Fixed #31026 -- Switched form rendering to template engine.

Thanks Carlton Gibson, Keryn Knight, Mariusz Felisiak, and Nick Pope
for reviews.

Co-authored-by: Johannes Hoppe <[email protected]>

django/forms/boundfield.py

@@ -1,11 +1,10 @@
 import re
 
 from django.core.exceptions import ValidationError
-from django.forms.utils import flatatt, pretty_name
+from django.forms.utils import pretty_name
 from django.forms.widgets import MultiWidget, Textarea, TextInput
 from django.utils.functional import cached_property
-from django.utils.html import conditional_escape, format_html, html_safe
-from django.utils.safestring import mark_safe
+from django.utils.html import format_html, html_safe
 from django.utils.translation import gettext_lazy as _
 
 __all__ = ('BoundField',)
@@ -75,7 +74,7 @@ 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())
+        return self.form.errors.get(self.name, self.form.error_class(renderer=self.form.renderer))
 
     def as_widget(self, widget=None, attrs=None, only_initial=False):
         """
@@ -177,11 +176,14 @@ def label_tag(self, contents=None, attrs=None, label_suffix=None):
                     attrs['class'] += ' ' + self.form.required_css_class
                 else:
                     attrs['class'] = self.form.required_css_class
-            attrs = flatatt(attrs) if attrs else ''
-            contents = format_html('<label{}>{}</label>', attrs, contents)
-        else:
-            contents = conditional_escape(contents)
-        return mark_safe(contents)
+        context = {
+            'form': self.form,
+            'field': self,
+            'label': contents,
+            'attrs': attrs,
+            'use_tag': bool(id_),
+        }
+        return self.form.render(self.form.template_name_label, context)
 
     def css_classes(self, extra_classes=None):
         """

django/forms/forms.py

@@ -4,15 +4,17 @@
 
 import copy
 import datetime
+import warnings
 
 from django.core.exceptions import NON_FIELD_ERRORS, ValidationError
 from django.forms.fields import Field, FileField
-from django.forms.utils import ErrorDict, ErrorList
+from django.forms.utils import ErrorDict, ErrorList, RenderableFormMixin
 from django.forms.widgets import Media, MediaDefiningClass
 from django.utils.datastructures import MultiValueDict
+from django.utils.deprecation import RemovedInDjango50Warning
 from django.utils.functional import cached_property
-from django.utils.html import conditional_escape, html_safe
-from django.utils.safestring import mark_safe
+from django.utils.html import conditional_escape
+from django.utils.safestring import SafeString, mark_safe
 from django.utils.translation import gettext as _
 
 from .renderers import get_default_renderer
@@ -49,8 +51,7 @@ def __new__(mcs, name, bases, attrs):
         return new_class
 
 
-@html_safe
-class BaseForm:
+class BaseForm(RenderableFormMixin):
     """
     The main implementation of all the Form logic. Note that this class is
     different than Form. See the comments by the Form class for more info. Any
@@ -62,6 +63,12 @@ class BaseForm:
     prefix = None
     use_required_attribute = True
 
+    template_name = 'django/forms/default.html'
+    template_name_p = 'django/forms/p.html'
+    template_name_table = 'django/forms/table.html'
+    template_name_ul = 'django/forms/ul.html'
+    template_name_label = 'django/forms/label.html'
+
     def __init__(self, data=None, files=None, auto_id='id_%s', prefix=None,
                  initial=None, error_class=ErrorList, label_suffix=None,
                  empty_permitted=False, field_order=None, use_required_attribute=None, renderer=None):
@@ -129,9 +136,6 @@ def order_fields(self, field_order):
         fields.update(self.fields)  # add remaining fields in original order
         self.fields = fields
 
-    def __str__(self):
-        return self.as_table()
-
     def __repr__(self):
         if self._errors is None:
             is_valid = "Unknown"
@@ -206,6 +210,12 @@ def _widget_data_value(self, widget, html_name):
 
     def _html_output(self, normal_row, error_row, row_ender, help_text_html, errors_on_separate_row):
         "Output HTML. Used by as_table(), as_ul(), as_p()."
+        warnings.warn(
+            'django.forms.BaseForm._html_output() is deprecated. '
+            'Please use .render() and .get_context() instead.',
+            RemovedInDjango50Warning,
+            stacklevel=2,
+        )
         # Errors that should be displayed above all fields.
         top_errors = self.non_field_errors().copy()
         output, hidden_fields = [], []
@@ -282,43 +292,48 @@ def _html_output(self, normal_row, error_row, row_ender, help_text_html, errors_
                 output.append(str_hidden)
         return mark_safe('\n'.join(output))
 
