# Django 5.2 documentation

# Source code for django.forms.boundfield

    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"
            # Preserve aria-describedby provided by the attrs argument so user
            # can set the desired order.
            if not attrs.get("aria-describedby") and not self.use_fieldset:
                if aria_describedby := self.aria_describedby:
                    attrs["aria-describedby"] = aria_describedby
            return attrs

        @property
        def aria_describedby(self):
            # Preserve aria-describedby set on the widget.
            if self.field.widget.attrs.get("aria-describedby"):
                return None
            aria_describedby = []
            if self.auto_id and not self.is_hidden:
                if self.help_text:
                    aria_describedby.append(f"{self.auto_id}_helptext")
                if self.errors:
                    aria_describedby.append(f"{self.auto_id}_error")
            return " ".join(aria_describedby)

        @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"]