Partially support nullable and list types

__tests__/starwars.api.ts

@@ -33,6 +33,16 @@ export interface ColorInput {
 
 // "SearchResult" is a union type and not supported
 
+export interface IQuery {
+  hero: ICharacter;
+  reviews: IReview[];
+  search: any;
+  character: ICharacter;
+  droid: IDroid;
+  human: IHuman;
+  starship: IStarship;
+}
+
 export const Query = {
   hero: <T extends Array<Field<any, any, any>>>(
     variables: { episode?: Variable<"episode"> | Episode },
@@ -91,6 +101,10 @@ export const Query = {
     new Field("starship", [new Argument("id", variables.id)], select(Starship)),
 };
 
+export interface IMutation {
+  createReview: IReview;
+}
+
 export const Mutation = {
   createReview: <T extends Array<Field<any, any, any>>>(
     variables: {
@@ -109,9 +123,17 @@ export const Mutation = {
     ),
 };
 
+export interface ICharacter {
+  id: string;
+  name: string;
+  friends: ICharacter[];
+  friendsConnection: IFriendsConnection;
+  appearsIn: Episode[];
+}
+
 export const Character = {
-  id: () => new Field<"id", [], string>("id"),
-  name: () => new Field<"name", [], string>("name"),
+  id: () => new Field<"id">("id"),
+  name: () => new Field<"name">("name"),
 
   friends: <T extends Array<Field<any, any, any>>>(
     select: (t: typeof Character) => T
@@ -133,16 +155,28 @@ export const Character = {
       select(FriendsConnection)
     ),
 
-  appearsIn: () => new Field<"appearsIn", [], Episode>("appearsIn"),
+  appearsIn: () => new Field<"appearsIn">("appearsIn"),
 };
 
+export interface IHuman {
+  id: string;
+  name: string;
+  homePlanet: string;
+  height: number;
+  mass: number;
+  friends: ICharacter[];
+  friendsConnection: IFriendsConnection;
+  appearsIn: Episode[];
+  starships: IStarship[];
+}
+
 export const Human = {
-  id: () => new Field<"id", [], string>("id"),
-  name: () => new Field<"name", [], string>("name"),
-  homePlanet: () => new Field<"homePlanet", [], string>("homePlanet"),
+  id: () => new Field<"id">("id"),
+  name: () => new Field<"name">("name"),
+  homePlanet: () => new Field<"homePlanet">("homePlanet"),
   height: (variables: { unit: unknown }) =>
-    new Field<"height", [/* @todo */], number>("height"),
-  mass: () => new Field<"mass", [], number>("mass"),
+    new Field<"height", [/* @todo */]>("height"),
+  mass: () => new Field<"mass">("mass"),
 
   friends: <T extends Array<Field<any, any, any>>>(
     select: (t: typeof Character) => T
@@ -164,16 +198,25 @@ export const Human = {
       select(FriendsConnection)
     ),
 
-  appearsIn: () => new Field<"appearsIn", [], Episode>("appearsIn"),
+  appearsIn: () => new Field<"appearsIn">("appearsIn"),
 
   starships: <T extends Array<Field<any, any, any>>>(
     select: (t: typeof Starship) => T
   ) => new Field("starships", [], select(Starship)),
 };
 
+export interface IDroid {
+  id: string;
+  name: string;
+  friends: ICharacter[];
+  friendsConnection: IFriendsConnection;
+  appearsIn: Episode[];
+  primaryFunction: string;
+}
+
 export const Droid = {
-  id: () => new Field<"id", [], string>("id"),
-  name: () => new Field<"name", [], string>("name"),
+  id: () => new Field<"id">("id"),
+  name: () => new Field<"name">("name"),
 
   friends: <T extends Array<Field<any, any, any>>>(
     select: (t: typeof Character) => T
@@ -195,13 +238,19 @@ export const Droid = {
       select(FriendsConnection)
     ),
 
-  appearsIn: () => new Field<"appearsIn", [], Episode>("appearsIn"),
-  primaryFunction: () =>
-    new Field<"primaryFunction", [], string>("primaryFunction"),
+  appearsIn: () => new Field<"appearsIn">("appearsIn"),
+  primaryFunction: () => new Field<"primaryFunction">("primaryFunction"),
 };
 
