires a block.",
      "The block's \"{\" must be on the same line as the function "
      "call's \")\".");
}

bool EnsureSingleStringArg(const FunctionCallNode* function,
                           const std::vector<Value>& args,
                           Err* err) {
  if (args.size() != 1) {
    *err = Err(function->function(), "Incorrect arguments.",
               "This function requires a single string argument.");
    return false;
  }
  return args[0].VerifyTypeIs(Value::STRING, err);
}

const Label& ToolchainLabelForScope(const Scope* scope) {
  return scope->settings()->toolchain_label();
}

Label MakeLabelForScope(const Scope* scope,
                        const FunctionCallNode* function,
                        const std::string& name) {
  const Label& toolchain_label = ToolchainLabelForScope(scope);
  return Label(scope->GetSourceDir(), name, toolchain_label.dir(),
               toolchain_label.name());
}

// static
const int NonNestableBlock::kKey = 0;

NonNestableBlock::NonNestableBlock(
    Scope* scope,
    const FunctionCallNode* function,
    const char* type_description)
    : scope_(scope),
      function_(function),
      type_description_(type_description),
      key_added_(false) {
}

NonNestableBlock::~NonNestableBlock() {
  if (key_added_)
    scope_->SetProperty(&kKey, nullptr);
}

bool NonNestableBlock::Enter(Err* err) {
  void* scope_value = scope_->GetProperty(&kKey, nullptr);
  if (scope_value) {
    // Existing block.
    const NonNestableBlock* existing =
        reinterpret_cast<const NonNestableBlock*>(scope_value);
    *err = Err(function_, "Can't nest these things.",
        std::string("You are trying to nest a ") + type_description_ +
        " inside a " + existing->type_description_ + ".");
    err->AppendSubErr(Err(existing->function_, "The enclosing block."));
    return false;
  }

  scope_->SetProperty(&kKey, this);
  key_added_ = true;
  return true;
}

namespace functions {

// assert ----------------------------------------------------------------------

const char kAssert[] = "assert";
const char kAssert_HelpShort[] =
    "assert: Assert an expression is true at generation time.";
const char kAssert_Help[] =
    "assert: Assert an expression is true at generation time.\n"
    "\n"
    "  assert(<condition> [, <error string>])\n"
    "\n"
    "  If the condition is false, the build will fail with an error. If the\n"
    "  optional second argument is provided, that string will be printed\n"
    "  with the error message.\n"
    "\n"
    "Examples:\n"
    "  assert(is_win)\n"
    "  assert(defined(sources), \"Sources must be defined\")\n";

Value RunAssert(Scope* scope,
                const FunctionCallNode* function,
                const std::vector<Value>& args,
                Err* err) {
  if (args.size() != 1 && args.size() != 2) {
    *err = Err(function->function(), "Wrong number of arguments.",
               "assert() takes one or two argument, "
               "were you expecting somethig else?");
  } else if (args[0].type() != Value::BOOLEAN) {
    *err = Err(function->function(), "Assertion value not a bool.");
  } else if (!args[0].boolean_value()) {
    if (args.size() == 2) {
      // Optional string message.
      if (args[1].type() != Value::STRING) {
        *err = Err(function->function(), "Assertion failed.",
            "<<<ERROR MESSAGE IS NOT A STRING>>>");
      } else {
        *err = Err(function->function(), "Assertion failed.",
            args[1].string_value());
      }
    } else {
      *err = Err(function->function(), "Assertion failed.");
    }

    if (args[0].origin()) {
      // If you do "assert(foo)" we'd ideally like to show you where foo was
      // set, and in this case the origin of the args will tell us that.
      // However, if you do "assert(foo && bar)" the source of the value will
      // be the assert like, which isn't so helpful.
      //
      // So we try to see if the args are from the same line or not. This will
      // break if you do "assert(\nfoo && bar)" and we may show the second line
      // as the source, oh well. The way around this is to check to see if the
      // origin node is inside our function call block.
      Location origin_location = args[0].origin()->GetRange().begin();
      if (origin_location.file() != function->function().location().file() ||
          origin_location.line_number() !=
              function->function().location().line_number()) {
        err->AppendSubErr(Err(args[0].origin()->GetRange(), "",
                              "This is where it was set."));
      }
    }
  }
  return Value();
}

