[ST-5243] Make splitChunks configurable (#167)

* [ST-5243] Make splitChunks configurable

* Add tests

---------

Co-authored-by: James ODonnell <james.odonnell@skyscanner.net>

packages/react-scripts/README.md

@@ -30,6 +30,7 @@ npm start
   - `babelIncludePrefixes`: An array of module name prefixes to opt into babel compilation, including local import module, e.g. `"../common"`. Includes `["@skyscanner/bpk-", "bpk-", "saddlebag-"]` by default.
   - `enableAutomaticChunking`: Boolean, opt in to automatic chunking of vendor, common and app code.
   - `vendorsChunkRegex`: String, Regex for picking what goes into the `vendors` chunk. See `cacheGroups` in webpack docs. Dependent on `enableAutomaticChunking` being enabled
+  - `splitChunksConfig`: Object, mapping to the [structure in the webpack docs](https://webpack.js.org/plugins/split-chunks-plugin/#optimizationsplitchunks). Applied only if `enableAutomaticChunking` is false, ignores `vendorsChunkRegex` if defined.
   - `amdExcludes`: Array of module names to exclude from AMD parsing. Incldues `["lodash"]` by default.
   - `externals`: exposing the Webpack config to modify externals, see [docs](https://webpack.js.org/configuration/externals/).
   - `ssrExternals`: Similar to above, but for `ssr.js` only.

packages/react-scripts/backpack-addons/README.md

@@ -14,6 +14,7 @@ Our react scripts fork includes a number of custom configuration items in order
 | **ssrExternals** | The same as above `externals` except used for server side rendering only in **ssr.js** | **{}** |
 | **enableAutomaticChunking** | Opts into automatic chunking of vender, common and app code.<br> When enabled the **splitChunks** plugin creates vender and common chunks which are split and when provided uses the `venderChunkRegex` to specify what is in each chunk.<br> When enabled **runtimeChunk** plugin creates a separate runtime chunk for projects to enable long term caching. | **false** |
 | **vendorsChunkRegex** | Regex for picking what goes into the vendors chunk. Requires enableAutomaticChunking to be enabled.<br> See [cacheGroups](https://webpack.js.org/plugins/split-chunks-plugin/#splitchunkscachegroups) docs for further details. |  |
+| **splitChunksConfig** | Object, mapping to the [structure in the webpack docs](https://webpack.js.org/plugins/split-chunks-plugin/#optimizationsplitchunks).<br> Applied only if `enableAutomaticChunking` is false, ignores `vendorsChunkRegex` if defined. |  |
 | **sassFunctions** | This function encodes svg content into `base64` when there is a `bpk-icon` in the.scss file. |  |
 
 ## How to add new feature

packages/react-scripts/backpack-addons/splitChunks.js

@@ -1,26 +1,93 @@
+/**
+ * Defines a webpack splitChunks configuration, optionally based on consumer configuration.
+ *
+ * For automatic configuration set enableAutomaticChunking and optionally provide a vendorsChunkRegex string, e.g:
+ *
+ * // package.json
+ * ...
+ * "backpack-react-scripts": {
+ *    ...
+ *    "enableAutomaticChunking": true,
+ *    "vendorsChunkRegex": "...",
+ *    ...
+ * }
+ * ...
+ *
+ * For custom configuration disable enableAutomaticChunking and provide a configuration object, e.g:
+ *
+ * // package.json
+ * ...
+ * "backpack-react-scripts": {
+ *    ...
+ *    "enableAutomaticChunking": false,
+ *    "splitChunksConfig": {
+ *       "chunks": "all",
+ *       ...
+ *       "cacheGroups": {
+ *         "vendors": {
+ *           "test": "..."
+ *         },
+ *         "customChunk": {
+ *           "test": "..."
+ *           "priority": 100,
+ *           "chunks": "all",
+ *           "name": "customChunk",
+ *         },
+ *      },
+ *    ...
+ * }
+ * ...
+ *
+ * References:
+ * https://webpack.js.org/plugins/split-chunks-plugin/#optimizationsplitchunks
+ * https://webpack.js.org/plugins/split-chunks-plugin/#splitchunkscachegroups
+ * https://twitter.com/wSokra/status/969633336732905474
+ * https://medium.com/webpack/webpack-4-code-splitting-chunk-graph-and-the-splitchunks-optimization-be739a861366
+ */
+
 'use strict';
 
 const paths = require('../config/paths');
 const appPackageJson = require(paths.appPackageJson);
 const bpkReactScriptsConfig = appPackageJson['backpack-react-scripts'] || {};
 
