feat(defaults): add support for default values for input types (#203)

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Changelog and release notes
 
+## Unreleased
+### Features
+- add support for default values in schema (#203)
+
 ## v0.15.0
 ### Features
 - **Breaking Change**: upgrade `graphql` to `^14.0.2`, `graphql-subscriptions` to `^1.0.0` and `@types/graphql` to `^14.0.2`

docs/getting-started.md

@@ -120,11 +120,11 @@ class NewRecipeDataInput {
 
 @ArgsType()
 class RecipesArgs {
-  @Field(type => Int, { nullable: true })
+  @Field(type => Int)
   @Min(0)
   skip: number = 0;
 
-  @Field(type => Int, { nullable: true })
+  @Field(type => Int)
   @Min(1) @Max(50)
   take: number = 25;
 }
@@ -159,7 +159,7 @@ input NewRecipeInput {
 }
 type Query {
   recipe(id: ID!): Recipe
-  recipes(skip: Int, take: Int): [Recipe!]!
+  recipes(skip: Int = 0, take: Int = 25): [Recipe!]!
 }
 type Mutation {
   addRecipe(newRecipeData: NewRecipeInput!): Recipe!

docs/interfaces-and-inheritance.md

@@ -51,10 +51,10 @@ While creating GraphQL API, it's a common pattern to have pagination args in res
 ```typescript
 @ArgsType()
 class PaginationArgs {
-  @Field(type => Int, { nullable: true })
+  @Field(type => Int)
   skip: number = 0;
 
-  @Field(type => Int, { nullable: true })
+  @Field(type => Int)
   take: number = 25;
 }
 ```
@@ -63,7 +63,7 @@ and then reuse it everywhere:
 ```typescript
 @ArgsType()
 class GetTodosArgs extends PaginationArgs {
-  @Field({ nullable: false })
+  @Field()
   onlyCompleted: boolean = false;
 }
 ```
@@ -83,7 +83,7 @@ class Student extends Person {
 }
 ```
 
-Note that both the subclass and the parent class must be decorated with the same type of decorator, like `@ObjectType()` in the example `Person -> Student` above. Mixing decorator types across parent and child classes is prohibited and might result in schema building error --- you can't e.g decorate the subclass with `@ObjectType()` and the parent with `@InputType()`.
+Note that both the subclass and the parent class must be decorated with the same type of decorator, like `@ObjectType()` in the example `Person -> Student` above. Mixing decorator types across parent and child classes is prohibited and might result in schema building error - you can't e.g decorate the subclass with `@ObjectType()` and the parent with `@InputType()`.
 
 ## Resolvers inheritance
 The special kind of inheritance in TypeGraphQL is a resolver classes inheritance. This pattern allows you to e.g. create a base CRUD resolver class for your resource/entity, so you don't have to repeat the common boilerplate code all the time.

docs/resolvers.md

@@ -2,7 +2,7 @@
 title: Resolvers
 ---
 
-Besides [declaring GraphQL's object types](./types-and-fields.md), TypeGraphQL allows to create queries, mutations and field resolvers in an easy way - like a normal class methods, similar to REST controllers in frameworks like Java's `Spring`, .NET `Web API` or TypeScript's [routing-controllers](https://github.com/typestack/routing-controllers).
+Besides [declaring GraphQL's object types](./types-and-fields.md), TypeGraphQL allows to create queries, mutations and field resolvers in an easy way - like a normal class methods, similar to REST controllers in frameworks like Java's `Spring`, .NET `Web API` or TypeScript's [`routing-controllers`](https://github.com/typestack/routing-controllers).
 
 ## Queries and mutations
 
@@ -54,14 +54,15 @@ class RecipeResolver {
 ### Arguments
 Usually queries have some arguments - it might be an id of the resource, the search phrase or pagination settings. TypeGraphQL allows you to define the arguments in two ways.
 
-First is the inline method using `@Arg()` decorator. The drawback is the need of repeating argument name (due to a reflection system limitation) in the decorator parameter.
+First is the inline method using `@Arg()` decorator. The drawback is the need of repeating argument name (due to a reflection system limitation) in the decorator parameter. As you can see below, you can also pass a `defaultValue` options that will be reflected in the GraphQL schema.
 ```typescript
 @Resolver()
 class RecipeResolver {
   // ...
   @Query(returns => [Recipe])
   async recipes(
     @Arg("title" { nullable: true }) title?: string,
+    @Arg("servings" { defaultValue: 2 }) servings: number,
   ): Promise<Recipe[]> {
     // ...
   }
@@ -81,17 +82,19 @@ class GetRecipesArgs {
   title?: string;
 }
 ```
-You can define default values for optional fields (remember about `nullable: true`!) as well as helper methods.
-Also, this way of declaring arguments allows you to perform validation.  You can find more details about this feature in [the validation docs](./validation.md).
+
+You can define default values for optional fields in the `@Field()` decorator using a `defaultValue` option or by using a property initializer - in both cases TypeGraphQL will reflect this in the schema by setting the default value and making the field nullable.
+
+Also, this way of declaring arguments allows you to perform validation. You can find more details about this feature in [the validation docs](./validation.md). You can also define a helper fields and methods for your args or input class.
 
