import re

from django.core.exceptions import ValidationError

from django.forms.utils import RenderableFieldMixin, pretty_name

from django.forms.widgets import MultiWidget, Textarea, TextInput

from django.utils.functional import cached_property

from django.utils.html import format_html, html_safe

from django.utils.translation import gettext_lazy as _

__all__ = ("BoundField",)

class BoundField(RenderableFieldMixin):

"A Field plus data"

def __init__(self, form, field, name):

self.form = form

self.field = field

self.name = name

self.html_name = form.add_prefix(name)

self.html_initial_name = form.add_initial_prefix(name)

self.html_initial_id = form.add_initial_prefix(self.auto_id)

if self.field.label is None:

self.label = pretty_name(name)

else:

self.label = self.field.label

self.help_text = field.help_text or ""

self.renderer = form.renderer

@cached_property

def subwidgets(self):

"""

Most widgets yield a single subwidget, but others like RadioSelect and

CheckboxSelectMultiple produce one subwidget for each choice.

This property is cached so that only one database query occurs when

rendering ModelChoiceFields.

"""

id_ = self.field.widget.attrs.get("id") or self.auto_id

attrs = {"id": id_} if id_ else {}

attrs = self.build_widget_attrs(attrs)

return [

BoundWidget(self.field.widget, widget, self.form.renderer)

for widget in self.field.widget.subwidgets(

self.html_name, self.value(), attrs=attrs

)

]

def __bool__(self):

# BoundField evaluates to True even if it doesn't have subwidgets.

return True

def __iter__(self):

return iter(self.subwidgets)

def __len__(self):

return len(self.subwidgets)

def __getitem__(self, idx):

# Prevent unnecessary reevaluation when accessing BoundField's attrs

# from templates.

if not isinstance(idx, (int, slice)):

raise TypeError(

"BoundField indices must be integers or slices, not %s."

% type(idx).__name__

)

return self.subwidgets[idx]

@property

def errors(self):

"""

Return an ErrorList (empty if there are no errors) for this field.

"""

return self.form.errors.get(

self.name, self.form.error_class(renderer=self.form.renderer)

)

@property

def template_name(self):

return self.field.template_name or self.form.renderer.field_template_name

def get_context(self):

return {"field": self}

def as_widget(self, widget=None, attrs=None, only_initial=False):

"""

Render the field by rendering the passed widget, adding any HTML

attributes passed as attrs. If a widget isn't specified, use the

field's default widget.

"""

widget = widget or self.field.widget

if self.field.localize:

widget.is_localized = True

attrs = attrs or {}

attrs = self.build_widget_attrs(attrs, widget)

if self.auto_id and "id" not in widget.attrs:

attrs.setdefault(

"id", self.html_initial_id if only_initial else self.auto_id

)

if only_initial and self.html_initial_name in self.form.data:

# Propagate the hidden initial value.

value = self.form._widget_data_value(

self.field.hidden_widget(),

self.html_initial_name,

)

else:

value = self.value()

return widget.render(

name=self.html_initial_name if only_initial else self.html_name,

value=value,

attrs=attrs,

renderer=self.form.renderer,

)

def as_text(self, attrs=None, **kwargs):

"""

Return a string of HTML for representing this as an <input type="text">.

"""

return self.as_widget(TextInput(), attrs, **kwargs)

def as_textarea(self, attrs=None, **kwargs):

"""Return a string of HTML for representing this as a <textarea>."""

return self.as_widget(Textarea(), attrs, **kwargs)

def as_hidden(self, attrs=None, **kwargs):

"""

Return a string of HTML for representing this as an <input type="hidden">.

"""

return self.as_widget(self.field.hidden_widget(), attrs, **kwargs)

@property

def data(self):

"""

Return the data for this BoundField, or None if it wasn't given.

"""

return self.form._widget_data_value(self.field.widget, self.html_name)

def value(self):

"""

Return the value for this BoundField, using the initial value if

the form is not bound or the data otherwise.

"""

data = self.initial

if self.form.is_bound:

data = self.field.bound_data(self.data, data)

return self.field.prepare_value(data)

def _has_changed(self):

field = self.field

if field.show_hidden_initial:

hidden_widget = field.hidden_widget()

initial_value = self.form._widget_data_value(

hidden_widget,

self.html_initial_name,

)

try:

initial_value = field.to_python(initial_value)

except ValidationError:

# Always assume data has changed if validation fails.

return True

else:

initial_value = self.initial

return field.has_changed(initial_value, self.data)

def label_tag(self, contents=None, attrs=None, label_suffix=None, tag=None):

"""

Wrap the given contents in a <label>, if the field has an ID attribute.

contents should be mark_safe'd to avoid HTML escaping. If contents

aren't given, use the field's HTML-escaped label.

If attrs are given, use them as HTML attributes on the <label> tag.

label_suffix overrides the form's label_suffix.