-module.exports = (isEnvDevelopment) => {
-  // Automatically split vendor and commons
-  // https://twitter.com/wSokra/status/969633336732905474
-  // https://medium.com/webpack/webpack-4-code-splitting-chunk-graph-and-the-splitchunks-optimization-be739a861366
-  return {
-    splitChunks: bpkReactScriptsConfig.enableAutomaticChunking
-    ? {
+module.exports = isEnvDevelopment => {
+  let splitChunksConfig = {};
+
+  // If opted in to automatic chunking, apply default configuration
+  if (bpkReactScriptsConfig.enableAutomaticChunking) {
+    splitChunksConfig = {
       chunks: 'all',
       name: isEnvDevelopment,
-      cacheGroups: bpkReactScriptsConfig.vendorsChunkRegex
-        ? {
-            vendors: {
-              test: new RegExp(bpkReactScriptsConfig.vendorsChunkRegex)
-            },
-          }
-        : {},
+      cacheGroups: {},
+    };
+    // Apply vendorsChunkRegex if provided
+    if (bpkReactScriptsConfig.vendorsChunkRegex) {
+      splitChunksConfig.cacheGroups = {
+        vendors: {
+          // Regexes are passed as strings in package.json config, but need constructed here.
+          test: new RegExp(bpkReactScriptsConfig.vendorsChunkRegex),
+        },
+      };
+    }
+  }
+  // If not opted in to automatic chunking, use custom configuration - if defined.
+  else if (bpkReactScriptsConfig.splitChunksConfig) {
+    splitChunksConfig = {
+      ...bpkReactScriptsConfig.splitChunksConfig,
+      name: isEnvDevelopment,
+    };
+    if (splitChunksConfig.cacheGroups) {
+      // Regexes are passed as strings in package.json config, but need constructed here.
+      for (let cacheGroup of Object.keys(splitChunksConfig.cacheGroups)) {
+        splitChunksConfig.cacheGroups[cacheGroup].test = new RegExp(
+          splitChunksConfig.cacheGroups[cacheGroup].test
+        );
       }
-    : {}
+    }
   }
-};
+
+  return {
+    splitChunks: splitChunksConfig,
+  };
+};

