From a9c0e6bd13e8686811dcbc6ab52da0ca81225de6 Mon Sep 17 00:00:00 2001
From: Mikhail Bodrov <bodrovmiha@yandex.ru>
Date: Wed, 1 May 2019 19:55:20 +0300
Subject: [PATCH] Cache checked files in fs (#8388)

* Cache checked files in fs

* Cache checked dirs in fs

* Refactoring isfile

* Add to change.md

* Use unem instead of const

* Update changelog
---
 CHANGELOG.md                                 |  1 +
 packages/jest-resolve/src/defaultResolver.ts | 57 ++++++++++++--------
 2 files changed, 35 insertions(+), 23 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6391a1227bfa..e8ed064057cf 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -37,6 +37,7 @@
 ### Performance
 
 - `[jest-runtime]` Fix module registry memory leak ([#8282](https://github.com/facebook/jest/pull/8282))
+- `[jest-resolve]` optimize resolve module path ([#8388](https://github.com/facebook/jest/pull/8388))
 
 ## 24.7.1
 
diff --git a/packages/jest-resolve/src/defaultResolver.ts b/packages/jest-resolve/src/defaultResolver.ts
index 44d94620b2b6..8a2e4c9d8c15 100644
--- a/packages/jest-resolve/src/defaultResolver.ts
+++ b/packages/jest-resolve/src/defaultResolver.ts
@@ -142,39 +142,50 @@ function resolveSync(
   }
 }
 
-/*
- * helper functions
- */
-function isFile(file: Config.Path): boolean {
-  let result;
+enum IPathType {
+  FILE = 1,
+  DIRECTORY = 2,
+  OTHER = 3,
+}
+const checkedPaths = new Map<string, IPathType>();
+function statSyncCached(path: string): number {
+  const result = checkedPaths.get(path);
+  if (result !== undefined) {
+    return result;
+  }
 
+  let stat;
   try {
-    const stat = fs.statSync(file);
-    result = stat.isFile() || stat.isFIFO();
+    stat = fs.statSync(path);
   } catch (e) {
-    if (!(e && e.code === 'ENOENT')) {
+    if (!(e && (e.code === 'ENOENT' || e.code === 'ENOTDIR'))) {
       throw e;
     }
-    result = false;
   }
 
-  return result;
-}
-
-function isDirectory(dir: Config.Path): boolean {
-  let result;
-
-  try {
-    const stat = fs.statSync(dir);
-    result = stat.isDirectory();
-  } catch (e) {
-    if (!(e && (e.code === 'ENOENT' || e.code === 'ENOTDIR'))) {
-      throw e;
+  if (stat) {
+    if (stat.isFile() || stat.isFIFO()) {
+      checkedPaths.set(path, IPathType.FILE);
+      return IPathType.FILE;
+    } else if (stat.isDirectory()) {
+      checkedPaths.set(path, IPathType.DIRECTORY);
+      return IPathType.DIRECTORY;
     }
-    result = false;
   }
 
-  return result;
+  checkedPaths.set(path, IPathType.OTHER);
+  return IPathType.OTHER;
+}
+
+/*
+ * helper functions
+ */
+function isFile(file: Config.Path): boolean {
+  return statSyncCached(file) === IPathType.FILE;
+}
+
+function isDirectory(dir: Config.Path): boolean {
+  return statSyncCached(dir) === IPathType.DIRECTORY;
 }
 
 function isCurrentDirectory(testPath: Config.Path): boolean {