// config ----------------------------------------------------------------------

const char kConfig[] = "config";
const char kConfig_HelpShort[] =
    "config: Defines a configuration object.";
const char kConfig_Help[] =
    "config: Defines a configuration object.\n"
    "\n"
    "  Configuration objects can be applied to targets and specify sets of\n"
    "  compiler flags, includes, defines, etc. They provide a way to\n"
    "  conveniently group sets of this configuration information.\n"
    "\n"
    "  A config is referenced by its label just like a target.\n"
    "\n"
    "  The values in a config are additive only. If you want to remove a flag\n"
    "  you need to remove the corresponding config that sets it. The final\n"
    "  set of flags, defines, etc. for a target is generated in this order:\n"
    "\n"
    "   1. The values specified directly on the target (rather than using a\n"
    "      config.\n"
    "   2. The configs specified in the target's \"configs\" list, in order.\n"
    "   3. Public_configs from a breadth-first traversal of the dependency\n"
    "      tree in the order that the targets appear in \"deps\".\n"
    "   4. All dependent configs from a breadth-first traversal of the\n"
    "      dependency tree in the order that the targets appear in \"deps\".\n"
    "\n"
    "Variables valid in a config definition\n"
    "\n"
    CONFIG_VALUES_VARS_HELP
    "  Nested configs: configs\n"
    "\n"
    "Variables on a target used to apply configs\n"
    "\n"
    "  all_dependent_configs, configs, public_configs\n"
    "\n"
    "Example\n"
    "\n"
    "  config(\"myconfig\") {\n"
    "    includes = [ \"include/common\" ]\n"
    "    defines = [ \"ENABLE_DOOM_MELON\" ]\n"
    "  }\n"
    "\n"
    "  executable(\"mything\") {\n"
    "    configs = [ \":myconfig\" ]\n"
    "  }\n";

Value RunConfig(const FunctionCallNode* function,
                const std::vector<Value>& args,
                Scope* scope,
                Err* err) {
  NonNestableBlock non_nestable(scope, function, "config");
  if (!non_nestable.Enter(err))
    return Value();

  if (!EnsureSingleStringArg(function, args, err) ||
      !EnsureNotProcessingImport(function, scope, err))
    return Value();

  Label label(MakeLabelForScope(scope, function, args[0].string_value()));

  if (g_scheduler->verbose_logging())
    g_scheduler->Log("Defining config", label.GetUserVisibleName(true));

  // Create the new config.
  scoped_ptr<Config> config(new Config(scope->settings(), label));
  config->set_defined_from(function);
  if (!Visibility::FillItemVisibility(config.get(), scope, err))
    return Value();

  // Fill the flags and such.
  const SourceDir& input_dir = scope->GetSourceDir();
  ConfigValuesGenerator gen(&config->own_values(), scope, input_dir, err);
  gen.Run();
  if (err->has_error())
    return Value();

  // Read sub-configs.
  const Value* configs_value = scope->GetValue(variables::kConfigs, true);
  if (configs_value) {
    ExtractListOfUniqueLabels(*configs_value, scope->GetSourceDir(),
                              ToolchainLabelForScope(scope),
                              &config->configs(), err);
  }
  if (err->has_error())
    return Value();

  // Save the generated item.
  Scope::ItemVector* collector = scope->GetItemCollector();
  if (!collector) {
    *err = Err(function, "Can't define a config in this context.");
    return Value();
  }
  collector->push_back(config.release());

