refactor: remove dead _failedTasks field and unused async-pageable.ts (#284)

Author: YunchuWang

packages/durabletask-js/src/task/composite-task.ts

@@ -9,14 +9,12 @@ import { Task } from "./task";
 export class CompositeTask<T> extends Task<T> {
   _tasks: Task<any>[] = [];
   _completedTasks: number;
-  _failedTasks: number;
 
   constructor(tasks: Task<any>[]) {
     super();
 
     this._tasks = tasks;
     this._completedTasks = 0;
-    this._failedTasks = 0;
 
     for (const task of tasks) {
       task._parent = this;

packages/durabletask-js/src/task/when-all-task.ts

@@ -11,8 +11,8 @@ export class WhenAllTask<T> extends CompositeTask<T[]> {
   constructor(tasks: Task<T>[]) {
     super(tasks);
 
-    // Note: Do NOT re-initialize _completedTasks or _failedTasks here.
-    // CompositeTask's constructor already initializes them to 0 and then
+    // Note: Do NOT re-initialize _completedTasks here.
+    // CompositeTask's constructor already initializes it to 0 and then
     // processes pre-completed children via onChildCompleted(), which
     // increments the counter. Re-initializing would wipe out that count
     // and cause the task to hang when some children are already complete.

packages/durabletask-js/src/utils/async-pageable.ts

@@ -256,4 +256,26 @@ describe("WhenAllTask", () => {
     expect(err.errors[0]).toBe(error0);
     expect(err.errors[1]).toBe(error2);
   });
+
+  // Issue #217: CompositeTask has no separate failed-task counter. `_completedTasks`
+  // counts every settled child alike, successful and failed, which is why the unused
+  // `_failedTasks` field was safe to delete.
+  it("should count both successful and failed children in completedTasks", () => {
+    const child1 = new CompletableTask<number>();
+    const child2 = new CompletableTask<number>();
+    const task = new WhenAllTask([child1, child2]);
+
+    child1.complete(1);
+    expect(task.completedTasks).toBe(1);
+    expect(task.pendingTasks()).toBe(1);
+
+    // The failing child increments the SAME counter as the successful one.
+    child2.fail("child failed");
+    expect(task.completedTasks).toBe(2);
+    expect(task.pendingTasks()).toBe(0);
+
+    // Every child is now settled, so wait-all completes the task as failed.
+    expect(task.isComplete).toBe(true);
+    expect(task.isFailed).toBe(true);
+  });
 });

packages/durabletask-js/test/when-all-task.spec.ts

@@ -148,4 +148,25 @@ describe("WhenAnyTask", () => {
     expect(task.isComplete).toBe(false);
     expect(task.isFailed).toBe(false);
   });
+
+  // Issue #217: a failed completion settles WhenAny immediately and is treated the
+  // same as a successful one — failures are not tracked separately, so a later
+  // successful child does not override the already-settled failed child.
+  it("should keep the first failed child as the result even if a later child succeeds", () => {
+    const child1 = new CompletableTask<number>();
+    const child2 = new CompletableTask<number>();
+    const task = new WhenAnyTask([child1, child2]);
+
+    child1.fail("first failed");
+
+    expect(task.isComplete).toBe(true);
+    // WhenAny itself is not failed — it simply returns the settled (failed) child.
+    expect(task.isFailed).toBe(false);
+    expect(task.getResult()).toBe(child1);
+
+    // A subsequent successful completion must not replace the already-settled failed child.
+    child2.complete(99);
+    expect(task.getResult()).toBe(child1);
+    expect(task.getResult().isFailed).toBe(true);
+  });
 });