effect-monocle
Hey there! This is a library aiming to provide monocle-ts API
for effect codebases. My motivation for creating it was to make transition
from fp-ts to effect easier because we rely heavily on monocle-ts in our codebase.
The overall tendency in the effect ecosystem is to ditch the optics whatsoever. I'm mostly
aligned with this view, so I'd like to emphasize that this library's main goal is to provide
a smooth transition path for those who are already using monocle-ts and want to switch to effect.
The goal is NOT to promote the use of optics.
The API
This library exposes a very small subset of the monocle-ts API. I basically rewrote parts I
use personally. If you need more, feel free to open an issue or a PR.
Along the way, I've made some changes to the API to make it more effect-friendly. Also, I've
included some changes to the API that I either wish were in the monocle-ts or have implemented
as a custom in-app code.
Notably,
- multi-parameter functions are implemented and exposed as duals, thus there are always
both data-first and data-last variants,
- the index module exposes a fully named
Lens and Optional modules, so the expected
usage is e.g Lens.prop instead of L.prop,
- I included a
Lens.extract / Optional.extract combinators, they are the moral equivalents
of type-level Extract<A, { [K in keyof A]: B } and are useful when creating an
optional from a discriminated union,
- I included
Lens.append / Lens.appendAll / Optional.append / Optional.appendAll
combinators that work on lenses / optionals focusing an array and they create a function
performing an append / extend on the focused array,
- I modified the signature of
Lens.prop / Optional.prop to accept multiple keys at once,
so one can write Lens.prop(lens, 'a', 'b', 'c') instead of
pipe(lens, Lens.prop('a'), Lens.prop('b'), Lens.prop('c')).
- I renamed
Lens.props / Optional.props to Lens.pick / Optional.pick to unify the naming
with @effect/schema, effect/Struct, etc.
- The
Lens<S, A> has a modify method so it should be used insteadf of L.modify
Please refer to the monocle-ts README and
the effect-monocle API docs for more information.
