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## Problem My DataWeave script threw an unresolved reference error when calling `partition` without an explicit import. The Arrays module must be imported to your DataWeave code by adding the line `import * from dw::core::Arrays` to the header of your DataWeave script docs. ## Input { "records": [ { "id": "ORD-1001", "email": "ana@example.com" }, { "id": "ORD-1002", "email": "bad-address" }, { "id": "ORD-1003", "email": "raj@example.org" }, { "id": "ORD-1004" }, { "id": "ORD-1005", "email": "mei@example.net" } ] } ## Working configuration %dw 2.0 // partition() lives in dw::core::Arrays — not imported by default import * from dw::core::Arrays output application/json // keys are ALWAYS success/failure — re-map them to domain names var split = payload.records partition (r) -> (r.email default "") matches /.+@.+\..+/ --- { accepted: split.success map (r) -> r.id, rejected: split.failure map (r) -> { id: r.id, reason: "missing or invalid email" }, retryCount: sizeOf(split.failure) } ## Output { "accepted": [ "ORD-1001", "ORD-1003", "ORD-1005" ], "rejected": [ { "id": "ORD-1002", "reason": "missing or invalid email" }, { "id": "ORD-1004", "reason": "missing or invalid email" } ], "retryCount": 2 } The `accepted` array contains IDs from records with valid emails, while the `rejected` array holds objects for records missing or invalidating email addresses. The `retryCount` field reports the size of the failure partition as two. ## The trap The trap is an unresolved reference error when calling `partition` without importing the Arrays module. ## What I do now I add `import * from dw::core::Arrays` to the DataWeave header before using `partition`. I map the `success` and `failure` keys to domain names like `accepted` and `rejected`. I calculate retry counts using `sizeOf` on the failure partition. Runs shown: DataWeave CLI 2.12.2 104 DataWeave patterns + 8 Exchange modules with 208 MUnit tests: github.com/shakarbisetty/mulesoft-cookbook | 60-second walkthroughs: youtube.com/@SanThaParv

## 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 2.12.2 104 DataWeave patterns + 8 Exchange modules with 208 MUnit tests: github.com/shakarbisetty/mulesoft-cookbook | 60-second walkthroughs: youtube.com/@SanThaParv

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