perf: only register ts-node once when loading TS config files (#12160)

jestjs · Dec 20, 2021 · 4113c1d · 4113c1d
1 parent 9969060
commit 4113c1d
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -11,6 +11,8 @@
 
 ### Performance
 
+- `jest-config` perf: only register ts-node once when loading TS config files ([#12160](https://github.com/facebook/jest/pull/12160))
+
 ## 27.4.5
 
 ### Fixes

diff --git a/packages/jest-config/src/readConfigFileAndSetRootDir.ts b/packages/jest-config/src/readConfigFileAndSetRootDir.ts
@@ -79,15 +79,15 @@ export default async function readConfigFileAndSetRootDir(
   return configObject;
 }
 
+let registerer: Service;
+
 // Load the TypeScript configuration
 const loadTSConfigFile = async (
   configPath: Config.Path,
 ): Promise<Config.InitialOptions> => {
-  let registerer: Service;
-
   // Register TypeScript compiler instance
   try {
-    registerer = require('ts-node').register({
+    registerer ||= require('ts-node').register({
       compilerOptions: {
         module: 'CommonJS',
       },