Followup to hasura/graphql-engine-mono#4713.
The `memoizeOn` method, part of `MonadSchema`, originally had the following type:
```haskell
memoizeOn
:: (HasCallStack, Ord a, Typeable a, Typeable b, Typeable k)
=> TH.Name
-> a
-> m (Parser k n b)
-> m (Parser k n b)
```
The reason for operating on `Parser`s specifically was that the `MonadSchema` effect would additionally initialize certain `Unique` values, which appear (nested in) the type of `Parser`.
hasura/graphql-engine-mono#518 changed the type of `memoizeOn`, to additionally allow memoizing `FieldParser`s. These also contained a `Unique` value, which was similarly initialized by the `MonadSchema` effect. The new type of `memoizeOn` was as follows:
```haskell
memoizeOn
:: forall p d a b
. (HasCallStack, HasDefinition (p n b) d, Ord a, Typeable p, Typeable a, Typeable b)
=> TH.Name
-> a
-> m (p n b)
-> m (p n b)
```
Note the type `p n b` of the value being memoized: by choosing `p` to be either `Parser k` or `FieldParser`, both can be memoized. Also note the new `HasDefinition (p n b) d` constraint, which provided a `Lens` for accessing the `Unique` value to be initialized.
A quick simplification is that the `HasCallStack` constraint has never been used by any code. This was realized in hasura/graphql-engine-mono#4713, by removing that constraint.
hasura/graphql-engine-mono#2980 removed the `Unique` value from our GraphQL-related types entirely, as their original purpose was never truly realized. One part of removing `Unique` consisted of dropping the `HasDefinition (p n b) d` constraint from `memoizeOn`.
What I didn't realize at the time was that this meant that the type of `memoizeOn` could be generalized and simplified much further. This PR finally implements that generalization. The new type is as follows:
```haskell
memoizeOn ::
forall a p.
(Ord a, Typeable a, Typeable p) =>
TH.Name ->
a ->
m p ->
m p
```
This change has a couple of consequences.
1. While constructing the schema, we often output `Maybe (Parser ...)`, to model that the existence of certain pieces of GraphQL schema sometimes depends on the permissions that a certain role has. The previous versions of `memoizeOn` were not able to handle this, as the only thing they could memoize was fully-defined (if not yet fully-evaluated) `(Field)Parser`s. This much more general API _would_ allow memoizing `Maybe (Parser ...)`s. However, we probably have to be continue being cautious with this: if we blindly memoize all `Maybe (Parser ...)`s, the resulting code may never be able to decide whether the value is `Just` or `Nothing` - i.e. it never commits to the existence-or-not of a GraphQL schema fragment. This would manifest as a non-well-founded knot tying, and this would get reported as an error by the implementation of `memoizeOn`.
tl;dr: This generalization _technically_ allows for memoizing `Maybe` values, but we probably still want to avoid doing so.
For this reason, the PR adds a specialized version of `memoizeOn` to `Hasura.GraphQL.Schema.Parser`.
2. There is no longer any need to connect the `MonadSchema` knot-tying effect with the `MonadParse` effect. In fact, after this PR, the `memoizeOn` method is completely GraphQL-agnostic, and so we implement hasura/graphql-engine-mono#4726, separating `memoizeOn` from `MonadParse` entirely - `memoizeOn` can be defined and implemented as a general Haskell typeclass method.
Since `MonadSchema` has been made into a single-type-parameter type class, it has been renamed to something more general, namely `MonadMemoize`. Its only task is to memoize arbitrary `Typeable p` objects under a combined key consisting of a `TH.Name` and a `Typeable a`.
Also for this reason, the new `MonadMemoize` has been moved to the more general `Control.Monad.Memoize`.
3. After this change, it's somewhat clearer what `memoizeOn` does: it memoizes an arbitrary value of a `Typeable` type. The only thing that needs to be understood in its implementation is how the manual blackholing works. There is no more semantic interaction with _any_ GraphQL code.
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/4725
Co-authored-by: Daniel Harvey <4729125+danieljharvey@users.noreply.github.com>
GitOrigin-RevId: 089fa2e82c2ce29da76850e994eabb1e261f9c92
### Description
I am not 100% sure about this PR; while I think the code is better this way, I'm willing to be convinced otherwise.
In short, this PR moves the `RoleName` field into the `SchemaContext`, instead of being a nebulous `Has RoleName` constraint on the reader monad. The major upside of this is that it makes it an explicit named field, rather than something that must be given as part of a tuple of arguments when calling `runReader`.
