function_read_file.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 "base/file_util.h"
#include "tools/gn/err.h"
#include "tools/gn/filesystem_utils.h"
#include "tools/gn/functions.h"
#include "tools/gn/input_conversion.h"
#include "tools/gn/input_file.h"
#include "tools/gn/scheduler.h"

// TODO(brettw) consider removing this. I originally wrote it for making the
// WebKit bindings but misundersood what was required, and didn't need to
// use this. This seems to have a high potential for misuse.

/*
read_file: Read a file into a variable.

  read_file(filename, how_to_read)

  Whitespace will be trimmed from the end of the file. Throws an error if the
  file can not be opened.

Arguments:

  filename:
      Filename to read, relative to the build file.

  input_conversion:
      Controls how the file is read and parsed. See "help input_conversion".

Example:

  lines = read_file("foo.txt", "list lines")
*/
Value ExecuteReadFile(Scope* scope,
                      const FunctionCallNode* function,
                      const std::vector<Value>& args,
                      Err* err) {
  if (args.size() != 2) {
    *err = Err(function->function(), "Wrong number of args to read_file",
               "I expected two arguments.");
    return Value();
  }
  if (!args[0].VerifyTypeIs(Value::STRING, err))
    return Value();

  // Compute the file name.
  const SourceDir& cur_dir = SourceDirForFunctionCall(function);
  SourceFile source_file = cur_dir.ResolveRelativeFile(args[0].string_value());
  base::FilePath file_path =
      scope->settings()->build_settings()->GetFullPath(source_file);

  // Ensure that everything is recomputed if the read file changes.
  g_scheduler->AddGenDependency(source_file);

  // Read contents.
  std::string file_contents;
  if (!file_util::ReadFileToString(file_path, &file_contents)) {
    *err = Err(args[0], "Could not read file.",
               "I resolved this to \"" + FilePathToUTF8(file_path) + "\".");
    return Value();
  }

  return ConvertInputToValue(file_contents, function, args[1], err);
}