  return Value();
}

// declare_args ----------------------------------------------------------------

const char kDeclareArgs[] = "declare_args";
const char kDeclareArgs_HelpShort[] =
    "declare_args: Declare build arguments.";
const char kDeclareArgs_Help[] =
    "declare_args: Declare build arguments.\n"
    "\n"
    "  Introduces the given arguments into the current scope. If they are\n"
    "  not specified on the command line or in a toolchain's arguments,\n"
    "  the default values given in the declare_args block will be used.\n"
    "  However, these defaults will not override command-line values.\n"
    "\n"
    "  See also \"gn help buildargs\" for an overview.\n"
    "\n"
    "  The precise behavior of declare args is:\n"
    "\n"
    "   1. The declare_arg block executes. Any variables in the enclosing\n"
    "      scope are available for reading.\n"
    "\n"
    "   2. At the end of executing the block, any variables set within that\n"
    "      scope are saved globally as build arguments, with their current\n"
    "      values being saved as the \"default value\" for that argument.\n"
    "\n"
    "   3. User-defined overrides are applied. Anything set in \"gn args\"\n"
    "      now overrides any default values. The resulting set of variables\n"
    "      is promoted to be readable from the following code in the file.\n"
    "\n"
    "  This has some ramifications that may not be obvious:\n"
    "\n"
    "    - You should not perform difficult work inside a declare_args block\n"
    "      since this only sets a default value that may be discarded. In\n"
    "      particular, don't use the result of exec_script() to set the\n"
    "      default value. If you want to have a script-defined default, set\n"
    "      some default \"undefined\" value like [], \"\", or -1, and after\n"
    "      the declare_args block, call exec_script if the value is unset by\n"
    "      the user.\n"
    "\n"
    "    - Any code inside of the declare_args block will see the default\n"
    "      values of previous variables defined in the block rather than\n"
    "      the user-overridden value. This can be surprising because you will\n"
    "      be used to seeing the overridden value. If you need to make the\n"
    "      default value of one arg dependent on the possibly-overridden\n"
    "      value of another, write two separate declare_args blocks:\n"
    "\n"
    "        declare_args() {\n"
    "          enable_foo = true\n"
    "        }\n"
    "        declare_args() {\n"
    "          # Bar defaults to same user-overridden state as foo.\n"
    "          enable_bar = enable_foo\n"
    "        }\n"
    "\n"
    "Example\n"
    "\n"
    "  declare_args() {\n"
    "    enable_teleporter = true\n"
    "    enable_doom_melon = false\n"
    "  }\n"
    "\n"
    "  If you want to override the (default disabled) Doom Melon:\n"
    "    gn --args=\"enable_doom_melon=true enable_teleporter=false\"\n"
    "  This also sets the teleporter, but it's already defaulted to on so\n"
    "  it will have no effect.\n";

Value RunDeclareArgs(Scope* scope,
                     const FunctionCallNode* function,
                     const std::vector<Value>& args,
                     BlockNode* block,
                     Err* err) {
  NonNestableBlock non_nestable(scope, function, "declare_args");
  if (!non_nestable.Enter(err))
    return Value();

  Scope block_scope(scope);
  block->Execute(&block_scope, err);
  if (err->has_error())
    return Value();

  // Pass the values from our scope into the Args object for adding to the
  // scope with the proper values (taking into account the defaults given in
  // the block_scope, and arguments passed into the build).
  Scope::KeyValueMap values;
  block_scope.GetCurrentScopeValues(&values);
  scope->settings()->build_settings()->build_args().DeclareArgs(
      values, scope, err);
  return Value();
}

// defined ---------------------------------------------------------------------

const char kDefined[] = "defined";
const char kDefined_HelpShort[] =
    "defined: Returns whether an identifier is defined.";
const char kDefined_Help[] =
    "defined: Returns whether an identifier is defined.\n"
    "\n"
    "  Returns true if the given argument is defined. This is most useful in\n"
    "  templates to assert that the caller set things up properly.\n"
    "\n"
    "  You can pass an identifier:\n"
    "    defined(foo)\n"
    "  which will return true or false depending on whether foo is defined in\n"
    "  the current scope.\n"
    "\n"
    "  You can also check a named scope:\n"
    "    defined(foo.bar)\n"
    "  which will return true or false depending on whether bar is defined in\n"
    "  the named scope foo. It will throw an error if foo is not defined or\n"
    "  is not a scope.\n"
    "\n"
    "Example:\n"
    "\n"
    "  template(\"mytemplate\") {\n"
    "    # To help users call this template properly...\n"
    "    assert(defined(invoker.sources), \"Sources must be defined\")\n"
    "\n"
    "    # If we want to accept an optional \"values\" argument, we don't\n"
    "    # want to dereference something that may not be defined.\n"
    "    if (defined(invoker.values)) {\n"
    "      values = invoker.values\n"
    "    } else {\n"
    "      values = \"some default value\"\n"
    "    }\n"
    "  }\n";

