fix(): workflow sdk step return function type infer (#7047)

packages/workflows-sdk/src/utils/_playground.ts

@@ -4,12 +4,10 @@ const step1 = createStep("step1", async (input: {}, context) => {
   return new StepResponse({ step1: ["step1"] })
 })
 
-const step2 = createStep(
-  "step2",
-  async (input: { filters: { id: string[] } }, context) => {
-    return new StepResponse({ step2: input })
-  }
-)
+type Step2Input = { filters: { id: string[] } } | { filters: { id: string } }
+const step2 = createStep("step2", async (input: Step2Input, context) => {
+  return new StepResponse({ step2: input })
+})
 
 const step3 = createStep("step3", async () => {
   return new StepResponse({ step3: "step3" })
@@ -21,7 +19,14 @@ const workflow = createWorkflow("workflow", function () {
   return step2({ filters: { id: step1Res.step1 } })
 })
 
-workflow()
+const workflow2 = createWorkflow("workflow", function () {
+  const step1Res = step1()
+  step3()
+  workflow()
+  return step2({ filters: { id: step1Res.step1 } })
+})
+
+workflow2()
   .run({})
   .then((res) => {
     console.log(res.result)

packages/workflows-sdk/src/utils/composer/type.ts

@@ -25,7 +25,10 @@ type StepFunctionReturnConfig<TOutput> = {
  * @typeParam TInput - The type of the input of the step.
  * @typeParam TOutput - The type of the output of the step.
  */
-export type StepFunction<TInput, TOutput = unknown> = (keyof TInput extends []
+export type StepFunction<
+  TInput,
+  TOutput = unknown
+> = (keyof TInput extends never
   ? // Function that doesn't expect any input
     {
       (): WorkflowData<TOutput> & StepFunctionReturnConfig<TOutput>