[Feature Request] manual or reactive trigger of v-text-field rules' validation

Problem to solve

When using rules in v-text-field, “When the input value changes, each element in the array will be validated.” Based on this definition, the validation event occurs only for the specific v-text-field that changes, without an option to trigger it manually; not even by clicking on the input. As a basic use-case, this may be necessary whenever validation conditions depend on any state of other inputs.

Repro steps on Vuetify v2.3.21: https://codepen.io/cTAlENtATI/pen/WNGoyvq

<v-text-field v-model="email1" :rules="[rules.email1]" />
<v-text-field v-model="email2" :rules="[rules.email2]" />

rules: {
  email1: value => value !== this.email2 || 'E-mails must differ.',
  email2: value => value !== this.email1 || 'E-mails must differ.',
},

1. The validation doesn’t initially occur until clicking on the input.
2. When changing one of the values, the error [dis]appears only on the current field, but stays displayed on the other one.
3. Unlike point 1, clicking on the other field doesn’t fix the validation issue until you start to type in a new input.

Proposed solution

At the very least, I would request for a workaround to be officially documented. As a feature suggestion, first option could be some manual trigger/prop to re-compute all validations, and a second option could be to reactively watch (in Vue-style) on the variables used in the (anonymous) rule function, so that it’ll re-validate when they change (making it trivial to combine with other reactive component properties).

[scscgit]

Note regarding duplicate issues:

• they don’t cover the scenario of reactive triggering (native to Vue) when a variable dependency (of a rule) referenced in the function changes
• #8698 probably only requires documenting the API for individual inputs
• #3530 (together with the previous issue) lacks the opposite scenario where we want to avoid ‘untouched’ inputs also immediately displaying their validation errors, as this side effect always occurs once we start to use the validate() workaround

Also about the last nextTick()-workaround-requiring issue that I had described (which is caused by Vue, but could be worth addressing if we have to use workarounds), I apologize that I wasn’t able to find time to properly analyze the root cause; but for anyone interested, here is my work-in-progress codepen where I was debugging how the issue only occurs between different email pairs: https://codepen.io/cTAlENtATI/pen/dypNbze

[KaelWD]

Duplicate of #8698 and maybe #3530