Fix exact imports with module/class name collision

[koxudaxi]

Fixes: #2984

Summary by CodeRabbit

• Bug Fixes

  • Fixed import path handling when exact imports are enabled to avoid unintended modification of relative import references.

• Tests

  • Added test coverage for module/class name collision scenarios with exact-imports enabled, including nested/deep module cases.

• New

  • Added generated model/response types to support the collision scenarios exercised by the new tests.

[coderabbitai]

📝 Walkthrough

Walkthrough

Adjusted import-path composition in parser: __change_from_import now only composes/short-circuits relative paths when exact imports are disabled, changing the condition to require a truthy from_ and non-exact-import mode before altering full_path. Added expected output files and tests for exact-imports collision cases.

Changes

Cohort / File(s)	Summary
Parser logic src/datamodel_code_generator/parser/base.py	Changed __change_from_import control flow: only modify/short-circuit relative import path composition when use_exact_imports is False and from_ is truthy (adjusted condition involving internal module or module/class collision).
Test expected outputs — shallow collision tests/data/expected/main/openapi/module_class_name_collision_exact_imports/A.py, tests/data/expected/main/openapi/module_class_name_collision_exact_imports/__init__.py	Added generated model A and package-level AGetResponse expected outputs for exact-imports scenario.
Test expected outputs — deep collision tests/data/expected/main/openapi/module_class_name_collision_deep_exact_imports/A/B.py, tests/data/expected/main/openapi/module_class_name_collision_deep_exact_imports/A/__init__.py, tests/data/expected/main/openapi/module_class_name_collision_deep_exact_imports/__init__.py	Added nested package A with model B and package-level BGetResponse expected outputs for deep exact-imports scenario.
Tests tests/main/openapi/test_main_openapi.py	Added two tests (shallow and deep) asserting behavior with --use-exact-imports against Pydantic v2; note: the diff shows duplicated pairs of these test definitions.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• feat: Add --module-split-mode option to generate one file per model (#1170) #2685 — Modifies the same import-resolution logic in src/datamodel_code_generator/parser/base.py, directly related to how relative vs exact imports are composed.

Suggested labels

breaking-change-analyzed

Poem

🐰 I hop through code where imports used to roam,
I stitch the paths so every module finds home,
Exact ones stay put, relatives only sway,
Tests and packages now agree and play,
A tidy hop — and then I munch a poem 🥕

🚥 Pre-merge checks | ✅ 6

✅ Passed checks (6 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and specifically summarizes the main change: fixing exact imports when module and class names collide, which directly addresses the primary objective of the PR.
Linked Issues check	✅ Passed	The PR directly addresses issue #2984 by fixing the import path composition logic in __change_from_import to prevent incorrect import statements when using exact imports with module/class name collisions.
Out of Scope Changes check	✅ Passed	All changes are in scope: the core fix modifies import logic, and test files add expected output and test cases specifically for the exact imports collision scenario.
Docstring Coverage	✅ Passed	Docstring coverage is 80.00% which is sufficient. The required threshold is 80.00%.
Merge Conflict Detection	✅ Passed	✅ No merge conflicts detected when merging into main

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✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch fix/exact-imports-module-class-collision

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[github-actions]

📚 Docs Preview: https://pr-2998.datamodel-code-generator.pages.dev

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (2b659f0) to head (a8d0b88).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main     #2998   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           94        94           
  Lines        18075     18081    +6     
  Branches      2090      2090           
=========================================
+ Hits         18075     18081    +6     

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

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[github-actions]

Breaking Change Analysis

Result: No breaking changes detected

Reasoning: This PR is a bug fix that corrects the behavior of the --use-exact-imports option when there are module/class name collisions. Previously, even with exact imports enabled, the code generator would modify import paths when a module name collided with a class name (e.g., module A containing class A). This was incorrect behavior that contradicted the purpose of --use-exact-imports. The fix adds a check not imports.use_exact to prevent the import path modification when exact imports are requested. This is a correction of broken behavior, not a breaking change - users who were using --use-exact-imports will now get the correct exact import paths they expected.

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This analysis was performed by Claude Code Action

[github-actions]

🎉 Released in 0.54.0

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