fix: Child.unref() unrefs stdio streams properly (#15275)

cli/tests/unit/spawn_test.ts

@@ -723,8 +723,29 @@ Deno.test(
     const program = `
 const child = await Deno.spawnChild(Deno.execPath(), {
   cwd: Deno.args[0],
+  stdout: "piped",
   args: ["run", "-A", "--unstable", Deno.args[1]],
 });
+const readable = child.stdout.pipeThrough(new TextDecoderStream());
+const reader = readable.getReader();
+// set up an interval that will end after reading a few messages from stdout, 
+// to verify that stdio streams are properly unrefed
+let count = 0;
+let interval;
+interval = setInterval(async () => {
+  count += 1;
+  if (count > 10) {
+    clearInterval(interval);
+    console.log("cleared interval");
+  }
+  const res = await reader.read();
+  if (res.done) {
+    throw new Error("stream shouldn't be done");
+  }
+  if (res.value.trim() != "hello from interval") {
+    throw new Error("invalid message received");
+  }
+}, 120);
 console.log("spawned pid", child.pid);
 child.unref();
 `;
@@ -740,15 +761,19 @@ setInterval(() => {
     // In this subprocess we are spawning another subprocess which has
     // an infite interval set. Following call would never resolve unless
     // child process gets unrefed.
-    const { success, stdout } = await Deno.spawn(Deno.execPath(), {
+    const { success, stdout, stderr } = await Deno.spawn(Deno.execPath(), {
       cwd,
       args: ["run", "-A", "--unstable", programFile, cwd, childProgramFile],
     });
 
     assert(success);
     const stdoutText = new TextDecoder().decode(stdout);
-    const pidStr = stdoutText.split(" ").at(-1);
+    const stderrText = new TextDecoder().decode(stderr);
+    assert(stderrText.length == 0);
+    const [line1, line2] = stdoutText.split("\n");
+    const pidStr = line1.split(" ").at(-1);
     assert(pidStr);
+    assertEquals(line2, "cleared interval");
     const pid = Number.parseInt(pidStr, 10);
     await Deno.remove(cwd, { recursive: true });
     // Child process should have been killed when parent process exits.

runtime/js/40_spawn.js

@@ -75,6 +75,7 @@
   class Child {
     #rid;
     #waitPromiseId;
+    #unrefed = false;
 
     #pid;
     get pid() {
@@ -132,6 +133,7 @@
         this.#stdoutRid = stdoutRid;
         this.#stdout = readableStreamForRid(stdoutRid, (promise) => {
           this.#stdoutPromiseId = promise[promiseIdSymbol];
+          if (this.#unrefed) core.unrefOp(this.#stdoutPromiseId);
         });
       }
 
@@ -139,6 +141,7 @@
         this.#stderrRid = stderrRid;
         this.#stderr = readableStreamForRid(stderrRid, (promise) => {
           this.#stderrPromiseId = promise[promiseIdSymbol];
+          if (this.#unrefed) core.unrefOp(this.#stderrPromiseId);
         });
       }
 
@@ -204,12 +207,14 @@
     }
 
     ref() {
+      this.#unrefed = false;
       core.refOp(this.#waitPromiseId);
       if (this.#stdoutPromiseId) core.refOp(this.#stdoutPromiseId);
       if (this.#stderrPromiseId) core.refOp(this.#stderrPromiseId);
     }
 
     unref() {
+      this.#unrefed = true;
       core.unrefOp(this.#waitPromiseId);
       if (this.#stdoutPromiseId) core.unrefOp(this.#stdoutPromiseId);
       if (this.#stderrPromiseId) core.unrefOp(this.#stderrPromiseId);