refactor: harden log stream writes

src/terminal/stream-writer.test.ts

@@ -0,0 +1,42 @@
+import { describe, expect, it, vi } from "vitest";
+
+import { createSafeStreamWriter } from "./stream-writer.js";
+
+describe("createSafeStreamWriter", () => {
+  it("signals broken pipes and closes the writer", () => {
+    const onBrokenPipe = vi.fn();
+    const writer = createSafeStreamWriter({ onBrokenPipe });
+    const stream = {
+      write: vi.fn(() => {
+        const err = new Error("EPIPE") as NodeJS.ErrnoException;
+        err.code = "EPIPE";
+        throw err;
+      }),
+    } as unknown as NodeJS.WriteStream;
+
+    expect(writer.writeLine(stream, "hello")).toBe(false);
+    expect(writer.isClosed()).toBe(true);
+    expect(onBrokenPipe).toHaveBeenCalledTimes(1);
+
+    onBrokenPipe.mockClear();
+    expect(writer.writeLine(stream, "again")).toBe(false);
+    expect(onBrokenPipe).toHaveBeenCalledTimes(0);
+  });
+
+  it("treats broken pipes from beforeWrite as closed", () => {
+    const onBrokenPipe = vi.fn();
+    const writer = createSafeStreamWriter({
+      onBrokenPipe,
+      beforeWrite: () => {
+        const err = new Error("EIO") as NodeJS.ErrnoException;
+        err.code = "EIO";
+        throw err;
+      },
+    });
+    const stream = { write: vi.fn(() => true) } as unknown as NodeJS.WriteStream;
+
+    expect(writer.write(stream, "hi")).toBe(false);
+    expect(writer.isClosed()).toBe(true);
+    expect(onBrokenPipe).toHaveBeenCalledTimes(1);
+  });
+});