Value RunDefined(Scope* scope,
                 const FunctionCallNode* function,
                 const ListNode* args_list,
                 Err* err) {
  const std::vector<const ParseNode*>& args_vector = args_list->contents();
  if (args_vector.size() != 1) {
    *err = Err(function, "Wrong number of arguments to defined().",
               "Expecting exactly one.");
    return Value();
  }

  const IdentifierNode* identifier = args_vector[0]->AsIdentifier();
  if (identifier) {
    // Passed an identifier "defined(foo)".
    if (scope->GetValue(identifier->value().value()))
      return Value(function, true);
    return Value(function, false);
  }

  const AccessorNode* accessor = args_vector[0]->AsAccessor();
  if (accessor) {
    // Passed an accessor "defined(foo.bar)".
    if (accessor->member()) {
      // The base of the accessor must be a scope if it's defined.
      const Value* base = scope->GetValue(accessor->base().value());
      if (!base) {
        *err = Err(accessor, "Undefined identifier");
        return Value();
      }
      if (!base->VerifyTypeIs(Value::SCOPE, err))
        return Value();

      // Check the member inside the scope to see if its defined.
      if (base->scope_value()->GetValue(accessor->member()->value().value()))
        return Value(function, true);
      return Value(function, false);
    }
  }

  // Argument is invalid.
  *err = Err(function, "Bad thing passed to defined().",
      "It should be of the form defined(foo) or defined(foo.bar).");
  return Value();
}

// getenv ----------------------------------------------------------------------

const char kGetEnv[] = "getenv";
const char kGetEnv_HelpShort[] =
    "getenv: Get an environment variable.";
const char kGetEnv_Help[] =
    "getenv: Get an environment variable.\n"
    "\n"
    "  value = getenv(env_var_name)\n"
    "\n"
    "  Returns the value of the given enironment variable. If the value is\n"
    "  not found, it will try to look up the variable with the \"opposite\"\n"
    "  case (based on the case of the first letter of the variable), but\n"
    "  is otherwise case-sensitive.\n"
    "\n"
    "  If the environment variable is not found, the empty string will be\n"
    "  returned. Note: it might be nice to extend this if we had the concept\n"
    "  of \"none\" in the language to indicate lookup failure.\n"
    "\n"
    "Example:\n"
    "\n"
    "  home_dir = getenv(\"HOME\")\n";

Value RunGetEnv(Scope* scope,
                const FunctionCallNode* function,
                const std::vector<Value>& args,
                Err* err) {
  if (!EnsureSingleStringArg(function, args, err))
    return Value();

  scoped_ptr<base::Environment> env(base::Environment::Create());

  std::string result;
  if (!env->GetVar(args[0].string_value().c_str(), &result))
    return Value(function, "");  // Not found, return empty string.
  return Value(function, result);
}

// import ----------------------------------------------------------------------

const char kImport[] = "import";
const char kImport_HelpShort[] =
    "import: Import a file into the current scope.";
const char kImport_Help[] =
    "import: Import a file into the current scope.\n"
    "\n"
    "  The import command loads the rules and variables resulting from\n"
    "  executing the given file into the current scope.\n"
    "\n"
    "  By convention, imported files are named with a .gni extension.\n"
    "\n"
    "  An import is different than a C++ \"include\". The imported file is\n"
    "  executed in a standalone environment from the caller of the import\n"
    "  command. The results of this execution are cached for other files that\n"
    "  import the same .gni file.\n"
    "\n"
    "  Note that you can not import a BUILD.gn file that's otherwise used\n"
    "  in the build. Files must either be imported or implicitly loaded as\n"
    "  a result of deps rules, but not both.\n"
    "\n"
    "  The imported file's scope will be merged with the scope at the point\n"
    "  import was called. If there is a conflict (both the current scope and\n"
    "  the imported file define some variable or rule with the same name but\n"
    "  different value), a runtime error will be thrown. Therefore, it's good\n"
    "  practice to minimize the stuff that an imported file defines.\n"
    "\n"
    "  Variables and templates beginning with an underscore '_' are\n"
    "  considered private and will not be imported. Imported files can use\n"
    "  such variables for internal computation without affecting other files.\n"
    "\n"
    "Examples:\n"
    "\n"
    "  import(\"//build/rules/idl_compilation_rule.gni\")\n"
    "\n"
    "  # Looks in the current directory.\n"
    "  import(\"my_vars.gni\")\n";

