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Add makeFederationSchemaPlugin. #19

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Add makeFederationSchemaPlugin. #19

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306 changes: 170 additions & 136 deletions src/index.ts
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Original file line number Diff line number Diff line change
@@ -1,152 +1,203 @@
import {
AugmentedGraphQLFieldResolver,
ObjectFieldResolver,
makeExtendSchemaPlugin,
makePluginByCombiningPlugins,
gql,
} from "graphile-utils";
import { Plugin } from "graphile-build";
import { Build, Plugin } from "graphile-build";
import { DirectiveNode } from "graphql";
import printFederatedSchema from "./printFederatedSchema";
import { ObjectTypeDefinition, Directive, StringValue } from "./AST";

/**
* This plugin installs the schema outlined in the Apollo Federation spec, and
* the resolvers and types required. Comments have been added to make things
* clearer for consumers, and the Apollo fields have been deprecated so that
* users unconcerned with federation don't get confused.
*
* https://www.apollographql.com/docs/apollo-server/federation/federation-spec/#federation-schema-specification
* This function allows users to create their own version of the schema plugin.
*/
const SchemaExtensionPlugin = makeExtendSchemaPlugin(build => {
const {
graphql: { GraphQLScalarType, getNullableType },
resolveNode,
$$isQuery,
$$nodeType,
getTypeByName,
inflection,
nodeIdFieldName,
} = build;
// Cache
let Query: any;
return {
typeDefs: gql`
"""
Used to represent a federated entity via its keys.
"""
scalar _Any

"""
Used to represent a set of fields. Grammatically, a field set is a
selection set minus the braces.
"""
scalar _FieldSet

"""
A union of all federated types (those that use the @key directive).
"""
union _Entity

"""
Describes our federated service.
"""
type _Service {
export function makeFederationSchemaPlugin<TSource = any, TContext = any>(
generator: (
build: Build
) =>
| AugmentedGraphQLFieldResolver<TSource, TContext>
| ObjectFieldResolver<TSource, TContext>
): Plugin {
/**
* This plugin installs the schema outlined in the Apollo Federation spec, and
* the resolvers and types required. Comments have been added to make things
* clearer for consumers, and the Apollo fields have been deprecated so that
* users unconcerned with federation don't get confused.
*
* https://www.apollographql.com/docs/apollo-server/federation/federation-spec/#federation-schema-specification
*/
const SchemaExtensionPlugin = makeExtendSchemaPlugin(build => {
const {
graphql: { GraphQLScalarType, getNullableType },
$$isQuery,
$$nodeType,
getTypeByName,
inflection,
} = build;
// Cache
let Query: any;
return {
typeDefs: gql`
"""
The GraphQL Schema Language definiton of our endpoint including the
Apollo Federation directives (but not their definitions or the special
Apollo Federation fields).
Used to represent a federated entity via its keys.
"""
sdl: String
@deprecated(reason: "Only Apollo Federation should use this")
}
scalar _Any

extend type Query {
"""
Fetches a list of entities using their representations; used for Apollo
Federation.
Used to represent a set of fields. Grammatically, a field set is a
selection set minus the braces.
"""
_entities(representations: [_Any!]!): [_Entity]!
@deprecated(reason: "Only Apollo Federation should use this")
scalar _FieldSet

"""
Entrypoint for Apollo Federation to determine more information about
this service.
A union of all federated types (those that use the @key directive).
"""
_service: _Service!
@deprecated(reason: "Only Apollo Federation should use this")
}
union _Entity

directive @external on FIELD_DEFINITION
directive @requires(fields: _FieldSet!) on FIELD_DEFINITION
directive @provides(fields: _FieldSet!) on FIELD_DEFINITION
directive @key(fields: _FieldSet!) on OBJECT | INTERFACE
`,
resolvers: {
Query: {
_entities(data, { representations }, context, resolveInfo) {
const {
graphile: { fieldContext },
} = resolveInfo;
return representations.map((representation: any) => {
if (!representation || typeof representation !== "object") {
throw new Error("Invalid representation");
}
const { __typename, [nodeIdFieldName]: nodeId } = representation;
if (!__typename || typeof nodeId !== "string") {
throw new Error("Failed to interpret representation");
}
return resolveNode(
nodeId,
build,
fieldContext,
data,
context,
resolveInfo
);
});
"""
Describes our federated service.
"""
type _Service {
"""
The GraphQL Schema Language definiton of our endpoint including the
Apollo Federation directives (but not their definitions or the special
Apollo Federation fields).
"""
sdl: String
@deprecated(reason: "Only Apollo Federation should use this")
}

extend type Query {
"""
Fetches a list of entities using their representations; used for Apollo
Federation.
"""
_entities(representations: [_Any!]!): [_Entity]!
@deprecated(reason: "Only Apollo Federation should use this")
"""
Entrypoint for Apollo Federation to determine more information about
this service.
"""
_service: _Service!
@deprecated(reason: "Only Apollo Federation should use this")
}

directive @external on FIELD_DEFINITION
directive @requires(fields: _FieldSet!) on FIELD_DEFINITION
directive @provides(fields: _FieldSet!) on FIELD_DEFINITION
directive @key(fields: _FieldSet!) on OBJECT | INTERFACE
`,
resolvers: {
Query: {
_entities: generator(build),
_service(_, _args, _context, { schema }) {
return schema;
},
},

