Fix memory leak in `fetch(url)` (#2989)

* Fix memory leak in `fetch(url)`

* Bump those numbers up

---------

Co-authored-by: Jarred Sumner <709451+Jarred-Sumner@users.noreply.github.com>

3 files changed, 115 insertions, 0 deletions

diff --git a/test/js/web/fetch/fetch-leak-test-fixture-2.js b/test/js/web/fetch/fetch-leak-test-fixture-2.js
new file mode 100644
index 000000000..7379b1b7b
--- /dev/null
+++ b/test/js/web/fetch/fetch-leak-test-fixture-2.js
@@ -0,0 +1,26 @@
+import { heapStats } from "bun:jsc";
+
+const { SERVER } = process.env;
+
+if (typeof SERVER === "undefined" || !SERVER?.length) {
+  throw new Error("SERVER environment variable is not set");
+}
+
+const COUNT = parseInt(process.env.COUNT || "20", 10);
+var oks = 0;
+await (async function runAll() {
+  for (let j = 0; j < COUNT; j++) {
+    oks += (await fetch(SERVER)).ok;
+  }
+})();
+
+if (oks !== COUNT) {
+  throw new Error("Not all requests succeeded");
+}
+
+await Bun.sleep(10);
+Bun.gc(true);
+
+if ((heapStats().objectTypeCounts.Response ?? 0) > 5) {
+  throw new Error("Too many Response objects: " + heapStats().objectTypeCounts.Response);
+}
diff --git a/test/js/web/fetch/fetch-leak-test-fixture.js b/test/js/web/fetch/fetch-leak-test-fixture.js
new file mode 100644
index 000000000..07275a425
--- /dev/null
+++ b/test/js/web/fetch/fetch-leak-test-fixture.js
@@ -0,0 +1,34 @@
+import { heapStats } from "bun:jsc";
+
+const { SERVER } = process.env;
+
+if (typeof SERVER === "undefined" || !SERVER?.length) {
+  throw new Error("SERVER environment variable is not set");
+}
+
+const COUNT = parseInt(process.env.COUNT || "50", 10);
+await (async function runAll() {
+  var fetches = new Array(COUNT);
+  let i = 0;
+  while (i < Math.max(COUNT - 32, 0)) {
+    for (let j = 0; j < 32; j++) {
+      fetches.push(fetch(SERVER));
+    }
+    await Promise.all(fetches.slice(i, i + 32));
+    i += 32;
+  }
+
+  while (i++ < COUNT) {
+    fetches.push(fetch(SERVER));
+  }
+
+  await Promise.all(fetches);
+  fetches.length = 0;
+  fetches = [];
+})();
+await Bun.sleep(10);
+Bun.gc(true);
+
+if ((heapStats().objectTypeCounts.Response ?? 0) > 10) {
+  throw new Error("Too many Response objects: " + heapStats().objectTypeCounts.Response);
+}
diff --git a/test/js/web/fetch/fetch-leak.test.js b/test/js/web/fetch/fetch-leak.test.js
new file mode 100644
index 000000000..fa8b225bd
--- /dev/null
+++ b/test/js/web/fetch/fetch-leak.test.js
@@ -0,0 +1,55 @@
+import { test, expect, describe } from "bun:test";
+import { join } from "node:path";
+import { bunEnv, bunExe } from "harness";
+
+describe("fetch doesn't leak", () => {
+  test("fixture #1", async () => {
+    const body = new Blob(["some body in here!".repeat(100)]);
+    const server = Bun.serve({
+      port: 0,
+
+      fetch(req) {
+        return new Response(body);
+      },
+    });
+
+    const proc = Bun.spawn({
+      env: {
+        ...bunEnv,
+        SERVER: `http://${server.hostname}:${server.port}`,
+      },
+      stderr: "inherit",
+      stdout: "inherit",
+      cmd: [bunExe(), join(import.meta.dir, "fetch-leak-test-fixture.js")],
+    });
+
+    const exitCode = await proc.exited;
+    server.stop(true);
+    expect(exitCode).toBe(0);
+  });
+
+  test("fixture #2", async () => {
+    const body = new Blob(["some body in here!".repeat(100)]);
+    const server = Bun.serve({
+      port: 0,
+
+      fetch(req) {
+        return new Response(body);
+      },
+    });
+
+    const proc = Bun.spawn({
+      env: {
+        ...bunEnv,
+        SERVER: `http://${server.hostname}:${server.port}`,
+      },
+      stderr: "inherit",
+      stdout: "inherit",
+      cmd: [bunExe(), join(import.meta.dir, "fetch-leak-test-fixture-2.js")],
+    });
+
+    const exitCode = await proc.exited;
+    server.stop(true);
+    expect(exitCode).toBe(0);
+  });
+});