Fix enum member default resolution

[koxudaxi]

Summary by CodeRabbit

• Bug Fixes

  • Corrected enum member resolution to properly evaluate and compare default values across different types (strings, integers, booleans), ensuring consistent member identification
  • Improved handling of discriminator-based mappings when using enum-typed schema fields

• New Features

  • Added optional string-to-value coercion mode for enum member lookup to enhance flexibility when matching enum members

[coderabbitai]

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📝 Walkthrough

Walkthrough

The PR improves enum member resolution by replacing string-quote heuristics with AST-based literal evaluation and JSON-semantics equality comparison. The parser uses these changes to resolve discriminator values to enum members with string coercion, allowing numeric and string defaults to match correctly.

Changes

Enum member resolution and discriminator coercion

Layer / File(s)	Summary
Enum member resolution core logic src/datamodel_code_generator/model/enum.py	Adds ast import and introduces evaluate_member_value (parses string defaults as Python literals via ast.literal_eval) and _json_value_equal (JSON-style equality: numeric types compare by value, booleans are type-sensitive). Rewrites Enum.find_member to evaluate and compare member defaults, with optional coerce_strings parameter for string-to-non-string matching.
Parser discriminator integration src/datamodel_code_generator/parser/base.py	Imports evaluate_member_value and updates _create_discriminator_data_type and _get_enum_discriminator_literal to use find_member(..., coerce_strings=True) for discriminator value resolution and derive discriminator literals from evaluated runtime enum defaults.
Unit tests for find_member and discriminator literal tests/parser/test_base.py	Updates find_member test cases for integer/string/mixed enums to verify coercion-only matching for numeric strings; adds assertions confirming quoted-value representations fail default lookups; introduces test_get_enum_discriminator_literal_with_escaped_value to verify unescaped default resolution.
Generated test fixtures tests/data/expected/main/jsonschema/dataclass_enum_member_special_defaults.py, tests/data/expected/main/jsonschema/enum_member_typed_defaults.py	Adds two fixture modules: a dataclass with Mode and Quoted enum defaults; a Pydantic model with StrOne and IntTwo enum-member defaults.
End-to-end CLI tests tests/main/jsonschema/test_main_jsonschema.py	Adds two integration tests generating dataclass and Pydantic BaseModel output from enum-default JSON schemas, verifying output correctness and module importability.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related PRs

• koxudaxi/datamodel-code-generator#3074: Updates discriminator enum member resolution to use evaluated enum member defaults instead of quoted/string forms.
• koxudaxi/datamodel-code-generator#2977: Changes enum member resolution to correctly handle falsy/numeric/boolean defaults without string/quote mismatches.
• koxudaxi/datamodel-code-generator#3070: Modifies discriminator logic to preserve non-string enum member defaults via updated literal/quote handling.

Suggested labels

breaking-change-analyzed, breaking-change

Poem

🐰 Enums were lost in quote-stripping haze,
Now ast.literal_eval lights the maze,
JSON equality makes numbers align,
Discriminators coerce—a cleaner design!
Booleans stay true to their type, not a lie.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'Fix enum member default resolution' directly describes the main change: improving how enum member defaults are resolved in the codebase.
Docstring Coverage	✅ Passed	Docstring coverage is 82.35% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix-enum-member-default-resolution

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[github-actions]

📚 Docs Preview: https://pr-3303.datamodel-code-generator.pages.dev

[codspeed-hq]

Merging this PR will improve performance by 28.57%

⚠️ 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 improved benchmarks
⏩ 98 skipped benchmarks¹

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	WallTime	test_perf_stripe_style_pydantic_v2	1.9 s	1.5 s	+30.4%
⚡	WallTime	test_perf_aws_style_openapi_pydantic_v2	1.8 s	1.4 s	+29.95%
⚡	WallTime	test_perf_openapi_large	2.7 s	2.1 s	+29.1%
⚡	WallTime	test_perf_graphql_style_pydantic_v2	754.8 ms	585 ms	+29.01%
⚡	WallTime	test_perf_duplicate_names	989.5 ms	767 ms	+29.01%
⚡	WallTime	test_perf_kubernetes_style_pydantic_v2	2.5 s	1.9 s	+29%
⚡	WallTime	test_perf_complex_refs	1.9 s	1.4 s	+28.66%
⚡	WallTime	test_perf_all_options_enabled	4.9 s	3.9 s	+28.11%
⚡	WallTime	test_perf_deep_nested	4.7 s	3.7 s	+28.01%
⚡	WallTime	test_perf_multiple_files_input	3.4 s	2.6 s	+27.28%
⚡	WallTime	test_perf_large_models_pydantic_v2	3.4 s	2.7 s	+25.84%

Tip

Curious why this is faster? Comment @codspeedbot explain why this is faster on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing fix-enum-member-default-resolution (6b16cad) with main (f204def)}

Footnotes

1. 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]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (2dbe5b5) to head (6b16cad).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##              main     #3303    +/-   ##
==========================================
  Coverage   100.00%   100.00%            
==========================================
  Files          116       116            
  Lines        26248     26364   +116     
  Branches      3328      3336     +8     
==========================================
+ Hits         26248     26364   +116     

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

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[github-actions]

Breaking Change Analysis

Result: No breaking changes detected

Reasoning: PR #3303 is a bug fix that corrects enum member default resolution. The changes to find_member() behavior (stricter type-aware matching, proper evaluation of string literals) fix incorrect behavior where defaults with special characters, mixed-type enums, or quoted values were resolved wrongly or not at all. The new coerce_strings parameter defaults to False (the correct strict behavior) and is set to True only internally for OpenAPI discriminator lookups. Generated code output only changes in cases where it was previously incorrect. These are correctness improvements, not behavioral changes that break previously working correct usage.

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This analysis was performed by Claude Code Action

[github-actions]

🎉 Released in 0.62.0

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