Default values for BelongsTo relations are shown on index/detail with an empty link

[sedlatschek]

• Laravel Version: 8.44.0
• Nova Version: 3.26.1
• PHP Version: 7.4.6
• Database Driver & Version: MySQL 5.7
• Operating System and Version: Win10
• Browser type and version: Chrome 88

Description:

There is a problem when having a nullable BelongsTo field with a default value. Even when the value of the field is null, the index and detail page show some value with an empty link.

// example field
BelongsTo::make('Organisation')->default(1) ->nullable(),

The value of organisation_id is null.

Yet on index and detail "1" is displayed with a link to /nova.

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

1. Create two models
2. Create a nullable belongsTo relation from one to the other
3. Set some default value in the BelongsTo nova field
4. Create a resource with the value null for the BelongsTo field
5. Go to resource index -> The BelongsTo field is not empty
6. Display a resource -> The BelongsTo field is not empty

[crynobone]

Yes, that's the current behavior for default. For such a requirement, you mostly just want a default value on creating.

https://crynobone.com/add-field-default-only-on-create-on-laravel-nova/

There a PR merged to add this for next major release.