-    def as_table(self):
-        "Return this form rendered as HTML <tr>s -- excluding the <table></table>."
-        return self._html_output(
-            normal_row='<tr%(html_class_attr)s><th>%(label)s</th><td>%(errors)s%(field)s%(help_text)s</td></tr>',
-            error_row='<tr><td colspan="2">%s</td></tr>',
-            row_ender='</td></tr>',
-            help_text_html='<br><span class="helptext">%s</span>',
-            errors_on_separate_row=False,
-        )
-
-    def as_ul(self):
-        "Return this form rendered as HTML <li>s -- excluding the <ul></ul>."
-        return self._html_output(
-            normal_row='<li%(html_class_attr)s>%(errors)s%(label)s %(field)s%(help_text)s</li>',
-            error_row='<li>%s</li>',
-            row_ender='</li>',
-            help_text_html=' <span class="helptext">%s</span>',
-            errors_on_separate_row=False,
-        )
-
-    def as_p(self):
-        "Return this form rendered as HTML <p>s."
-        return self._html_output(
-            normal_row='<p%(html_class_attr)s>%(label)s %(field)s%(help_text)s</p>',
-            error_row='%s',
-            row_ender='</p>',
-            help_text_html=' <span class="helptext">%s</span>',
-            errors_on_separate_row=True,
-        )
+    def get_context(self):
+        fields = []
+        hidden_fields = []
+        top_errors = self.non_field_errors().copy()
+        for name, bf in self._bound_items():
+            bf_errors = self.error_class(bf.errors, renderer=self.renderer)
+            if bf.is_hidden:
+                if bf_errors:
+                    top_errors += [
+                        _('(Hidden field %(name)s) %(error)s') % {'name': name, 'error': str(e)}
+                        for e in bf_errors
+                    ]
+                hidden_fields.append(bf)
+            else:
+                errors_str = str(bf_errors)
+                # RemovedInDjango50Warning.
+                if not isinstance(errors_str, SafeString):
+                    warnings.warn(
+                        f'Returning a plain string from '
+                        f'{self.error_class.__name__} is deprecated. Please '
+                        f'customize via the template system instead.',
+                        RemovedInDjango50Warning,
+                    )
+                    errors_str = mark_safe(errors_str)
+                fields.append((bf, errors_str))
+        return {
+            'form': self,
+            'fields': fields,
+            'hidden_fields': hidden_fields,
+            'errors': top_errors,
+        }
 
     def non_field_errors(self):
         """
         Return an ErrorList of errors that aren't associated with a particular
         field -- i.e., from Form.clean(). Return an empty ErrorList if there
         are none.
         """
-        return self.errors.get(NON_FIELD_ERRORS, self.error_class(error_class='nonfield'))
+        return self.errors.get(
+            NON_FIELD_ERRORS,
+            self.error_class(error_class='nonfield', renderer=self.renderer),
+        )
 
     def add_error(self, field, error):
         """
@@ -360,9 +375,9 @@ def add_error(self, field, error):
                     raise ValueError(
                         "'%s' has no field named '%s'." % (self.__class__.__name__, field))
                 if field == NON_FIELD_ERRORS:
-                    self._errors[field] = self.error_class(error_class='nonfield')
+                    self._errors[field] = self.error_class(error_class='nonfield', renderer=self.renderer)
                 else:
-                    self._errors[field] = self.error_class()
+                    self._errors[field] = self.error_class(renderer=self.renderer)
             self._errors[field].extend(error_list)
             if field in self.cleaned_data:
                 del self.cleaned_data[field]

django/forms/formsets.py

@@ -1,11 +1,10 @@
 from django.core.exceptions import ValidationError
 from django.forms import Form
 from django.forms.fields import BooleanField, IntegerField
-from django.forms.utils import ErrorList
+from django.forms.renderers import get_default_renderer
+from django.forms.utils import ErrorList, RenderableFormMixin
 from django.forms.widgets import CheckboxInput, HiddenInput, NumberInput
 from django.utils.functional import cached_property
-from django.utils.html import html_safe
-from django.utils.safestring import mark_safe
 from django.utils.translation import gettext_lazy as _, ngettext
 