 ```typescript
 @ArgsType()
 class GetRecipesArgs {
-  @Field(type => Int, { nullable: true })
+  @Field(type => Int, { defaultValue: 0 })
   @Min(0)
-  skip = 0;
+  skip: number;
 
-  @Field(type => Int, { nullable: true })
+  @Field(type => Int)
   @Min(1) @Max(50)
   take = 25;
 
@@ -125,7 +128,7 @@ class RecipeResolver {
 This declarations will result in the following part of the schema in SDL:
 ```graphql
 type Query {
-  recipes(skip: Int, take: Int, title: String): [Recipe!]
+  recipes(skip: Int = 0, take: Int = 25, title: String): [Recipe!]
 }
 ```
 

docs/types-and-fields.md

@@ -50,7 +50,7 @@ For simple types (like `string` or `boolean`) it's enough but unfortunately, due
 
 Why function syntax, not simple `{ type: Rate }` config object? Because this way we solve problems with circular dependencies (e.g. Post <--> User), so it was adopted as a convention. You can use the shorthand syntax `@Field(() => Rate)` if you want to save some keystrokes but it might be less readable for others.
 
-For nullable properties like `averageRating` (it might be not defined when recipe has no ratings yet), we mark the class property as optional with `?:` operator and also have to pass `{ nullable: true }` decorator parameter. Be aware that when you declare your type as `string | null`, you need to explicitly provide the type to the `@Field` decorator.
+For nullable properties like `averageRating` (it might be not defined when recipe has no ratings yet), we mark the class property as optional with `?:` operator and also have to pass `{ nullable: true }` decorator parameter. Be aware that when you declare your type as a nullable union (e.g. `string | null`), you need to explicitly provide the type to the `@Field` decorator.
 
 In the config object we can also provide `description` and `deprecationReason` for GraphQL schema purposes.
 

examples/automatic-validation/recipes-arguments.ts

@@ -3,11 +3,11 @@ import { ArgsType, Field, Int } from "../../src";
 
 @ArgsType()
 export class RecipesArguments {
-  @Field(type => Int, { nullable: true })
+  @Field(type => Int)
   @Min(0)
   skip: number = 0;
 
-  @Field(type => Int, { nullable: true })
+  @Field(type => Int)
   @Min(1)
   @Max(50)
   take: number = 10;

examples/middlewares/recipe/recipe.args.ts

@@ -3,11 +3,11 @@ import { ArgsType, Field, Int } from "../../../src";
 
 @ArgsType()
 export class RecipesArgs {
-  @Field(type => Int, { nullable: true })
+  @Field(type => Int)
   @Min(0)
   skip: number = 0;
 
-  @Field(type => Int, { nullable: true })
+  @Field(type => Int)
   @Min(1)
   @Max(50)
   take: number = 10;

examples/resolvers-inheritance/resource/resource.resolver.ts

@@ -30,10 +30,10 @@ export abstract class BaseResourceResolver<TResource extends Resource> {
 
 @ArgsType()
 export class GetAllArgs {
-  @Field(type => Int, { nullable: true })
+  @Field(type => Int)
   skip: number = 0;
 
-  @Field(type => Int, { nullable: true })
+  @Field(type => Int)
   take: number = 10;
 }
 

examples/simple-usage/recipe-resolver.ts

@@ -44,7 +44,7 @@ export class RecipeResolver implements ResolverInterface<Recipe> {
   @FieldResolver()
   ratingsCount(
     @Root() recipe: Recipe,
-    @Arg("minRate", type => Int, { nullable: true }) minRate: number = 0.0,
+    @Arg("minRate", type => Int, { defaultValue: 0.0 }) minRate: number,
   ): number {
     return recipe.ratings.filter(rating => rating >= minRate).length;
   }

examples/simple-usage/schema.gql

@@ -26,7 +26,7 @@ type Recipe {
   description: String
   ratings: [Int!]!
   creationDate: DateTime!
-  ratingsCount(minRate: Int): Int!
+  ratingsCount(minRate: Int = 0): Int!
   averageRating: Float
 }
 

src/decorators/types.ts

@@ -21,6 +21,7 @@ export type SubscriptionTopicFunc = (
 
 export interface DecoratorTypeOptions {
   nullable?: boolean;
+  defaultValue?: any;
 }
 export interface TypeOptions extends DecoratorTypeOptions {
   array?: boolean;

src/errors/ConflictingDefaultValuesError.ts

@@ -0,0 +1,16 @@
+export class ConflictingDefaultValuesError extends Error {
+  constructor(
+    typeName: string,
+    fieldName: string,
+    defaultValueFromDecorator: any,
+    defaultValueFromInitializer: any,
+  ) {
+    super(
+      `The '${fieldName}' field of '${typeName}' has conflicting default values. ` +
+        `Default value from decorator ('${defaultValueFromDecorator}') ` +
+        `is not equal to the property initializer value ('${defaultValueFromInitializer}').`,
+    );
+
+    Object.setPrototypeOf(this, new.target.prototype);
+  }
+}

