fix: create correct types for lists

src/create-schema-customization/__tests__/build-types.test.ts

@@ -203,4 +203,30 @@ describe(`Build objectType`, () => {
       })
     })
   })
+
+  it(`creates correct types for lists`, () => {
+    const gatsbyNodeDefs = createGatsbyNodeDefinitions([
+      {
+        remoteTypeName: `Category`,
+        queries: `{
+          categories {
+            optionalListOfOptionalType
+            optionalListOfRequiredType
+            requiredListOfOptionalType
+            requiredListOfRequiredType
+          }
+        }`,
+      },
+    ])
+    const context = createTestContext({ gatsbyNodeDefs })
+    const categoryDef = buildTypeDefinition(context, `Category`)
+    const categoryFields = (categoryDef as GatsbyGraphQLObjectType).config.fields
+
+    expect(categoryFields).toMatchObject({
+      optionalListOfOptionalType: { type: `[TestApiCategory]` },
+      optionalListOfRequiredType: { type: `[TestApiCategory!]` },
+      requiredListOfOptionalType: { type: `[TestApiCategory]!` },
+      requiredListOfRequiredType: { type: `[TestApiCategory!]!` },
+    })
+  })
 })

src/create-schema-customization/__tests__/fixtures/schema-blog.graphql

@@ -37,6 +37,11 @@ type Category implements Named {
   id: ID!
   entries: [Entry]
   displayName: String!
+
+  optionalListOfOptionalType: [Category]
+  optionalListOfRequiredType: [Category!]
+  requiredListOfOptionalType: [Category]!
+  requiredListOfRequiredType: [Category!]!
 }
 
 type Guest implements Entry & Named {

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

@@ -169,17 +169,23 @@ function toGatsbyType(
  * i.e. wrapType(`JSON`, myRemoteListOfJSONType) => `[JSON]`
  */
 function wrap(typeName: string, remoteType: GraphQLType): string {
-  let wrappedType = typeName
+  const wrappingTypes: GraphQLType[] = []
   let currentRemoteType = remoteType
   while (isWrappingType(currentRemoteType)) {
-    if (isListType(currentRemoteType)) {
-      wrappedType = `[${wrappedType}]`
-    }
-    if (isNonNullType(currentRemoteType)) {
+    wrappingTypes.push(currentRemoteType)
+    currentRemoteType = currentRemoteType.ofType
+  }
+
+  let wrappedType = typeName
+  for (const wrappingType of wrappingTypes.reverse()) {
+    if (isNonNullType(wrappingType)) {
       wrappedType = `${wrappedType}!`
     }
-    currentRemoteType = currentRemoteType.ofType
+    if (isListType(wrappingType)) {
+      wrappedType = `[${wrappedType}]`
+    }
   }
+
   return wrappedType
 }