Class ReplaceChange

packages/schematics/angular/utility/change.ts:108–139

 * Will replace text from the source code.
 */
export class ReplaceChange implements Change {
  order: number;
  description: string;

  constructor(
    public path: string,
    private pos: number,
    public oldText: string,
    public newText: string,
  ) {
    if (pos < 0) {
      throw new Error('Negative positions are invalid');
    }
    this.description = `Replaced ${oldText} into position ${pos} of ${path} with ${newText}`;
    this.order = pos;
  }

  apply(host: Host): Promise<void> {
    return host.read(this.path).then((content) => {
      const prefix = content.substring(0, this.pos);
      const suffix = content.substring(this.pos + this.oldText.length);
      const text = content.substring(this.pos, this.pos + this.oldText.length);

      if (text !== this.oldText) {
        return Promise.reject(new Error(`Invalid replace: "${text}" != "${this.oldText}".`));
      }

      // TODO: throw error if oldText doesn't match removed string.
      return host.write(this.path, `${prefix}${this.newText}${suffix}`);
    });
  }
}

export function applyToUpdateRecorder(recorder: UpdateRecorder, changes: Change[]): void {
  for (const change of changes) {