Improve documention of resolve function (info param)

[odigity]

I've read all the docs at graphql.org and the READMEs for graphql-js and express-graphql, and I cannot find a reference for the resolver function signature.

The GraphQL docs suggest:

(obj, args, context)

obj         The previous object, which for a field on the root Query type is often not used.
args        The arguments provided to the field in the GraphQL query.
context     A value which is provided to every resolver and holds important contextual information like the currently logged in user, or access to a database.

But my brief testing with my new express-graphql server I just made (first one) suggests the signature GraphQL.js uses is:

(args, context, obj)

From my console debugging:

JSON.stringify(args) -> { "foo": "bar" }
Object.keys(context) ->
    _consuming,     baseUrl,            method,         session,
    _dumped,        client,             next,           sessionCookies,
    _events,        complete,           originalUrl,    sessionKey,
    _eventsCount,   connection,         params,         sessionOptions,
    _maxListeners,  domain,             query,          socket,
    _parsedUrl,     headers,            rawHeaders,     statusCode,
    _passport,      httpVersion,        rawTrailers,    statusMessage,
    _readableState, httpVersionMajor,   read,           trailers,
                    httpVersionMinor,   readable,       upgrade,
                                        res,            url,
Object.keys(obj) -> fieldName, fieldNodes, fragments, operation, parentType, path, returnType, rootValue, schema, variableValues

(I just learned GraphQL/GraphQL.js last week, so I might be missing something obvious.)

[DxCx]

wait.. what?
what is the current signature of the function under debug in this case?
and how the scheme looks like?

anyway, resolver signature should be:
obj, args, context, info

obj -> the object resolved, (rootQuery argument for root types (such as Query))
args -> { [key: string]: any } GraphQL Arguments, nothing much to eleborate
context -> shared object used for side effects
info -> Object containing information about the execution info, (context) in your case above

[odigity]

(Sorry, I had typos in the first post which I just fixed.)

What you described is not what I'm seeing. In my root resolvers, the first arg in the list is an object of input arguments for that field, and the second arg is clearly the context object.

[jonirrings]

@odigity just have a look at the source code and you find the signature. that is the way I find it in v0.5 update, that's when I met the error too.

[wincent]

If you look at the source, you can see the resolve function is passed source, args, context, info. You can see some example resolvers in starWarsSchema, which is linked to from the README.

The best non-source documentation for this is probably the "Execution" page on graphql.org, although it doesn't mention the info parameter and should perhaps be updated. Anybody care to submit a PR for that?

[odigity]

As I explained in careful detail in my initial post, the signature you're describing does not the match the results I'm getting. For example, I'm seeing args in the first position.

[wincent]

Do you have some sample code that we could look at? The snippets in your post aren't something that I could run and try to repro what you're seeing.

[odigity]

It'll take some time, but I'll try to get to it soon.

[jbinto]

The GraphQLResolveInfo flow type is useful:

graphql-js/src/type/definition.js

Lines 584 to 595 in bacd412

	export type GraphQLResolveInfo = {
	fieldName: string;
	fieldNodes: Array<FieldNode>;
	returnType: GraphQLOutputType;
	parentType: GraphQLCompositeType;
	path: ResponsePath;
	schema: GraphQLSchema;
	fragments: { [fragmentName: string]: FragmentDefinitionNode };
	rootValue: mixed;
	operation: OperationDefinitionNode;
	variableValues: { [variableName: string]: mixed };
	};

[leebyron]

Closing this issue since it is starting to age.

The flow types and documentation should help, and you can also check out some of the examples and tests in this repository to see how resolvers are called with values.

What you might be running into is the default resolver, which attempts to look for a method on the source object with the name of the field requested, and if found calls that. In that case, source is not provided as a first argument since you can access that value with this.