Nullable lists are transformed into non-nullable lists about gatsby-graphql-toolkit

[Leksat]

Could someone take a look at the PR? #87

[vladar]

I skimmed through code and don't see how this can happen. Can you provide some quick reproduction project for further investigation?

[vladar]

Type conversion usually happens here:

gatsby-graphql-toolkit/src/create-schema-customization/transform-fields/field-transformers.ts

Lines 156 to 184 in c9328e2

	function toGatsbyType(
	context: ISchemaCustomizationContext,
	remoteType: GraphQLType
	) {
	const namedType = getNamedType(remoteType)
	const gatsbyTypeName = context.typeNameTransform.toGatsbyTypeName(
	namedType.name
	)
	return wrap(gatsbyTypeName, remoteType)
	}
	/**
	* Wraps a type with the NON_NULL and LIST_OF types of the referenced remote type
	* i.e. wrapType(`JSON`, myRemoteListOfJSONType) => `[JSON]`
	*/
	function wrap(typeName: string, remoteType: GraphQLType): string {
	let wrappedType = typeName
	let currentRemoteType = remoteType
	while (isWrappingType(currentRemoteType)) {
	if (isListType(currentRemoteType)) {
	wrappedType = `[${wrappedType}]`
	}
	if (isNonNullType(currentRemoteType)) {
	wrappedType = `${wrappedType}!`
	}
	currentRemoteType = currentRemoteType.ofType
	}
	return wrappedType
	}

[feedm3]

Better late than never 😄 The issue is still there so I took some time to create a reproduction project.

• GraphQL server: https://codesandbox.io/s/graphql-gatsbyjs-gatsby-graphql-toolkit-issues-39-jcs1l
• Gatsby client: https://codesandbox.io/s/gatsby-gatsbyjs-gatsby-graphql-toolkit-issues-39-j5ltu

I couldn't make the request from the CodeSandbox Gatsby project to the GraphQL project work. You can download both projects as .zip file (CodeSandbox > Menu > File > Export to ZIP) and run them locally without any further adjustments.

GraphQL Server

The GraphQL server has a minimal schema with 2 lists. One with mandatory entries and one with optional entries:

type Todo {
  id: ID!
  ...
  mandatoryTextEntries: [String!]!
  optionalTextEntries: [String]!
}

The schema is also correct in the GraphiQL client:

Test data is already setup so running the query

query getTodos {
  todos {
    mandatoryTextEntries
    optionalTextEntries
  }
}

will return the following valid result:

{
  "data": {
    "todos": [
      {
        "mandatoryTextEntries": [
          "entry 1",
          "entry 2"
        ],
        "optionalTextEntries": [
          "entry 1",
          "entry 2",
          null,
          "entry 4"
        ]
      },
      {
        "mandatoryTextEntries": [],
        "optionalTextEntries": []
      }
    ]
  }
}

Gatsby client

The data gets sources by the toolkit in gatsby-node.js.

Starting the development server, the ExmapleTodo type is available. Looking closer to the fields in the GraphiQl client reveals, that the optionalTextEntries list now has mandatory entries. Also, the list itself is now optional:

As example data has one null entry in the optionalTextEntries array, this query

query getTodos {
  allExampleTodo {
    nodes {
      mandatoryTextEntries
      optionalTextEntries
    }
  }
}

results in an error, as there are no optional entries allowed anymore:

I hope I can help find the bug 🙂

[Leksat]

Confirming. Source field: [Type]! is translated to field: [Type!].

[andrezimpel]

Can confirm. Schema customization doesn't seam to be a way to work around this.

[andrezimpel]

Type conversion usually happens here:

gatsby-graphql-toolkit/src/create-schema-customization/transform-fields/field-transformers.ts

Lines 156 to 184 in c9328e2

	function toGatsbyType(
	context: ISchemaCustomizationContext,
	remoteType: GraphQLType
	) {
	const namedType = getNamedType(remoteType)
	const gatsbyTypeName = context.typeNameTransform.toGatsbyTypeName(
	namedType.name
	)
	return wrap(gatsbyTypeName, remoteType)
	}
	/**
	* Wraps a type with the NON_NULL and LIST_OF types of the referenced remote type
	* i.e. wrapType(`JSON`, myRemoteListOfJSONType) => `[JSON]`
	*/
	function wrap(typeName: string, remoteType: GraphQLType): string {
	let wrappedType = typeName
	let currentRemoteType = remoteType
	while (isWrappingType(currentRemoteType)) {
	if (isListType(currentRemoteType)) {
	wrappedType = `[${wrappedType}]`
	}
	if (isNonNullType(currentRemoteType)) {
	wrappedType = `${wrappedType}!`
	}
	currentRemoteType = currentRemoteType.ofType
	}
	return wrappedType
	}

@vladar so does this mean isListType or isNonNullType is not correct, right?

[Leksat]

A release? 🙏

(This is a really confusing bug 😅)