fix(runtime): attach the stdin input listener per-controller so two apps share one stdin (#118)

The terminal raw-mode toggle is refcounted per-stdin (a WeakMap shared across
controllers) so one app's unmount can't drop raw mode while another still needs
it — vue's deliberate improvement over Ink, whose per-App counts let the first
unmount disable raw for everyone. But the "data" input listener was ALSO gated
on that shared refcount, so when two apps (separate createApp/stdout) shared one
stdin, only the first app's handleData ever attached and the second was
permanently deaf — and it didn't even self-heal when the first unmounted (Ink at
least does, via its per-App readable listeners).

Make the "data" listener (and its synchronous clearInputState cleanup: parser
reset, pending-escape flush, listener detach) PER-CONTROLLER, gated on this
controller's own localRefs, while keeping the raw-mode enable/disable on the
shared refcount. Because vue uses the "data" (push) event, every listener gets
every chunk, so both apps now receive input — strictly better than Ink's
"readable" (pull) model where the first-registered listener drains the buffer.

Single-app behavior is byte-identical: with one controller localRefs and the
shared refs move 1:1, so the same-tick swap (parser reset + listener re-attach)
fires at exactly the same moments as before.

Test: two apps sharing one stdin both receive a keystroke, and the second keeps
receiving after the first unmounts while raw mode stays enabled (shared ref);
raw mode disables only when the last app unmounts.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/runtime-tests/integration/composables/raw-mode-lifecycle.test.tsx

@@ -177,3 +177,67 @@ test("teardown disables raw mode synchronously so a signal exit can't leave the
   expect(setRawModeCalls).toEqual([true, false]);
   expect(refCount()).toBe(0);
 });
+
+// Two independent apps (separate createApp/stdout) sharing ONE stdin. The
+// terminal raw-mode toggle is refcounted per-stdin (shared) so the first app's
+// unmount can't drop raw mode while the second still needs it — vue's deliberate
+// improvement over Ink, whose per-App counts let the first unmount disable raw
+// for everyone. But the INPUT listener is per-controller: each app attaches its
+// own "data" handler, so BOTH receive every keystroke (vue's push model has no
+// drain race), and the second keeps receiving after the first unmounts.
+//
+// Before the per-controller-listener fix the "data" handler was attached only
+// when the SHARED refcount went 0→1, so the second app's handler never attached
+// and it was permanently deaf (worse than Ink, which at least self-heals when
+// the first app unmounts).
+test("two apps sharing one stdin both receive input; the second keeps receiving after the first unmounts", async () => {
+  const aKeys: string[] = [];
+  const bKeys: string[] = [];
+
+  const AppA = defineComponent(() => {
+    useInput((input) => aKeys.push(input));
+    return () => <Text>a</Text>;
+  });
+  const AppB = defineComponent(() => {
+    useInput((input) => bKeys.push(input));
+    return () => <Text>b</Text>;
+  });
+
+  const stdout1 = makeFakeWritable();
+  const stdout2 = makeFakeWritable();
+  const { stream: stdin, setRawModeCalls, refCount } = makeSpyStdin();
+
+  const appA = createApp(AppA);
+  const appB = createApp(AppB);
+  appA.mount({ stdout: stdout1, stdin, debug: true, exitOnCtrlC: false });
+  appB.mount({ stdout: stdout2, stdin, debug: true, exitOnCtrlC: false });
+  await settle();
+
+  // Raw mode enabled exactly once (shared refcount); both apps hold the one ref.
+  expect(setRawModeCalls).toEqual([true]);
+  expect(refCount()).toBe(1);
+
+  // Both apps receive the same keystroke.
+  (stdin as unknown as PassThrough).write("z");
+  await settle();
+  expect(aKeys).toEqual(["z"]);
+  expect(bKeys).toEqual(["z"]);
+
+  // First app unmounts: raw mode must STAY on (B still holds the shared ref),
+  // and B must keep receiving — A must not.
+  appA.unmount();
+  await settle();
+  expect(setRawModeCalls).toEqual([true]);
+  expect(refCount()).toBe(1);
+
+  (stdin as unknown as PassThrough).write("y");
+  await settle();
+  expect(aKeys).toEqual(["z"]);
+  expect(bKeys).toEqual(["z", "y"]);
+
+  // Second app unmounts: now raw mode is disabled and the ref released.
+  appB.unmount();
+  await settle();
+  expect(setRawModeCalls).toEqual([true, false]);
+  expect(refCount()).toBe(0);
+});

