Fix DictField HTML input returning empty dict for missing fields by veeceey · Pull Request #9891 · encode/django-rest-framework

veeceey · 2026-02-08T23:06:22Z

Summary

parse_html_dict always returned an empty MultiValueDict when no matching keys were found in the HTML form input, making it impossible to distinguish between:

A field that was not specified in the form data
A field that was specified but had no values

This caused DictField to treat missing fields as if they contained an empty dict, breaking required, default, and partial update logic for multipart/form-data requests.

Changes

rest_framework/utils/html.py: Added a default parameter to parse_html_dict (consistent with how parse_html_list already works). Returns default when no matching keys are found in the input.
rest_framework/fields.py: Updated DictField.get_value to pass default=empty so that missing fields are correctly treated as not provided. Also updated DictField.to_internal_value to pass default=data so inner MultiValueDict data is preserved when no dot-separated sub-keys are found.
rest_framework/serializers.py: Updated Serializer.get_value to use the new default= parameter instead of or empty for consistency.
tests/test_fields.py: Added 4 new test cases for DictField HTML form input covering:
- Valid dict input via QueryDict with dot-separated keys
- Missing field with a default value
- Missing field that is not required (should be skipped)
- Missing field that is required (should fail validation)

Test plan

All existing DictField tests pass
All 4 new test cases pass
Full test_fields.py, test_serializer.py, and test_parsers.py suites pass (401 passed, 1 pre-existing failure unrelated to this change)
Verify in a real Django project with multipart/form-data requests that DictField partial updates work correctly

…input (encode#6234) When using DictField with HTML form (multipart/form-data) input, parse_html_dict always returned an empty MultiValueDict when no matching keys were found. This made it impossible to distinguish between an unspecified field and an empty input, causing issues with required/default field handling. This aligns parse_html_dict with parse_html_list by adding a default parameter that is returned when no matching keys are found. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

veeceey · 2026-02-19T04:59:16Z

Hi maintainers, friendly ping on this PR. It's been open for about 10 days without any review activity. Would really appreciate any feedback or direction when you get a chance. Happy to make adjustments if needed. Thank you!

browniebroke · 2026-02-20T18:05:24Z

rest_framework/serializers.py

        # nested HTML forms.
        if html.is_html_input(dictionary):
-            return html.parse_html_dict(dictionary, prefix=self.field_name) or empty
+            return html.parse_html_dict(dictionary, prefix=self.field_name, default=empty)


If I revert this change the tests still pass, so that tells me that this is no test for it, please add (at least) a test that fails on main and passes on this branch when this is added

browniebroke · 2026-02-20T18:14:25Z

tests/test_fields.py

+            data = serializers.DictField(child=serializers.CharField())
+
+        serializer = TestSerializer(data=QueryDict('data.a=1&data.b=2'))
+        assert serializer.is_valid()


Small detail, but can we please tweak these asserrt to show the serializer errors when they fail? That will give much better test output:

Suggested change

assert serializer.is_valid()

assert serializer.is_valid(), serializer.errors

Some for the other assert serializer.is_valid() in the other tests

browniebroke · 2026-02-20T18:17:04Z

rest_framework/fields.py

        """
        if html.is_html_input(data):
-            data = html.parse_html_dict(data)
+            data = html.parse_html_dict(data, default=data)


Wouldn't a better default be an empty dict here?

Suggested change

data = html.parse_html_dict(data, default=data)

data = html.parse_html_dict(data, default={})

browniebroke · 2026-02-20T18:18:36Z

rest_framework/utils/html.py



-def parse_html_dict(dictionary, prefix=''):
+def parse_html_dict(dictionary, prefix='', default=None):


Looks consistent with what we do for parsing html list 👍🏻 :

#5927

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Pull request overview

This pull request fixes a bug where DictField could not distinguish between a field that was not specified in HTML form data versus a field that was specified but had no values. This caused issues with required fields, default values, and partial updates when using multipart/form-data requests.

Changes:

Added a default parameter to parse_html_dict() to return a specified value when no matching keys are found (consistent with parse_html_list)
Updated DictField.get_value() and Serializer.get_value() to pass default=empty so missing fields are correctly detected
Updated DictField.to_internal_value() to pass default=data to preserve inner MultiValueDict data when no nested keys exist
Added comprehensive test coverage for DictField HTML form input scenarios

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
rest_framework/utils/html.py	Added `default` parameter to `parse_html_dict()` to handle missing fields correctly
rest_framework/fields.py	Updated `DictField.get_value()` and `to_internal_value()` to use the new `default` parameter
rest_framework/serializers.py	Updated `Serializer.get_value()` to use explicit `default=empty` parameter for consistency
tests/test_fields.py	Added 4 test cases covering various DictField HTML form input scenarios

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browniebroke reviewed Feb 20, 2026

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Fix DictField HTML input returning empty dict for missing fields#9891

Fix DictField HTML input returning empty dict for missing fields#9891
veeceey wants to merge 1 commit intoencode:mainfrom
veeceey:fix/issue-6234-dictfield-html-parsing

veeceey commented Feb 8, 2026 •

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	assert serializer.is_valid()
	assert serializer.is_valid(), serializer.errors

	data = html.parse_html_dict(data, default=data)
	data = html.parse_html_dict(data, default={})



		def parse_html_dict(dictionary, prefix=''):
		def parse_html_dict(dictionary, prefix='', default=None):

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veeceey commented Feb 19, 2026

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veeceey commented Feb 8, 2026 •

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