angular-docs-cn/packages/compiler-cli/src/transformers/metadata_reader.ts

/**
 * @license
 * Copyright Google Inc. All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */

import * as ts from 'typescript';

import {METADATA_VERSION, ModuleMetadata} from '../metadata';

import {DTS} from './util';

export interface MetadataReaderHost {
  getSourceFileMetadata(filePath: string): ModuleMetadata|undefined;
  cacheMetadata?(fileName: string): boolean;
  fileExists(filePath: string): boolean;
  readFile(filePath: string): string;
}

export interface MetadataReaderCache {
  /**
   * @internal
   */
  data: Map<string, ModuleMetadata[]|undefined>;
}

export function createMetadataReaderCache(): MetadataReaderCache {
  const data = new Map<string, ModuleMetadata[]|undefined>();
  return {data};
}

export function readMetadata(
    filePath: string, host: MetadataReaderHost, cache?: MetadataReaderCache): ModuleMetadata[]|
    undefined {
  let metadatas = cache && cache.data.get(filePath);
  if (metadatas) {
    return metadatas;
  }
  if (host.fileExists(filePath)) {
    // If the file doesn't exists then we cannot return metadata for the file.
    // This will occur if the user referenced a declared module for which no file
    // exists for the module (i.e. jQuery or angularjs).
    if (DTS.test(filePath)) {
      metadatas = readMetadataFile(host, filePath);
      if (!metadatas) {
        // If there is a .d.ts file but no metadata file we need to produce a
        // metadata from the .d.ts file as metadata files capture reexports
        // (starting with v3).
        metadatas = [upgradeMetadataWithDtsData(
            host, {'__symbolic': 'module', 'version': 1, 'metadata': {}}, filePath)];
      }
    } else {
      const metadata = host.getSourceFileMetadata(filePath);
      metadatas = metadata ? [metadata] : [];
    }
  }
  if (cache && (!host.cacheMetadata || host.cacheMetadata(filePath))) {
    cache.data.set(filePath, metadatas);
  }
  return metadatas;
}


function readMetadataFile(host: MetadataReaderHost, dtsFilePath: string): ModuleMetadata[]|
    undefined {
  const metadataPath = dtsFilePath.replace(DTS, '.metadata.json');
  if (!host.fileExists(metadataPath)) {
    return undefined;
  }
  try {
    const metadataOrMetadatas = JSON.parse(host.readFile(metadataPath));
    const metadatas: ModuleMetadata[] = metadataOrMetadatas ?
        (Array.isArray(metadataOrMetadatas) ? metadataOrMetadatas : [metadataOrMetadatas]) :
        [];
    if (metadatas.length) {
      let maxMetadata = metadatas.reduce((p, c) => p.version > c.version ? p : c);
      if (maxMetadata.version < METADATA_VERSION) {
        metadatas.push(upgradeMetadataWithDtsData(host, maxMetadata, dtsFilePath));
      }
    }
    return metadatas;
  } catch (e) {
    console.error(`Failed to read JSON file ${metadataPath}`);
    throw e;
  }
}

function upgradeMetadataWithDtsData(
    host: MetadataReaderHost, oldMetadata: ModuleMetadata, dtsFilePath: string): ModuleMetadata {
  // patch v1 to v3 by adding exports and the `extends` clause.
  // patch v3 to v4 by adding `interface` symbols for TypeAlias
  let newMetadata: ModuleMetadata = {
    '__symbolic': 'module',
    'version': METADATA_VERSION,
    'metadata': {...oldMetadata.metadata},
  };
  if (oldMetadata.exports) {
    newMetadata.exports = oldMetadata.exports;
  }
  if (oldMetadata.importAs) {
    newMetadata.importAs = oldMetadata.importAs;
  }
  if (oldMetadata.origins) {
    newMetadata.origins = oldMetadata.origins;
  }
  const dtsMetadata = host.getSourceFileMetadata(dtsFilePath);
  if (dtsMetadata) {
    for (let prop in dtsMetadata.metadata) {
      if (!newMetadata.metadata[prop]) {
        newMetadata.metadata[prop] = dtsMetadata.metadata[prop];
      }
    }

    // Only copy exports from exports from metadata prior to version 3.
    // Starting with version 3 the collector began collecting exports and
    // this should be redundant. Also, with bundler will rewrite the exports
    // which will hoist the exports from modules referenced indirectly causing
    // the imports to be different than the .d.ts files and using the .d.ts file
    // exports would cause the StaticSymbolResolver to redirect symbols to the
    // incorrect location.
    if ((!oldMetadata.version || oldMetadata.version < 3) && dtsMetadata.exports) {
      newMetadata.exports = dtsMetadata.exports;
    }
  }
  return newMetadata;
}