Fix Pydantic v2 discriminated unions in array fields

[koxudaxi]

Fixes: #2904

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📥 Commits

Reviewing files that changed from the base of the PR and between 3db6667 and ffcd38b.

⛔ Files ignored due to path filters (1)

• tests/data/openapi/discriminator_in_array_underscore.yaml is excluded by !tests/data/**/*.yaml and included by none

📒 Files selected for processing (6)

• src/datamodel_code_generator/model/pydantic_v2/base_model.py
• src/datamodel_code_generator/parser/base.py
• src/datamodel_code_generator/types.py
• tests/data/expected/main/openapi/discriminator/in_array_collapse_root_models_pydantic_v2.py
• tests/data/expected/main/openapi/discriminator/in_array_underscore_pydantic_v2.py
• tests/main/openapi/test_main_openapi.py

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[github-actions]

📚 Docs Preview: https://pr-2907.datamodel-code-generator.pages.dev

[codspeed-hq]

CodSpeed Performance Report

Merging #2907 will not alter performance

_{Comparing fix/discriminator-in-list-pydantic-v2 (ffcd38b) with main (3db6667)}

⚠️ Unknown Walltime execution environment detected

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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 (3db6667) to head (ffcd38b).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2907   +/-   ##
=======================================
  Coverage   99.38%   99.38%           
=======================================
  Files          92       92           
  Lines       16374    16400   +26     
  Branches     1940     1947    +7     
=======================================
+ Hits        16273    16299   +26     
  Misses         52       52           
  Partials       49       49           

Flag	Coverage Δ
unittests	99.38% <100.00%> (+<0.01%)	⬆️

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[koxudaxi]

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[github-actions]

Breaking Change Analysis

Result: No breaking changes detected

Reasoning: This PR is a bug fix for Pydantic v2 discriminated unions in array fields (#2904). The changes modify how discriminated unions are rendered when they appear inside array fields - now correctly generating Annotated[Union, Field(discriminator='...')] syntax. While the generated code output changes for this specific scenario, this is fixing incorrect behavior rather than breaking working functionality. Users who had schemas with discriminated unions in arrays were previously getting invalid or non-functional output; now they get correct Pydantic v2 discriminator syntax. The addition of a discriminator field to the DataType class is an additive change that doesn't affect existing custom templates unless they explicitly handle the new field. No CLI options, APIs, default behaviors, Python version requirements, or error handling patterns were changed.

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This analysis was performed by Claude Code Action

[github-actions]

🎉 Released in 0.52.0

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