Coverage collection fails due to ecgtools/pydantic 2.11 incompatibility

[lewisjared]

Summary

Running pytest with --cov flag fails when importing climate_ref due to an incompatibility between ecgtools and pydantic 2.11+.

Error

PydanticSchemaGenerationError: Unable to generate pydantic-core schema for 
<class 'pydantic.deprecated.decorator.ValidatedFunction.create_model.<locals>.DecoratorBaseModel'>

Root Cause

The ecgtools package uses the deprecated @pydantic.validate_arguments decorator which was removed/broken in pydantic 2.11:

# ecgtools/builder.py:148
@pydantic.validate_arguments
def build(self, ...):

Import Chain

1. conftest.py imports climate_ref.cli
2. cli imports datasets
3. datasets imports ecgtools.Builder
4. ecgtools uses deprecated @pydantic.validate_arguments
5. pydantic 2.11+ fails to generate schema

Current State

• climate-ref-core requires pydantic>=2.10.6
• Installed: pydantic 2.11.4
• ecgtools 2024.7.31 has no upper bound on pydantic
• Tests pass without --cov, only coverage collection triggers the import error
• make test-ref works (coverage shows 88.77%)

Potential Solutions

1. Pin pydantic < 2.11 in project dependencies

   "pydantic>=2.10.6,<2.11"

2. Wait for ecgtools fix - upstream needs to migrate from deprecated decorator

3. Lazy import ecgtools - defer import until actually needed, avoiding the conftest import chain

Environment

• pydantic: 2.11.4
• ecgtools: 2024.7.31
• Python: 3.11.14