Value RunImport(Scope* scope,
                const FunctionCallNode* function,
                const std::vector<Value>& args,
                Err* err) {
  if (!EnsureSingleStringArg(function, args, err))
    return Value();

  const SourceDir& input_dir = scope->GetSourceDir();
  SourceFile import_file =
      input_dir.ResolveRelativeFile(args[0], err,
          scope->settings()->build_settings()->root_path_utf8());
  if (!err->has_error()) {
    scope->settings()->import_manager().DoImport(import_file, function,
                                                 scope, err);
  }
  return Value();
}

// set_sources_assignment_filter -----------------------------------------------

const char kSetSourcesAssignmentFilter[] = "set_sources_assignment_filter";
const char kSetSourcesAssignmentFilter_HelpShort[] =
    "set_sources_assignment_filter: Set a pattern to filter source files.";
const char kSetSourcesAssignmentFilter_Help[] =
    "set_sources_assignment_filter: Set a pattern to filter source files.\n"
    "\n"
    "  The sources assignment filter is a list of patterns that remove files\n"
    "  from the list implicitly whenever the \"sources\" variable is\n"
    "  assigned to. This is intended to be used to globally filter out files\n"
    "  with platform-specific naming schemes when they don't apply, for\n"
    "  example, you may want to filter out all \"*_win.cc\" files on non-\n"
    "  Windows platforms.\n"
    "\n"
    "  Typically this will be called once in the master build config script\n"
    "  to set up the filter for the current platform. Subsequent calls will\n"
    "  overwrite the previous values.\n"
    "\n"
    "  If you want to bypass the filter and add a file even if it might\n"
    "  be filtered out, call set_sources_assignment_filter([]) to clear the\n"
    "  list of filters. This will apply until the current scope exits\n"
    "\n"
    "How to use patterns\n"
    "\n"
    "  File patterns are VERY limited regular expressions. They must match\n"
    "  the entire input string to be counted as a match. In regular\n"
    "  expression parlance, there is an implicit \"^...$\" surrounding your\n"
    "  input. If you want to match a substring, you need to use wildcards at\n"
    "  the beginning and end.\n"
    "\n"
    "  There are only two special tokens understood by the pattern matcher.\n"
    "  Everything else is a literal.\n"
    "\n"
    "   * Matches zero or more of any character. It does not depend on the\n"
    "     preceding character (in regular expression parlance it is\n"
    "     equivalent to \".*\").\n"
    "\n"
    "  \\b Matches a path boundary. This will match the beginning or end of\n"
    "     a string, or a slash.\n"
    "\n"
    "Pattern examples\n"
    "\n"
    "  \"*asdf*\"\n"
    "      Matches a string containing \"asdf\" anywhere.\n"
    "\n"
    "  \"asdf\"\n"
    "      Matches only the exact string \"asdf\".\n"
    "\n"
    "  \"*.cc\"\n"
    "      Matches strings ending in the literal \".cc\".\n"
    "\n"
    "  \"\\bwin/*\"\n"
    "      Matches \"win/foo\" and \"foo/win/bar.cc\" but not \"iwin/foo\".\n"
    "\n"
    "Sources assignment example\n"
    "\n"
    "  # Filter out all _win files.\n"
    "  set_sources_assignment_filter([ \"*_win.cc\", \"*_win.h\" ])\n"
    "  sources = [ \"a.cc\", \"b_win.cc\" ]\n"
    "  print(sources)\n"
    "  # Will print [ \"a.cc\" ]. b_win one was filtered out.\n";

Value RunSetSourcesAssignmentFilter(Scope* scope,
                                    const FunctionCallNode* function,
                                    const std::vector<Value>& args,
                                    Err* err) {
  if (args.size() != 1) {
    *err = Err(function, "set_sources_assignment_filter takes one argument.");
  } else {
    scoped_ptr<PatternList> f(new PatternList);
    f->SetFromValue(args[0], err);
    if (!err->has_error())
      scope->set_sources_assignment_filter(std::move(f));
  }
  return Value();
}

