Fix incomplete activation validation in HausdorffDTLoss

[aymuos15]

The validation check for mutually exclusive activation options was incomplete - it only checked sigmoid and softmax but not other_act, despite the error message explicitly mentioning other_act.

Without this check, passing e.g. sigmoid=True, other_act=relu silently stacks both activations in forward() (other_act(sigmoid(x))) instead of applying only one, producing an incorrect loss with no warning.

Before:

if int(sigmoid) + int(softmax) > 1:
    raise ValueError("... [sigmoid=True, softmax=True, other_act is not None].")

After:

if int(sigmoid) + int(softmax) + int(other_act is not None) > 1:
    raise ValueError("... [sigmoid=True, softmax=True, other_act is not None].")

This is consistent with the validation in dice.py and tversky.py which correctly include all three options in the check.

Added tests for:

• sigmoid=True with other_act
• softmax=True with other_act
• All three options combined

Types of changes

• Non-breaking change (fix or new feature that would not break existing functionality).

[coderabbitai]

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📥 Commits

Reviewing files that changed from the base of the PR and between 65beb58 and 484bc7a.

📒 Files selected for processing (2)

• monai/losses/hausdorff_loss.py
• tests/losses/test_hausdorff_loss.py

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📝 Walkthrough

Walkthrough

The change enhances validation in HausdorffDTLoss to enforce mutual exclusivity among activation function parameters: sigmoid, softmax, and other_act. Previously, the validation only checked sigmoid and softmax, allowing incompatible combinations involving other_act. The fix extends the incompatibility guard to include all three parameters. Corresponding test coverage is added to assert ValueError is raised for all invalid option combinations.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 33.33% 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
Title check	✅ Passed	Title clearly and specifically describes the main change: fixing incomplete activation validation in HausdorffDTLoss.
Description check	✅ Passed	Description covers the problem, solution, code changes, and test additions. Matches template structure with Types of changes checked appropriately.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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