Fix handling of falsy default values for enums in set-default-enum-member option by kkinugasa · Pull Request #2977 · koxudaxi/datamodel-code-generator

kkinugasa · 2026-02-02T13:26:03Z

Summary by CodeRabbit

Bug Fixes
- Corrected enum member matching so falsy defaults (e.g., 0, empty string, False) are honored rather than treated as absent.
Tests
- Added test coverage validating default enum member selection for falsy default values in JSON Schema generation.
Samples
- Added expected output illustrating enums and a model using falsy default enum members.

coderabbitai · 2026-02-02T13:26:21Z

📝 Walkthrough

Walkthrough

Updated enum default handling so falsy defaults (e.g., 0, "") are treated as valid enum members instead of being coerced away; adjusted checks to distinguish None from other falsy values and added tests + expected output for falsy-default enum members.

Changes

Cohort / File(s)	Summary
Enum matching logic `src/datamodel_code_generator/model/enum.py`	Compute `field_default` using `"" if field.default is None else field.default` so falsy defaults (0, '') are preserved for member matching.
Parser default check `src/datamodel_code_generator/parser/base.py`	Changed conditional from `if not model_field.default` to `if model_field.default is None` so non-None falsy defaults are processed for enum member assignment.
Tests — CLI integration `tests/main/jsonschema/test_main_jsonschema.py`	Added `test_main_jsonschema_falsy_default_enum_member` to exercise `--set-default-enum-member` with falsy defaults.
Tests — Expected output `tests/data/expected/main/jsonschema/falsy_default_enum_member.py`	New expected fixture defining enums and a model where falsy defaults are set to enum members (e.g., `Status.integer_0`, `Name.field_`, `Active.boolean_False`).

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

Suggested labels

breaking-change-analyzed, breaking-change

Poem

🐰 I hopped through defaults, small and sly,
Zero and empty no longer pass by.
With None distinguished, the members align,
Enums now greet their rightful sign—
A tiny hop, and the code feels spry!

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 75.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The pull request title clearly and concisely describes the main change: fixing handling of falsy default values for enums with the set-default-enum-member option.
Linked Issues check	✅ Passed	All coding requirements from issue `#2976` are met: field default handling changed from truthiness to None check in parser/base.py, enum member value matching updated in model/enum.py, and test coverage added.
Out of Scope Changes check	✅ Passed	All changes directly address the bug fix described in issue `#2976`; no out-of-scope modifications detected.

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ilovelinux

It looks good but we need a unit test to cover that edge case. It will help us to verify the fix and prevent any future regressions 🙂

kkinugasa · 2026-02-02T14:56:48Z

Thanks for the suggestion. I’ve added a unit test to cover that falsy default enum edge case to verify the fix and help prevent future regressions.

codspeed-hq · 2026-02-02T15:57:40Z

Merging this PR will not alter performance

⚠️

Unknown Walltime execution environment detected

Using the Walltime instrument on standard Hosted Runners will lead to inconsistent data.

For the most accurate results, we recommend using CodSpeed Macro Runners: bare-metal machines fine-tuned for performance measurement consistency.

✅ 11 untouched benchmarks
⏩ 98 skipped benchmarks¹

_{Comparing kkinugasa:fix/2976-falsy-default-enum-number (1ee71db) with main (365419e)}

98 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

codecov · 2026-02-02T16:00:45Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (365419e) to head (1ee71db).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main     #2977   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           94        94           
  Lines        17780     17782    +2     
  Branches      2044      2044           
=========================================
+ Hits         17780     17782    +2

Flag	Coverage Δ
unittests	`100.00% <100.00%> (ø)`

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Copilot

Pull request overview

This PR fixes a bug where falsy default values (0, False, empty string) for enum fields were not being converted to their corresponding enum members when using the --set-default-enum-member flag. The issue occurred because the code was using truthy checks (if not model_field.default) instead of explicit None checks (if model_field.default is None).

