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Addresses #7279 : consistent formatting btw list serializers and list field errors#9837

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p-r-a-v-i-n:fix/7279-listserializer-errors
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Addresses #7279 : consistent formatting btw list serializers and list field errors#9837
p-r-a-v-i-n wants to merge 6 commits intoencode:mainfrom
p-r-a-v-i-n:fix/7279-listserializer-errors

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@p-r-a-v-i-n p-r-a-v-i-n commented Nov 26, 2025 •
edited by browniebroke
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Fix #7279

This pr changes the formatting of list serializer errors.

  • previously list serializer returing errors in list format.
  • It was adding empty dict ("{}") for every valid item in the list
  • this format was not consistent with the list field error format.
  • this is previous sample format
{
    'list_serializer': [
        {},
        {'num': [ErrorDetail(string='Must be a valid boolean.', code='invalid')]},
        {},
        {'num': [ErrorDetail(string='Must be a valid boolean.', code='invalid')]}
    ],
    
    'list_field': {
        1: [ErrorDetail(string='This dictionary may not be empty.', code='empty')],
        3: [ErrorDetail(string='This dictionary may not be empty.', code='empty')]
    }
}

Changes:

  • returning dict instead of the list bcs :

    • it is easier to handle dict compare to list for clients
    • if there 100 items in which 99 are valid then it would add 99 "{}" in the list.
    • both list field and list serializer errors are consistent.

  • here is the updated sample format

{
    'list_serializer': {
        0: {'num': [ErrorDetail(string='Must be a valid boolean.', code='invalid')]},
        1: {'num': [ErrorDetail(string='Must be a valid boolean.', code='invalid')]}
    },
    
    'list_field': {
        1: [ErrorDetail(string='This dictionary may not be empty.', code='empty')],
        3: [ErrorDetail(string='This dictionary may not be empty.', code='empty')]
    }
}

for clarity I can add more example if needed.

@p-r-a-v-i-n p-r-a-v-i-n marked this pull request as draft November 26, 2025 05:59
@p-r-a-v-i-n p-r-a-v-i-n marked this pull request as ready for review November 26, 2025 06:45
browniebroke
browniebroke reviewed Nov 26, 2025
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here is the updated sample format

{
    'list_serializer': {
        0: {'num': [ErrorDetail(string='Must be a valid boolean.', code='invalid')]},
        1: {'num': [ErrorDetail(string='Must be a valid boolean.', code='invalid')]}
    },
    
    'list_field': {
        1: [ErrorDetail(string='This dictionary may not be empty.', code='empty')],
        3: [ErrorDetail(string='This dictionary may not be empty.', code='empty')]
    }
}

The top level structure is indeed a dict, but the values of this dict aren't consistent: in the list serializer case, they are dict[str, list[ErrorDetail]] while in the list field they are list[ErrorDetail].

Is that right or am I missing something?

EDIT: I think I got it, ignore this comment

@auvipy auvipy requested review from auvipy and Copilot November 26, 2025 16:05
Copilot AI reviewed Nov 26, 2025
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Pull request overview

This PR changes the error format for ListSerializer to use a dict-based structure (with indices as keys) instead of a list-based structure (with empty dicts for valid items). This improves consistency with how ListField handles errors and makes error handling easier for API clients.

  • Changed error structure from list to dict format for ListSerializer
  • Only invalid item indices are included in error dict (no empty placeholders for valid items)
  • Ensures consistency between ListSerializer and ListField error formats

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File Description
rest_framework/serializers.py Modified to_internal_value to collect errors in a dict keyed by index instead of a list with empty dicts for valid items
tests/test_serializer_lists.py Added comprehensive tests for dict-based error format and consistency between ListSerializer and ListField
tests/test_serializer_bulk_update.py Updated expected error format in tests to use dict structure with indices as keys

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ListField validation errors are inconsistent with ListSerializer

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