Fix ParAff cancellation (#131)

Fixes #130

Author: natefaubion

src/Control/Monad/Aff.js

@@ -536,7 +536,9 @@ var Aff = function () {
         joins[jid] = join;
 
         return function() {
-          delete joins[jid];
+          if (joins !== null) {
+            delete joins[jid];
+          }
         };
       };
     }
@@ -937,14 +939,20 @@ var Aff = function () {
     }
 
     // Cancels the entire tree. If there are already subtrees being canceled,
-    // we need to first cancel those joins. This is important so that errors
-    // don't accidentally get swallowed by irrelevant join callbacks.
+    // we need to first cancel those joins. We will then add fresh joins for
+    // all pending branches including those that were in the process of being
+    // canceled.
     function cancel(error, cb) {
       interrupt = util.left(error);
-
+      var innerKills;
       for (var kid in kills) {
         if (kills.hasOwnProperty(kid)) {
-          kills[kid]();
+          innerKills = kills[kid];
+          for (kid in innerKills) {
+            if (innerKills.hasOwnProperty(kid)) {
+              innerKills[kid]();
+            }
+          }
         }
       }
 

test/Test/Main.purs

@@ -513,6 +513,25 @@ test_kill_parallel_alt = assert "kill/parallel/alt" do
   _ ← try $ joinFiber f2
   eq "killedfookilledbardone" <$> readRef ref
 
+test_kill_parallel_alt_finalizer ∷ ∀ eff. TestAff eff Unit
+test_kill_parallel_alt_finalizer = assert "kill/parallel/alt/finalizer" do
+  ref ← newRef ""
+  f1 ← forkAff $ sequential $
+    parallel (delay (Milliseconds 10.0)) <|> parallel do
+      bracket
+        (pure unit)
+        (\_ → do
+          delay (Milliseconds 10.0)
+          modifyRef ref (_ <> "killed"))
+        (\_ → delay (Milliseconds 20.0))
+  f2 ← forkAff do
+    delay (Milliseconds 15.0)
+    killFiber (error "Nope") f1
+    modifyRef ref (_ <> "done")
+  _ ← try $ joinFiber f1
+  _ ← try $ joinFiber f2
+  eq "killeddone" <$> readRef ref
+
 test_fiber_map ∷ ∀ eff. TestAff eff Unit
 test_fiber_map = assert "fiber/map" do
   ref ← newRef 0
@@ -628,6 +647,7 @@ main = do
     test_parallel_alt_sync
     test_parallel_mixed
     test_kill_parallel_alt
+    test_kill_parallel_alt_finalizer
     test_avar_order
     test_efffn
     test_fiber_map