From bc1c6841f536bc17f1287ca0e54f0b4ec38b00c5 Mon Sep 17 00:00:00 2001
From: Simen Bekkhus <sbekkhus91@gmail.com>
Date: Thu, 23 Apr 2020 17:40:12 +0200
Subject: [PATCH] fix: pass custom cached realpath function to `resolve`
 (#9873)

---
 CHANGELOG.md                                 |  1 +
 packages/jest-resolve/src/defaultResolver.ts | 20 +++++++++++++++++---
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index ec36a2f6f407..9be830431972 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -15,6 +15,7 @@
 ### Performance
 
 - `[jest-resolve]` Update `resolve` to a version using native `realpath`, which is faster than the default JS implementation ([#9872](https://github.com/facebook/jest/pull/9872))
+- `[jest-resolve]` Pass custom cached `realpath` function to `resolve` ([#9873](https://github.com/facebook/jest/pull/9873))
 
 ## 25.4.0
 
diff --git a/packages/jest-resolve/src/defaultResolver.ts b/packages/jest-resolve/src/defaultResolver.ts
index 2481a8c606c4..0e20699364ba 100644
--- a/packages/jest-resolve/src/defaultResolver.ts
+++ b/packages/jest-resolve/src/defaultResolver.ts
@@ -52,6 +52,7 @@ export default function defaultResolver(
 
 export function clearDefaultResolverCache(): void {
   checkedPaths.clear();
+  checkedRealpathPaths.clear();
 }
 
 enum IPathType {
@@ -89,8 +90,14 @@ function statSyncCached(path: string): IPathType {
   return IPathType.OTHER;
 }
 
-function tolerantRealpath(path: Config.Path): Config.Path {
-  let result: Config.Path | undefined = undefined;
+const checkedRealpathPaths = new Map<string, string>();
+function realpathCached(path: Config.Path): Config.Path {
+  let result = checkedRealpathPaths.get(path);
+
+  if (result !== undefined) {
+    return result;
+  }
+
   try {
     result = realpath(path);
   } catch (error) {
@@ -103,6 +110,13 @@ function tolerantRealpath(path: Config.Path): Config.Path {
     result = path;
   }
 
+  checkedRealpathPaths.set(path, result);
+
+  if (path !== result) {
+    // also cache the result in case it's ever referenced directly - no reason to `realpath` that as well
+    checkedRealpathPaths.set(result, result);
+  }
+
   return result;
 }
 
@@ -118,5 +132,5 @@ function isDirectory(dir: Config.Path): boolean {
 }
 
 function realpathSync(file: Config.Path): Config.Path {
-  return tolerantRealpath(file);
+  return realpathCached(file);
 }