RFC 7807 Error Envelope with DataWeave Try Function

#rfc7807 #dataweave #try #errors

Problem

My script failed when try lacked an explicit import from dw::Runtime. The runtime reported Unable to resolve reference of: try during execution. The documentation describes try as a function that returns a Result object for handling errors docs.

Input

{
  "order": { "id": "ORD-2001", "total": "12.5O" }
}

Working configuration

%dw 2.0
// try() lives in dw::Runtime — not imported by default
import try from dw::Runtime
// RFC 7807 media type is accepted as-is by the JSON writer
output application/problem+json
var attempt = try(() -> payload.order.total as Number)
---
if (attempt.success) { total: attempt.result }
else {
  "type": "https://example.com/problems/invalid-total",
  "title": "Invalid order total",
  "status": 400,
  "detail": attempt.error.message,
  "instance": "/orders/" ++ payload.order.id,
  "errorKind": attempt.error.kind
}

Output

{
  "type": "https://example.com/problems/invalid-total",
  "title": "Invalid order total",
  "status": 400,
  "detail": "Cannot coerce String (12.5O) to Number",
  "instance": "/orders/ORD-2001",
  "errorKind": "InvalidNumberException"
}

The detail field contains the string Cannot coerce String (12.5O) to Number. The errorKind field holds the value InvalidNumberException.

The trap

The missing import causes a resolution failure when the script executes. Running fail_noimport.dwl produces an exit code of 255 and reports Unable to resolve reference of: try.

What I do now

I always add import try from dw::Runtime at the top of every script that uses the function. I verify the import exists before running the transformation to prevent resolution errors.

Runs shown: DataWeave CLI 2.12.2

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