 __all__ = ('BaseFormSet', 'formset_factory', 'all_valid')
@@ -50,8 +49,7 @@ def clean(self):
         return cleaned_data
 
 
-@html_safe
-class BaseFormSet:
+class BaseFormSet(RenderableFormMixin):
     """
     A collection of instances of the same Form class.
     """
@@ -63,6 +61,10 @@ class BaseFormSet:
             '%(field_names)s. You may need to file a bug report if the issue persists.'
         ),
     }
+    template_name = 'django/forms/formsets/default.html'
+    template_name_p = 'django/forms/formsets/p.html'
+    template_name_table = 'django/forms/formsets/table.html'
+    template_name_ul = 'django/forms/formsets/ul.html'
 
     def __init__(self, data=None, files=None, auto_id='id_%s', prefix=None,
                  initial=None, error_class=ErrorList, form_kwargs=None,
@@ -85,9 +87,6 @@ def __init__(self, data=None, files=None, auto_id='id_%s', prefix=None,
             messages.update(error_messages)
         self.error_messages = messages
 
-    def __str__(self):
-        return self.as_table()
-
     def __iter__(self):
         """Yield the forms in the order they should be rendered."""
         return iter(self.forms)
@@ -110,15 +109,20 @@ def __bool__(self):
     def management_form(self):
         """Return the ManagementForm instance for this FormSet."""
         if self.is_bound:
-            form = ManagementForm(self.data, auto_id=self.auto_id, prefix=self.prefix)
+            form = ManagementForm(self.data, auto_id=self.auto_id, prefix=self.prefix, renderer=self.renderer)
             form.full_clean()
         else:
-            form = ManagementForm(auto_id=self.auto_id, prefix=self.prefix, initial={
-                TOTAL_FORM_COUNT: self.total_form_count(),
-                INITIAL_FORM_COUNT: self.initial_form_count(),
-                MIN_NUM_FORM_COUNT: self.min_num,
-                MAX_NUM_FORM_COUNT: self.max_num
-            })
+            form = ManagementForm(
+                auto_id=self.auto_id,
+                prefix=self.prefix,
+                initial={
+                    TOTAL_FORM_COUNT: self.total_form_count(),
+                    INITIAL_FORM_COUNT: self.initial_form_count(),
+                    MIN_NUM_FORM_COUNT: self.min_num,
+                    MAX_NUM_FORM_COUNT: self.max_num,
+                },
+                renderer=self.renderer,
+            )
         return form
 
     def total_form_count(self):
@@ -177,6 +181,7 @@ def _construct_form(self, i, **kwargs):
             # incorrect validation for extra, optional, and deleted
             # forms in the formset.
             'use_required_attribute': False,
+            'renderer': self.renderer,
         }
         if self.is_bound:
             defaults['data'] = self.data
@@ -212,7 +217,8 @@ def empty_form(self):
             prefix=self.add_prefix('__prefix__'),
             empty_permitted=True,
             use_required_attribute=False,
-            **self.get_form_kwargs(None)
+            **self.get_form_kwargs(None),
+            renderer=self.renderer,
         )
         self.add_fields(form, None)
         return form
@@ -338,7 +344,7 @@ def full_clean(self):
         self._non_form_errors.
         """
         self._errors = []
-        self._non_form_errors = self.error_class(error_class='nonform')
+        self._non_form_errors = self.error_class(error_class='nonform', renderer=self.renderer)
         empty_forms_count = 0
 
         if not self.is_bound:  # Stop further processing.
@@ -387,7 +393,8 @@ def full_clean(self):
         except ValidationError as e:
             self._non_form_errors = self.error_class(
                 e.error_list,
-                error_class='nonform'
+                error_class='nonform',
+                renderer=self.renderer,
             )
 
     def clean(self):
@@ -450,29 +457,14 @@ def media(self):
         else:
             return self.empty_form.media
 