packages/react-scripts/backpack-addons/splitChunks.test.js

@@ -0,0 +1,234 @@
+'use strict';
+
+jest.mock('../config/paths', () => ({
+  appPackageJson: './test/mockPackage.json',
+}));
+
+describe('splitChunks', () => {
+  const mockData = {
+    name: 'test',
+    version: '1.0.0',
+    'backpack-react-scripts': {},
+  };
+
+  let isEnvDevelopment = true;
+
+  beforeEach(() => {
+    jest.resetModules();
+  });
+
+  test('should return default if no config defined', () => {
+    jest.doMock('./test/mockPackage.json', () => ({
+      ...mockData,
+      'backpack-react-scripts': {},
+    }));
+    const splitChunks = require('../backpack-addons/splitChunks');
+
+    let res = splitChunks(isEnvDevelopment);
+
+    expect(res).toEqual({ splitChunks: {} });
+  });
+
+  test('should apply basic defaults if automatic chunking enabled without vendors regex', () => {
+    jest.doMock('./test/mockPackage.json', () => ({
+      ...mockData,
+      'backpack-react-scripts': {
+        enableAutomaticChunking: true,
+      },
+    }));
+    const splitChunks = require('../backpack-addons/splitChunks');
+
+    let res = splitChunks(isEnvDevelopment);
+
+    expect(res).toEqual({
+      splitChunks: { chunks: 'all', name: true, cacheGroups: {} },
+    });
+  });
+
+  test('should return empty if automatic chunking false and no other config is defined', () => {
+    jest.doMock('./test/mockPackage.json', () => ({
+      ...mockData,
+      'backpack-react-scripts': {
+        enableAutomaticChunking: false,
+      },
+    }));
+    const splitChunks = require('../backpack-addons/splitChunks');
+
+    let res = splitChunks(isEnvDevelopment);
+
+    expect(res).toEqual({ splitChunks: {} });
+  });
+
+  test('should apply basic defaults and cacheGroup with vendors RegExp when automatic chunking enabled and vendors regex provided', () => {
+    jest.doMock('./test/mockPackage.json', () => ({
+      ...mockData,
+      'backpack-react-scripts': {
+        enableAutomaticChunking: true,
+        vendorsChunkRegex: '[\\/]node_modules[\\/]',
+      },
+    }));
+    const splitChunks = require('../backpack-addons/splitChunks');
+
+    let res = splitChunks(isEnvDevelopment);
+
+    expect(res).toEqual({
+      splitChunks: {
+        chunks: 'all',
+        name: true,
+        cacheGroups: { vendors: { test: expect.any(RegExp) } },
+      },
+    });
+  });
+
+  test('should return empty when automatic chunking disabled and vendors regex provided', () => {
+    jest.doMock('./test/mockPackage.json', () => ({
+      ...mockData,
+      'backpack-react-scripts': {
+        enableAutomaticChunking: false,
+        vendorsChunkRegex: '[\\/]node_modules[\\/]',
+      },
+    }));
+    const splitChunks = require('../backpack-addons/splitChunks');
+
+    let res = splitChunks(isEnvDevelopment);
+
+    expect(res).toEqual({ splitChunks: {} });
+  });
+
+  test('should ignore custom config when automatic chunking enabled and splitChunksConfig is also defined', () => {
+    jest.doMock('./test/mockPackage.json', () => ({
+      ...mockData,
+      'backpack-react-scripts': {
+        enableAutomaticChunking: true,
+        splitChunksConfig: {
+          cacheGroups: {
+            vendors: {
+              test: '[\\/]node_modules[\\/]',
+            },
+            someCustomChunk: {
+              test: '[\\/]some_regex[\\/]',
+              priority: 100,
+              chunks: 'all',
+              name: 'someCustomChunk',
+            },
+          },
+        },
+      },
+    }));
+    const splitChunks = require('../backpack-addons/splitChunks');
+
+    let res = splitChunks(isEnvDevelopment);
+
+    expect(res).toEqual({
+      splitChunks: { chunks: 'all', name: true, cacheGroups: {} },
+    });
+  });
+
+  test('should not ignore custom config when automatic chunking disabled and splitChunksConfig is defined', () => {
+    jest.doMock('./test/mockPackage.json', () => ({
+      ...mockData,
+      'backpack-react-scripts': {
+        enableAutomaticChunking: false,
+        splitChunksConfig: {
+          chunks: 'all',
+          cacheGroups: {
+            vendors: {
+              test: '[\\/]node_modules[\\/]',
+            },
+          },
+        },
+      },
+    }));
+    const splitChunks = require('../backpack-addons/splitChunks');
+
+    let res = splitChunks(isEnvDevelopment);
+
+    expect(res).toEqual({
+      splitChunks: {
+        chunks: 'all',
+        name: true,
+        cacheGroups: {
+          vendors: {
+            test: expect.any(RegExp),
+          },
+        },
+      },
+    });
+  });
+
+  test('should apply only the name field when splitChunks is empty', () => {
+    jest.doMock('./test/mockPackage.json', () => ({
+      ...mockData,
+      'backpack-react-scripts': {
+        enableAutomaticChunking: false,
+        splitChunksConfig: {},
+      },
+    }));
+    const splitChunks = require('../backpack-addons/splitChunks');
+
+    let res = splitChunks(isEnvDevelopment);
+
+    expect(res).toEqual({ splitChunks: { name: true } });
+  });
+
+  test('should apply Regexes when multiple cacheGroups are applied', () => {
+    jest.doMock('./test/mockPackage.json', () => ({
+      ...mockData,
+      'backpack-react-scripts': {
+        enableAutomaticChunking: false,
+        splitChunksConfig: {
+          chunks: 'all',
+          cacheGroups: {
+            vendors: {
+              test: '[\\/]node_modules[\\/]',
+            },
+            someCustomChunk: {
+              test: '[\\/]some_regex[\\/]',
+              priority: 100,
+              chunks: 'all',
+              name: 'someCustomChunk',
+            },
+          },
+        },
+      },
+    }));
+    const splitChunks = require('../backpack-addons/splitChunks');
+
+    let res = splitChunks(isEnvDevelopment);
+
+    expect(res).toEqual({
+      splitChunks: {
+        chunks: 'all',
+        name: true,
+        cacheGroups: {
+          vendors: {
+            test: expect.any(RegExp),
+          },
+          someCustomChunk: {
+            test: expect.any(RegExp),
+            priority: 100,
+            chunks: 'all',
+            name: 'someCustomChunk',
+          },
+        },
+      },
+    });
+  });
+
+  test('should apply isEnvDevelopment boolean as name value', () => {
+    let isEnvDevelopment = false;
+    jest.doMock('./test/mockPackage.json', () => ({
+      ...mockData,
+      'backpack-react-scripts': {
+        enableAutomaticChunking: true,
+      },
+    }));
+    const splitChunks = require('../backpack-addons/splitChunks');
+
+    let res = splitChunks(isEnvDevelopment);
+
+    expect(res).toEqual({
+      splitChunks: { chunks: 'all', name: false, cacheGroups: {} },
+    });
+  });
+});

packages/react-scripts/package.json

@@ -21,6 +21,9 @@
     "utils",
     "backpack-addons"
   ],
+  "scripts": {
+    "test:addons": "jest --testPathPattern=backpack-addons"
+  },
   "bin": {
     "react-scripts": "./bin/react-scripts.js"
   },