- Avoid a few banana brackets `(| ... |)`, often by just using local `let` bindings
- Use proper `Arrows` syntax rather than helpers like `>->`
- Use monadic `do` syntax instead of `Arrows` syntax where possible
- Avoid `traverseA @Maybe`, in favor of a `case`
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/6751
GitOrigin-RevId: c07b22a1a259db6d135486ec71a716705e280717
TL;DR
---
We go from this:
```haskell
(|
withRecordInconsistency
( (|
modifyErrA
( do
(info, dependencies) <- liftEitherA -< buildRelInfo relDef
recordDependencies -< (metadataObject, schemaObject, dependencies)
returnA -< info
)
|) (addTableContext @b table . addRelationshipContext)
)
|) metadataObject
```
to this:
```haskell
withRecordInconsistencyM metadataObject $ do
modifyErr (addTableContext @b table . addRelationshipContext) $ do
(info, dependencies) <- liftEither $ buildRelInfo relDef
recordDependenciesM metadataObject schemaObject dependencies
return info
```
Background
---
We use Haskell's `Arrows` language extension to gain some syntactic sugar when working with `Arrow`s. `Arrow`s are a programming abstraction comparable to `Monad`s.
Unfortunately the syntactic sugar provided by this language extension is not very sweet.
This PR shows how we can sometimes avoid using `Arrow`s altogether, without loss of functionality or correctness. It is a demo of a technique that can be used to cut down the amount of `Arrows`-based code in our codebase by about half.
Approach
---
Although _in general_ not every `Monad` is an `Arrow`, specific `Arrow` instantiations are exactly as powerful as their `Monad` equivalents. Otherwise they wouldn't be very equivalent, would they?
Just like `liftEither` interprets the `Either e` monad into an arbitrary monad implementing `MonadError e`, we add `interpA` which interprets certain concrete monads such as `Writer w` into specific arrows, e.g. ones satisfying `ArrowWriter w`. This means that the part of the code that only uses such interpretable effects can be written _monadically_, and then used in _arrow_ constructions down the line.
This approach cannot be used for arrow effects which do not have a monadic equivalent. In our codebase, the only instance of this is `ArrowCache m`, implemented by the `Rule m` arrow. So code written with `ArrowCache m` in the context cannot be rewritten monadically using this technique.
See also
---
- #1827
- #2210
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/3543
Co-authored-by: jkachmar <8461423+jkachmar@users.noreply.github.com>
GitOrigin-RevId: eb79619c95f7a571bce99bc144ce42ee65d08505
This commit applies ormolu to the whole Haskell code base by running `make format`.
For in-flight branches, simply merging changes from `main` will result in merge conflicts.
To avoid this, update your branch using the following instructions. Replace `<format-commit>`
by the hash of *this* commit.
$ git checkout my-feature-branch
$ git merge <format-commit>^ # and resolve conflicts normally
$ make format
$ git commit -a -m "reformat with ormolu"
$ git merge -s ours post-ormolu
https://github.com/hasura/graphql-engine-mono/pull/2404
GitOrigin-RevId: 75049f5c12f430c615eafb4c6b8e83e371e01c8e
This PR only contains minor changes to documentation that I have collected over some time, revising text as I was passing by.
https://github.com/hasura/graphql-engine-mono/pull/2346
Co-authored-by: Rikin Kachhia <54616969+rikinsk@users.noreply.github.com>
GitOrigin-RevId: f3329f3212b831f1f3c74a299734faff337b1017