-    def as_table(self):
-        "Return this formset rendered as HTML <tr>s -- excluding the <table></table>."
-        # XXX: there is no semantic division between forms here, there
-        # probably should be. It might make sense to render each form as a
-        # table row with each field as a td.
-        forms = ' '.join(form.as_table() for form in self)
-        return mark_safe(str(self.management_form) + '\n' + forms)
-
-    def as_p(self):
-        "Return this formset rendered as HTML <p>s."
-        forms = ' '.join(form.as_p() for form in self)
-        return mark_safe(str(self.management_form) + '\n' + forms)
-
-    def as_ul(self):
-        "Return this formset rendered as HTML <li>s."
-        forms = ' '.join(form.as_ul() for form in self)
-        return mark_safe(str(self.management_form) + '\n' + forms)
+    def get_context(self):
+        return {'formset': self}
 
 
 def formset_factory(form, formset=BaseFormSet, extra=1, can_order=False,
                     can_delete=False, max_num=None, validate_max=False,
                     min_num=None, validate_min=False, absolute_max=None,
-                    can_delete_extra=True):
+                    can_delete_extra=True, renderer=None):
     """Return a FormSet for the given form class."""
     if min_num is None:
         min_num = DEFAULT_MIN_NUM
@@ -498,6 +490,7 @@ def formset_factory(form, formset=BaseFormSet, extra=1, can_order=False,
         'absolute_max': absolute_max,
         'validate_min': validate_min,
         'validate_max': validate_max,
+        'renderer': renderer or get_default_renderer(),
     }
     return type(form.__name__ + 'FormSet', (formset,), attrs)
 

django/forms/jinja2/django/forms/attrs.html

@@ -0,0 +1 @@
+{% for name, value in attrs.items() %}{% if value is not sameas False %} {{ name }}{% if value is not sameas True %}="{{ value }}"{% endif %}{% endif %}{% endfor %}

django/forms/jinja2/django/forms/default.html

@@ -0,0 +1 @@
+{% include "django/forms/table.html" %}

django/forms/jinja2/django/forms/errors/dict/default.html

@@ -0,0 +1 @@
+{% include "django/forms/errors/dict/ul.html" %}

django/forms/jinja2/django/forms/errors/dict/text.txt

@@ -0,0 +1,3 @@
+{% for field, errors in errors %}* {{ field }}
+{% for error in errors %}  * {{ error }}
+{% endfor %}{% endfor %}

django/forms/jinja2/django/forms/errors/dict/ul.html

@@ -0,0 +1 @@
+{% if errors %}<ul class="{{ error_class }}">{% for field, error in errors %}<li>{{ field }}{{ error }}</li>{% endfor %}</ul>{% endif %}

django/forms/jinja2/django/forms/errors/list/default.html

@@ -0,0 +1 @@
+{% include "django/forms/errors/list/ul.html" %}

django/forms/jinja2/django/forms/errors/list/text.txt

@@ -0,0 +1,2 @@
+{% for error in errors %}* {{ error }}
+{% endfor %}

django/forms/jinja2/django/forms/errors/list/ul.html

@@ -0,0 +1 @@
+{% if errors %}<ul class="{{ error_class }}">{% for error in errors %}<li>{{ error }}</li>{% endfor %}</ul>{% endif %}

django/forms/jinja2/django/forms/formsets/default.html

@@ -0,0 +1 @@
+{{ formset.management_form }}{% for form in formset %}{{ form }}{% endfor %}

django/forms/jinja2/django/forms/formsets/p.html

@@ -0,0 +1 @@
+{{ formset.management_form }}{% for form in formset %}{{ form.as_p() }}{% endfor %}

django/forms/jinja2/django/forms/formsets/table.html

@@ -0,0 +1 @@
+{{ formset.management_form }}{% for form in formset %}{{ form.as_table() }}{% endfor %}

django/forms/jinja2/django/forms/formsets/ul.html

@@ -0,0 +1 @@
+{{ formset.management_form }}{% for form in formset %}{{ form.as_ul() }}{% endfor %}

django/forms/jinja2/django/forms/label.html

@@ -0,0 +1 @@
+{% if use_tag %}<label{% if attrs %}{% include 'django/forms/attrs.html' %}{% endif %}>{{ label }}</label>{% else %}{{ label }}{% endif %}