fix(pi): stop blank input placeholders from failing the run

packages/provider-pi/src/server/adapter.test.ts

@@ -3080,6 +3080,40 @@ describe("PiAdapterV2", () => {
     }).pipe(Effect.scoped, Effect.provide(layerTest)),
   );
 
+  it.effect("asks an input dialog's title when its placeholder is blank", () =>
+    Effect.gen(function* () {
+      const fake = yield* makeFakePi;
+      const { runtime, takeEvent } = yield* openRuntime(fake);
+      yield* runtime.ensureThread({
+        threadId: THREAD_ID,
+        modelSelection: modelSelection("default"),
+        runtimePolicy,
+      });
+      const title = "Which database?\n1. Postgres\n2. Type something.\nType your answer:";
+      yield* fake.emit({
+        type: "extension_ui_request",
+        id: "ui-input",
+        method: "input",
+        title,
+        placeholder: "",
+      });
+      const event = yield* takeEvent(
+        (event) =>
+          event.type === "turn_item.updated" && event.turnItem.type === "user_input_request",
+      );
+      if (event.type !== "turn_item.updated" || event.turnItem.type !== "user_input_request") {
+        return assert.fail("expected a user input request");
+      }
+      assert.equal(decodeUserInputQuestions(event.turnItem.questions)[0]?.question, title);
+      yield* runtime.respondToRuntimeRequest({
+        requestId: event.turnItem.requestId,
+        answers: { "ui-input": "SQLite" },
+      });
+      const response = yield* fake.takeRequest("extension_ui_response");
+      assert.equal(response["value"], "SQLite");
+    }).pipe(Effect.scoped, Effect.provide(layerTest)),
+  );
+
   it.effect("keeps the complete editor prefill editable and returns exact edited text", () =>
     Effect.gen(function* () {
       const fake = yield* makeFakePi;

packages/provider-pi/src/server/adapter.ts

@@ -3321,7 +3321,11 @@ function piQuestion(
               value: "",
             },
           ];
-  const question = recordString(event, "message") ?? recordString(event, "placeholder") ?? title;
+  // Extensions may send a blank placeholder, which is not a valid question.
+  const question =
+    [recordString(event, "message"), recordString(event, "placeholder")].find(
+      (text) => text !== undefined && text.trim().length > 0,
+    ) ?? title;
   return {
     id: questionId,
     header: title,