3.6.3. Workflow Constraints

This chapter lists constraints of defining a workflow or its steps.

Workflow Constraints#

No Async Functions#

The function passed to createWorkflow can’t be an async function:

Code
1// Don't2const myWorkflow = createWorkflow(3  "hello-world", 4  async function (input: WorkflowInput) {5  // ...6})7
8// Do9const myWorkflow = createWorkflow(10  "hello-world", 11  function (input: WorkflowInput) {12  // ...13})

No Direct Variable Manipulation#

You can’t directly manipulate variables within the workflow's constructor function.

Instead, use transform from the Workflows SDK:

Code
1// Don't2const myWorkflow = createWorkflow(3  "hello-world", 4  function (input: WorkflowInput) {5  const str1 = step1(input)6  const str2 = step2(input)7
8  return new WorkflowResponse({9    message: `${str1}${str2}`,10  })11})12
13// Do14const myWorkflow = createWorkflow(15  "hello-world", 16  function (input: WorkflowInput) {17  const str1 = step1(input)18  const str2 = step2(input)19
20  const result = transform(21    {22      str1,23      str2,24    },25    (input) => ({26      message: `${input.str1}${input.str2}`,27    })28  )29
30  return new WorkflowResponse(result)31})

Create Dates in transform#

When you use new Date() in a workflow's constructor function, the date is evaluated when Medusa creates the internal representation of the workflow, not during execution.

Instead, create the date using transform.

For example:

Code
1// Don't2const myWorkflow = createWorkflow(3  "hello-world", 4  function (input: WorkflowInput) {5  const today = new Date()6
7  return new WorkflowResponse({8    today,9  })10})11
12// Do13const myWorkflow = createWorkflow(14  "hello-world", 15  function (input: WorkflowInput) {16  const today = transform({}, () => new Date())17
18  return new WorkflowResponse({19    today,20  })21})

No If Conditions#

You can't use if-conditions in a workflow.

Instead, use when-then from the Workflows SDK:

Code
1// Don't2const myWorkflow = createWorkflow(3  "hello-world", 4  function (input: WorkflowInput) {5  if (input.is_active) {6    // perform an action7  }8})9
10// Do (explained in the next chapter)11const myWorkflow = createWorkflow(12  "hello-world", 13  function (input: WorkflowInput) {14  when(input, (input) => {15    return input.is_active16  })17  .then(() => {18    // perform an action19  })20})

You can also pair multiple when-then blocks to implement an if-else condition as explained in this chapter.

No Conditional Operators#

You can't use conditional operators in a workflow, such as ?? or ||.

Instead, use transform to store the desired value in a variable.

Logical Or (||) Alternative#

Code
1// Don't2const myWorkflow = createWorkflow(3  "hello-world", 4  function (input: WorkflowInput) {5    const message = input.message || "Hello"6})7
8// Do9// other imports...10import { transform } from "@medusajs/framework/workflows-sdk"11
12const myWorkflow = createWorkflow(13  "hello-world", 14  function (input: WorkflowInput) {15    const message = transform(16      {17        input,18      },19      (data) => data.input.message || "hello"20    )21})

Nullish Coalescing (??) Alternative#

Code
1// Don't2const myWorkflow = createWorkflow(3  "hello-world", 4  function (input: WorkflowInput) {5    const message = input.message ?? "Hello"6})7
8// Do9// other imports...10import { transform } from "@medusajs/framework/workflows-sdk"11
12const myWorkflow = createWorkflow(13  "hello-world", 14  function (input: WorkflowInput) {15    const message = transform(16      {17        input,18      },19      (data) => data.input.message ?? "hello"20    )21})

Double Not (!!) Alternative#

Code
1// Don't2const myWorkflow = createWorkflow(3  "hello-world", 4  function (input: WorkflowInput) {5    step1({6      isActive: !!input.is_active,7    })8})9
10// Do11// other imports...12import { transform } from "@medusajs/framework/workflows-sdk"13
14const myWorkflow = createWorkflow(15  "hello-world", 16  function (input: WorkflowInput) {17    const isActive = transform(18      {19        input,20      },21      (data) => !!data.input.is_active22    )23    24    step1({25      isActive,26    })27})

Ternary Alternative#

Code
1// Don't2const myWorkflow = createWorkflow(3  "hello-world", 4  function (input: WorkflowInput) {5    step1({6      message: input.is_active ? "active" : "inactive",7    })8})9
10// Do11// other imports...12import { transform } from "@medusajs/framework/workflows-sdk"13
14const myWorkflow = createWorkflow(15  "hello-world", 16  function (input: WorkflowInput) {17    const message = transform(18      {19        input,20      },21      (data) => {22        return data.input.is_active ? "active" : "inactive"23      }24    )25    26    step1({27      message,28    })29})

Optional Chaining (?.) Alternative#

Code
1// Don't2const myWorkflow = createWorkflow(3  "hello-world", 4  function (input: WorkflowInput) {5    step1({6      name: input.customer?.name,7    })8})9
10// Do11// other imports...12import { transform } from "@medusajs/framework/workflows-sdk"13
14const myWorkflow = createWorkflow(15  "hello-world", 16  function (input: WorkflowInput) {17    const name = transform(18      {19        input,20      },21      (data) => data.input.customer?.name22    )23    24    step1({25      name,26    })27})

Step Constraints#

Returned Values#

A step must only return serializable values, such as primitive values or an object.

Values of other types, such as Maps, aren't allowed.

Code
1// Don't2import { 3  createStep,4  StepResponse,5} from "@medusajs/framework/workflows-sdk"6
7const step1 = createStep(8  "step-1",9  (input, { container }) => {10    const myMap = new Map()11
12    // ...13
14    return new StepResponse({15      myMap,16    })17  }18)19
20// Do21import { 22  createStep,23  StepResponse,24} from "@medusajs/framework/workflows-sdk"25
26const step1 = createStep(27  "step-1",28  (input, { container }) => {29    const myObj: Record<string, unknown> = {}30
31    // ...32
33    return new StepResponse({34      myObj,35    })36  }37)