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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
114 lines
3.8 KiB
Haskell
114 lines
3.8 KiB
Haskell
{-# LANGUAGE TemplateHaskell #-}
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module Hasura.RemoteSchema.MetadataAPI.Permission
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( AddRemoteSchemaPermission (..),
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DropRemoteSchemaPermissions (..),
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runDropRemoteSchemaPermissions,
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runAddRemoteSchemaPermissions,
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)
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where
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import Control.Lens ((^.))
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import Data.Aeson.TH qualified as J
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import Data.HashMap.Strict qualified as Map
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import Data.Text.Extended
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import Hasura.Base.Error
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import Hasura.EncJSON
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import Hasura.GraphQL.Schema.Options qualified as Options
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import Hasura.Prelude
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import Hasura.RQL.Types.Common
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import Hasura.RQL.Types.Metadata
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import Hasura.RQL.Types.Metadata.Object
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import Hasura.RQL.Types.SchemaCache
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import Hasura.RQL.Types.SchemaCache.Build
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import Hasura.RemoteSchema.Metadata
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import Hasura.RemoteSchema.SchemaCache.Permission
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import Hasura.Server.Types
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import Hasura.Session
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data AddRemoteSchemaPermission = AddRemoteSchemaPermission
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{ _arspRemoteSchema :: RemoteSchemaName,
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_arspRole :: RoleName,
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_arspDefinition :: RemoteSchemaPermissionDefinition,
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_arspComment :: Maybe Text
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}
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deriving (Show, Eq, Generic)
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instance NFData AddRemoteSchemaPermission
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$(J.deriveJSON hasuraJSON ''AddRemoteSchemaPermission)
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data DropRemoteSchemaPermissions = DropRemoteSchemaPermissions
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{ _drspRemoteSchema :: RemoteSchemaName,
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_drspRole :: RoleName
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}
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deriving (Show, Eq, Generic)
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instance NFData DropRemoteSchemaPermissions
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$(J.deriveJSON hasuraJSON ''DropRemoteSchemaPermissions)
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runAddRemoteSchemaPermissions ::
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( QErrM m,
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CacheRWM m,
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HasServerConfigCtx m,
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MetadataM m
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) =>
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AddRemoteSchemaPermission ->
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m EncJSON
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runAddRemoteSchemaPermissions q = do
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metadata <- getMetadata
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remoteSchemaPermsCtx <- _sccRemoteSchemaPermsCtx <$> askServerConfigCtx
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unless (remoteSchemaPermsCtx == Options.EnableRemoteSchemaPermissions) $ do
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throw400 ConstraintViolation $
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"remote schema permissions can only be added when "
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<> "remote schema permissions are enabled in the graphql-engine"
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remoteSchemaMap <- scRemoteSchemas <$> askSchemaCache
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remoteSchemaCtx <-
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onNothing (Map.lookup name remoteSchemaMap) $
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throw400 NotExists $
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"remote schema " <> name <<> " doesn't exist"
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when (doesRemoteSchemaPermissionExist metadata name role) $
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throw400 AlreadyExists $
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"permissions for role: "
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<> role <<> " for remote schema:"
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<> name <<> " already exists"
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void $ resolveRoleBasedRemoteSchema role name (_rscIntroOriginal remoteSchemaCtx) providedSchemaDoc
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buildSchemaCacheFor (MORemoteSchemaPermissions name role) $
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MetadataModifier $
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metaRemoteSchemas . ix name . rsmPermissions %~ (:) remoteSchemaPermMeta
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pure successMsg
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where
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AddRemoteSchemaPermission name role defn comment = q
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remoteSchemaPermMeta = RemoteSchemaPermissionMetadata role defn comment
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providedSchemaDoc = _rspdSchema defn
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doesRemoteSchemaPermissionExist :: Metadata -> RemoteSchemaName -> RoleName -> Bool
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doesRemoteSchemaPermissionExist metadata remoteSchemaName roleName =
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any ((== roleName) . _rspmRole) $ metadata ^. (metaRemoteSchemas . ix remoteSchemaName . rsmPermissions)
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runDropRemoteSchemaPermissions ::
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( QErrM m,
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CacheRWM m,
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MetadataM m
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) =>
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DropRemoteSchemaPermissions ->
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m EncJSON
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runDropRemoteSchemaPermissions (DropRemoteSchemaPermissions name roleName) = do
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metadata <- getMetadata
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remoteSchemaMap <- scRemoteSchemas <$> askSchemaCache
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void $
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onNothing (Map.lookup name remoteSchemaMap) $
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throw400 NotExists $
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"remote schema " <> name <<> " doesn't exist"
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unless (doesRemoteSchemaPermissionExist metadata name roleName) $
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throw400 NotExists $
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"permissions for role: "
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<> roleName <<> " for remote schema:"
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<> name <<> " doesn't exist"
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buildSchemaCacheFor (MORemoteSchemaPermissions name roleName) $
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dropRemoteSchemaPermissionInMetadata name roleName
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pure successMsg
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