Django form field validator not raising error on field in template

Question

Tried using this (Django: How to set DateField to only accept Today & Future dates) SO post to have form raise error in template when a date field is given value less than current date (which, based on another SO answer (https://stackoverflow.com/a/22513989/8236733), I thought was done via the form field validators (see https://docs.djangoproject.com/en/2.0/ref/forms/validation/#cleaning-a-specific-field-attribute)). However, this does not seem to be working when inputting supposedly invalid values in the form template.

forms.py:

import datetime

from django import forms

from .models import Post


class MyForm(forms.Form):
    title = forms.CharField(max_length=100, required=True, help_text='Give a title',
                            widget=forms.TextInput(attrs={'size': '50rem'}))
    post = forms.CharField(max_length=280, required=True,
                           widget=forms.Textarea(attrs={'rows': 5}))
    expire_date = forms.DateField(  
        widget=forms.TextInput(attrs=
        {
            'class':'datepicker', # to use jquery datepicker
        }),
        required=True
    )
    expire_time = forms.TimeField(
        input_formats=['%H:%M %p'],
        widget=forms.TextInput(attrs=
        {
            'class':'timepicker', # to use jquery timepicker
        }),
        required=True)

    class Meta:
        model = Post
        fields = ('title', 'post', 'expire_date', 'expire_time',)

    def clean_date(self): # see https://docs.djangoproject.com/en/dev/ref/forms/validation/#cleaning-a-specific-field-attribute
        date = self.cleaned_data['expire_date']
        print(date)
        if date < datetime.date.today():
            raise forms.ValidationError("The date cannot be in the past!")
        return date

Relevant template snippet:

 <form method="post">
                {% csrf_token %}
                {% for field in listing_form %}
                <p>
                    {{ field.label_tag }}
                <div class="ui input">{{ field }}</div>
                {% if field.help_text %}
                <small class="ui inverted">{{ field.help_text }}</small>
                {% endif %}
                {% for error in field.errors %}
                <p style="color: red">{{ error }}</p>
                {% endfor %}
                </p>
                {% endfor %}
                <button class="ui inverted button" type="submit">submit</button>
                <div class="ui divider"></div>

                </small>
            </form>

Attempting to submit this form with some past date does not raise any error in the teplate and the form's is_valid() method raises no error in the backend view.

New to django, so is there something I am missing here? Do I need to somehow attach the validation method to the particular field in some way?

score 1 · Accepted Answer · answered Jun 02 '18 at 11:22

Apparently it is important that the form method for cleaning / validating a particular form field follow a particular naming convention: clean_<field name>. This is shown implicitly in the docs (https://docs.djangoproject.com/en/2.0/ref/forms/validation/#cleaning-a-specific-field-attribute), but never stated outright. Changing the clean_... method in the form class in the original post to have the following code seems to have fixed the problem.

class MyForm(forms.Form):
    ....
    expire_date = forms.DateField(  
        widget=forms.TextInput(attrs=
        {
            'class':'datepicker', # to use jquery datepicker
        }),
        required=True
    )
    ....
    class Meta:
        model = Post
        fields = ('title', 'post', 'expire_date', 'expire_time',)

    def clean_expire_date(self): 
                date = self.cleaned_data['expire_date']
                print(date)
                if date < datetime.date.today():
                    raise forms.ValidationError("The date cannot be in the past!")
                return date

If anyone knows where in the docs this naming convention is more explicitly specified, please let me know.

This is absolutely explicitly stated in that very page you link to: "The `clean_()` method is called on a form subclass – where `` is replaced with the name of the form field attribute ... For example, if you wanted to validate that the contents of a `CharField` called `serialnumber` was unique, `clean_serialnumber()` would be the right place to do this." — Daniel Roseman, Jun 02 '18 at 11:50
@DanielRoseman I'd argue that, looking only at the docs, it's not totally clear that the naming really matters. Eg. the docs say " write a cleaning method that operates on the _recipients_ field, like so: `def clean_recipients(self):`..." Reading this, I had assumed that the method naming was _purely for simplicity's sake_ (did not know how django knew to check the validator when the form was submitted, but I did not assume that the actual name of the function was the key (though now with hindsight, I can see how another who also already knew the answer would write the docs as they are)) — lampShadesDrifter, Jun 02 '18 at 12:12

Django form field validator not raising error on field in template

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