# check_registry()

## check_registry( category: str, registry: Mapping[str, DriverEntry], driver_config: type[BaseModel], ) → None[source]

Verify every pattern in `registry` can produce a valid config block for `category`.

[`config_block()`](https://dev.nominal.io/instro/ref/library/instro.lib.discover.DiscoveredInstrument.md#instro.lib.discover.DiscoveredInstrument.config_block "instro.lib.discover.DiscoveredInstrument.config_block") emits `num_channels` exactly
when the matched [`IdnPattern`](https://dev.nominal.io/instro/ref/library/instro.lib.registry.IdnPattern.md#instro.lib.registry.IdnPattern "instro.lib.registry.IdnPattern") carries one, and each category’s driver config either
requires that field or forbids it (`extra="forbid"`). So a pattern must carry a count when
the model requires one and must not when the model has no such field. The requirement is read
from the model so the registry and the schema cannot drift apart.

Run by the registry tests for every category rather than at import time: a bad pattern is a
contributor mistake, and an import-time failure in one category would take `match_idn()` and
`instro discover` down for all of them.

Parameters:
:   - **category**

      Category name, used in the error message (e.g. `"psu"`).
    - **registry**

      The category’s `<CAT>_VENDOR_REGISTRY` mapping.
    - **driver_config**

      The category’s driver config Pydantic model; whether its `num_channels`
      field is required decides which direction is enforced.

Raises:
:   [**ValueError**](https://docs.python.org/3/builtins/exceptions.html#ValueError "(in Python v3.15)") – a pattern lacks `num_channels` where the config requires it, or carries one
    where the config has no such field.