https://sonarly.com/issue/35153?type=bug
UpdateField mutation fails with "Cannot return null for non-nullable field Relation.type" when querying relation metadata for fields with null or incomplete settings.
Fix: ## Changes Made
Modified the `fromMorphOrRelationFlatFieldMetadataToRelationDto` converter function to safely handle missing `settings.relationType`:
1. **from-morph-or-relation-flat-field-metadata-to-relation-dto.util.ts**:
- Added optional chaining to safely access `sourceFlatFieldMetadata.settings?.relationType`
- Return `null` early if relationType is missing, preventing undefined from being assigned to the non-nullable `type` field
- Changed from inline object return to explicit null check + return block
2. **resolve-morph-relations-from-flat-field-metadata.util.ts**:
- Updated to handle potential null return from converter
- Changed from direct return to storing result in variable, then conditionally wrapping in array
- Uses `flatMap` pattern: returns `[relationDto]` if valid, empty array `[]` if null
## Why This Fix Works
The GraphQL schema defines `Relation.type` as non-nullable (RelationDTO), but the parent field `relation` on FieldMetadata is nullable. When the converter returns `null`, GraphQL correctly resolves the parent `relation` field as `null` instead of throwing "Cannot return null for non-nullable field".
This matches the existing pattern in the codebase where:
- `resolveRelationFromFlatFieldMetadata` already returns `RelationDTO | null`
- The dataloader already expects `RelationDTO | null` (dataloader.service.ts:157)
- 10+ other files in the codebase use `settings?.relationType` with optional chaining
## Root Cause Addressed
Legacy relation fields created before settings validation was enforced (pre-Oct 2025 refactor, pre-Mar 2026 SDK validation) may have null or incomplete settings. The fix gracefully handles these fields by returning null for the entire relation instead of attempting to construct a RelationDTO with undefined type, which violated the GraphQL schema constraint.
Sonarly Claude Code
76ad4101e4