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Modyra

ADR 0221: A server validator carries no message of its own

Status: Accepted

Context

Section titled “Context”

A Studio server validator declared an optional errorMessage, and the Studio inspector offered an “Error message” input to fill it. No part of the system read it. The generated form calls the host’s implementation, and the messages a user sees are the ones that implementation returns. The project’s serverErrorMapping behavior names message as a field of the server’s response. The live preview’s mock answers with its own refusal text, or with forceError when that is set. An author who typed a message saw it saved, exported and shown back in the inspector, and never saw it on a field.

A field that nothing honors cannot stay that way. Three options were left: honor it only in the preview, honor it everywhere, or remove it.

Decision

Section titled “Decision”

StudioServerValidator has no message field, and the inspector offers no message input for a server validator. The text of a server refusal belongs to the server: the host implementation in a generated form, and the mock’s configuration (forceError, or its default refusal) in the preview.

The deciding principle is the smallest public surface: removing the field adds nothing a consumer must learn, and leaves 1.0 nothing to keep stable for it. A routing decision run through TypeSafe returned the same answer (remove, 75%; preview only, 25%; everywhere, 0%).

Consequences

Section titled “Consequences”
  • An author cannot write the refusal text for a server check in Studio. The server must supply it, as it already had to.
  • Project documents saved with an errorMessage still load. The key is no longer part of the type, nothing reads it, and an edit through the inspector keeps it as an unknown property instead of stripping it. It is inert, not migrated.
  • If design-time refusal text is wanted later, it comes back as a new decision with a reader on every path, not as a field waiting for one.

Alternatives rejected

Section titled “Alternatives rejected”
  • Preview only. The mock would use errorMessage as its refusal text. The preview would then show a message that the generated form never shows, so the preview would promise behavior the product does not have.
  • Everywhere. Code generation would replace the host’s messages with the authored one. That overrides the server’s own explanation, for example a coupon rejected for expiry would read as rejected for country. It would also need a second message path next to serverErrorMapping.

Verification

Section titled “Verification”

StudioServerValidator has no errorMessage member, so TypeScript rejects any code that reads or writes it (npm run typecheck in the studio packages). The studio-model, studio-ui and studio-codegen tests build their fixtures without it. No test asserts that the inspector lacks the input. A reintroduced input would also need the type member back, so it would fail the typecheck first.

Security and privacy

Section titled “Security and privacy”

None. Refusal text was never transmitted or rendered from this field. Removing it changes no trust boundary.