Map OpenAPI Discriminator mapping's values to their real value in enums by ilovelinux · Pull Request #3074 · koxudaxi/datamodel-code-generator

ilovelinux · 2026-04-05T19:01:02Z

Context

OpenAPI Discriminator mapping field is a key-value dictionary.
Both the keys and the values of the dictionary must be strings.
Despite they are strings, the mapping happens:
1. Converting any received value to string.
2. Comparing the converted value with the keys in the dictionary.

Ref: https://swagger.io/specification/#options-for-mapping-values-to-schemas

What's changed

Now mapping's keys are mapped to their real enum values, if available
Otherwise, old behavior kicks-in

Notes

Fix: OpenAPI integer discriminator with multiple enum values generates string Literals #3073

Summary by CodeRabbit

Bug Fixes
- Improved handling of discriminator fields to properly resolve multiple mapped values
- Enhanced discriminator type generation for complex inheritance scenarios

coderabbitai · 2026-04-05T19:01:19Z

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📝 Walkthrough

Walkthrough

This PR fixes integer discriminator handling in OpenAPI schema generation. When a discriminator property has multiple enum values, the parser now correctly generates integer literals instead of string literals, and refactors the discriminator value resolution logic based on a use_enum_values_in_discriminator flag.

Changes

Cohort / File(s)	Summary
Discriminator Logic Refactoring `src/datamodel_code_generator/parser/base.py`	Refactored discriminator data type creation to branch on `use_enum_values_in_discriminator`: when enabled, preserves enum-field-name behavior; when disabled, resolves discriminator values to mapped enum members' defaults (stripping quoted defaults for string-like cases). Simplified control flow by removing conditional gating around enum source lookup in `get_discriminator_field_value`.
Test Fixture Updates `tests/data/expected/main/openapi/discriminator/integer_mapping.py`	Added `IntEnum` member `integer_3 = 3` to `Kind1` and expanded `Bar.kind` discriminator type from `Literal[2]` to `Literal[2, 3]`, fixing the generation of integer literals for multi-value integer discriminators.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

PR #3070: Modifies discriminator handling in src/datamodel_code_generator/parser/base.py with related changes to how enum-backed discriminators are resolved.

Suggested labels

breaking-change-analyzed, breaking-change

Suggested reviewers

koxudaxi

Poem

🐰 A hop, a skip, through enum space,
Where integers lost their rightful place—
No more as strings do they pretend,
Literals fixed, from start to end! ✨

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 50.00% 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.
Linked Issues check	✅ Passed	The PR implementation directly addresses issue `#3073` by mapping discriminator values to real enum types (integers) instead of string literals, as evidenced by the code changes mapping discriminator values through enum resolution.
Out of Scope Changes check	✅ Passed	All changes are directly related to fixing the discriminator enum-value mapping issue: refactoring discriminator data type creation logic and updating corresponding test expectations.
Title check	✅ Passed	The title clearly identifies the main change: mapping OpenAPI discriminator mapping values to real enum values instead of string literals, which directly corresponds to the core objective of the PR.

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codspeed-hq · 2026-04-05T19:04:17Z

Merging this PR will degrade performance by 15.48%

⚠️

Unknown Walltime execution environment detected

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

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Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

❌ 11 regressed benchmarks
⏩ 98 skipped benchmarks¹

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	`BASE`	`HEAD`	Efficiency
❌	WallTime	`test_perf_all_options_enabled`	6 s	6.8 s	-12.57%
❌	WallTime	`test_perf_deep_nested`	5.6 s	6.4 s	-12.7%
❌	WallTime	`test_perf_openapi_large`	2.6 s	3.1 s	-14.69%
❌	WallTime	`test_perf_kubernetes_style_pydantic_v2`	2.4 s	2.8 s	-13.66%
❌	WallTime	`test_perf_duplicate_names`	964.4 ms	1,119.3 ms	-13.84%
❌	WallTime	`test_perf_multiple_files_input`	3.4 s	3.9 s	-13.31%
❌	WallTime	`test_perf_large_models_pydantic_v2`	3.3 s	3.9 s	-15.48%
❌	WallTime	`test_perf_stripe_style_pydantic_v2`	1.8 s	2.1 s	-12.91%
❌	WallTime	`test_perf_graphql_style_pydantic_v2`	751.9 ms	868.9 ms	-13.46%
❌	WallTime	`test_perf_complex_refs`	2 s	2.3 s	-12.6%
❌	WallTime	`test_perf_aws_style_openapi_pydantic_v2`	1.7 s	2 s	-14.33%

_{Comparing ilovelinux:fix/ilovelinux-3073-enum-literal-values (5d8f912) with main (92bdc27)}

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 · 2026-04-05T19:06:00Z

Codecov Report

❌ Patch coverage is 95.65217% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 99.99%. Comparing base (92bdc27) to head (5d8f912).

Files with missing lines	Patch %	Lines
src/datamodel_code_generator/parser/base.py	95.65%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##              main    #3074      +/-   ##
===========================================
- Coverage   100.00%   99.99%   -0.01%     
===========================================
  Files           87       87              
  Lines        18306    18313       +7     
  Branches      2091     2095       +4     
===========================================
+ Hits         18306    18312       +6     
- Partials         0        1       +1

Flag	Coverage Δ
unittests	`99.99% <95.65%> (-0.01%)`	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

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ilovelinux · 2026-04-05T19:14:17Z

This PR is draft because of the following tasks:

Check how this works with changes implemented in Fix non-string OpenAPI discriminator literals #3070 which solve a similar problem. There may be duplicate logic now.
CC: @koxudaxi
Review & evaluate potential corner-cases.

ilovelinux added 2 commits April 5, 2026 20:45

Expand existing test

e23d1c6

Map discriminator mapping values with real enum values

a07509f

ilovelinux self-assigned this Apr 5, 2026

ilovelinux marked this pull request as draft April 5, 2026 19:14

ilovelinux changed the title ~~Draft: Map OpenAPI Discriminator mapping's values to their real value in enums~~ Map OpenAPI Discriminator mapping's values to their real value in enums Apr 5, 2026

Merge branch 'main' into fix/ilovelinux-3073-enum-literal-values

5d8f912

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Map OpenAPI Discriminator mapping's values to their real value in enums #3074

Map OpenAPI Discriminator mapping's values to their real value in enums #3074
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ilovelinux:fix/ilovelinux-3073-enum-literal-values

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