Fix title ignored when creating enums from merging `allOf`'s or `anyOf`'s objects by ilovelinux · Pull Request #2975 · koxudaxi/datamodel-code-generator

ilovelinux · 2026-01-31T13:28:49Z

The issue:

x_enum_varnames was passed to JsonSchemaObject using the variable name instead of its alias.

The consequence:

x_enum_varnames was not correctly recognized, and therefore ignored

The solution:

x_enum_varnames is now passed as x-enum-varnames (its alias) and it's no longer ignored

The fix above unveiled an incorrect behavior when no title is set but type can be inferred and used as title. A fix has been applied about that.

Summary by CodeRabbit

Bug Fixes
- Improved enum metadata and naming for schemas using const in oneOf/anyOf: enum members now get descriptive, conventional names instead of generic numeric identifiers.
- Fixed const value extraction so generated enum names correctly match their underlying values.

_{✏️ Tip: You can customize this high-level summary in your review settings.}

…eaad of its alias

…an be inferred and used as name

coderabbitai · 2026-01-31T13:29:07Z

📝 Walkthrough

Walkthrough

The parser stops adding a generated varname when a title is absent during const-based oneOf/anyOf extraction, and synthetic enum objects now set x-enum-varnames and default via a merged metadata dictionary instead of passing varnames directly.

Changes

Cohort / File(s)	Summary
Parser Logic Updates `src/datamodel_code_generator/parser/jsonschema.py`	Removed automatic varname addition when no title is present in `_extract_const_enum_from_combined`; changed `_create_synthetic_enum_obj` to construct `x-enum-varnames` and conditional `default` via a merged dict.
Test Expectations `tests/data/expected/main/jsonschema/oneof_const_enum_int.py`	Renamed `StatusCode` IntEnum members from `integer_200`, `integer_404`, `integer_500` to `OK`, `Not_Found`, `Server_Error` to reflect updated naming logic.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Suggested labels

breaking-change-analyzed, breaking-change

Poem

🐰 I nibbled at enums through the night,
Titles kept if they shone so bright,
Numbers dressed up with names that sing,
Merged metadata, a tidy thing,
Hoppity-hop, the parser's light!

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The PR title clearly and specifically describes the main fix: addressing the issue where title values are ignored when creating enums from merged allOf/anyOf objects.
Linked Issues check	✅ Passed	The changes directly address issue `#2974` by fixing how x-enum-varnames is passed and handling cases where no title is set, enabling proper enum member naming from schema titles.
Out of Scope Changes check	✅ Passed	All changes are directly related to fixing title handling in enum generation from combined schemas; no unrelated modifications detected.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.

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codspeed-hq · 2026-01-31T13:31:56Z

Merging this PR will not alter performance

⚠️

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.

✅ 11 untouched benchmarks
⏩ 98 skipped benchmarks¹

_{Comparing ilovelinux:fix/2974-use-title-for-enum (ce2d14d) with main (4661406)}

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. ↩

coderabbitai

Actionable comments posted: 0

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

src/datamodel_code_generator/parser/jsonschema.py (1)

855-868: ⚠️ Potential issue | 🟠 Major

Mixed title/no-title enums can lose all titles.

Line 855-868: if any item lacks a title and inferred_type is set, varnames becomes shorter than enum_values, so all titles are dropped. This contradicts “use title when available” for mixed cases.

✅ Suggested fix (preserve titles when present, keep legacy behavior when none)

@@
-        inferred_type: str | None = None
+        inferred_type: str | None = None
+        has_title = False
@@
-            if item.title:
-                varnames.append(item.title)
-            elif inferred_type is None and const_value is not None:
-                match const_value:
-                    case str():
-                        inferred_type = "string"
-                    case bool():  # bool must come before int (bool is subclass of int)
-                        inferred_type = "boolean"
-                    case int():
-                        inferred_type = "integer"
-                    case float():
-                        inferred_type = "number"
-            else:
-                varnames.append(str(const_value))
+            if item.title:
+                has_title = True
+                varnames.append(item.title)
+            else:
+                if inferred_type is None and const_value is not None:
+                    match const_value:
+                        case str():
+                            inferred_type = "string"
+                        case bool():  # bool must come before int (bool is subclass of int)
+                            inferred_type = "boolean"
+                        case int():
+                            inferred_type = "integer"
+                        case float():
+                            inferred_type = "number"
+                varnames.append(str(const_value))
@@
-        if not enum_values:  # pragma: no cover
+        if not enum_values:  # pragma: no cover
             return None
+        if not has_title and inferred_type is not None:
+            varnames = []

codecov · 2026-01-31T13:33:22Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (4661406) to head (ce2d14d).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main     #2975   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           94        94           
  Lines        17781     17780    -1     
  Branches      2044      2044           
=========================================
- Hits         17781     17780    -1

