feat: Implement getCacheKey

package.json

@@ -49,6 +49,7 @@
     "sort": "npx sort-package-json"
   },
   "dependencies": {
+    "@jest/create-cache-key-function": "^27.5.1",
     "camelcase": "^6.3.0",
     "chokidar": "^3.5.3",
     "connect": "^3.7.0",
@@ -62,6 +63,7 @@
     "ws": "^8.5.0"
   },
   "devDependencies": {
+    "@jest/transform": "^27.5.1",
     "@swc/core": "^1.2.154",
     "@swc/jest": "^0.2.20",
     "@testing-library/jest-dom": "^5.16.2",

src/preconfigTransform/css.ts

@@ -1,8 +1,8 @@
 'use strict';
 
-import { processCss } from '../transform';
+import { processCss, getCacheKey } from '../transform';
 
 function process(src: string, filename: string) {
   return processCss(src, filename);
 }
-export default { process };
+export default { process, getCacheKey };

src/preconfigTransform/file.ts

@@ -1,8 +1,8 @@
 'use strict';
 
-import { processFile } from '../transform';
+import { processFile, getCacheKey } from '../transform';
 
 function process(src: string, filename: string) {
   return processFile(src, filename);
 }
-export default { process };
+export default { process, getCacheKey };

src/preconfigTransform/fileCRA.ts

@@ -1,8 +1,8 @@
 'use strict';
 
-import { processFileCRA } from '../transform';
+import { processFileCRA, getCacheKey } from '../transform';
 
 function process(src: string, filename: string) {
   return processFileCRA(src, filename);
 }
-export default { process };
+export default { process, getCacheKey };

src/transform.ts

@@ -1,5 +1,8 @@
 import path from 'path';
+import * as crypto from 'crypto';
 import camelcase from 'camelcase';
+import createCacheKey from '@jest/create-cache-key-function';
+import type { TransformOptions } from '@jest/transform';
 
 function getRelativeFilename(filename: string): string {
   return filename.split(process.cwd())[1];
@@ -105,3 +108,17 @@ document.body.appendChild(style);
 
 module.exports = exportedTokens`;
 }
+
+// Without implementing `cacheKeyFunction`, Jest still caches the result of the transformer
+// So what's the point of write a custom `getCacheKey`???
+const cacheKeyFunction = createCacheKey();
+export function getCacheKey(src: string, filename: string, ...rest: any[]) {
+  // @ts-expect-error - type overload is confused
+  const baseCacheKey = cacheKeyFunction(src, filename, ...rest);
+
+  // signature mismatch between Jest <27 og >=27
+  const options: TransformOptions =
+    typeof rest[0] === 'string' ? rest[1] : rest[0];
+
+  return crypto.createHash('md5').update(baseCacheKey).digest('hex');
+}