test: add abort .bind() behavioral tests (#7174)

src/infra/abort-pattern.test.ts

@@ -0,0 +1,72 @@
+import { describe, expect, it } from "vitest";
+
+/**
+ * Regression test for #7174: Memory leak from closure-wrapped controller.abort().
+ *
+ * Using `() => controller.abort()` creates a closure that captures the
+ * surrounding lexical scope (controller, timer, locals).  In long-running
+ * processes these closures accumulate and prevent GC.
+ *
+ * The fix is `controller.abort.bind(controller)` which creates a minimal
+ * bound function with no scope capture.
+ *
+ * This test verifies the behavioral equivalence of .bind() for both the
+ * setTimeout and addEventListener use-cases.
+ */
+describe("abort pattern: .bind() vs arrow closure (#7174)", () => {
+  it("controller.abort.bind(controller) aborts the signal", () => {
+    const controller = new AbortController();
+    const boundAbort = controller.abort.bind(controller);
+    expect(controller.signal.aborted).toBe(false);
+    boundAbort();
+    expect(controller.signal.aborted).toBe(true);
+  });
+
+  it("bound abort works with setTimeout", async () => {
+    const controller = new AbortController();
+    const timer = setTimeout(controller.abort.bind(controller), 10);
+    expect(controller.signal.aborted).toBe(false);
+    await new Promise((r) => setTimeout(r, 50));
+    expect(controller.signal.aborted).toBe(true);
+    clearTimeout(timer);
+  });
+
+  it("bound abort works as addEventListener callback and can be removed", () => {
+    const parent = new AbortController();
+    const child = new AbortController();
+    const onAbort = child.abort.bind(child);
+
+    parent.signal.addEventListener("abort", onAbort, { once: true });
+    expect(child.signal.aborted).toBe(false);
+
+    parent.abort();
+    expect(child.signal.aborted).toBe(true);
+  });
+
+  it("removeEventListener works with saved .bind() reference", () => {
+    const parent = new AbortController();
+    const child = new AbortController();
+    const onAbort = child.abort.bind(child);
+
+    parent.signal.addEventListener("abort", onAbort);
+    // Remove before parent aborts — child should NOT be aborted
+    parent.signal.removeEventListener("abort", onAbort);
+    parent.abort();
+    expect(child.signal.aborted).toBe(false);
+  });
+
+  it("bound abort forwards abort through combined signals", () => {
+    // Simulates the combineAbortSignals pattern from pi-tools.abort.ts
+    const signalA = new AbortController();
+    const signalB = new AbortController();
+    const combined = new AbortController();
+
+    const onAbort = combined.abort.bind(combined);
+    signalA.signal.addEventListener("abort", onAbort, { once: true });
+    signalB.signal.addEventListener("abort", onAbort, { once: true });
+
+    expect(combined.signal.aborted).toBe(false);
+    signalA.abort();
+    expect(combined.signal.aborted).toBe(true);
+  });
+});