However, the downside is that it breaks the helper permissions functions of `Schema.Table`, which relied on `Has RoleName r`. This PR makes the choice of passing the role name explicitly to all of those functions, which in turn means first explicitly fetching the role name in a lot of places. It makes it more explicit when a schema building block relies on the role name, but is a bit verbose...
### Alternatives
Some alternatives worth considering:
- attempting something like `Has context r, Has RoleName context`, which would allow them to be independent from the context but still fetch the role name from the reader, but might require type annotations to not be ambiguous
- keeping the permission functions the same, with `Has RoleName r`, and introducing a bunch of newtypes instead of using tuples to explicitly implement all the required `Has` instances
- changing the permission functions to `Has SchemaContext r`, since they are functions used only to build the schema, and therefore may be allowed to be tied to the context.
What do y'all think?
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/5073
GitOrigin-RevId: 8fd09fafb54905a4d115ef30842d35da0c3db5d2
This introduces an `ErrorMessage` newtype which wraps `Text` in a manner which is designed to be easy to construct, and difficult to deconstruct.
It provides functionality similar to `Data.Text.Extended`, but designed _only_ for error messages. Error messages are constructed through `fromString`, concatenation, or the `toErrorValue` function, which is designed to be overridden for all meaningful domain types that might show up in an error message. Notably, there are not and should never be instances of `ToErrorValue` for `String`, `Text`, `Int`, etc. This is so that we correctly represent the value in a way that is specific to its type. For example, all `Name` values (from the _graphql-parser-hs_ library) are single-quoted now; no exceptions.
I have mostly had to add `instance ToErrorValue` for various backend types (and also add newtypes where necessary). Some of these are not strictly necessary for this changeset, as I had bigger aspirations when I started. These aspirations have been tempered by trying and failing twice.
As such, in this changeset, I have started by introducing this type to the `parseError` and `parseErrorWith` functions. In the future, I would like to extend this to the `QErr` record and the various `throwError` functions, but this is a much larger task and should probably be done in stages.
For now, `toErrorMessage` and `fromErrorMessage` are provided for conversion to and from `Text`, but the intent is to stop exporting these once all error messages are converted to the new type.
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/5018
GitOrigin-RevId: 84b37e238992e4312255a87ca44f41af65e2d89a
This moves `MkTypename` and `NamingCase` into their own modules, with the intent of reducing the scope of the schema parsers code, and trying to reduce imports of large modules when small ones will do.
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/4978
GitOrigin-RevId: 19541257fe010035390f6183a4eaa37bae0d3ca1
The code that builds the GraphQL schema, and `buildGQLContext` in particular, is partial: not every value of `(ServerConfigCtx, GraphQLQueryType, SourceCache, HashMap RemoteSchemaName (RemoteSchemaCtx, MetadataObject), ActionCache, AnnotatedCustomTypes)` results in a valid GraphQL schema. When it fails, we want to be able to return better error messages than we currently do.
The key thing that is missing is a way to trace back GraphQL type information to their origin from the Hasura metadata. Currently, we have a number of correctness checks of our GraphQL schema. But these correctness checks only have access to pure GraphQL type information, and hence can only report errors in terms of that. Possibly the worst is the "conflicting definitions" error, which, in practice, can only be debugged by Hasura engineers. This is terrible DX for customers.
This PR allows us to print better error messages, by adding a field to the `Definition` type that traces the GraphQL type to its origin in the metadata. So the idea is simple: just add `MetadataObjId`, or `Maybe` that, or some other sum type of that, to `Definition`.
However, we want to avoid having to import a `Hasura.RQL` module from `Hasura.GraphQL.Parser`. So we instead define this additional field of `Definition` through a new type parameter, which is threaded through in `Hasura.GraphQL.Parser`. We then define type synonyms in `Hasura.GraphQL.Schema.Parser` that fill in this type parameter, so that it is not visible for the majority of the codebase.
The idea of associating metadata information to `Definition`s really comes to fruition when combined with hasura/graphql-engine-mono#4517. Their combination would allow us to use the API of fatal errors (just like the current `MonadError QErr`) to report _inconsistencies_ in the metadata. Such inconsistencies are then _automatically_ ignored. So no ad-hoc decisions need to be made on how to cut out inconsistent metadata from the GraphQL schema. This will allow us to report much better errors, as well as improve the likelihood of a successful HGE startup.
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/4770
Co-authored-by: Samir Talwar <47582+SamirTalwar@users.noreply.github.com>
GitOrigin-RevId: 728402b0cae83ae8e83463a826ceeb609001acae
This is a first step towards clarifying the role of `UnpreparedValue` as part of the IR. It certainly does not belong in the parser framework.
