Properly handle zero-length array in Promise.inParallel()

haxetink · Jun 19, 2017 · 9322794 · 9322794
1 parent 3eb290c
commit 9322794
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Showing 2 changed files with 48 additions and 36 deletions.
diff --git a/src/tink/core/Promise.hx b/src/tink/core/Promise.hx
@@ -85,42 +85,44 @@ abstract Promise<T>(Surprise<T, Error>) from Surprise<T, Error> to Surprise<T, E
     return Future.async(function(cb) p.get().handle(cb), true);
 
   static public function inParallel<T>(a:Array<Promise<T>>, ?lazy:Bool):Promise<Array<T>> 
-    return Future.async(function (cb) {
-      var result = [], 
-          pending = a.length,
-          links:CallbackLink = null,
-          sync = false;
-
-      function done(o) {
-        if (links == null) sync = true;
-        else links.dissolve();
-        cb(o);
-      }
-
-      function fail(e:Error) {
-        done(Failure(e));
-      }
-      function set(index, value) {
-        result[index] = value;
-        if (--pending == 0) 
-          done(Success(result));
-      }
-
-      var linkArray = [];
-
-      for (i in 0...a.length) {
-        if (sync) break;
-        linkArray.push(a[i].handle(function (o) switch o {
-          case Success(v): set(i, v);
-          case Failure(e): fail(e);
-        }));
-      };
-
-      links = linkArray;
-
-      if (sync) 
-        links.dissolve();
-    }, lazy);
+    return 
+      if(a.length == 0) Future.sync(Success([]))
+      else Future.async(function (cb) {
+        var result = [], 
+            pending = a.length,
+            links:CallbackLink = null,
+            sync = false;
+
+        function done(o) {
+          if (links == null) sync = true;
+          else links.dissolve();
+          cb(o);
+        }
+
+        function fail(e:Error) {
+          done(Failure(e));
+        }
+        function set(index, value) {
+          result[index] = value;
+          if (--pending == 0) 
+            done(Success(result));
+        }
+
+        var linkArray = [];
+
+        for (i in 0...a.length) {
+          if (sync) break;
+          linkArray.push(a[i].handle(function (o) switch o {
+            case Success(v): set(i, v);
+            case Failure(e): fail(e);
+          }));
+        };
+
+        links = linkArray;
+
+        if (sync) 
+          links.dissolve();
+      }, lazy);
 
   static public function inSequence<T>(a:Array<Promise<T>>):Promise<Array<T>> {
 

diff --git a/tests/Promises.hx b/tests/Promises.hx
@@ -40,7 +40,17 @@ class Promises extends Base {
     assertFalse(done);
     t.trigger(Failure(new Error('test')));
     assertTrue(done);
+
+
+    counter = 0;
+    var p = Promise.inParallel([], true);
+    assertEquals(0, counter);
+    p.handle(function (o) {
+      assertTrue(o.isSuccess());
+    });
+    assertEquals(0, counter);  
   }
+
   function testInSequence() {
     var counter = 0;
     function make(fail:Bool)