Rendering a read-only ArrayField with choices crashes.

[David Svenson]

If an ArrayField is included in an admin.ModelAdmin and has_change_permission returns False (making the field read-only), an exception is thrown when the field is supposed to be rendered.

This is the stacktrace after Django tries to render the field in django/contrib/admin/templates/admin/includes/fieldset.html

Traceback (most recent call last):
  File ".venv/lib/python3.10/site-packages/django/core/handlers/exception.py", line 47, in inner
    response = get_response(request)
  File ".venv/lib/python3.10/site-packages/django/core/handlers/base.py", line 204, in _get_response
    response = response.render()
  File ".venv/lib/python3.10/site-packages/django/template/response.py", line 105, in render
    self.content = self.rendered_content
  File ".venv/lib/python3.10/site-packages/django/template/response.py", line 83, in rendered_content
    return template.render(context, self._request)
  File ".venv/lib/python3.10/site-packages/django/template/backends/django.py", line 61, in render
    return self.template.render(context)
  File ".venv/lib/python3.10/site-packages/django/template/base.py", line 170, in render
    return self._render(context)
  File ".venv/lib/python3.10/site-packages/django/template/base.py", line 162, in _render
    return self.nodelist.render(context)
  File ".venv/lib/python3.10/site-packages/django/template/base.py", line 938, in render
    bit = node.render_annotated(context)
  File ".venv/lib/python3.10/site-packages/django/template/base.py", line 905, in render_annotated
    return self.render(context)
  File ".venv/lib/python3.10/site-packages/django/template/loader_tags.py", line 150, in render
    return compiled_parent._render(context)
  File ".venv/lib/python3.10/site-packages/django/template/base.py", line 162, in _render
    return self.nodelist.render(context)
  File ".venv/lib/python3.10/site-packages/django/template/base.py", line 938, in render
    bit = node.render_annotated(context)
  File ".venv/lib/python3.10/site-packages/django/template/base.py", line 905, in render_annotated
    return self.render(context)
  File ".venv/lib/python3.10/site-packages/django/template/loader_tags.py", line 150, in render
    return compiled_parent._render(context)
  File ".venv/lib/python3.10/site-packages/django/template/base.py", line 162, in _render
    return self.nodelist.render(context)
  File ".venv/lib/python3.10/site-packages/django/template/base.py", line 938, in render
    bit = node.render_annotated(context)
  File ".venv/lib/python3.10/site-packages/django/template/base.py", line 905, in render_annotated
    return self.render(context)
  File ".venv/lib/python3.10/site-packages/django/template/loader_tags.py", line 62, in render
    result = block.nodelist.render(context)
  File ".venv/lib/python3.10/site-packages/django/template/base.py", line 938, in render
    bit = node.render_annotated(context)
  File ".venv/lib/python3.10/site-packages/django/template/base.py", line 905, in render_annotated
    return self.render(context)
  File ".venv/lib/python3.10/site-packages/django/template/loader_tags.py", line 62, in render
    result = block.nodelist.render(context)
  File ".venv/lib/python3.10/site-packages/django/template/base.py", line 938, in render
    bit = node.render_annotated(context)
  File ".venv/lib/python3.10/site-packages/django/template/base.py", line 905, in render_annotated
    return self.render(context)
  File ".venv/lib/python3.10/site-packages/django/template/defaulttags.py", line 214, in render
    nodelist.append(node.render_annotated(context))
  File ".venv/lib/python3.10/site-packages/django/template/base.py", line 905, in render_annotated
    return self.render(context)
  File ".venv/lib/python3.10/site-packages/django/template/loader_tags.py", line 195, in render
    return template.render(context)
  File ".venv/lib/python3.10/site-packages/django/template/base.py", line 172, in render
    return self._render(context)
  File ".venv/lib/python3.10/site-packages/django/template/base.py", line 162, in _render
    return self.nodelist.render(context)
  File ".venv/lib/python3.10/site-packages/django/template/base.py", line 938, in render
    bit = node.render_annotated(context)
  File ".venv/lib/python3.10/site-packages/django/template/base.py", line 905, in render_annotated
    return self.render(context)
  File ".venv/lib/python3.10/site-packages/django/template/defaulttags.py", line 214, in render
    nodelist.append(node.render_annotated(context))
  File ".venv/lib/python3.10/site-packages/django/template/base.py", line 905, in render_annotated
    return self.render(context)
  File ".venv/lib/python3.10/site-packages/django/template/defaulttags.py", line 214, in render
    nodelist.append(node.render_annotated(context))
  File ".venv/lib/python3.10/site-packages/django/template/base.py", line 905, in render_annotated
    return self.render(context)
  File ".venv/lib/python3.10/site-packages/django/template/defaulttags.py", line 315, in render
    return nodelist.render(context)
  File ".venv/lib/python3.10/site-packages/django/template/base.py", line 938, in render
    bit = node.render_annotated(context)
  File ".venv/lib/python3.10/site-packages/django/template/base.py", line 905, in render_annotated
    return self.render(context)
  File ".venv/lib/python3.10/site-packages/django/template/defaulttags.py", line 315, in render
    return nodelist.render(context)
  File ".venv/lib/python3.10/site-packages/django/template/base.py", line 938, in render
    bit = node.render_annotated(context)
  File ".venv/lib/python3.10/site-packages/django/template/base.py", line 905, in render_annotated
    return self.render(context)
  File ".venv/lib/python3.10/site-packages/django/template/base.py", line 988, in render
    output = self.filter_expression.resolve(context)
  File ".venv/lib/python3.10/site-packages/django/template/base.py", line 671, in resolve
    obj = self.var.resolve(context)
  File ".venv/lib/python3.10/site-packages/django/template/base.py", line 796, in resolve
    value = self._resolve_lookup(context)
  File ".venv/lib/python3.10/site-packages/django/template/base.py", line 858, in _resolve_lookup
    current = current()
  File ".venv/lib/python3.10/site-packages/django/contrib/admin/helpers.py", line 239, in contents
    result_repr = display_for_field(value, f, self.empty_value_display)
  File ".venv/lib/python3.10/site-packages/django/contrib/admin/utils.py", line 385, in display_for_field
    return dict(field.flatchoices).get(value, empty_value_display)