Changes:

Fixed condition in __set_default_enum_member to check for None explicitly instead of using truthy evaluation
Fixed string conversion in find_member to handle falsy values correctly
Added test coverage for falsy default values (integer 0 and empty string)

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/datamodel_code_generator/parser/base.py	Changed falsy check to explicit None check in `__set_default_enum_member`
src/datamodel_code_generator/model/enum.py	Fixed default value conversion to handle None separately from falsy values in `find_member`
tests/main/jsonschema/test_main_jsonschema.py	Added test for falsy default enum values
tests/data/jsonschema/falsy_default_enum_number.json	Test input with integer 0 and empty string defaults
tests/data/expected/main/jsonschema/falsy_default_enum_number.py	Expected output showing correct enum member assignment

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ilovelinux

Good job! LGTM!

github-actions · 2026-02-07T07:26:13Z

Breaking Change Analysis

Result: No breaking changes detected

Reasoning: This PR is a bug fix, not a breaking change. The changes fix incorrect handling of falsy default values (0, "", False) when using the --set-default-enum-member option. Previously, falsy defaults were incorrectly treated as absent/None due to Python's truthiness evaluation (not model_field.default and field.default or ""). The fix changes these to explicit None checks (model_field.default is None and if field.default is None else). While this does change generated output for schemas with falsy enum defaults, it corrects the behavior to match what users would expect - the enum member reference is now properly set as the default. This is fixing a bug to align with documented feature behavior, not changing intended functionality.

This analysis was performed by Claude Code Action

github-actions · 2026-02-14T16:21:34Z

🎉 Released in 0.54.0

This PR is now available in the latest release. See the release notes for details.

Fix handling of falsy default values for enums and model fields

5deb68d

ilovelinux requested changes Feb 2, 2026

View reviewed changes

Add tests and JSON schema for handling falsy default enum values

a4f2eb9

kkinugasa requested a review from ilovelinux February 2, 2026 15:03

ilovelinux requested a review from Copilot February 2, 2026 16:00

Copilot started reviewing on behalf of ilovelinux February 2, 2026 16:00 View session

Copilot AI reviewed Feb 2, 2026

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ilovelinux requested changes Feb 2, 2026

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Comment thread tests/main/jsonschema/test_main_jsonschema.py Outdated

Comment thread src/datamodel_code_generator/model/enum.py Outdated

kkinugasa added 3 commits February 3, 2026 08:44

simplify handling default field values in Enum class

1ef402f

rename test file name

d89c6ed

remove unnecessary freeze_time with statement

a7e2fc4

kkinugasa requested a review from ilovelinux February 3, 2026 00:33

ilovelinux previously approved these changes Feb 3, 2026

View reviewed changes

ilovelinux requested a review from koxudaxi February 3, 2026 10:31

test: add boolean false case to falsy default enum member fixture

1ee71db

koxudaxi dismissed ilovelinux’s stale review via 1ee71db February 7, 2026 05:47

koxudaxi approved these changes Feb 7, 2026

View reviewed changes

koxudaxi merged commit 9554fb6 into koxudaxi:main Feb 7, 2026
38 of 40 checks passed

github-actions Bot added the breaking-change-analyzed label Feb 7, 2026

coderabbitai Bot mentioned this pull request Feb 10, 2026

Nullable enums from JSON Schema to TypedDicts are missing | None #2986

Closed

github-actions Bot mentioned this pull request Feb 14, 2026

Enum default=0 is not converted to enum member with --set-default-enum-member #2976

Closed

coderabbitai Bot mentioned this pull request Mar 11, 2026

Default values for required fields are sometimes rendered and sometimes not #3048

Closed

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Summary by CodeRabbit

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kkinugasa commented Feb 2, 2026

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Merging this PR will not alter performance

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github-actions Bot commented Feb 7, 2026

Breaking Change Analysis

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kkinugasa commented Feb 2, 2026 •

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