From 688f0aa873495042996a269e791d89073f7d59a0 Mon Sep 17 00:00:00 2001
From: Simen Bekkhus <sbekkhus91@gmail.com>
Date: Wed, 30 Dec 2020 17:24:40 +0100
Subject: [PATCH] cache lookups

---
 packages/jest-runtime/src/index.ts | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/packages/jest-runtime/src/index.ts b/packages/jest-runtime/src/index.ts
index 04bcaff6242c..a4992f045f4f 100644
--- a/packages/jest-runtime/src/index.ts
+++ b/packages/jest-runtime/src/index.ts
@@ -165,7 +165,8 @@ export default class Runtime {
   private readonly _moduleMocker: ModuleMocker;
   private _isolatedModuleRegistry: ModuleRegistry | null;
   private _moduleRegistry: ModuleRegistry;
-  private readonly _esmoduleRegistry: Map<string, EsmModuleCache>;
+  private readonly _esmoduleRegistry: Map<Config.Path, EsmModuleCache>;
+  private readonly _cjsNamedExports: Map<Config.Path, Set<string>>;
   private readonly _testPath: Config.Path;
   private readonly _resolver: Resolver;
   private _shouldAutoMock: boolean;
@@ -214,6 +215,7 @@ export default class Runtime {
     this._isolatedMockRegistry = null;
     this._moduleRegistry = new Map();
     this._esmoduleRegistry = new Map();
+    this._cjsNamedExports = new Map();
     this._testPath = testPath;
     this._resolver = resolver;
     this._scriptTransformer = new ScriptTransformer(config, this._cacheFS);
@@ -551,21 +553,29 @@ export default class Runtime {
   }
 
   private getExportsOfCjs(modulePath: Config.Path) {
+    const cachedNamedExports = this._cjsNamedExports.get(modulePath);
+
+    if (cachedNamedExports) {
+      return cachedNamedExports;
+    }
+
     const transformedCode =
       this._fileTransforms.get(modulePath)?.code ?? this.readFile(modulePath);
 
     const {exports, reexports} = parseCjs(transformedCode);
 
-    let namedExports = new Set(exports);
+    const namedExports = new Set(exports);
 
     reexports.forEach(reexport => {
       const resolved = this._resolveModule(modulePath, reexport);
 
       const exports = this.getExportsOfCjs(resolved);
 
-      namedExports = new Set([...namedExports, ...exports]);
+      exports.forEach(namedExports.add, namedExports);
     });
 
+    this._cjsNamedExports.set(modulePath, namedExports);
+
     return namedExports;
   }
 
@@ -858,6 +868,7 @@ export default class Runtime {
     this._mockRegistry.clear();
     this._moduleRegistry.clear();
     this._esmoduleRegistry.clear();
+    this._cjsNamedExports.clear();
 
     if (this._environment) {
       if (this._environment.global) {