// print -----------------------------------------------------------------------

const char kPrint[] = "print";
const char kPrint_HelpShort[] =
    "print: Prints to the console.";
const char kPrint_Help[] =
    "print: Prints to the console.\n"
    "\n"
    "  Prints all arguments to the console separated by spaces. A newline is\n"
    "  automatically appended to the end.\n"
    "\n"
    "  This function is intended for debugging. Note that build files are run\n"
    "  in parallel so you may get interleaved prints. A buildfile may also\n"
    "  be executed more than once in parallel in the context of different\n"
    "  toolchains so the prints from one file may be duplicated or\n"
    "  interleaved with itself.\n"
    "\n"
    "Examples:\n"
    "  print(\"Hello world\")\n"
    "\n"
    "  print(sources, deps)\n";

Value RunPrint(Scope* scope,
               const FunctionCallNode* function,
               const std::vector<Value>& args,
               Err* err) {
  std::string output;
  for (size_t i = 0; i < args.size(); i++) {
    if (i != 0)
      output.push_back(' ');
    output.append(args[i].ToString(false));
  }
  output.push_back('\n');

  const BuildSettings::PrintCallback& cb =
      scope->settings()->build_settings()->print_callback();
  if (cb.is_null())
    printf("%s", output.c_str());
  else
    cb.Run(output);

  return Value();
}

// -----------------------------------------------------------------------------

FunctionInfo::FunctionInfo()
    : self_evaluating_args_runner(nullptr),
      generic_block_runner(nullptr),
      executed_block_runner(nullptr),
      no_block_runner(nullptr),
      help_short(nullptr),
      help(nullptr),
      is_target(false) {
}

FunctionInfo::FunctionInfo(SelfEvaluatingArgsFunction seaf,
                           const char* in_help_short,
                           const char* in_help,
                           bool in_is_target)
    : self_evaluating_args_runner(seaf),
      generic_block_runner(nullptr),
      executed_block_runner(nullptr),
      no_block_runner(nullptr),
      help_short(in_help_short),
      help(in_help),
      is_target(in_is_target) {
}

FunctionInfo::FunctionInfo(GenericBlockFunction gbf,
                           const char* in_help_short,
                           const char* in_help,
                           bool in_is_target)
    : self_evaluating_args_runner(nullptr),
      generic_block_runner(gbf),
      executed_block_runner(nullptr),
      no_block_runner(nullptr),
      help_short(in_help_short),
      help(in_help),
      is_target(in_is_target) {
}

FunctionInfo::FunctionInfo(ExecutedBlockFunction ebf,
                           const char* in_help_short,
                           const char* in_help,
                           bool in_is_target)
    : self_evaluating_args_runner(nullptr),
      generic_block_runner(nullptr),
      executed_block_runner(ebf),
      no_block_runner(nullptr),
      help_short(in_help_short),
      help(in_help),
      is_target(in_is_target) {
}

FunctionInfo::FunctionInfo(NoBlockFunction nbf,
                           const char* in_help_short,
                           const char* in_help,
                           bool in_is_target)
    : self_evaluating_args_runner(nullptr),
      generic_block_runner(nullptr),
      executed_block_runner(nullptr),
      no_block_runner(nbf),
      help_short(in_help_short),
      help(in_help),
      is_target(in_is_target) {
}

// Setup the function map via a static initializer. We use this because it
// avoids race conditions without having to do some global setup function or
// locking-heavy singleton checks at runtime. In practice, we always need this
// before we can do anything interesting, so it's OK to wait for the
// initializer.
struct FunctionInfoInitializer {
  FunctionInfoMap map;

  FunctionInfoInitializer() {
    #define INSERT_FUNCTION(command, is_target) \
        map[k##command] = FunctionInfo(&Run##command, \
                                       k##command##_HelpShort, \
                                       k##command##_Help, \
                                       is_target);

