I just came across some aspects of this in trying to use addMocksToSchema and hitting the underlying issue. I thought I would share my findings here and the workaround I’ve found.
When using the high level functions like addResolversToSchema, you want to make sure you are updating the resolvers in place which will use the existing schema: addResolversToSchema({ schema, resolvers, updateResolversInPlace:true })
With the lower-level functions like mapSchema, the associated __resolveReference resolvers for any defined Entities are lost in normalization. The workaround by @vad3x can be used to fix this, but you don’t need to worry about the prefix which could be simplified to the following:
function fixResolveReferenceNormalization(originalSchema, normalizedSchema) {
const typeMap = originalSchema.getTypeMap();
const mockedTypeMap = normalizedSchema.getTypeMap();
for (const [name, type] of Object.entries(typeMap)) {
if (isObjectType(type) && typeMap[name].resolveReference) {
mockedTypeMap[name].resolveReference = typeMap[name].resolveReference;
}
}
}
Basically copying the entity.__resolveReference implementation from the original schema to the normalized schema.
If you are using addMocksToSchema, it uses all of this under the hood, but you have to call this after buildSubgraphSchema is called. This ends up wiping out the _Entity union definition that is added for you by buildSubgraphSchema in the normalization process. This is an easier workaround where you can just define that in addMocksToSchema:
const mockedSchema = addMocksToSchema({
schema,
resolvers: {
_Entity: {
__resolveType(parent) {
return parent.__typename;
},
},
},
preserveResolvers: true,
mocks,
});
Now you have a mocked schema, but it will be missing the entity.__resolveReference which you can add back with the function referenced as the workaround for mapSchema:
const mockedSchema = addMocksToSchema({
schema,
resolvers: {
_Entity: {
__resolveType(parent) {
return parent.__typename;
},
},
},
preserveResolvers: true,
mocks,
});
fixResolveReferenceNormalization(schema, mockedSchema);
schema = mockedSchema;
Whew, all the normalization basically removes the _Entity union definition aspects and Entity __resolverReference definitions. From what I can see, this normalization is happening with copying schema artifacts into a new schema object that uses the standard graphql objects (like GraphQLObjectType) and there is also a toConfig helper method that is used in copying the old config to the new object.