What is the `Cacheable` type class about?
```haskell
class Eq a => Cacheable a where
unchanged :: Accesses -> a -> a -> Bool
default unchanged :: (Generic a, GCacheable (Rep a)) => Accesses -> a -> a -> Bool
unchanged accesses a b = gunchanged (from a) (from b) accesses
```
Its only method is an alternative to `(==)`. The added value of `unchanged` (and the additional `Accesses` argument) arises _only_ for one type, namely `Dependency`. Indeed, the `Cacheable (Dependency a)` instance is non-trivial, whereas every other `Cacheable` instance is completely boilerplate (and indeed either generated from `Generic`, or simply `unchanged _ = (==)`). The `Cacheable (Dependency a)` instance is the only one where the `Accesses` argument is not just passed onwards.
The only callsite of the `unchanged` method is in the `ArrowCache (Rule m)` method. That is to say that the `Cacheable` type class is used to decide when we can re-use parts of the schema cache between Metadata operations.
So what is the `Cacheable (Dependency a)` instance about? Normally, the output of a `Rule m a b` is re-used when the new input (of type `a`) is equal to the old one. But sometimes, that's too coarse: it might be that a certain `Rule m a b` only depends on a small part of its input of type `a`. A `Dependency` allows us to spell out what parts of `a` are being depended on, and these parts are recorded as values of types `Access a` in the state `Accesses`.
If the input `a` changes, but not in a way that touches the recorded `Accesses`, then the output `b` of that rule can be re-used without recomputing.
So now you understand _why_ we're passing `Accesses` to the `unchanged` method: `unchanged` is an equality check in disguise that just needs some additional context.
But we don't need to pass `Accesses` as a function argument. We can use the `reflection` package to pass it as type-level context. So the core of this PR is that we change the instance declaration from
```haskell
instance (Cacheable a) => Cacheable (Dependency a) where
```
to
```haskell
instance (Given Accesses, Eq a) => Eq (Dependency a) where
```
and use `(==)` instead of `unchanged`.
If you haven't seen `reflection` before: it's like a `MonadReader`, but it doesn't require a `Monad`.
In order to pass the current `Accesses` value, instead of simply passing the `Accesses` as a function argument, we need to instantiate the `Given Accesses` context. We use the `give` method from the `reflection` package for that.
```haskell
give :: forall r. Accesses -> (Given Accesses => r) -> r
unchanged :: (Given Accesses => Eq a) => Accesses -> a -> a -> Bool
unchanged accesses a b = give accesses (a == b)
```
With these three components in place, we can delete the `Cacheable` type class entirely.
The remainder of this PR is just to remove the `Cacheable` type class and its instances.
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/6877
GitOrigin-RevId: 7125f5e11d856e7672ab810a23d5bf5ad176e77f
When building under the `dev.sh`-adjusted `cabal.local` files, it's not possible to build all Haskell components:
```shell
$ cabal build all all:tests all:benchmarks
[... snipped ...]
[1 of 1] Compiling Harness.GraphqlEnginePro ( src/Harness/GraphqlEnginePro.hs, /home/auke/graphql-engine-mono/dist-newstyle/build/x86_64-linux/ghc-9.2.5/test-harness-pro-0.1.0.0/opt/build/Harness/GraphqlEnginePro.o, /home/auke/graphql-engine-mono/dist-newstyle/build/x86_64-linux/ghc-9.2.5/test-harness-pro-0.1.0.0/opt/build/Harness/GraphqlEnginePro.dyn_o )
src/Harness/GraphqlEnginePro.hs:13:1: error:
Could not find module 'Control.Concurrent.Extended'
There are files missing in the 'graphql-engine-1.0.0' package,
try running 'ghc-pkg check'.
Use -v (or `:set -v` in ghci) to see a list of the files searched for.
|
13 | import Control.Concurrent.Extended (sleep)
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
src/Harness/GraphqlEnginePro.hs:14:1: error:
Could not find module 'Data.Environment'
There are files missing in the 'graphql-engine-1.0.0' package,
try running 'ghc-pkg check'.
Use -v (or `:set -v` in ghci) to see a list of the files searched for.
|
14 | import Data.Environment qualified as Env
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
```
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/6962
GitOrigin-RevId: dd7992dfa4e5b999f9b3d39389121bde1465965d
## Description
Reordering the flow so that things are presented in the order in which a user would arrive at the particular step.
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/6935
GitOrigin-RevId: 5c04bc4142f3417cfb2eab0d057d0e264adf3f6b
Rather than varying it, let's just use `postgis/postgis` everywhere.
This uses the latest version of PostGIS, in which some of the raster codes have changed. This seems benign (it's just one digit) in the hex stream. I can't find the relevant release notes though.
Also syncs _images.go_ and _databases.yaml_ so we use the same thing where possible.
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/6903
GitOrigin-RevId: bb5c56f2e7ff69e4c008f1d658850af08c96badc
We currently have a fairly intricate way of running our PostgreSQL and MSSQL integration tests (not the API tests). By splitting them out, we can simplify this a lot. Most prominently, we can rely on Cabal to be our argument parser instead of writing our own.
We can also simplify how they're run in CI. They are currently (weirdly) run alongside the Python integration tests. This breaks them out into their own jobs for better visibility, and to avoid conflating the two.
The changes are as follows:
- The "unit" tests that rely on a running PostgreSQL database are extracted out to a new test directory so they can be run separately.
- Most of the `Main` module comes with them.
- We now refer to these as "integration" tests instead.
- Likewise for the "unit" tests that rely on a running MS SQL Server database. These are a little simpler and we can use `hspec-discover`, with a `SpecHook` to extract the connection string from an environment variable.
- Henceforth, these are the MS SQL Server integration tests.
- New CI jobs have been added for each of these.
- There wasn't actually a job for the MS SQL Server integration tests. It's pretty amazing they still run well.
- The "haskell-tests" CI job, which used to run the PostgreSQL integration tests, has been removed.
- The makefiles and contributing guide have been updated to run these.
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/6912
GitOrigin-RevId: 67bbe2941bba31793f63d04a9a693779d4463ee1
### Description
This monster of a PR took way too long. As the title suggests, it reduces the schema context carried in the readers to the very strict minimum. In practice, that means that to build a source, we only require:
- the global `SchemaContext`
- the global `SchemaOptions` (soon to be renamed `SchemaSourceOptions`)
- that source's `SourceInfo`
Furthermore, _we no longer carry "default" customization options throughout the schema_. All customization information is extracted from the `SourceInfo`, when required. This prevents an entire category of bugs we had previously encountered, such as parts of the code using uninitialized / unupdated customization info.
In turn, this meant that we could remove the explicit threading of the `SourceInfo` throughout the schema, since it is now always available through the reader context.
Finally, this meant making a few adjustments to relay and actions as well, such as the introduction of a new separate "context" for actions, and a change to how we create some of the action-specific postgres scalar parsers.
I'll highlight with review comments the areas of interest.
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/6709
GitOrigin-RevId: ea80fddcb24e2513779dd04b0b700a55f0028dd1
- 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
