From 563d9c565c7e00ae6d13307737da63df99e68b9b Mon Sep 17 00:00:00 2001
From: Simen Bekkhus <sbekkhus91@gmail.com>
Date: Thu, 23 Apr 2020 09:05:18 +0200
Subject: [PATCH] fix: pass custom cached realpath function to `resolve`

---
 CHANGELOG.md                                 |  1 +
 packages/jest-resolve/src/defaultResolver.ts | 49 ++++++++++++++------
 2 files changed, 36 insertions(+), 14 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7f1165f46273..1b51d48e0c9e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,7 @@
 
 ### Fixes
 
+- `[jest-resolve]` Pass custom cached `realpath` function to `resolve` ([#9873](https://github.com/facebook/jest/pull/9873))
 - `[jest-runtime]` Support importing CJS from ESM using `import` statements ([#9850](https://github.com/facebook/jest/pull/9850))
 - `[jest-runtime]` Support importing parallel dynamic `import`s ([#9858](https://github.com/facebook/jest/pull/9858))
 
diff --git a/packages/jest-resolve/src/defaultResolver.ts b/packages/jest-resolve/src/defaultResolver.ts
index 30a7d7948881..0d796e88abe2 100644
--- a/packages/jest-resolve/src/defaultResolver.ts
+++ b/packages/jest-resolve/src/defaultResolver.ts
@@ -42,26 +42,17 @@ export default function defaultResolver(
     paths: options.paths,
     preserveSymlinks: false,
     // @ts-ignore: https://github.com/DefinitelyTyped/DefinitelyTyped/pull/44137
-    realpathSync: realpath,
+    realpathSync,
   });
 
-  try {
-    // Dereference symlinks to ensure we don't create a separate
-    // module instance depending on how it was referenced.
-    const resolved = realpath(result);
-
-    if (resolved) {
-      return resolved;
-    }
-  } catch {
-    // ignore
-  }
-
-  return result;
+  // Dereference symlinks to ensure we don't create a separate
+  // module instance depending on how it was referenced.
+  return realpathSync(result);
 }
 
 export function clearDefaultResolverCache(): void {
   checkedPaths.clear();
+  checkedRealpathPaths.clear();
 }
 
 enum IPathType {
@@ -99,6 +90,32 @@ function statSyncCached(path: string): IPathType {
   return IPathType.OTHER;
 }
 
+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 {
+    // ignore
+  }
+
+  if (!result) {
+    result = path;
+  }
+
+  checkedRealpathPaths.set(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;
+}
+
 /*
  * helper functions
  */
@@ -109,3 +126,7 @@ function isFile(file: Config.Path): boolean {
 function isDirectory(dir: Config.Path): boolean {
   return statSyncCached(dir) === IPathType.DIRECTORY;
 }
+
+function realpathSync(file: Config.Path): Config.Path {
+  return realpathCached(file);
+}