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

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Copilot

Pull request overview

Fixes enum member naming for enums synthesized from oneOf/anyOf const-combinations by correctly propagating x-enum-varnames into the synthetic JsonSchemaObject, allowing per-item title values to be used for enum member names.

Changes:

Update synthetic enum schema creation to populate x-enum-varnames via its alias so Pydantic recognizes it.
Adjust const-enum extraction logic around how varnames and inferred enum type are derived.
Update expected JSON Schema output for an integer const oneOf enum to use titles as member names.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
tests/data/expected/main/jsonschema/oneof_const_enum_int.py	Updates expected enum member names to reflect per-item `title` usage.
src/datamodel_code_generator/parser/jsonschema.py	Fixes passing `x-enum-varnames` into synthetic enum schema objects and tweaks const-enum extraction behavior.

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github-actions · 2026-01-31T21:13:56Z

Breaking Change Analysis

Result: Breaking changes detected

Reasoning: This PR fixes a bug where the title field in oneOf/anyOf const schema constructs was being ignored. While this is a bug fix (the tool now correctly respects user-specified titles), it changes the generated enum member names for any schema that had title fields in these constructs. Users who have code referencing the old enum member names (like StatusCode.integer_200) would need to update to use the new names (like StatusCode.OK). This constitutes a breaking change in generated code output, even though the new behavior is the correct/intended one.

Content for Release Notes

Code Generation Changes

Enum member names from oneOf/anyOf const constructs now use title field when provided - Previously, when creating enums from oneOf/anyOf constructs with const values, the title field was incorrectly ignored and enum member names were generated using the pattern {type}_{value} (e.g., integer_200). Now, when a title is specified, it is correctly used as the enum member name (e.g., OK instead of integer_200). Users who have code depending on the previously generated enum member names will need to update their references. (Fix title ignored when creating enums from merging allOf's or anyOf's objects #2975)

Before:
```
class StatusCode(IntEnum):
    integer_200 = 200
    integer_404 = 404
    integer_500 = 500
```
After:
```
class StatusCode(IntEnum):
    OK = 200
    Not_Found = 404
    Server_Error = 500
```

This analysis was performed by Claude Code Action

github-actions · 2026-02-14T16:21:30Z

🎉 Released in 0.54.0

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

ilovelinux added 2 commits January 31, 2026 14:17

Fix x_enum_varnames ignored because class variable name was used inst…

dd7713b

…eaad of its alias

Keep existing behavior when title isn't defined and the enum's type c…

b185ec5

…an be inferred and used as name

ilovelinux requested review from Copilot and koxudaxi January 31, 2026 13:28

Copilot started reviewing on behalf of ilovelinux January 31, 2026 13:30 View session

coderabbitai Bot reviewed Jan 31, 2026

View reviewed changes

Copilot AI reviewed Jan 31, 2026

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Comment thread src/datamodel_code_generator/parser/jsonschema.py

Copilot AI reviewed Jan 31, 2026

View reviewed changes

Improve fix for unveiled incorrect behavior

ce2d14d

koxudaxi approved these changes Jan 31, 2026

View reviewed changes

koxudaxi merged commit 365419e into koxudaxi:main Jan 31, 2026
37 checks passed

github-actions Bot added breaking-change-analyzed breaking-change labels Jan 31, 2026

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

Use title for enum naming #2974

Closed

coderabbitai Bot mentioned this pull request Feb 19, 2026

Description not propagated to enum fields docstring #3003

Open

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Fix title ignored when creating enums from merging `allOf`'s or `anyOf`'s objects#2975

Fix title ignored when creating enums from merging `allOf`'s or `anyOf`'s objects#2975
koxudaxi merged 3 commits intokoxudaxi:mainfrom
ilovelinux:fix/2974-use-title-for-enum

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