fix(image-pipeline): preserve worker errors and skip aborted histograms

tests/preview-renderer.test.ts

@@ -0,0 +1,87 @@
+// @vitest-environment jsdom
+
+import { beforeEach, describe, expect, it, vi } from "vitest";
+
+import { emptyHistogram } from "@/lib/image-pipeline/histogram";
+
+const histogramMocks = vi.hoisted(() => ({
+  computeHistogram: vi.fn(),
+}));
+
+const renderCoreMocks = vi.hoisted(() => ({
+  applyPipelineStep: vi.fn(),
+}));
+
+const sourceLoaderMocks = vi.hoisted(() => ({
+  loadSourceBitmap: vi.fn(),
+}));
+
+vi.mock("@/lib/image-pipeline/histogram", async () => {
+  const actual = await vi.importActual<typeof import("@/lib/image-pipeline/histogram")>(
+    "@/lib/image-pipeline/histogram",
+  );
+  return {
+    ...actual,
+    computeHistogram: histogramMocks.computeHistogram,
+  };
+});
+
+vi.mock("@/lib/image-pipeline/render-core", () => ({
+  applyPipelineStep: renderCoreMocks.applyPipelineStep,
+}));
+
+vi.mock("@/lib/image-pipeline/source-loader", () => ({
+  loadSourceBitmap: sourceLoaderMocks.loadSourceBitmap,
+}));
+
+describe("preview-renderer cancellation", () => {
+  beforeEach(() => {
+    vi.resetModules();
+    histogramMocks.computeHistogram.mockReset();
+    renderCoreMocks.applyPipelineStep.mockReset();
+    sourceLoaderMocks.loadSourceBitmap.mockReset();
+    histogramMocks.computeHistogram.mockReturnValue(emptyHistogram());
+    sourceLoaderMocks.loadSourceBitmap.mockResolvedValue({ width: 1, height: 1 });
+    renderCoreMocks.applyPipelineStep.mockImplementation(() => {});
+    vi.spyOn(HTMLCanvasElement.prototype, "getContext").mockReturnValue({
+      drawImage: vi.fn(),
+      getImageData: vi.fn(() => ({ data: new Uint8ClampedArray([0, 0, 0, 255]) })),
+    } as unknown as CanvasRenderingContext2D);
+    vi.stubGlobal("requestAnimationFrame", ((callback: FrameRequestCallback) => {
+      callback(0);
+      return 1;
+    }) as typeof requestAnimationFrame);
+  });
+
+  it("skips histogram work when cancellation lands after step application", async () => {
+    const { renderPreview } = await import("@/lib/image-pipeline/preview-renderer");
+
+    let abortedReads = 0;
+    const signal = {
+      get aborted() {
+        abortedReads += 1;
+        return abortedReads >= 3;
+      },
+    } as AbortSignal;
+
+    await expect(
+      renderPreview({
+        sourceUrl: "https://cdn.example.com/source.png",
+        steps: [
+          {
+            nodeId: "light-1",
+            type: "light-adjust",
+            params: { exposure: 0.1 },
+          },
+        ],
+        previewWidth: 1,
+        includeHistogram: true,
+        signal,
+      }),
+    ).rejects.toMatchObject({
+      name: "AbortError",
+    });
+
+    expect(histogramMocks.computeHistogram).not.toHaveBeenCalled();
+  });
+});