any-component-style-budget-checker.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 path from 'path';
import { Compiler } from 'webpack';
import { Budget, Type } from '../../browser/schema';
import { ThresholdSeverity, calculateThresholds, checkThresholds } from '../../utils/bundle-calculator';
import { addError, addWarning } from '../../utils/webpack-diagnostics';
import { isWebpackFiveOrHigher } from '../../utils/webpack-version';

const PLUGIN_NAME = 'AnyComponentStyleBudgetChecker';

/**
 * Check budget sizes for component styles by emitting a warning or error if a
 * budget is exceeded by a particular component's styles.
 */
export class AnyComponentStyleBudgetChecker {
  private readonly budgets: Budget[];

  constructor(budgets: Budget[]) {
    this.budgets = budgets.filter((budget) => budget.type === Type.AnyComponentStyle);
  }

  apply(compiler: Compiler) {
    compiler.hooks.compilation.tap(PLUGIN_NAME, (compilation) => {
      const afterOptimizeChunkAssets = () => {
        // In AOT compilations component styles get processed in child compilations.
        // tslint:disable-next-line: no-any
        const parentCompilation = (compilation.compiler as any).parentCompilation;
        if (!parentCompilation) {
          return;
        }

        const cssExtensions = [
          '.css',
          '.scss',
          '.less',
          '.styl',
          '.sass',
        ];

        const componentStyles = Object.keys(compilation.assets)
          .filter((name) => cssExtensions.includes(path.extname(name)))
          .map((name) => ({
            size: compilation.assets[name].size(),
            label: name,
          }));
        const thresholds = flatMap(this.budgets, (budget) => calculateThresholds(budget));

        for (const {size, label} of componentStyles) {
          for (const {severity, message} of checkThresholds(thresholds[Symbol.iterator](), size, label)) {
            switch (severity) {
              case ThresholdSeverity.Warning:
                addWarning(compilation, message);
                break;
              case ThresholdSeverity.Error:
                addError(compilation, message);
                break;
              default:
                assertNever(severity);
                break;
            }
          }
        }
      };

      if (isWebpackFiveOrHigher()) {
        // webpack 5 migration "guide"
        // https://github.com/webpack/webpack/blob/07fc554bef5930f8577f91c91a8b81791fc29746/lib/Compilation.js#L535-L539
        // TODO_WEBPACK_5 const stage = Compilation.PROCESS_ASSETS_STAGE_OPTIMIZE + 1;
        const stage = 101;
        // tslint:disable-next-line: no-any
        (compilation.hooks as any).processAssets.tap({name: PLUGIN_NAME, stage}, afterOptimizeChunkAssets);
      } else {
        compilation.hooks.afterOptimizeChunkAssets.tap(PLUGIN_NAME, afterOptimizeChunkAssets);
      }
    });
  }
}

function assertNever(input: never): never {
  throw new Error(`Unexpected call to assertNever() with input: ${
      JSON.stringify(input, null /* replacer */, 4 /* tabSize */)}`);
}

function flatMap<T, R>(list: T[], mapper: (item: T, index: number, array: T[]) => IterableIterator<R>): R[] {
  return ([] as R[]).concat(...list.map(mapper).map((iterator) => Array.from(iterator)));

}