Summary

This PR fixes a bug in DataCollector._validate_model_reporter() where method reporters were never validated due to incorrect conditional logic.

The Bug

Original Code (lines 166-168 in datacollection.py)

# Type 2: Method of class/instance
if not callable(reporter) and not isinstance(reporter, types.LambdaType):
    pass

Why This Was Wrong

Method reporters were completely skipped during validation.

The Fix

# Type 2: Method of class/instance (bound methods are callable)
if callable(reporter) and not isinstance(reporter, types.LambdaType):
    try:
        reporter()  # Call without args for bound methods
    except Exception as e:
        raise RuntimeError(
            f"Method reporter '{name}' failed validation: {e!s}"
        ) from e

Key Changes

Why reporter() Instead of reporter(model)?

Looking at how collect() calls method reporters (line 341):

# Bound methods: called WITHOUT arguments (self is already bound)
self.model_vars[var].append(deepcopy(reporter()))

Bound methods like self.some_method already have self bound, so they're called with no arguments.

Comparison Table

Tests Added

Added TestMethodReporterValidation class to tests/test_datacollector.py:

Test Results

$ pytest tests/test_datacollector.py -v
20 passed  # 15 original + 5 new

Files Changed

Backwards Compatibility

✅ All 363 existing tests pass
✅ Working method reporters unaffected
✅ Only broken reporters now fail with clear error message