cli: remove jest script module cache

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

.changeset/full-chefs-roll.md

@@ -0,0 +1,5 @@
+---
+'@backstage/cli': patch
+---
+
+Removed the script transform cache from the default Jest configuration. The script cache provided a moderate performance boost, but it is incomatible with Jest 30.

packages/cli/config/jestCachingModuleLoader.js

@@ -16,29 +16,12 @@
 
 const { default: JestRuntime } = require('jest-runtime');
 
-const scriptTransformCache = new Map();
-
 module.exports = class CachingJestRuntime extends JestRuntime {
   constructor(config, ...restArgs) {
     super(config, ...restArgs);
     this.allowLoadAsEsm = config.extensionsToTreatAsEsm.includes('.mts');
   }
 
-  // This may or may not be a good idea. Theoretically I don't know why this would impact
-  // test correctness and flakiness, but it seems like it may introduce flakiness and strange failures.
-  // It does seem to speed up test execution by a fair amount though.
-  createScriptFromCode(scriptSource, filename) {
-    let script = scriptTransformCache.get(scriptSource);
-    if (!script) {
-      script = super.createScriptFromCode(scriptSource, filename);
-      // Tried to store the script object in a WeakRef here. It starts out at
-      // about 90% hit rate, but eventually drops all the way to 20%, and overall
-      // it seemed to increase memory usage by 20% or so.
-      scriptTransformCache.set(scriptSource, script);
-    }
-    return script;
-  }
-
   // Unfortunately we need to use this unstable API to make sure that .js files
   // are only loaded as modules where ESM is supported, i.e. Node.js packages.
   unstable_shouldLoadAsEsm(path, ...restArgs) {