src/errors/index.ts

@@ -4,6 +4,7 @@ export * from "./ArgumentValidationError";
 export * from "./CannotDetermineTypeError";
 export * from "./ForbiddenError";
 export * from "./GeneratingSchemaError";
+export * from "./ConflictingDefaultValuesError";
 export * from "./MissingSubscriptionTopicsError";
 export * from "./NoExplicitTypeError";
 export * from "./ReflectMetadataMissingError";

src/helpers/types.ts

@@ -44,7 +44,7 @@ export function wrapWithTypeOptions<T extends GraphQLType>(
   if (typeOptions.array) {
     gqlType = new GraphQLList(new GraphQLNonNull(gqlType));
   }
-  if (!typeOptions.nullable) {
+  if (!typeOptions.nullable && typeOptions.defaultValue === undefined) {
     gqlType = new GraphQLNonNull(gqlType);
   }
   return gqlType as T;

src/schema/schema-generator.ts

@@ -36,6 +36,7 @@ import {
   UnionResolveTypeError,
   GeneratingSchemaError,
   MissingSubscriptionTopicsError,
+  ConflictingDefaultValuesError,
 } from "../errors";
 import { ResolverFilterData, ResolverTopicData } from "../interfaces";
 import { getFieldMetadataFromInputType, getFieldMetadataFromObjectType } from "./utils";
@@ -104,6 +105,30 @@ export abstract class SchemaGenerator {
     }
   }
 
+  private static getDefaultValue(
+    typeInstance: { [property: string]: unknown },
+    typeOptions: TypeOptions,
+    fieldName: string,
+    typeName: string,
+  ): unknown | undefined {
+    const defaultValueFromInitializer = typeInstance[fieldName];
+    if (
+      typeOptions.defaultValue !== undefined &&
+      defaultValueFromInitializer !== undefined &&
+      typeOptions.defaultValue !== defaultValueFromInitializer
+    ) {
+      throw new ConflictingDefaultValuesError(
+        typeName,
+        fieldName,
+        typeOptions.defaultValue,
+        defaultValueFromInitializer,
+      );
+    }
+    return typeOptions.defaultValue !== undefined
+      ? typeOptions.defaultValue
+      : defaultValueFromInitializer;
+  }
+
   private static buildTypesInfo() {
     this.unionTypesInfo = getMetadataStorage().unions.map<UnionTypeInfo>(unionMetadata => {
       return {
@@ -276,6 +301,7 @@ export abstract class SchemaGenerator {
         );
         return superClassTypeInfo ? superClassTypeInfo.type : undefined;
       };
+      const inputInstance = new (inputType.target as any)();
       return {
         target: inputType.target,
         type: new GraphQLInputObjectType({
@@ -284,9 +310,17 @@ export abstract class SchemaGenerator {
           fields: () => {
             let fields = inputType.fields!.reduce<GraphQLInputFieldConfigMap>(
               (fieldsMap, field) => {
+                field.typeOptions.defaultValue = this.getDefaultValue(
+                  inputInstance,
+                  field.typeOptions,
+                  field.name,
+                  inputType.name,
+                );
+
                 fieldsMap[field.schemaName] = {
                   description: field.description,
                   type: this.getGraphQLInputType(field.name, field.getType(), field.typeOptions),
+                  defaultValue: field.typeOptions.defaultValue,
                 };
                 return fieldsMap;
               },
@@ -410,6 +444,7 @@ export abstract class SchemaGenerator {
         args[param.name] = {
           description: param.description,
           type: this.getGraphQLInputType(param.name, param.getType(), param.typeOptions),
+          defaultValue: param.typeOptions.defaultValue,
         };
       } else if (param.kind === "args") {
         const argumentType = getMetadataStorage().argumentTypes.find(
@@ -433,10 +468,18 @@ export abstract class SchemaGenerator {
     argumentType: ClassMetadata,
     args: GraphQLFieldConfigArgumentMap = {},
   ) {
+    const argumentInstance = new (argumentType.target as any)();
     argumentType.fields!.forEach(field => {
+      field.typeOptions.defaultValue = this.getDefaultValue(
+        argumentInstance,
+        field.typeOptions,
+        field.name,
+        argumentType.name,
+      );
       args[field.schemaName] = {
         description: field.description,
         type: this.getGraphQLInputType(field.name, field.getType(), field.typeOptions),
+        defaultValue: field.typeOptions.defaultValue,
       };
     });
   }

src/schema/utils.ts

@@ -16,6 +16,7 @@ export function getFieldMetadataFromInputType(type: GraphQLInputObjectType) {
       fieldsMap[fieldName] = {
         type: superField.type,
         description: superField.description,
+        defaultValue: superField.defaultValue,
       };
       return fieldsMap;
     },