Merge branch 'improve GC of mostSuccessOf* methods' into dev-orl

Author: oldratlee

cffu-core/src/main/java/io/foldright/cffu/CompletableFutureUtils.java

@@ -717,9 +717,11 @@ private static <T> CompletableFuture<T> f_mostSuccessTupleWithEhOf0(
 
     private static <T> CompletableFuture<T> f_mostSuccessTupleOf0(
             Executor executorWhenTimeout, long timeout, TimeUnit unit, CompletionStage<?>[] stages) {
-        // MUST be *Non-Minimal* CF instances in order to read results(`getSuccessNow`),
-        // otherwise UnsupportedOperationException
-        final CompletableFuture<Object>[] cfArray = toNonMinCfArray0(stages);
+        // 1. MUST be non-minimal-stage CF instances in order to read results(`getSuccessNow`), otherwise UnsupportedOpException.
+        // 2. SHOULD copy input cfs(by calling `exceptionally` method) to avoid memory leaks,
+        //    otherwise all input cfs would be retained until output cf completes.
+        CompletableFuture<?>[] cfArray = mapArray(stages, CompletableFuture[]::new,
+                s -> toNonMinCf0(s).exceptionally(v -> null));
         return cffuCompleteOnTimeout(CompletableFuture.allOf(cfArray), null, timeout, unit, executorWhenTimeout)
                 .handle((unused, ex) -> f_tupleOf0(f_mGetSuccessNow0(null, cfArray)));
     }
@@ -944,9 +946,11 @@ private static <T> CompletableFuture<List<T>> mostSuccessResultsOf0(
                     .handle((unused, ex) -> arrayList(getSuccessNow(f, valueIfNotSuccess)));
         }
 
-        // MUST be non-minimal-stage CF instances in order to read results(`getSuccessNow`),
-        // otherwise UnsupportedOperationException
-        final CompletableFuture<T>[] cfArray = toNonMinCfArray0(cfs);
+        // 1. MUST be non-minimal-stage CF instances in order to read results(`getSuccessNow`), otherwise UnsupportedOpException.
+        // 2. SHOULD copy input cfs(by calling `exceptionally` method) to avoid memory leaks,
+        //    otherwise all input cfs would be retained until output cf completes.
+        CompletableFuture<T>[] cfArray = mapArray(cfs, CompletableFuture[]::new,
+                s -> LLCF.<T>toNonMinCf0(s).exceptionally(v -> valueIfNotSuccess));
         return cffuCompleteOnTimeout(CompletableFuture.allOf(cfArray), null, timeout, unit, executorWhenTimeout)
                 .handle((unused, ex) -> arrayList(f_mGetSuccessNow0(valueIfNotSuccess, cfArray)));
     }

cffu-core/src/test/java/io/foldright/cffu/LLCFTest.kt

@@ -25,6 +25,46 @@ class LLCFTest : FunSpec({
         LLCF.f_toCf0(FooCs(incomplete)) shouldBeSameInstanceAs incomplete
     }
 
+    test("toNonMinCfArray0") {
+        val minStages = arrayOf(
+            completedStage(n),
+            testCffuFac.completedStage(n),
+        )
+        LLCF.toNonMinCfArray0(minStages).forEachIndexed { idx, f ->
+            if (isJava9Plus()) {
+                f.shouldNotBeSameInstanceAs(minStages[idx])
+            } else {
+                if (idx == 0)
+                    f.shouldBeSameInstanceAs(minStages[idx])
+                else {
+                    f.shouldNotBeSameInstanceAs(minStages[idx])
+                    f.shouldBeSameInstanceAs((minStages[idx] as Cffu<Int>).cffuUnwrap())
+                }
+            }
+            f.shouldBeCompleted()
+            f.join() shouldBe n
+            LLCF.isMinStageCf(f).shouldBeFalse()
+            f.shouldNotBeMinimalStage()
+        }
+
+        val cfs = arrayOf<CompletionStage<Int>>(
+            completedFuture(n),
+            testCffuFac.completedFuture(n),
+        )
+        LLCF.toNonMinCfArray0(cfs).forEachIndexed { idx, f ->
+            if (idx == 0)
+                f.shouldBeSameInstanceAs(cfs[idx])
+            else {
+                f.shouldNotBeSameInstanceAs(cfs[idx])
+                f.shouldBeSameInstanceAs((cfs[idx] as Cffu<Int>).cffuUnwrap())
+            }
+            f.shouldBeCompleted()
+            f.join() shouldBe n
+            LLCF.isMinStageCf(f).shouldBeFalse()
+            f.shouldNotBeMinimalStage()
+        }
+    }
+
     test("f_toCfCopy0") {
         arrayOf(
             completedStage(n),