Any reason translation registration needs a validator instance?

[RangelReale]

Each translation has a registration function with this signature:

func RegisterDefaultTranslations(v *validator.Validate, trans ut.Translator) (err error)

It needs a *validator.Validate instance because it calls RegisterTranslation on it, but I can't see why it couldn't just only register them in ut.Translator together with translateFunc, and the validator instance would then fetch this list from it. This would enable creating multiple Validator instances using the same Translator, which is impossible today as registering translations in each instace overrides the Translator instance and errors out on duplicated translation.

For example, we could change the translator registration code to this (current code is commented before the changes):

		if t.customTransFunc != nil && t.customRegisFunc != nil {
			// err = v.RegisterTranslation(t.tag, trans, t.customRegisFunc, t.customTransFunc)
			err = t.customRegisFunc(trans, t.customTransFunc)(trans)
		} else if t.customTransFunc != nil && t.customRegisFunc == nil {
			// err = v.RegisterTranslation(t.tag, trans, registrationFunc(t.tag, t.translation, t.override), t.customTransFunc)
			err = registrationFunc(t.tag, t.translation, t.override, t.customTransFunc)(trans)
		} else if t.customTransFunc == nil && t.customRegisFunc != nil {
			// err = v.RegisterTranslation(t.tag, trans, t.customRegisFunc, translateFunc)
			err = t.customRegisFunc(trans, translateFunc)(trans)
		} else {
			// err = v.RegisterTranslation(t.tag, trans, registrationFunc(t.tag, t.translation, t.override), translateFunc)
			err = registrationFunc(t.tag, t.translation, t.override, translateFunc)(trans)
		}

We would need to modify Translator.Add to accept and store a translateFunc, and some function to fetch this list. This translateFunc has no hard binding to a Validator instance, so it should not be a problem.

Then we could have a method like func (v *Validate) RegisterTranslationInstance(trans ut.Translator) that would just copy the list from trans.translations to its internal v.transTagFunc to keep the same pattern as today.

[RangelReale]

My use case is that I need different rules for the same struct in different parts of my code, so I would need a new Validate instance for each function call, but without this I would need to reload and parse all translationsagain every time.

[zemzale]

I would like to add here that having multiple Validate instances is an anti-pattern since the validator is designed to be a singleton. It does caching to improve performance.

See more here:
https://pkg.go.dev/github.com/go-playground/validator/v10#hdr-Singleton

[RangelReale]

yes, I decided to stop overthinking problems in the future and just using a singleton, thanks!

[RangelReale]

Hmm I see, universal-translator is a separate package that is meant to only handle the strings part. Will have to think more about this.

[RangelReale]

I created a PR #1079 with a simpler solution to this problem, please see what you think.