From 15326986114a386046a5f672c5907b6f7305b4c3 Mon Sep 17 00:00:00 2001
From: Yosh <github@yosh.is>
Date: Fri, 25 Aug 2023 13:16:21 +0200
Subject: [PATCH] handle empty lists for `join`

---
 src/future/join/array.rs     | 11 ++++++++++-
 src/future/join/vec.rs       | 11 ++++++++++-
 src/future/try_join/array.rs | 11 ++++++++++-
 src/future/try_join/vec.rs   | 11 ++++++++++-
 4 files changed, 40 insertions(+), 4 deletions(-)

diff --git a/src/future/join/array.rs b/src/future/join/array.rs
index 4db6447..ca628a4 100644
--- a/src/future/join/array.rs
+++ b/src/future/join/array.rs
@@ -95,7 +95,7 @@ where
 
         let mut readiness = this.wakers.readiness().lock().unwrap();
         readiness.set_waker(cx.waker());
-        if !readiness.any_ready() {
+        if *this.pending != 0 && !readiness.any_ready() {
             // Nothing is ready yet
             return Poll::Pending;
         }
@@ -193,6 +193,15 @@ mod test {
         });
     }
 
+    #[test]
+    fn empty() {
+        futures_lite::future::block_on(async {
+            let data: [future::Ready<()>; 0] = [];
+            let fut = data.join();
+            assert_eq!(fut.await, []);
+        });
+    }
+
     #[test]
     fn debug() {
         let mut fut = [future::ready("hello"), future::ready("world")].join();
diff --git a/src/future/join/vec.rs b/src/future/join/vec.rs
index e847832..15b67bf 100644
--- a/src/future/join/vec.rs
+++ b/src/future/join/vec.rs
@@ -87,7 +87,7 @@ where
 
         let mut readiness = this.wakers.readiness().lock().unwrap();
         readiness.set_waker(cx.waker());
-        if !readiness.any_ready() {
+        if *this.pending != 0 && !readiness.any_ready() {
             // Nothing is ready yet
             return Poll::Pending;
         }
@@ -187,6 +187,15 @@ mod test {
         });
     }
 
+    #[test]
+    fn empty() {
+        futures_lite::future::block_on(async {
+            let data: Vec<future::Ready<()>> = vec![];
+            let fut = data.join();
+            assert_eq!(fut.await, vec![]);
+        });
+    }
+
     #[test]
     fn debug() {
         let mut fut = vec![future::ready("hello"), future::ready("world")].join();
diff --git a/src/future/try_join/array.rs b/src/future/try_join/array.rs
index 5406f74..3aee1e2 100644
--- a/src/future/try_join/array.rs
+++ b/src/future/try_join/array.rs
@@ -95,7 +95,7 @@ where
 
         let mut readiness = this.wakers.readiness().lock().unwrap();
         readiness.set_waker(cx.waker());
-        if !readiness.any_ready() {
+        if *this.pending != 0 && !readiness.any_ready() {
             // Nothing is ready yet
             return Poll::Pending;
         }
@@ -200,6 +200,15 @@ mod test {
         })
     }
 
+    #[test]
+    fn empty() {
+        futures_lite::future::block_on(async {
+            let data: [future::Ready<io::Result<()>>; 0] = [];
+            let res = data.try_join().await;
+            assert_eq!(res.unwrap(), []);
+        });
+    }
+
     #[test]
     fn one_err() {
         futures_lite::future::block_on(async {
diff --git a/src/future/try_join/vec.rs b/src/future/try_join/vec.rs
index 9c2f800..203a7ce 100644
--- a/src/future/try_join/vec.rs
+++ b/src/future/try_join/vec.rs
@@ -96,7 +96,7 @@ where
 
         let mut readiness = this.wakers.readiness().lock().unwrap();
         readiness.set_waker(cx.waker());
-        if !readiness.any_ready() {
+        if *this.pending != 0 && !readiness.any_ready() {
             // Nothing is ready yet
             return Poll::Pending;
         }
@@ -201,6 +201,15 @@ mod test {
         })
     }
 
+    #[test]
+    fn empty() {
+        futures_lite::future::block_on(async {
+            let data: Vec<future::Ready<io::Result<()>>> = vec![];
+            let res = data.try_join().await;
+            assert_eq!(res.unwrap(), vec![]);
+        });
+    }
+
     #[test]
     fn one_err() {
         futures_lite::future::block_on(async {