packages/runtime/src/render.ts

@@ -1499,13 +1499,13 @@ function createStdinController(
       }
       const state = getRawModeState(stdin);
       if (state.refs === 0) {
-        // If a same-tick swap left raw mode physically enabled (its disable is
-        // still queued), don't re-ref or re-toggle — just cancel the pending
-        // disable. Ink (App.tsx:331-344) skips stdin.ref()/setRawMode(true) here
-        // when isRawModeAlreadyEnabled; re-issuing them is a redundant ioctl AND
-        // an unbalanced ref() (the deferred disable would bail on refs>0 and never
-        // unref). setEncoding('utf8') and the data listener still run: encoding is
-        // idempotent and the listener was detached synchronously in releaseRawMode.
+        // SHARED (per-stdin) terminal raw-mode enable. If a same-tick swap left
+        // raw mode physically enabled (its disable is still queued), don't re-ref
+        // or re-toggle — just cancel the pending disable. Ink (App.tsx:331-344)
+        // skips stdin.ref()/setRawMode(true) when isRawModeAlreadyEnabled;
+        // re-issuing them is a redundant ioctl AND an unbalanced ref() (the
+        // deferred disable would bail on refs>0 and never unref). setEncoding is
+        // idempotent so it stays here.
         const alreadyEnabled = state.pendingDisable;
         state.pendingDisable = false;
         if (!alreadyEnabled) {
@@ -1513,6 +1513,17 @@ function createStdinController(
           appCtx.setRawMode(true);
         }
         if (typeof (stdin as any).setEncoding === "function") (stdin as any).setEncoding("utf8");
+      }
+      if (localRefs === 0) {
+        // PER-CONTROLLER input listener. Each controller (one per render tree)
+        // attaches its OWN handleData → its OWN parser → its OWN event emitter,
+        // gated on THIS controller's ref count, NOT the shared one. So two apps
+        // sharing one stdin both receive every keystroke: vue's 'data' (push)
+        // event broadcasts to every listener — unlike Ink's 'readable' (pull)
+        // model where the first-registered listener drains the buffer and a
+        // second same-stdin app stays deaf until the first unmounts
+        // (App.tsx:278-313). The terminal raw-mode toggle above stays shared so
+        // one app's unmount can't drop raw mode while another still needs it.
         stdin.on("data", handleData);
       }
       state.refs++;
@@ -1538,19 +1549,22 @@ function createStdinController(
       const state = getRawModeState(stdin);
       state.refs = Math.max(0, state.refs - 1);
       localRefs = Math.max(0, localRefs - 1);
-      if (state.refs === 0) {
-        // Stop owning input SYNCHRONOUSLY on the last release, matching Ink's
-        // clearInputState (App.tsx:212-216,357): reset the parser, cancel the
-        // pending-escape flush, and detach the data/readable listeners NOW — so a
-        // partial escape buffered before a same-render useInput swap cannot leak
-        // into the replacement. (A same-tick re-acquire re-attaches the listener
-        // with a fresh parser; deferring this is the bug — the gated microtask
-        // below short-circuits when refs is back >0, so the reset never ran.)
+      if (localRefs === 0) {
+        // PER-CONTROLLER: stop THIS controller owning input SYNCHRONOUSLY when its
+        // own last useInput releases, matching Ink's clearInputState
+        // (App.tsx:212-216,357): reset its parser, cancel its pending-escape flush,
+        // and detach its data/readable listeners NOW — so a partial escape buffered
+        // before a same-render useInput swap cannot leak into the replacement. (A
+        // same-tick re-acquire re-attaches the listener with a fresh parser.)
+        // Gated on localRefs, not the shared refcount: another app on the same
+        // stdin keeps its own listener and parser intact.
         inputParser.reset();
         clearPendingFlush();
         stdin.off("readable", handleReadable);
         stdin.off("data", handleData);
-        // Defer ONLY the terminal raw-mode toggle (Ink defers just disableRawMode,
+      }
+      if (state.refs === 0) {
+        // Defer ONLY the SHARED terminal raw-mode toggle (Ink defers just disableRawMode,
         // App.tsx:359-368): when components swap (v-if/key change), Vue unmounts
         // the old before mounting the new, so refs briefly hits 0. Disabling
         // synchronously would drop raw mode between the two mounts; the microtask