feat(workflows-sdk): Allow a step to not define an expected input

.changeset/hip-turtles-smell.md

@@ -0,0 +1,5 @@
+---
+"@medusajs/workflows-sdk": patch
+---
+
+feat(workflows-sdk): Allow a step to not define an expected input

packages/workflows-sdk/src/utils/composer/create-step.ts

@@ -128,7 +128,9 @@ function applyStep<
           context: transactionContext.context,
         }
 
-        const argInput = await resolveValue(input, transactionContext)
+        const argInput = input
+          ? await resolveValue(input, transactionContext)
+          : undefined
         const stepResponse: StepResponse<any, any> = await invokeFn.apply(
           this,
           [argInput, executionContext]

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

@@ -21,13 +21,25 @@ export type StepFunctionResult<TOutput extends unknown | unknown[] = unknown> =
  * @typeParam TInput - The type of the input of the step.
  * @typeParam TOutput - The type of the output of the step.
  */
-export type StepFunction<TInput extends object = object, TOutput = unknown> = {
-  (input: { [K in keyof TInput]: WorkflowData<TInput[K]> }): WorkflowData<{
+export type StepFunction<
+  TInput extends object = object,
+  TOutput = unknown
+> = (TInput extends unknown
+  ? // Function that doesn't expect any input
+    {
+      (): WorkflowData<{
+        [K in keyof TOutput]: TOutput[K]
+      }>
+    }
+  : // function that expects an input object
+    {
+      (input: { [K in keyof TInput]: WorkflowData<TInput[K]> }): WorkflowData<{
+        [K in keyof TOutput]: TOutput[K]
+      }>
+    }) &
+  WorkflowDataProperties<{
     [K in keyof TOutput]: TOutput[K]
   }>
-} & WorkflowDataProperties<{
-  [K in keyof TOutput]: TOutput[K]
-}>
 
 export type WorkflowDataProperties<T = unknown> = {
   __type: Symbol