pkg/polymer/lib/src/paths.dart

// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

/**
 * Holds path information that is used by the WebUI compiler to find files,
 * compute their output location and relative paths between them.
 */
library polymer.src.paths;

import 'info.dart' show UrlInfo;
import 'messages.dart';
import 'summary.dart';
import 'utils.dart' show path, pathToUrl;

/**
 * Stores information about paths and computes mappings between input and output
 * path locations.
 */
class PathMapper {
  /**
   * Common prefix to all input paths that are read from the file system. The
   * output generated by the compiler will reflect the directory structure
   * starting from [_baseDir]. For instance, if [_baseDir] is `a/b/c` and
   * [_outputDir] is `g/h/`, then the corresponding output file for
   * `a/b/c/e/f.html` will be under `g/h/e/f.html.dart`.
   */
  final String _baseDir;

  /** Base path where all output is generated. */
  final String _outputDir;

  /** The package root directory. */
  final String packageRoot;

  /** Whether to add prefixes and to output file names. */
  final bool _mangleFilenames;

  final bool _rewriteUrls;

  bool get _rewritePackageImports => _rewriteUrls || !_mangleFilenames;

  /** Default prefix added to all filenames. */
  static const String _DEFAULT_PREFIX = '_';

  PathMapper(String baseDir, String outputDir, this.packageRoot,
      bool forceMangle, this._rewriteUrls)
      : _baseDir = baseDir,
        _outputDir = outputDir,
        _mangleFilenames = forceMangle || (baseDir == outputDir);

  /** Add a prefix and [suffix] if [_mangleFilenames] is true */
  String mangle(String name, String suffix, [bool forceSuffix = false]) =>
    _mangleFilenames ? "$_DEFAULT_PREFIX$name$suffix"
        : (forceSuffix ? "$name$suffix" : name);

  /**
   * Checks that `input.resolvedPath` is a valid input path. It must be in
   * [_baseDir] and must not be in the [_outputDir]. If not, an error message
   * is added to [messages].
   */
  bool checkInputPath(UrlInfo input, Messages messages) {
    if (_mangleFilenames) return true;
    var canonicalized = path.normalize(input.resolvedPath);
    var parentDir = '..${path.separator}';
    if (!path.relative(canonicalized, from: _outputDir).startsWith(parentDir)) {
      messages.error(
          'The file ${input.resolvedPath} cannot be processed. '
          'Files cannot be under the output folder (${_outputDir}).',
          input.sourceSpan);
      return false;
    }
    if (path.relative(canonicalized, from: _baseDir).startsWith(parentDir)) {
      messages.error(
          'The file ${input.resolvedPath} cannot be processed. '
          'All processed files must be under the base folder (${_baseDir}), you'
          ' can specify the base folder using the --basedir flag.',
          input.sourceSpan);
      return false;
    }
    return true;
  }

  /**
   * The path to the output file corresponding to [input], by adding
   * [_DEFAULT_PREFIX] and a [suffix] to its file name.
   */
  String outputPath(String input, String suffix, [bool forceSuffix = false]) =>
      path.join(outputDirPath(input),
          mangle(path.basename(input), suffix, forceSuffix));

  /** The path to the output file corresponding to [info]. */
  String outputLibraryPath(LibrarySummary lib) =>
      path.join(outputDirPath(lib.dartCodeUrl.resolvedPath),
          lib.outputFilename);

  /** The corresponding output directory for [input]'s directory. */
  String outputDirPath(String input) {
    return _rewritePackages(path.normalize(
          path.join(_outputDir, path.relative(
              path.dirname(input), from: _baseDir))));
  }

  /**
   * We deal with `packages/` directories in a very special way. We assume it
   * points to resources loaded from other pub packages. If an output directory
   * is specified, the compiler will create a packages symlink so that
   * `package:` imports work.
   *
   * To make it possible to share components through pub, we allow using tags of
   * the form `<link rel="import" href="packages/...">`, so that you can
   * refer to components within the packages symlink.  Regardless of whether an
   * --out option was given to the compiler, we don't want to generate files
   * inside `packages/` for those components.  Instead we will generate such
   * code in a special directory called `_from_packages/`.
   */
  String _rewritePackages(String outputPath) {
    // TODO(jmesserly): this should match against packageRoot instead.
    if (!outputPath.contains('packages')) return outputPath;
    if (!_rewritePackageImports) return outputPath;
    var segments = path.split(outputPath);
    return path.joinAll(
        segments.map((s) => s == 'packages' ? '_from_packages' : s));
  }

  /**
   * Returns a url to import/export the output library represented by [target]
   * from the output library of [src]. In other words, a url to import or export
   * `target.outputFilename` from `src.outputFilename`.
   */
  String importUrlFor(LibrarySummary src, LibrarySummary target) {
    if (!_rewritePackageImports &&
        target.dartCodeUrl.url.startsWith('package:')) {
      return pathToUrl(path.join(path.dirname(target.dartCodeUrl.url),
            target.outputFilename));
    }
    var srcDir = path.dirname(src.dartCodeUrl.resolvedPath);
    var relDir = path.relative(
        path.dirname(target.dartCodeUrl.resolvedPath), from: srcDir);
    return pathToUrl(_rewritePackages(path.normalize(
          path.join(relDir, target.outputFilename))));
  }

  /**
   * Transforms a [target] url seen in [src] (e.g. a Dart import, a .css href in
   * an HTML file, etc) into a corresponding url from the output file associated
   * with [src]. This will keep 'package:', 'dart:', path-absolute, and absolute
   * urls intact, but it will fix relative paths to walk from the output
   * directory back to the input directory. An exception will be thrown if
   * [target] is not under [_baseDir].
   */
  String transformUrl(String src, String target) {
    var uri = Uri.parse(target);
    if (uri.isAbsolute) return target;
    if (!uri.scheme.isEmpty) return target;
    if (!uri.host.isEmpty) return target;
    if (uri.path.isEmpty) return target;  // Implies standalone ? or # in URI.
    if (path.isAbsolute(target)) return target;

    return pathToUrl(path.normalize(path.relative(
          path.join(path.dirname(src), target), from: outputDirPath(src))));
  }
}

/**
 * Returns a "mangled" name, with a prefix and [suffix] depending on the
 * compiler's settings. [forceSuffix] causes [suffix] to be appended even if
 * the compiler is not mangling names.
 */
typedef String NameMangler(String name, String suffix, [bool forceSuffix]);