Log Level Datatype.

The package provides a LogLevel type for defining logging callbacks without depending on a particular logging framework.

Log Level Datatype

This package provides a Haskell log-level datatype. It allows to specify APIs with logging-callbacks without depending on a particular logging framework.

There is a large number of different Haskell logging frameworks that support different use cases and backends. As a consequence these framework make different trade-offs with respect to their architecture and implementation. Often they have complex internals and many external dependencies.

While logging frameworks differ a lot in their internals and backends, they tend to have similar frontends. In particular, many software components depend for logging only on a callback function that typically has a type similar to

loggingCallback ∷ LogLevel → Text → IO ()

The only framework-specific dependency is the LogLevel type. This type is in most cases similar, often isomorphic, and sometimes even identical across different frameworks.

It is unfortunate that a software component has to depend on a particular logging framework (and all of the frameworks dependencies) just for using the LogLevel type that is almost identical throughout most logging frameworks.

This package allows software components to include logging callbacks in their APIs without depending on a particular logging framework.

Even more complex logging callbacks often have a type along the lines of

genericLoggingCallback ∷ c a ⇒ LogLevel → a → IO ()

where c is a constraint made up from common type classes like ToJSON, Serializable, NFData, or Generic.