+export interface IFriendsConnection {
+  totalCount: number;
+  edges: IFriendsEdge[];
+  friends: ICharacter[];
+  pageInfo: IPageInfo;
+}
+
 export const FriendsConnection = {
-  totalCount: () => new Field<"totalCount", [], number>("totalCount"),
+  totalCount: () => new Field<"totalCount">("totalCount"),
 
   edges: <T extends Array<Field<any, any, any>>>(
     select: (t: typeof FriendsEdge) => T
@@ -216,31 +265,54 @@ export const FriendsConnection = {
   ) => new Field("pageInfo", [], select(PageInfo)),
 };
 
+export interface IFriendsEdge {
+  cursor: string;
+  node: ICharacter;
+}
+
 export const FriendsEdge = {
-  cursor: () => new Field<"cursor", [], string>("cursor"),
+  cursor: () => new Field<"cursor">("cursor"),
 
   node: <T extends Array<Field<any, any, any>>>(
     select: (t: typeof Character) => T
   ) => new Field("node", [], select(Character)),
 };
 
+export interface IPageInfo {
+  startCursor: string;
+  endCursor: string;
+  hasNextPage: boolean;
+}
+
 export const PageInfo = {
-  startCursor: () => new Field<"startCursor", [], string>("startCursor"),
-  endCursor: () => new Field<"endCursor", [], string>("endCursor"),
-  hasNextPage: () => new Field<"hasNextPage", [], boolean>("hasNextPage"),
+  startCursor: () => new Field<"startCursor">("startCursor"),
+  endCursor: () => new Field<"endCursor">("endCursor"),
+  hasNextPage: () => new Field<"hasNextPage">("hasNextPage"),
 };
 
+export interface IReview {
+  stars: number;
+  commentary: string;
+}
+
 export const Review = {
-  stars: () => new Field<"stars", [], number>("stars"),
-  commentary: () => new Field<"commentary", [], string>("commentary"),
+  stars: () => new Field<"stars">("stars"),
+  commentary: () => new Field<"commentary">("commentary"),
 };
 
+export interface IStarship {
+  id: string;
+  name: string;
+  length: number;
+  coordinates: number[];
+}
+
 export const Starship = {
-  id: () => new Field<"id", [], string>("id"),
-  name: () => new Field<"name", [], string>("name"),
+  id: () => new Field<"id">("id"),
+  name: () => new Field<"name">("name"),
   length: (variables: { unit: unknown }) =>
-    new Field<"length", [/* @todo */], number>("length"),
-  coordinates: () => new Field<"coordinates", [], number>("coordinates"),
+    new Field<"length", [/* @todo */]>("length"),
+  coordinates: () => new Field<"coordinates">("coordinates"),
 };
 
 export const query = <T extends Array<Field<any, any, any>>>(

__tests__/starwars.test.ts

@@ -22,6 +22,7 @@ describe("starwars schema", () => {
           // @fix TypeScript currently has issues deriving `Field` types when we have
           // two `Selector` objects with identical fields that reference each other.
           //
+          // ex. type ExampleQuery = Result<IQuery, typeof operation.selectionSet.selections>
           // t.friends(t => [t.id(), t.name(), t.appearsIn()]),
 
           t.starships((t) => [t.id(), t.name()]),

src/Client.ts

@@ -7,11 +7,14 @@ export class Client {
   // @todo
 }
 
-export const execute = <T extends Array<Field<any, any, any, any>>>(
+export const execute = <
+  RootType,
+  SelectionSet extends Array<Field<any, any, any>>
+>(
   endpoint: string,
-  operation: Operation<T>
+  operation: Operation<SelectionSet>
   /* @todo variables?: Variables */
-): Promise<ExecutionResult<Result<T>>> =>
+): Promise<ExecutionResult<Result<RootType, SelectionSet>>> =>
   fetch(endpoint, {
     method: "post",
     headers: { "Content-Type": "application/json" },
@@ -20,7 +23,9 @@ export const execute = <T extends Array<Field<any, any, any, any>>>(
       // variables,
       query: operation.toString(),
     }),
-  }).then((res) => res.json()) as Promise<ExecutionResult<Result<T>>>;
+  }).then((res) => res.json()) as Promise<
+    ExecutionResult<Result<RootType, SelectionSet>>
+  >;
 
 // @todo we lose out type-saftey going through this (need to fix the `Selector` type param)
 //

src/Codegen.ts

@@ -40,6 +40,28 @@ const toPrimitive = (
   }
 };
 
