From aead60f6782f30d52ec9f14caccbec68f745fd66 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Linus=20Unneb=C3=A4ck?= <linus@folkdatorn.se>
Date: Thu, 28 Sep 2017 17:55:28 +0100
Subject: [PATCH] Cache pending promises

---
 index.js  | 12 ++++--------
 readme.md |  2 +-
 test.js   | 10 ++++++++--
 3 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/index.js b/index.js
index 9a67ae8..ad49270 100644
--- a/index.js
+++ b/index.js
@@ -40,15 +40,11 @@ module.exports = (fn, opts) => {
 			});
 		};
 
+		setData(key, ret);
+
 		if (isPromise(ret) && opts.cachePromiseRejection === false) {
-			// Only cache resolved promises unless `cachePromiseRejection` is set to `true`
-			ret
-				.then(() => {
-					setData(key, ret);
-				})
-				.catch(() => {});
-		} else {
-			setData(key, ret);
+			// Remove rejected promises from cache unless `cachePromiseRejection` is set to `true`
+			ret.catch(() => cache.delete(key));
 		}
 
 		return ret;
diff --git a/readme.md b/readme.md
index 749d361..ee9d89e 100644
--- a/readme.md
+++ b/readme.md
@@ -104,7 +104,7 @@ You could for example change it to only cache on the first argument `x => JSON.s
 Type: `Object`<br>
 Default: `new Map()`
 
-Use a different cache storage. Must implement the following methods: `.has(key)`, `.get(key)`, `.set(key, value)`, and optionally `.clear()`. You could for example use a `WeakMap` instead or [`quick-lru`](https://github.com/sindresorhus/quick-lru) for a LRU cache.
+Use a different cache storage. Must implement the following methods: `.has(key)`, `.get(key)`, `.set(key, value)`, `.delete(key)`, and optionally `.clear()`. You could for example use a `WeakMap` instead or [`quick-lru`](https://github.com/sindresorhus/quick-lru) for a LRU cache.
 
 ##### cachePromiseRejection
 
diff --git a/test.js b/test.js
index 77c6e9c..d4b06d6 100644
--- a/test.js
+++ b/test.js
@@ -87,8 +87,14 @@ test('do not cache rejected promises', async t => {
 	});
 
 	await t.throws(memoized(), 'foo bar');
-	t.is(await memoized(), 2);
-	t.is(await memoized(), 2);
+
+	const first = memoized();
+	const second = memoized();
+	const third = memoized();
+
+	t.is(await first, 2);
+	t.is(await second, 2);
+	t.is(await third, 2);
 });
 
 test('cache rejected promises if enabled', async t => {