What is the difference between DocumentNode vs Schema vs TypeDefs ?

[hazem-alabiad]

What is the difference between DocumentNode vs Schema vs TypeDefs ?

[smolinari]

A DocumentNode or query is the return GraphQL document of the query string (schema/ GraphQL SDL) you use as a client query, which is usually wrapped by gql. It's the result of the string literal. It's similar to typeDefs on the server, as the queries match closely the typeDefs on the server, in order to get a response from the GraphQL endpoint.

A Schema is what is used to create GraphQL type definitions and client queries. They are written in GraphQL's DSL.
https://www.apollographql.com/docs/apollo-server/schema/schema/

TypeDefs are the definitions of schema, after being ran through the gql method or the strings themselves, and used in the Apollo Server to generate the endpoint type definitions (what you also see with introspection in the Playground within Queries and Mutations). In addition to the typeDefs you also have resolvers (they make up the Queries and Mutations) which use the type definitions to form the response objects and to check for the proper arg or input object types.

Hope that helped and didn't confuse you even more. 😁

Scott

[glasser]

@smolinari I appreciate your attempt to help here, but this isn't quite correct. DocumentNode is not a string. Schema in this context might mean GraphQLSchema which is not DSL. TypeDefs can be ran through gql or can still be strings. My response below is a bit more precise.

[smolinari]

@glasser - I've updated my reply to me more concise. I've also replied assuming hazemalabiad is a beginner to GraphQL/ Apollo. I also knew how these terms confused me, when I began, and as you can see, I still have a hard time with it.

Scott

[glasser]

There are three types that can represent a GraphQL schema:

• A string written in the GraphQL language, often called SDL, like type Query { field: ID! }.
• An "abstract syntax tree" representing how a GraphQL language string is parsed. The root of this tree is called DocumentNode, because the top level of GraphQL syntax is called Document. You can get this from the graphql-js parse function or the graphql-tag/apollo-server gql function (which is a memoizing version of parse).
• A GraphQLSchema object, which represents the schema more directly than as a parsed syntax tree. For example, this object contains a map from type name to objects representing that type (but doesn't have the concept of "ordering" between the types), whereas the DocumentNode keeps track of the order of declarations but doesn't have an easy way to jump directly from a name to the declaration. (Also note that GraphQLSchema does not contain all information from the AST; for example, it does not track arbitrary directive applications other than via the astNode field.) More notably, the GraphQLSchema object can have resolver functions attached to it, and the AST and string cannot.

(Also note that GraphQL language strings and DocumentNodes can represent operations (queries, mutations, etc) too, whereas GraphQLSchema objects are always schemas.)

typeDefs is a name given to arguments/options in various places in Apollo Server, not a type like the ones above. It is an option that takes either a string or a DocumentNode (or an array of one of those types).