BelongsTo fails validation when creating if already exists on another record

[grantholle]

• Laravel Version: 11.8.0
• Nova Version: 4.34.2
• PHP Version: 8.3.3
• Database Driver & Version: Postgres 14
• Operating System and Version: macOS 14.5
• Browser type and version: Brave v1.66.113

Description:

When attempting to create a resource with a BelongsTo relation value that already is associated with another resource, it will fail validation with the message "This {field resource name} may not be associated with this resource."

I can, however, save the BelongsTo as null and update it with the same resource value that was used when trying to create it.

Detailed steps to reproduce the issue on a fresh Nova installation:

1. Create a BelongsTo relationship and field on a model.
2. Create a new resource in Nova with a value for the BelongsTo field.
3. Attempt to create another resource with the same BelongsTo field value.
4. See validation message.
5. Save as an empty/null value.
6. Update the resource with the original BelongsTo value.
7. Updates successfully.

[crynobone]

Please provide full reproducing repository based on fresh installation as suggested in the bug report template (or you can refer to https://github.com/nova-issues for example)

[grantholle]

I tried but can't reproduce it. That's a great feeling.

[grantholle]

I found it had to do with my reciprocal relationship. Just needed to be refactored.