[FIXED] flask-wtform placeholder behavior

Issue

Form:

class SignUpForm(Form):
    username = TextField("Username: ",validators=[Required(),Length(3,24)])

why does this work?

form = SignUpForm()
form.username(placeholder="username")

but not when you directly use placeholder as an argument for the SignUpForm?

class SignUpForm(Form):
        username = TextField("Username: ",placeholder="username",validators=[Required(),Length(3,24)])

it gives out this error TypeError: __init__() got an unexpected keyword argument 'placeholder'

Im a bit puzzled by this because defining it directly on the class should just be the same as doing form.username(placeholder="username") but why does it give out an error?

Solution

Defining a field is different than rendering a field. Calling a field to render it accepts arbitrary keyword args to add attributes to the input. The library is just not designed to take arbitrary args when defining the field.

If you want a shortcut to render a field with the label as the placeholder, you can write a Jinja macro.

{% macro form_field(field) %}
{{ field(placeholder=field.label.text) }}
{% endmacro %}

Answered By - davidism