Fix const in anyOf/oneOf to generate Literal type

[koxudaxi]

Fixes: #2085

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📥 Commits

Reviewing files that changed from the base of the PR and between 602c45a and 5f78c55.

⛔ Files ignored due to path filters (1)

• tests/data/jsonschema/anyof_const_with_constraints.json is excluded by !tests/data/**/*.json and included by none

📒 Files selected for processing (12)

• src/datamodel_code_generator/parser/jsonschema.py
• tests/data/expected/main/jsonschema/all_of_any_of_base_class_ref.py
• tests/data/expected/main/jsonschema/anyof_const_with_constraints.py
• tests/data/expected/main/jsonschema/discriminator_with_external_references_folder/inner_folder/artificial_folder/type_1.py
• tests/data/expected/main/jsonschema/discriminator_with_external_references_folder/inner_folder/schema.py
• tests/data/expected/main/jsonschema/discriminator_with_external_references_folder/inner_folder/type_2.py
• tests/data/expected/main/jsonschema/discriminator_with_external_references_folder/subfolder/type_5.py
• tests/data/expected/main/jsonschema/discriminator_with_external_references_folder/type_4.py
• tests/data/expected/main/jsonschema/oneof_const_mixed_with_ref.py
• tests/data/expected/main/jsonschema/oneof_const_with_properties.py
• tests/data/expected/main/openapi/const.py
• tests/data/expected/main/openapi/const_field.py

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[github-actions]

📚 Docs Preview: https://pr-2864.datamodel-code-generator.pages.dev

[codspeed-hq]

CodSpeed Performance Report

Merging #2864 will not alter performance

_{Comparing fix/const-literal-in-anyof (5f78c55) with main (602c45a)}

⚠️ 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.

Summary

✅ 11 untouched
⏩ 98 skipped¹

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 99.38%. Comparing base (602c45a) to head (5f78c55).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2864   +/-   ##
=======================================
  Coverage   99.38%   99.38%           
=======================================
  Files          91       91           
  Lines       15555    15555           
  Branches     1827     1827           
=======================================
  Hits        15460    15460           
  Misses         50       50           
  Partials       45       45           

Flag	Coverage Δ
unittests	99.38% <100.00%> (ø)

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[github-actions]

Breaking Change Analysis

Result: Breaking changes detected

Reasoning: This PR changes the generated code output for schemas with const values in anyOf/oneOf constructs. Previously, const values generated inferred base types (str, int, bool) but now they generate Literal types with the exact const value. This is visible in multiple test file changes where types like str became Literal["value"]. While this is technically a bug fix that improves type safety, it changes the generated code output which existing users may depend on, making it a breaking change for code generation.

Content for Release Notes

Code Generation Changes

• Fields with const values in anyOf/oneOf now generate Literal types instead of inferred base types - Previously, a const value like "MODE_2D" in an anyOf/oneOf schema would generate str type. Now it generates Literal["MODE_2D"]. This change affects type hints in generated models and may require updates to code that type-checks against the generated output. For example:

  # Before (v0.x)
  map_view_mode: str = Field("MODE_2D", alias="mapViewMode", const=True)
  apiVersion: str = Field('v1', const=True)
  
  # After (this PR)
  map_view_mode: Literal["MODE_2D"] = Field("MODE_2D", alias="mapViewMode", const=True)
  apiVersion: Literal['v1'] = Field('v1', const=True)

  This is a bug fix that makes the generated code more type-safe, but downstream code performing type comparisons or using isinstance(field, str) checks may need adjustment. (Fix const in anyOf/oneOf to generate Literal type #2864)

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This analysis was performed by Claude Code Action

[github-actions]

🎉 Released in 0.51.0

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