fix: lower length of key to improve usage in win32

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 - `[jest-changed-files]` Support Sapling ([#13941](https://github.com/facebook/jest/pull/13941))
 - `[jest-cli, jest-config, @jest/core, jest-haste-map, @jest/reporters, jest-runner, jest-runtime, @jest/types]` Add `workerThreads` configuration option to allow using [worker threads](https://nodejs.org/dist/latest/docs/api/worker_threads.html) for parallelization ([#13939](https://github.com/facebook/jest/pull/13939))
+- `[@jest/create-cache-key-function]` Allow passing `length` argument to `createCacheKey()` function and set its default value to `16` on Windows ([#13827](https://github.com/facebook/jest/pull/13827))
 - `[jest-worker]` Add `start` method to worker farms ([#13937](https://github.com/facebook/jest/pull/13937))
 
 ### Fixes

packages/jest-create-cache-key-function/README.md

@@ -10,14 +10,15 @@ $ npm install --save-dev @jest/create-cache-key-function
 
 ## API
 
-### `createCacheKey(files?: Array<string>, values?: Array<String>): GetCacheKeyFunction`
+### `createCacheKey(files?: Array<string>, values?: Array<String>, length?: number): GetCacheKeyFunction`
 
-Get a function that can generate cache keys using source code, provided files and provided values.
+Returns a function that can be used to generate cache keys based on source code of provided files and provided values.
 
 #### Parameters
 
 - `files`: [Optional] Array of absolute paths to files whose code should be accounted for when generating cache key
 - `values`: [Optional] Array of string values that should be accounted for when generating cache key
+- `length`: [Optional] Length of the resulting key. The default is `32`, or `16` on Windows.
 
 **Note:**
 

packages/jest-create-cache-key-function/src/__tests__/index.test.ts

@@ -9,17 +9,22 @@ import {interopRequireDefault} from 'jest-util';
 
 let NODE_ENV: string;
 let BABEL_ENV: string;
+let PLATFORM: string;
 
 beforeEach(() => {
   NODE_ENV = process.env.NODE_ENV;
   process.env.NODE_ENV = 'test';
   BABEL_ENV = process.env.BABEL_ENV;
   process.env.BABEL_ENV = 'test';
+  PLATFORM = process.platform;
 });
 
 afterEach(() => {
   process.env.NODE_ENV = NODE_ENV;
   process.env.BABEL_ENV = BABEL_ENV;
+  Object.defineProperty(process, 'platform', {  
+    value: PLATFORM,
+  });
 });
 
 test('creation of a cache key', () => {
@@ -44,3 +49,19 @@ test('creation of a cache key', () => {
   expect(hashA).not.toEqual(hashB);
   expect(hashA).not.toEqual(hashC);
 });
+
+test('creation of a cache key on win32', () => {
+  Object.defineProperty(process, 'platform', {  
+    value: 'win32',
+  });
+  const createCacheKeyFunction = interopRequireDefault(
+    require('../index'),
+  ).default;
+  const createCacheKey = createCacheKeyFunction([], ['value']);
+  const hashA = createCacheKey('test', 'test.js', null, {
+    config: {},
+    instrument: false,
+  });
+
+  expect(hashA).toHaveLength(16);
+});

packages/jest-create-cache-key-function/src/index.ts

@@ -40,7 +40,11 @@ type NewGetCacheKeyFunction = (
 
 type GetCacheKeyFunction = OldGetCacheKeyFunction | NewGetCacheKeyFunction;
 
-function getGlobalCacheKey(files: Array<string>, values: Array<string>) {
+function getGlobalCacheKey(
+  files: Array<string>,
+  values: Array<string>,
+  length: number,
+) {
   return [
     process.env.NODE_ENV,
     process.env.BABEL_ENV,
@@ -52,10 +56,13 @@ function getGlobalCacheKey(files: Array<string>, values: Array<string>) {
       createHash('sha1'),
     )
     .digest('hex')
-    .substring(0, 32);
+    .substring(0, length);
 }
 
-function getCacheKeyFunction(globalCacheKey: string): GetCacheKeyFunction {
+function getCacheKeyFunction(
+  globalCacheKey: string,
+  length: number,
+): GetCacheKeyFunction {
   return (sourceText, sourcePath, configString, options) => {
     // Jest 27 passes a single options bag which contains `configString` rather than as a separate argument.
     // We can hide that API difference, though, so this module is usable for both jest@<27 and jest@>=27
@@ -71,13 +78,22 @@ function getCacheKeyFunction(globalCacheKey: string): GetCacheKeyFunction {
       .update('\0', 'utf8')
       .update(instrument ? 'instrument' : '')
       .digest('hex')
-      .substring(0, 32);
+      .substring(0, length);
   };
 }
 
+/**
+ * Returns a function that can be used to generate cache keys based on source code of provided files and provided values.
+ *
+ * @param files - Array of absolute paths to files whose code should be accounted for when generating cache key
+ * @param values - Array of string values that should be accounted for when generating cache key
+ * @param length - Length of the resulting key. The default is `32`, or `16` on Windows.
+ * @returns A function that can be used to generate cache keys.
+ */
 export default function createCacheKey(
   files: Array<string> = [],
   values: Array<string> = [],
+  length = process.platform === 'win32' ? 16 : 32,
 ): GetCacheKeyFunction {
-  return getCacheKeyFunction(getGlobalCacheKey(files, values));
+  return getCacheKeyFunction(getGlobalCacheKey(files, values, length), length);
 }