"""

contents = contents or self.label

if label_suffix is None:

label_suffix = (

self.field.label_suffix

if self.field.label_suffix is not None

else self.form.label_suffix

)

# Only add the suffix if the label does not end in punctuation.

# Translators: If found as last label character, these punctuation

# characters will prevent the default label_suffix to be appended to the label

if label_suffix and contents and contents[-1] not in _(":?.!"):

contents = format_html("{}{}", contents, label_suffix)

widget = self.field.widget

id_ = widget.attrs.get("id") or self.auto_id

if id_:

id_for_label = widget.id_for_label(id_)

if id_for_label:

attrs = {**(attrs or {}), "for": id_for_label}

if self.field.required and hasattr(self.form, "required_css_class"):

attrs = attrs or {}

if "class" in attrs:

attrs["class"] += " " + self.form.required_css_class

else:

attrs["class"] = self.form.required_css_class

context = {

"field": self,

"label": contents,

"attrs": attrs,

"use_tag": bool(id_),

"tag": tag or "label",

}

return self.form.render(self.form.template_name_label, context)

def legend_tag(self, contents=None, attrs=None, label_suffix=None):

"""

Wrap the given contents in a <legend>, if the field has an ID

attribute. Contents should be mark_safe'd to avoid HTML escaping. If

contents aren't given, use the field's HTML-escaped label.

If attrs are given, use them as HTML attributes on the <legend> tag.

label_suffix overrides the form's label_suffix.

"""

return self.label_tag(contents, attrs, label_suffix, tag="legend")

def css_classes(self, extra_classes=None):

"""

Return a string of space-separated CSS classes for this field.

"""

if hasattr(extra_classes, "split"):

extra_classes = extra_classes.split()

extra_classes = set(extra_classes or [])

if self.errors and hasattr(self.form, "error_css_class"):

extra_classes.add(self.form.error_css_class)

if self.field.required and hasattr(self.form, "required_css_class"):

extra_classes.add(self.form.required_css_class)

return " ".join(extra_classes)

@property

def is_hidden(self):

"""Return True if this BoundField's widget is hidden."""

return self.field.widget.is_hidden

@property

def auto_id(self):

"""

Calculate and return the ID attribute for this BoundField, if the

associated Form has specified auto_id. Return an empty string otherwise.

"""

auto_id = self.form.auto_id # Boolean or string

if auto_id and "%s" in str(auto_id):

return auto_id % self.html_name

elif auto_id:

return self.html_name

return ""

@property

def id_for_label(self):

"""

Wrapper around the field widget's `id_for_label` method.

Useful, for example, for focusing on this field regardless of whether

it has a single widget or a MultiWidget.

"""

widget = self.field.widget

id_ = widget.attrs.get("id") or self.auto_id

return widget.id_for_label(id_)

@cached_property

def initial(self):

return self.form.get_initial_for_field(self.field, self.name)

def build_widget_attrs(self, attrs, widget=None):

widget = widget or self.field.widget

attrs = dict(attrs) # Copy attrs to avoid modifying the argument.

if (

widget.use_required_attribute(self.initial)

and self.field.required

and self.form.use_required_attribute

):

# MultiValueField has require_all_fields: if False, fall back

# on subfields.

if (

hasattr(self.field, "require_all_fields")

and not self.field.require_all_fields

and isinstance(self.field.widget, MultiWidget)

):

for subfield, subwidget in zip(self.field.fields, widget.widgets):

subwidget.attrs["required"] = (

subwidget.use_required_attribute(self.initial)

and subfield.required

)

else:

attrs["required"] = True

if self.field.disabled:

attrs["disabled"] = True

if not widget.is_hidden and self.errors:

attrs["aria-invalid"] = "true"

# If a custom aria-describedby attribute is given (either via the attrs

# argument or widget.attrs) and help_text is used, the custom

# aria-described by is preserved so user can set the desired order.

if (

not attrs.get("aria-describedby")

and not widget.attrs.get("aria-describedby")

and self.field.help_text

and not self.use_fieldset

and self.auto_id

and not self.is_hidden

):

attrs["aria-describedby"] = f"{self.auto_id}_helptext"

return attrs

@property

def widget_type(self):

return re.sub(

r"widget$|input$", "", self.field.widget.__class__.__name__.lower()

)

@property

def use_fieldset(self):

"""

Return the value of this BoundField widget's use_fieldset attribute.

"""

return self.field.widget.use_fieldset

@html_safe

class BoundWidget:

"""

A container class used for iterating over widgets. This is useful for

widgets that have choices. For example, the following can be used in a

template:

{% for radio in myform.beatles %}

<label for="{{ radio.id_for_label }}">

{{ radio.choice_label }}

<span class="radio">{{ radio.tag }}</span>

</label>

{% endfor %}

"""

def __init__(self, parent_widget, data, renderer):

self.parent_widget = parent_widget

self.data = data

self.renderer = renderer

def __str__(self):

return self.tag(wrap_label=True)

def tag(self, wrap_label=False):

context = {"widget": {**self.data, "wrap_label": wrap_label}}

return self.parent_widget._render(self.template_name, context, self.renderer)

@property

def template_name(self):

if "template_name" in self.data:

return self.data["template_name"]

return self.parent_widget.template_name

@property

def id_for_label(self):

return self.data["attrs"].get("id")

@property

def choice_label(self):

return self.data["label"]