    INSERT_FUNCTION(Action, true)
    INSERT_FUNCTION(ActionForEach, true)
    INSERT_FUNCTION(Copy, true)
    INSERT_FUNCTION(Executable, true)
    INSERT_FUNCTION(Group, true)
    INSERT_FUNCTION(LoadableModule, true)
    INSERT_FUNCTION(SharedLibrary, true)
    INSERT_FUNCTION(SourceSet, true)
    INSERT_FUNCTION(StaticLibrary, true)
    INSERT_FUNCTION(Target, true)

    INSERT_FUNCTION(Assert, false)
    INSERT_FUNCTION(Config, false)
    INSERT_FUNCTION(DeclareArgs, false)
    INSERT_FUNCTION(Defined, false)
    INSERT_FUNCTION(ExecScript, false)
    INSERT_FUNCTION(ForEach, false)
    INSERT_FUNCTION(ForwardVariablesFrom, false)
    INSERT_FUNCTION(GetEnv, false)
    INSERT_FUNCTION(GetLabelInfo, false)
    INSERT_FUNCTION(GetPathInfo, false)
    INSERT_FUNCTION(GetTargetOutputs, false)
    INSERT_FUNCTION(Import, false)
    INSERT_FUNCTION(Print, false)
    INSERT_FUNCTION(ProcessFileTemplate, false)
    INSERT_FUNCTION(ReadFile, false)
    INSERT_FUNCTION(RebasePath, false)
    INSERT_FUNCTION(SetDefaults, false)
    INSERT_FUNCTION(SetDefaultToolchain, false)
    INSERT_FUNCTION(SetSourcesAssignmentFilter, false)
    INSERT_FUNCTION(Template, false)
    INSERT_FUNCTION(Tool, false)
    INSERT_FUNCTION(Toolchain, false)
    INSERT_FUNCTION(ToolchainArgs, false)
    INSERT_FUNCTION(WriteFile, false)

    #undef INSERT_FUNCTION
  }
};
const FunctionInfoInitializer function_info;

const FunctionInfoMap& GetFunctions() {
  return function_info.map;
}

Value RunFunction(Scope* scope,
                  const FunctionCallNode* function,
                  const ListNode* args_list,
                  BlockNode* block,
                  Err* err) {
  const Token& name = function->function();

  const FunctionInfoMap& function_map = GetFunctions();
  FunctionInfoMap::const_iterator found_function =
      function_map.find(name.value());
  if (found_function == function_map.end()) {
    // No built-in function matching this, check for a template.
    const Template* templ =
        scope->GetTemplate(function->function().value().as_string());
    if (templ) {
      Value args = args_list->Execute(scope, err);
      if (err->has_error())
        return Value();
      return templ->Invoke(scope, function, args.list_value(), block, err);
    }

    *err = Err(name, "Unknown function.");
    return Value();
  }

  if (found_function->second.self_evaluating_args_runner) {
    // Self evaluating args functions are special weird built-ins like foreach.
    // Rather than force them all to check that they have a block or no block
    // and risk bugs for new additions, check a whitelist here.
    if (found_function->second.self_evaluating_args_runner != &RunForEach) {
      if (!VerifyNoBlockForFunctionCall(function, block, err))
        return Value();
    }
    return found_function->second.self_evaluating_args_runner(
        scope, function, args_list, err);
  }

  // All other function types take a pre-executed set of args.
  Value args = args_list->Execute(scope, err);
  if (err->has_error())
    return Value();

  if (found_function->second.generic_block_runner) {
    if (!block) {
      FillNeedsBlockError(function, err);
      return Value();
    }
    return found_function->second.generic_block_runner(
        scope, function, args.list_value(), block, err);
  }

  if (found_function->second.executed_block_runner) {
    if (!block) {
      FillNeedsBlockError(function, err);
      return Value();
    }

    Scope block_scope(scope);
    block->Execute(&block_scope, err);
    if (err->has_error())
      return Value();

    Value result = found_function->second.executed_block_runner(
        function, args.list_value(), &block_scope, err);
    if (err->has_error())
      return Value();

    if (!block_scope.CheckForUnusedVars(err))
      return Value();
    return result;
  }

  // Otherwise it's a no-block function.
  if (!VerifyNoBlockForFunctionCall(function, block, err))
    return Value();
  return found_function->second.no_block_runner(scope, function,
                                                args.list_value(), err);
}

}  // namespace functions