# `data.conflict_unmapped`

Write can break a rule its `conflict:` doesn't map.

Area 6, [Reads and writes](../topics/reads-and-writes.md); not declinable; the next step is usually the agent's.

Each unique rule and restricting reference a write can break needs an arm
in `conflict:`; there is no catch-all:

```jadpo
entity Customer {
    id: Uuid
    email: Email {
        unique: true
    }
}

action register(email: Customer.email) -> Customer {
    return Customer.create {
        set: {
            email: email
        }
    }
}
```

```text
error: `Customer.create` can break `Customer.email`, and nothing maps it
 --> main.jadpo:9:12
  |
9 |     return Customer.create {
  |            ^^^^^^^^^^^^^^^ can be refused
  reason: A write is refused when it would give two records the same values a unique rule covers; it needs an arm in `conflict:` naming the `conflict` failure the caller gets, since there is no catch-all.
  next: Add `conflict: { Customer.email: SomeFailure }` to the block (agent)
  rule: data.conflict_unmapped
  help: https://jadpo.dev/docs/errors/data.conflict_unmapped

check failed: 1 error, 1 file
```