fix: _AllowedSurfaceIDs.__call__ silently returning None on malformed surface info

[Copilot]

_AllowedSurfaceIDs.__call__ silently swallowed KeyError/IndexError and returned None, causing a confusing downstream TypeError: argument of type 'NoneType' is not iterable in _SurfaceIds.validate.

Context

When a surface entry in _get_surfaces_info() is missing the surface_id key or has an empty surface_id list, the method caught both exceptions and fell off the end, returning None. Callers like _SurfaceIds.validate then failed with a TypeError that gave no indication of the actual root cause.

Change Summary

• _AllowedSurfaceIDs.__call__: replaced the silent catch-all with a per-surface loop that raises a descriptive LookupError naming the offending surface and whether the failure was a missing key or empty index:

# Before
try:
    return [info["surface_id"][0] for _, info in surface_info.items()]
except (KeyError, IndexError):
    pass  # silently returns None

# After
for surface_name, info in surface_info.items():
    try:
        surface_ids.append(info["surface_id"][0])
    except KeyError:
        raise LookupError(f"Failed to retrieve valid surface_id key for surface '{surface_name}'.")
    except IndexError:
        raise LookupError(f"Failed to retrieve valid surface_id index for surface '{surface_name}'.")
return surface_ids

• Tests: added three unit tests covering the KeyError path, the IndexError (empty list) path, and propagation through _SurfaceIds.validate.

Rationale

Raising a LookupError with the surface name pinpoints the bad data immediately, rather than silently producing None and letting an unrelated TypeError surface elsewhere.

Impact

_AllowedSurfaceIDs.__call__ and any callers that previously received None (e.g., _SurfaceIds.validate, _get_surface_ids) will now get a clear LookupError instead of a silent None or a misleading TypeError.

[codacy-production]

Up to standards ✅

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[Copilot]

Pull request overview

This PR improves error reporting in the field data surface-ID lookup path by ensuring malformed surface metadata triggers a descriptive exception at the source, rather than returning None and failing later with an unrelated TypeError.

Changes:

• Updated _AllowedSurfaceIDs.__call__ to iterate per-surface and raise a descriptive LookupError on missing surface_id or empty surface_id list.
• Added unit tests covering both malformed-surface-info cases and verifying _SurfaceIds.validate propagates the LookupError.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/ansys/fluent/core/field_data_interfaces.py	Replace silent exception swallow/implicit None return with explicit per-surface LookupErrors containing the surface name and failure mode.
tests/test_field_data.py	Add regression tests for missing surface_id key, empty surface_id list, and propagation through _SurfaceIds.validate.

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