perf: do not hash cache key, jest does it underneath

package.json

@@ -78,7 +78,8 @@
   },
   "peerDependencies": {
     "babel-core": "^7.0.0-0",
-    "jest": "^23.0.0 || ^24.0.0",
+    "babel-jest": "^23.0.0",
+    "jest": "^23.0.0",
     "typescript": "2.x"
   },
   "devDependencies": {

src/utils/constants.ts

@@ -9,4 +9,5 @@ export const TSCONFIG_GLOBALS_KEY = 'ts-jest';
 export const PACKAGE_JSON = 'package.json';
 export const MY_PACKAGE_CONTENT = readFileSync(
   resolve(__dirname, '..', '..', PACKAGE_JSON),
+  'utf8',
 );

src/utils/get-babel-rc.ts

@@ -6,7 +6,6 @@ import {
   PACKAGE_JSON,
   BABEL_CONFIG_KEY,
 } from './constants';
-import { BabelTransformOptions } from '../types';
 
 const babelReaders = [
   {

src/utils/get-cache-key.ts

@@ -1,4 +1,3 @@
-import { createHash } from 'crypto';
 import { JestCacheKeyOptions } from '../types';
 import { relative } from 'path';
 import { MY_PACKAGE_CONTENT } from './constants';
@@ -14,20 +13,14 @@ export default function getCacheKey(
   const jestConfig: jest.ProjectConfig = JSON.parse(jestConfigString) || {};
   delete jestConfig.cacheDirectory;
   delete jestConfig.name;
-  const hash = createHash('md5')
-    .update(MY_PACKAGE_CONTENT)
-    .update('\0', 'utf8')
-    .update(fileData)
-    .update('\0', 'utf8')
-    .update(relative(rootDir, filePath))
-    .update('\0', 'utf8')
-    .update(jestConfigString)
-    .update('\0', 'utf8')
-    .update(JSON.stringify(getTSConfig(jestConfig)))
-    .update('\0', 'utf8');
-  const babelRc = getBabelRC(filePath);
-  if (babelRc) {
-    hash.update(JSON.stringify(babelRc)).update('\0', 'utf8');
-  }
-  return hash.update(instrument ? 'instrument' : '').digest('hex');
+  // jest creates hash under the hoods
+  return JSON.stringify([
+    MY_PACKAGE_CONTENT,
+    fileData,
+    relative(rootDir, filePath),
+    jestConfig,
+    getTSConfig(jestConfig),
+    getBabelRC(filePath),
+    instrument,
+  ]);
 }