graphql-engine/server/src-lib/Hasura/Metadata/DTO/MetadataV3.hs
Jesse Hallett 84fd5910b0 server: polymorphic codec for metadata sources
This PR expands the OpenAPI specification generated for metadata to include separate definitions for `SourceMetadata` for each native database type, and for DataConnector.

For the most part the changes add `HasCodec` implementations, and don't modify existing code otherwise.

The generated OpenAPI spec can be used to generate TypeScript definitions that distinguish different source metadata types based on the value of the `kind` properly. There is a problem: because the specified `kind` value for a data connector source is any string, when TypeScript gets a source with a `kind` value of, say, `"postgres"`, it cannot unambiguously determine whether the source is postgres, or a data connector. For example,

```ts
function consumeSourceMetadata(source: SourceMetadata) {
    if (source.kind === "postgres" || source.kind === "pg") {
        // At this point TypeScript infers that `source` is either an instance
        // of `PostgresSourceMetadata`, or `DataconnectorSourceMetadata`. It
        // can't narrow further.
        source
    }
    if (source.kind === "something else") {
        // TypeScript infers that this `source` must be an instance of
        // `DataconnectorSourceMetadata` because `source.kind` does not match
        // any of the other options.
        source
    }
}
```

The simplest way I can think of to fix this would be to add a boolean property to the `SourceMetadata` type along the lines of `isNative` or `isDataConnector`. This could be a field that only exists in serialized data, like the metadata version field. The combination of one of the native database names for `kind`, and a true value for `isNative` would be enough for TypeScript to unambiguously distinguish the source kinds.

But note that in the current state TypeScript is able to reference the short `"pg"` name correctly!

~~Tests are not passing yet due to some discrepancies in DTO serialization vs existing Metadata serialization. I'm working on that.~~

The placeholders that I used for table and function metadata are not compatible with the ordered JSON serialization in use. I think the best solution is to write compatible codecs for those types in another PR. For now I have disabled some DTO tests for this PR.

Here are the generated [OpenAPI spec](https://github.com/hasura/graphql-engine-mono/files/9397333/openapi.tar.gz) based on these changes, and the generated [TypeScript client code](https://github.com/hasura/graphql-engine-mono/files/9397339/client-typescript.tar.gz) based on that spec.

Ticket: [MM-66](https://hasurahq.atlassian.net/browse/MM-66)

PR-URL: https://github.com/hasura/graphql-engine-mono/pull/5582
GitOrigin-RevId: e1446191c6c832879db04f129daa397a3be03f62
2022-08-25 18:36:02 +00:00

58 lines
3.5 KiB
Haskell

module Hasura.Metadata.DTO.MetadataV3 (MetadataV3 (..)) where
import Autodocodec (Autodocodec (Autodocodec), HasCodec (codec), object, optionalField, requiredFieldWith, (.=))
import Autodocodec.OpenAPI ()
import Data.Aeson (FromJSON, ToJSON)
import Data.OpenApi qualified as OpenApi
import Hasura.Metadata.DTO.Placeholder (PlaceholderArray, PlaceholderObject)
import Hasura.Metadata.DTO.Utils (versionField)
import Hasura.Prelude
import Hasura.RQL.Types.Metadata.Common (Sources, sourcesCodec)
-- | Revision 3 of the Metadata export format. Note that values of the types,
-- 'PlaceholderArray' and 'PlaceholderObject' are placeholders that will
-- eventually be expanded to represent more detail.
data MetadataV3 = MetadataV3
{ metaV3Sources :: Sources,
metaV3RemoteSchemas :: Maybe PlaceholderArray,
metaV3QueryCollections :: Maybe PlaceholderArray,
metaV3Allowlist :: Maybe PlaceholderArray,
metaV3Actions :: Maybe PlaceholderArray,
metaV3CustomTypes :: Maybe PlaceholderObject,
metaV3CronTriggers :: Maybe PlaceholderArray,
metaV3RestEndpoints :: Maybe PlaceholderArray,
metaV3ApiLimits :: Maybe PlaceholderObject,
metaV3MetricsConfig :: Maybe PlaceholderObject,
metaV3InheritedRoles :: Maybe PlaceholderArray,
metaV3GraphqlSchemaIntrospection :: Maybe PlaceholderObject,
metaV3Network :: Maybe PlaceholderObject,
metaV3BackendConfigs :: Maybe PlaceholderObject
}
deriving stock (Show, Eq, Generic)
deriving (FromJSON, ToJSON, OpenApi.ToSchema) via (Autodocodec MetadataV3)
-- | Codecs simultaneously provide serialization logic for a type, and
-- documentation. A codec can be used to generate a specification in OpenAPI or
-- another format that matches the JSON serialization of the same type.
-- Documentation strings (the second argument to 'optionalField' and to
-- 'requiredField') appear in the generated specification for users' reference.
instance HasCodec MetadataV3 where
codec =
object "MetadataV3" $
MetadataV3
<$ versionField 3
<*> requiredFieldWith "sources" sourcesCodec "configured databases" .= metaV3Sources
<*> optionalField "remote_schemas" "merge remote GraphQL schemas and provide a unified GraphQL API" .= metaV3RemoteSchemas
<*> optionalField "query_collections" "group queries using query collections" .= metaV3QueryCollections
<*> optionalField "allowlist" "safe GraphQL operations - when allow lists are enabled only these operations are allowed" .= metaV3Allowlist
<*> optionalField "actions" "action definitions which extend Hasura's schema with custom business logic using custom queries and mutations" .= metaV3Actions
<*> optionalField "custom_types" "custom type definitions" .= metaV3CustomTypes
<*> optionalField "cron_triggers" "reliably trigger HTTP endpoints to run custom business logic periodically based on a cron schedule" .= metaV3CronTriggers
<*> optionalField "rest_endpoints" "REST interfaces to saved GraphQL queries and mutations" .= metaV3RestEndpoints
<*> optionalField "api_limits" "limts to depth and/or rate of API requests" .= metaV3ApiLimits
<*> optionalField "metrics_config" "TODO" .= metaV3MetricsConfig
<*> optionalField "inherited_roles" "an inherited role is a way to create a new role which inherits permissions from two or more roles" .= metaV3InheritedRoles
<*> optionalField "graphql_schema_introspection" "TODO" .= metaV3GraphqlSchemaIntrospection
<*> optionalField "network" "TODO" .= metaV3Network
<*> optionalField "backend_configs" "TODO" .= metaV3BackendConfigs