+const renderInterfaceField = (field: GraphQLField<any, any, any>): string => {
+  const isList =
+    field.type instanceof GraphQLList ||
+    (field.type instanceof GraphQLNonNull &&
+      field.type.ofType instanceof GraphQLList);
+  const isNonNull = field.type instanceof GraphQLNonNull;
+  const baseType = getBaseOutputType(field.type);
+
+  if (baseType instanceof GraphQLScalarType) {
+    return `${field.name}: ${toPrimitive(baseType)}` + (isList ? "[]" : "");
+  } else if (baseType instanceof GraphQLEnumType) {
+    return `${field.name}: ${baseType.name}` + (isList ? "[]" : "");
+  } else if (
+    baseType instanceof GraphQLInterfaceType ||
+    baseType instanceof GraphQLObjectType
+  ) {
+    return `${field.name}: I${baseType.name}` + (isList ? "[]" : "");
+  } else {
+    return `${field.name}: any`;
+  }
+};
+
 export class Codegen {
   private readonly printer = ts.createPrinter();
   private readonly source: ts.SourceFile;
@@ -137,7 +159,12 @@ export class Codegen {
   private interfaceType(type: GraphQLInterfaceType): string {
     const fields = Object.values(type.getFields());
 
+    // @note Render interface types and selector objects
     return `
+      export interface I${type.name} {
+        ${fields.map(renderInterfaceField).join("\n")}
+      }
+
       export const ${type.name} = {
         ${fields.map((field) => this.field(field)).join("\n")}
       }
@@ -155,6 +182,10 @@ export class Codegen {
     const fields = Object.values(type.getFields());
 
     return `
+      export interface I${type.name} {
+        ${fields.map(renderInterfaceField).join("\n")}
+      }
+
       export const ${type.name} = {
         ${fields.map((field) => this.field(field)).join("\n")}
       }
@@ -211,10 +242,8 @@ export class Codegen {
       return args.length > 0
         ? `${name}: (variables: { ${args
             .map((a) => `${a.name}: unknown`)
-            .join(
-              ", "
-            )} }) => new Field<"${name}", [/* @todo */], ${fieldType}>("${name}"),`
-        : `${name}: () => new Field<"${name}", [], ${fieldType}>("${name}"),`;
+            .join(", ")} }) => new Field<"${name}", [/* @todo */]>("${name}"),`
+        : `${name}: () => new Field<"${name}">("${name}"),`;
     } else {
       const renderArgument = (arg: GraphQLArgument): string => {
         const _base = getBaseInputType(arg.type);

src/Operation.ts

@@ -24,21 +24,27 @@ import {
   nonNullTypeOf,
 } from "./AST";
 
-export type Result<Selection extends Array<Field<any, any, any, any>>> = {
-  [Key in Selection[number]["name"]]: Selection[number] extends infer U
-    ? U extends Field<Key, any, infer ValueOrSelection, infer Type>
-      ? ValueOrSelection extends Primitive
-        ? Type // derive nullable and array scalars here
-        : ValueOrSelection extends Array<Field<any, any, any, any>>
-        ? Type extends Array<any>
-          ? Array<Result<ValueOrSelection>> | null
-          : Result<ValueOrSelection> // Derive nullable and array objects here
-        : never
-      : never
-    : never;
-};
-
-export class Operation<T extends Array<Field<any, any, any, any>>> {
+export type Result<
+  Type, // @note Has to be object or array! (right?)
+  SelectionSet extends Array<Field<any, any, any>>
+> = Type extends Array<infer T>
+  ? T extends Primitive
+    ? // @note Return scalar array
+      Array<T>
+    : // @note Wrap complex object in array
+      Array<Result<T, SelectionSet>>
+  : {
+      // @note Build out complex object
+      [Key in SelectionSet[number]["name"]]: Type[Key] extends Primitive
+        ? Type[Key]
+        : SelectionSet[number] extends infer U
+        ? U extends Field<Key, any, infer Selections>
+          ? Result<Type[Key], Selections>
+          : never
+        : never;
+    };
+
+export class Operation<T extends Array<Field<any, any, any>>> {
   constructor(
     public readonly name: string,
     // @todo support `mutation` and `subscription` operations
@@ -83,16 +89,12 @@ export class SelectionSet<T extends Array<Field<any, any, any>>> {
 export class Field<
   Name extends string,
   Arguments extends Argument<string, any>[] | never = never,
-  SelectionSetOrValue extends
-    | Primitive
-    | Field<any, any, any>[]
-    | undefined = undefined,
-  Type = unknown
+  SelectionSet extends Field<any, any, any>[] | never = never
 > {
   constructor(
     public readonly name: Name,
     public readonly args?: Arguments,
-    public readonly selectionSet?: SelectionSetOrValue
+    public readonly selectionSet?: SelectionSet
   ) {}
 
   get ast(): FieldNode {