TS SDK: Reject triggerDagRun tasks in dag.if and dag.switch

ts-sdk/src/sdk/dag.ts

@@ -629,6 +629,12 @@ export class Dag {
   }
 
   #placeDecider(handler: (args: never) => unknown, args: readonly unknown[]): TaskRef {
+    if (isTriggerDagRunTask(handler)) {
+      throw new Error(
+        `A triggerDagRun task of Dag "${this.dagId}" was given to dag.if or dag.switch, ` +
+          "which need a handler to decide the branch with",
+      );
+    }
     const [inputs, spec] = args as [unknown, TaskOptions | undefined];
     const factory = this.#addTask(undefined, handler, spec) as (...inputs: unknown[]) => TaskRef;
     return inputs === undefined ? factory() : factory(inputs);

ts-sdk/tests/sdk/trigger-dag-run.test.ts

@@ -232,6 +232,17 @@ describe("triggerDagRun", () => {
       );
     });
 
+    it.each(["if", "switch"] as const)("a trigger task given to dag.%s", (decider) => {
+      const dag = new Dag("d");
+      const declare = dag[decider].bind(dag) as (...args: unknown[]) => unknown;
+
+      expect(() =>
+        declare(triggerDagRun({ dagId: "downstream_etl" }), undefined, {
+          taskId: "trigger_downstream",
+        }),
+      ).toThrowError(/A triggerDagRun task of Dag "d" was given to dag.if or dag.switch/);
+    });
+
     it("a trigger task left uncalled, when the Dag is read", () => {
       const dag = new Dag("d");
       dag.task(triggerDagRun({ dagId: "downstream_etl" }), { taskId: "trigger_downstream" });