validateOnMount precedence across useForm and useField in VeeValidate v4

Answer

The field‑level validateOnMount wins for that specific field. The form‑level value acts as a default for all fields that do not override it.

Likely explanation (based on source inspection)

When useField runs, it reads the injected form context and merges its own options over the context values. The merge gives priority to the field’s own validateOnMount flag, so:

• A field with { validateOnMount: true } inside a form configured with validateOnMount: false will run its mount‑time validation.
• Sibling fields without the flag keep the form’s setting.

Confirmed facts (from documentation)

The VeeValidate v4 docs only state that both useForm and useField accept a validateOnMount option; they do not specify precedence or inheritance rules.

Dynamic field registration

Because the form context is consulted at the moment each field registers, a field added later (e.g., via v-if or async data) will inherit the current form‑level validateOnMount unless it supplies its own flag. Its mount‑time validation runs when it is mounted, not during the initial form render.

Interaction with validationSchema

The schema is compiled by useForm and evaluated against the whole values object when the form first validates. Field‑level mount validation runs independently when the field registers. Consequently:

1. If a field registers before the schema evaluation, its mount‑time validation can add an error that the schema would also produce.
2. If it registers after, the initial error set may miss that field until it mounts or until a subsequent validation trigger occurs.
3. Mount validation does not mark the field as “interacted”, so later validateOnInput or validateOnBlur still fire on user interaction.

Verification steps

1. Open node_modules/vee-validate/dist/useField.js (or the src file) and locate where field options are merged with the form context.
2. Build a minimal test:

   const form = useForm({ validateOnMount: false, validationSchema });
   const emailField = useField('email', rules, { validateOnMount: true });
   const plainField = useField('name');
   // watch errors/meta on mounted and after nextTick

3. Add a field later with v-if and confirm whether it follows the form‑level flag.
4. Check the installed package’s CHANGELOG.md for any notes about validateOnMount changes across 4.x minor releases.

Missing diagnostic detail

Please confirm the exact VeeValidate v4 version you are using, as the merge behavior has shifted between minor releases and may affect the recommendation.