_service(_, _args, _context, { schema }) {
return schema;
_Service: {
sdl(schema) {
return printFederatedSchema(schema);
},
},
},

_Service: {
sdl(schema) {
return printFederatedSchema(schema);
_Entity: {
__resolveType(value) {
// This uses the same resolution as the Node interface, which can be found in graphile-build's NodePlugin
if (value === $$isQuery) {
if (!Query) Query = getTypeByName(inflection.builtin("Query"));
return Query;
} else if (value[$$nodeType]) {
return getNullableType(value[$$nodeType]);
}
},
},
},

_Entity: {
__resolveType(value) {
// This uses the same resolution as the Node interface, which can be found in graphile-build's NodePlugin
if (value === $$isQuery) {
if (!Query) Query = getTypeByName(inflection.builtin("Query"));
return Query;
} else if (value[$$nodeType]) {
return getNullableType(value[$$nodeType]);
}
},
_Any: new GraphQLScalarType({
name: "_Any",
serialize(value: any) {
return value;
},
}),
},
};
});

_Any: new GraphQLScalarType({
name: "_Any",
serialize(value: any) {
return value;
},
}),
},
/*
* This plugin adds types to the _Entity union defined above.
*/
const EntityPlugin: Plugin = builder => {
// Add our collected types to the _Entity union
builder.hook("GraphQLUnionType:types", (types, build, context) => {
const { Self } = context;
// If it's not the _Entity union, don't change it.
if (Self.name !== "_Entity") {
return types;
}

// If it's not the _Entity union, don't change it.
if (Self.name !== "_Entity") {
return types;
}
const { scopeByType } = build;

const newTypes = [...types];
for (const [type] of scopeByType) {
if (
type.astNode &&
type.astNode.directives &&
type.astNode.directives.some(
(directive: DirectiveNode) => directive.name.value === "key"
)
) {
newTypes.push(type);
}
}

// Add our types to the entity types
return newTypes;
});
};

return makePluginByCombiningPlugins(SchemaExtensionPlugin, EntityPlugin);
}

/**
* This plugin adds the federation-specific schema parts for resolving entities by nodeId.
*/
const FederationSchemaNodeIdPlugin = makeFederationSchemaPlugin(build => {
const { resolveNode, nodeIdFieldName } = build;
return (data, { representations }, context, resolveInfo) => {
const {
graphile: { fieldContext },
} = resolveInfo;
return representations.map((representation: any) => {
if (!representation || typeof representation !== "object") {
throw new Error("Invalid representation");
}
const { __typename, [nodeIdFieldName]: nodeId } = representation;
if (!__typename || typeof nodeId !== "string") {
throw new Error("Failed to interpret representation");
}
return resolveNode(
nodeId,
build,
fieldContext,
data,
context,
resolveInfo
);
});
};
});

/*
* This plugin adds the `@key(fields: "nodeId")` directive to the types that
* implement the Node interface, and adds these types to the _Entity union
* defined above.
* implement the Node interface and marks them to be added to the _Entity union.
*/
const AddKeyPlugin: Plugin = builder => {
builder.hook("build", build => {
build.federationEntityTypes = [];
return build;
});

const AddKeyNodeIdPlugin: Plugin = builder => {
// Find out what types implement the Node interface
builder.hook("GraphQLObjectType:interfaces", (interfaces, build, context) => {
const { getTypeByName, inflection, nodeIdFieldName } = build;
Expand All @@ -165,9 +216,6 @@ const AddKeyPlugin: Plugin = builder => {
return interfaces;
}

// Add this to the list of types to be in the _Entity union
build.federationEntityTypes.push(Self);

/*
* We're going to add the `@key(fields: "nodeId")` directive to this type.
* First, we need to generate an `astNode` as if the type was generateted
Expand All @@ -187,23 +235,9 @@ const AddKeyPlugin: Plugin = builder => {
// We're not changing the interfaces, so return them unmodified.
return interfaces;
});

// Add our collected types to the _Entity union
builder.hook("GraphQLUnionType:types", (types, build, context) => {
const { Self } = context;
// If it's not the _Entity union, don't change it.
if (Self.name !== "_Entity") {
return types;
}
const { federationEntityTypes } = build;

// Add our types to the entity types
return [...types, ...federationEntityTypes];
});
};

// Our federation implementation combines these two plugins:
export default makePluginByCombiningPlugins(
SchemaExtensionPlugin,
AddKeyPlugin
FederationSchemaNodeIdPlugin,
AddKeyNodeIdPlugin
);