feat(workflows): Workflow DX (#5607)

packages/workflows/src/utils/composer/parallelize.ts

@@ -0,0 +1,58 @@
+import { CreateWorkflowComposerContext, WorkflowData } from "./type"
+import { SymbolMedusaWorkflowComposerContext } from "./helpers"
+
+/**
+ * Parallelize multiple steps.
+ * The steps will be run in parallel. The result of each step will be returned as part of the result array.
+ * Each StepResult can be accessed from the resulted array in the order they were passed to the parallelize function.
+ *
+ * @param steps
+ *
+ * @example
+ * ```ts
+ * import { createWorkflow, WorkflowData, parallelize } from "@medusajs/workflows"
+ * import { createProductStep, getProductStep, createPricesStep, attachProductToSalesChannelStep } from "./steps"
+ *
+ * interface MyWorkflowData {
+ *   title: string
+ * }
+ *
+ * const myWorkflow = createWorkflow("my-workflow", (input: WorkflowData<MyWorkflowData>) => {
+ *   const product = createProductStep(input)
+ *
+ *   const [prices, productSalesChannel] = parallelize(
+ *      createPricesStep(product),
+ *      attachProductToSalesChannelStep(product)
+ *   )
+ *
+ *   const id = product.id
+ *   return getProductStep(product.id)
+ * })
+ */
+export function parallelize<TResult extends WorkflowData[]>(
+  ...steps: TResult
+): TResult {
+  if (!global[SymbolMedusaWorkflowComposerContext]) {
+    throw new Error(
+      "parallelize must be used inside a createWorkflow definition"
+    )
+  }
+
+  const parallelizeBinder = (
+    global[SymbolMedusaWorkflowComposerContext] as CreateWorkflowComposerContext
+  ).parallelizeBinder
+
+  const resultSteps = steps.map((step) => step)
+
+  return parallelizeBinder<TResult>(function (
+    this: CreateWorkflowComposerContext
+  ) {
+    const stepOntoMerge = steps.shift()!
+    this.flow.mergeActions(
+      stepOntoMerge.__step__,
+      ...steps.map((step) => step.__step__)
+    )
+
+    return resultSteps as unknown as TResult
+  })
+}