From 4bac1128e61058160116df3dd1467a3414b10224 Mon Sep 17 00:00:00 2001
From: Aarni Koskela <akx@iki.fi>
Date: Fri, 10 Feb 2017 15:52:26 +0200
Subject: [PATCH 1/2] Instantiate default cache directory lazily, and only once

When using `cacheDirectory=true`, the `findCacheDir` module
is repeatedly called, and it does some synchronous filesystem
calls under the hood. However, since `findCacheDir` is more
or less a pure function, it's probably safe to call it only
once during process lifetime.
---
 src/fs-cache.js | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/fs-cache.js b/src/fs-cache.js
index 69530b4d..206c74a3 100644
--- a/src/fs-cache.js
+++ b/src/fs-cache.js
@@ -161,13 +161,19 @@ const handleCache = function(directory, params, callback) {
  *
  *   });
  */
+
+var defaultCacheDirectory = null;  // Lazily instantiated when needed
+
 module.exports = function(params, callback) {
   let directory;
 
   if (typeof params.directory === "string") {
     directory = params.directory;
   } else {
-    directory = findCacheDir({ name: "babel-loader" }) || os.tmpdir();
+    if (defaultCacheDirectory === null) {
+      defaultCacheDirectory = findCacheDir({ name: "babel-loader" }) || os.tmpdir();
+    }
+    directory = defaultCacheDirectory;
   }
 
   handleCache(directory, params, callback);

From 9b63ffb86f934732caafa8623b44b048574f1405 Mon Sep 17 00:00:00 2001
From: Aarni Koskela <akx@iki.fi>
Date: Fri, 10 Feb 2017 15:54:06 +0200
Subject: [PATCH 2/2] Cache resolve-rc results

---
 src/fs-cache.js   | 4 ++--
 src/resolve-rc.js | 9 +++++++--
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/src/fs-cache.js b/src/fs-cache.js
index 206c74a3..05b77130 100644
--- a/src/fs-cache.js
+++ b/src/fs-cache.js
@@ -15,6 +15,8 @@ const os = require("os");
 const path = require("path");
 const zlib = require("zlib");
 
+let defaultCacheDirectory = null;  // Lazily instantiated when needed
+
 /**
  * Read the contents from the compressed file.
  *
@@ -162,8 +164,6 @@ const handleCache = function(directory, params, callback) {
  *   });
  */
 
-var defaultCacheDirectory = null;  // Lazily instantiated when needed
-
 module.exports = function(params, callback) {
   let directory;
 
diff --git a/src/resolve-rc.js b/src/resolve-rc.js
index 30b84f8b..25a03c6b 100644
--- a/src/resolve-rc.js
+++ b/src/resolve-rc.js
@@ -10,6 +10,8 @@ const path = require("path");
 const exists = require("./utils/exists")({});
 const read = require("./utils/read")({});
 
+const cache = {};
+
 const find = function find(start, rel) {
   const file = path.join(start, rel);
 
@@ -27,6 +29,9 @@ const find = function find(start, rel) {
 
 module.exports = function(loc, rel) {
   rel = rel || ".babelrc";
-
-  return find(loc, rel);
+  const cacheKey = `${loc}/${rel}`;
+  if (!(cacheKey in cache)) {
+    cache[cacheKey] = find(loc, rel);
+  }
+  return cache[cacheKey];
 };