Yes, that is kind of what is expected as it's not a merge, but just adding missing keys (defaults) to the main level. In most cases merging would be wrong anyway, but I think that for validate it should do an exception.

Needs a fix in vendor/rockettheme/toolbox/Blueprints/src/BlueprintSchema.php line 509 and 514.

Should be fixed in toolbox.

What is the target milestone/version?

Next version, it'll be out today.

This still does not work for me with 1.7.12. And yes, I've done a composer update.

I tested adding the field into a page.

I'm getting this error when trying to enter invalid value:

Invalid input in "PLUGIN_RATINGS.RATING_LABEL"
Save Failed: Form validation failed, please check your input

So the validation surely works, at least in admin and with flex objects.

Seems not to be the case for frontend forms. I am using this form field template to test (i've manually modified the max to 10, but the code should limit it to 5)

{% extends "forms/field.html.twig" %}

{% set originalValue = value %}

{% block input %}
    <fieldset class="rating-input {{ form_field_wrapper_classes }} {{ field.wrapper_classes }}">
        {# It is important to count from max to min, as this is required by the css. #}
        {% for i in 10..field.validate.min|default(1) %}
            {% set id = field.id|default(field.name) ~ '-star' ~ i %}
            <input type="radio"
                   value="{{ i|e }}"
                   id="{{ id|e }}"
                   name="{{ (scope ~ field.name)|fieldName }}"
                   class="{{ form_field_rating_classes }} {{ field.classes }}"
                   {% if i == value %}checked="checked" {% endif %}
                   {% if field.disabled or isDisabledToggleable %}disabled="disabled"{% endif %}
                   {% if required %}required="required"{% endif %}
                   {% if field.tabindex %}tabindex="{{ field.tabindex }}"{% endif %}
                   min="{{ field.validate.min|default(1) }}"
                   max="{{ field.validate.max|default(5) }}"
                   step="{{ field.validate.step|default(1) }}"
            />
            <label for="{{ id|e }}" title="{{ field.titles[i]|t|default(i ~ ' ' ~ 'PLUGIN_RATINGS.STARS'|t) }}"></label>
        {% endfor %}
    </fieldset>

{% endblock %}

And you must make sure when adding the form, you must set it to required.

Now I got the following yaml file:

        - name: stars
          type: rating
          label: PLUGIN_RATINGS.RATING_LABEL
          validate:
            required: true

Maybe the problem only occurs because I've added the form via code?
https://github.com/NicoHood/grav-plugin-ratings/blob/master/ratings.php#L112

Steps to reproduce:

1. Download grav https://getgrav.org/downloads
2. install database plugin https://github.com/getgrav/grav-plugin-database
3. install my ratings plugin https://github.com/NicoHood/grav-plugin-ratings
4. modify the config as written above
5. modify the template as written above
6. Add {% include 'partials/ratings-form.html.twig' %} to the base.html template somewhere to test
7. Open the browser and give a 10 star rating. no error pops up.

Ready to test example:
grav-admin.zip

I reopened the issue so I won't forget it.