Exception Type: TypeError at /admin/companies/company/1/change/
Exception Value: unhashable type: 'list'

I haven't given much thought to how to solve this but I guess either contents or display_for_field has to handle the ArrayField or there should be some way to call get_FOO_display in this case.

[Mariusz Felisiak]

Thanks for the report. ArrayField must have choices to reproduce this issue, e.g.

    field_2 = ArrayField(models.IntegerField(), choices=[
        ([1, 2, 3], "base choice"),
        ([1, 2], "1st choice"),
        ([2, 3], "2nd choice"),
    ])

We could try to call make_hashable() on the flatchoices and value:

django/contrib/admin/utils.py

@@ -10 +10 @@
 from django.forms.utils import pretty_name
 from django.urls import NoReverseMatch, reverse
 from django.utils import formats, timezone
+from django.utils.hashable import make_hashable
 from django.utils.html import format_html
 from django.utils.regex_helper import _lazy_re_compile
 from django.utils.text import capfirst
@@ -401 +402 @@
     from django.contrib.admin.templatetags.admin_list import _boolean_icon
 
     if getattr(field, "flatchoices", None):
-        return dict(field.flatchoices).get(value, empty_value_display)
+        return dict(make_hashable(field.flatchoices)).get(make_hashable(value), empty_value_display)
     # BooleanField needs special-case null-handling, so it comes before the
     # general null test.
     elif isinstance(field, models.BooleanField):

but this can cause a performance regression.

[David Wobrock]

​PR

[Carlton Gibson <carlton@…>]

In 897f38f:

Fixed #33927 -- Fixed crash when displaying ArrayField with choices in admin.