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/4588
GitOrigin-RevId: d1582a0b266729b79e00d31057178a4099168e6d
### Description
The main goal of this PR is, as stated, to remove the circular dependency in the schema building code. This cycle arises from the existence of remote relationships: when we build the schema for a source A, a remote relationship might force us to jump to the schema of a source B, or some remote schema. As a result, we end up having to do a dispatch from a "leaf" of the schema, similar to the one done at the root. In turn, this forces us to carry along in the schema a lot of information required for that dispatch, AND it forces us to import the instances in scope, creating an import loop.
As discussed in #4489, this PR implements the "dependency injection" solution: we pass to the schema a function to call to do the dispatch, and to get a generated field for a remote relationship. That way, this function can be chosen at the root level, and the leaves need not be aware of the overall context.
This PR grew a bit bigger than that, however; in an attempt to try and remove the `SourceCache` from the schema altogether, it changed a lot of functions across the schema building code, to thread along the `SourceInfo b` of the source being built. This avoids having to do cache lookups within a given source. A few cases remain, such as relay, that we might try to tackle in a subsequent PR.
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/4557
GitOrigin-RevId: 9388e48372877520a72a9fd1677005df9f7b2d72
### Description
This PR moves Hasura-specific schema functions from `Hasura.GraphQL.Parser.Class` into `Hasura.GraphQL.Schema.Common`. It also removes the two corresponding monad aliases, and consequently harmonizes several parts of the code to use the same common constraint.
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/3947
GitOrigin-RevId: 40985a7d86da97a311bd480f9a57cc18c350c2a8
We build the GraphQL schema by combining building blocks such as `tableSelectionSet` and `columnParser`. These building blocks individually build `{InputFields,Field,}Parser` objects. Those object specify the valid GraphQL schema.
Since the GraphQL schema is role-dependent, at some point we need to know what fragment of the GraphQL schema a specific role is allowed to access, and this is stored in `{Sel,Upd,Ins,Del}PermInfo` objects.
We have passed around these permission objects as function arguments to the schema building blocks since we first started dealing with permissions during the PDV refactor - see hasura/graphql-engine@5168b99e46 in hasura/graphql-engine#4111. This means that, for instance, `tableSelectionSet` has as its type:
```haskell
tableSelectionSet ::
forall b r m n.
MonadBuildSchema b r m n =>
SourceName ->
TableInfo b ->
SelPermInfo b ->
m (Parser 'Output n (AnnotatedFields b))
```
There are three reasons to change this.
1. We often pass a `Maybe (xPermInfo b)` instead of a proper `xPermInfo b`, and it's not clear what the intended semantics of this is. Some potential improvements on the data types involved are discussed in issue hasura/graphql-engine-mono#3125.
2. In most cases we also already pass a `TableInfo b`, and together with the `MonadRole` that is usually also in scope, this means that we could look up the required permissions regardless: so passing the permissions explicitly undermines the "single source of truth" principle. Breaking this principle also makes the code more difficult to read.
3. We are working towards role-based parsers (see hasura/graphql-engine-mono#2711), where the `{InputFields,Field,}Parser` objects are constructed in a role-invariant way, so that we have a single object that can be used for all roles. In particular, this means that the schema building blocks _need_ to be constructed in a role-invariant way. While this PR doesn't accomplish that, it does reduce the amount of role-specific arguments being passed, thus fixing hasura/graphql-engine-mono#3068.
Concretely, this PR simply drops the `xPermInfo b` argument from almost all schema building blocks. Instead these objects are looked up from the `TableInfo b` as-needed. The resulting code is considerably simpler and shorter.
One way to interpret this change is as follows. Before this PR, we figured out permissions at the top-level in `Hasura.GraphQL.Schema`, passing down the obtained `xPermInfo` objects as required. After this PR, we have a bottom-up approach where the schema building blocks themselves decide whether they want to be included for a particular role.
So this moves some permission logic out of `Hasura.GraphQL.Schema`, which is very complex.
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/3608
GitOrigin-RevId: 51a744f34ec7d57bc8077667ae7f9cb9c4f6c962
This PR simplifies the types that represent a remote relationship in IR so that they can be reused in other parts (in remote schema types) which could have remote relationships.
The comments on the PR explain the main changes.
PR-URL: https://github.com/hasura/graphql-engine-mono/pull/2979
GitOrigin-RevId: 559c51d9d6ae79e2183ce4347018741b9096ac74
