Django Forms translate standard error message - django

Question

All my translations work except the error messages generated by forms.
This is the start of my form:
class MyForm(forms.Form):
first_name = forms.CharField(label=_("First name"), min_length=3, required=True)
Now the label "First name" translates fine to "Vorname" because I made a .po file and compiled etc..
However when entering only 2 characters the resulting error is in English and not in (this case) German, see screen print below.
I have looked in Github Django repository django/conf/locale/de etc. but could not find the string "Please lengthen etc." there.
So my question is: how do I get this error message to translate? I assume Django has a standard method and that this string is already in some .po file somewhere within the Django project?

Answer 1

Adding an oninvalid attribute to to that field's widget would work.
class MyForm(forms.Form):
first_name = forms.CharField(label=_("First name"), min_length=3, required=True)
def __init__(self, *args, **kwargs):
super(MyForm, self).__init__(*args, **kwargs)
self.fields['first_name'].widget.attrs={
'oninvalid':"this.setCustomValidity('{German stuff}')",
'oninput':"this.setCustomValidity('')"
}
Edit 1
I've also learned you must add an oninput which then clears the message. I'm looking into other ways, because this solution would always show the same message no matter the validation error- is empty or is less 3 chars = same msg
Edit 2
This requires some extra javascript, but you should only have to do it once.
There might be more error messages, I only tested it on a Select
references = https://developer.mozilla.org/en-US/docs/Learn/Forms/Form_validation#validating_forms_using_javascript
form.py
class MyForm(forms.Form):
first_name = forms.CharField(label=_("First name"), min_length=3, required=True)
def __init__(self, *args, **kwargs):
super(MyForm, self).__init__(*args, **kwargs)
self.fields['first_name'].widget.attrs={
'oninvalid':"germanValidationMsg(this)",
'oninput':"this.setCustomValidity('')"
}
germanvalidation.js
function germanValidationMsg(e){
// dictionary of validations and their status
console.log(e.validity)
if (e.validity['badInput']){
e.setCustomValidity('German badInput Msg');
} else if (e.validity['patternMismatch']){
e.setCustomValidity('German patternMismatch Msg');
} else if (e.validity['rangeOverflow']){
e.setCustomValidity('German rangeOverflow Msg');
} else if (e.validity['rangeUnderflow']){
e.setCustomValidity('German rangeUnderflow Msg');
} else if (e.validity['stepMismatch']){
e.setCustomValidity('German stepMismatch Msg');
} else if (e.validity['tooLong']){
e.setCustomValidity('German tooLong Msg');
} else if (e.validity['tooShort']){
e.setCustomValidity('German tooShort Msg');
} else if (e.validity['typeMismatch']){
e.setCustomValidity('German typeMismatch Msg');
} else if (e.validity['valueMissing']){
e.setCustomValidity('German valueMissing Msg');
//} else if (e.validity['customError']){
// // customError always seems to be true?
// e.setCustomValidity('German customError Msg');
} else if (e.validity['valid']){
e.setCustomValidity('');
};
};