Provide GraphQL resolver functions information about the context in which they have been invoked.
npm install graphql-resolvers-ast --save
GraphQL resolvers are not typically aware of the context in which they are running. For example a resolver within User is not aware if the data is needed for the post author, the author of a comment, the User who is following another User, or the User who is being followed.
graphql-resolvers-ast provides context information for a resolver, including:
- What operation is being performed, e.g. Query or Mutation.
- Which resolver is running, e.g. [ 'Post', 'editor' ].
- What is it resolving in the GraphQL operation, e.g. [ 'getUser', 'posts', 0, 'Post', 'editor' ].
- What type of result it is to return, e.g. 'User' or '[User!]!'.
- Which fields from the result will GraphQL return.
Information is returned on fragments if any. Overlapping fragments are handled.
const resolversAst = require('graphql-resolvers-ast');
const resolvers = {
User: {
posts (parent, args, content, ast) {
const context = resolversAst(ast);
console.log(context);
return /* call backend server for appropriate posts */;
}
},
};const typeDefs = `
type User {
email: String
posts: [Post!]
}
type Post {
body: String
draft: Boolean
achieved: Boolean
editor: User
}
type Query {
getUser (keyInt: Int, keyStr: String): User
}
`;
const query = `
query {
getUser (keyInt: 1, keyStr: "a") {
email
posts {
body
editor {
email
}
}
}
}
`;
const resolvers = {
Post: {
editor (parent, args, content, ast) {
const context = resolversAst(ast);
return { email: 'editor@gmail.com' };
/* resolvers.Post.editor is called twice during the query. The context values returned are:
{ operation: 'Query',
schema: [ 'Post', 'editor' ],
resolverPath: [ 'getUser', 'User', 'posts', 0, 'Post', 'editor', 'User' ],
resolveTo: 'User',
fields: [
[{ kind: 'Field', name: 'email', hasSelections: false }]
],
args: {},
fragments: {}
}
and
{ operation: 'Query',
schema: [ 'Post', 'editor' ],
resolverPath: [ 'getUser', 'User', 'posts', 1, 'Post', 'editor', 'User' ],
resolveTo: 'User',
fields: [
[{ kind: 'Field', name: 'email', hasSelections: false }]
],
args: {},
fragments: {}
}
*/
}
},
User: {
posts (parent, args, content, ast) {
const context = resolversAst(ast);
return [
{ body: ' post1 ', draft: true, achieved: true },
{ body: ' post2 ', draft: false, achieved: true }
];
/* resolvers.User.posts is called once for this query. context contains:
{ operation: 'Query',
schema: [ 'User', 'posts' ],
resolverPath: [ 'getUser', 'User', 'posts', '[Post!]' ],
resolveTo: '[Post!]',
fields: [
[ { kind: 'Field', name: 'body', hasSelections: false },
{ kind: 'Field', name: 'editor', hasSelections: true } ]
],
args: {},
fragments: {}
}
*/
}
},
Query: {
getUser (parent, args, content, ast) {
const context = resolversAst(ast);
return { email: ' email1@gmail.com ' };
/* resolvers.Query.getUser is called once for this query. context contains:
{ operation: 'Query',
schema: [ 'Query', 'getUser' ],
resolverPath: [ 'getUser', 'User' ],
resolveTo: 'User',
fields: [
[ { kind: 'Field', name: 'email', hasSelections: false },
{ kind: 'Field', name: 'posts', hasSelections: true } ]
],
args: { keyInt: 1, keyStr: 'a' },
fragments: {}
}
*/
}
}
};Overlapping fragments result in multiple context.fields entries.
const query = `
query {
getUser {
email
posts {
body
}
}
... QueryFragment
}
fragment QueryFragment on Query {
getUser {
posts {
draft
}
... GetUserFragment
}
}
fragment GetUserFragment on User {
posts {
achieved
}
}`;
const resolvers = {
User: {
posts (parent, args, content, ast) {
const context = resolversAst(ast);
return [
{ body: ' post1 ', draft: true, achieved: true },
{ body: ' post2 ', draft: false, achieved: true }
];
/* resolvers.User.posts is called once for this query. context contains:
{ operation: 'Query',
schema: [ 'User', 'posts' ],
resolverPath: [ 'getUser', 'User', 'posts' ],
resolveTo: '[Post!]',
fields: [
[ { kind: 'Field', name: 'body', hasSelections: false } ],
[ { kind: 'Field', name: 'draft', hasSelections: false } ],
[ { kind: 'Field', name: 'achieved', hasSelections: false } ]
],
args: {},
fragments: {
QueryFragment: {
kind: 'FragmentDefinition',
name: 'QueryFragment',
hasSelections: true
},
GetUserFragment: {
kind: 'FragmentDefinition',
name: 'GetUserFragment',
hasSelections: true
}
}
}
*/
}
},
Query: {
getUser (parent, args, content, ast) {
const context = resolversAst(ast);
return { email: ' email1@gmail.com ' };
/* resolvers.Query.getUser is called once for this query. context contains:
{ operation: 'Query',
schema: [ 'Query', 'getUser' ],
resolverPath: [ 'Query', 'getUser' ],
resolveTo: 'User',
fields: [
[ { kind: 'Field', name: 'email', hasSelections: false },
{ kind: 'Field', name: 'posts', hasSelections: true } ],
[ { kind: 'Field', name: 'posts', hasSelections: true },
{ kind: 'FragmentSpread', name: 'GetUserFragment', hasSelections: false } ]
],
args: {},
fragments: {
QueryFragment: {
kind: 'FragmentDefinition',
name: 'QueryFragment',
hasSelections: true
},
GetUserFragment: {
kind: 'FragmentDefinition',
name: 'GetUserFragment',
hasSelections: true
}
}
}
*/
}
}
};Copyright (c) 2017 John J. Szwaronek
Licensed under the MIT license.