Type-graphql cannot determine input type, even if I created a dto input file.

[SirMishaa]

Hello,
In my case, GraphQL input of class are useless because I'm creating my own input in my dto folder.

// -- dto/create-brand.input.ts
import { Field, InputType } from '@nestjs/graphql';
import { Product } from '@domain/product/model/product.entity';

@InputType()
export class CreateBrandInput {
  @Field(() => String)
  name!: string;

  @Field(() => [Product], { nullable: 'itemsAndList' })
  products?: Array<Product>;
}

But this does not seem to be enough, if the @InputType decorator is not also in the entity, an error occurs.

// -- brand.model.ts
@Entity()
@ObjectType()
@InputType('BrandInput')
export class Brand extends BaseEntity {  // .... Some fields }

The problem is that by putting it on, it creates an input with the whole class in the GraphQL schema (which is useless in my case).

input CreateBrandInput {
  name: String!
  products: [ProductInput]
}

input BrandInput { 
  createdAt: String!
  id: String!
  name: String!
  products: [ProductInput]!
}

Here, BrandInput is useless, cause for creating a new Brand, I'm gonna use my own input, CreateBrandInput.

But If I'm removing the @InputType in the file brand.model.ts, I've got an error (Error: Cannot determine a GraphQL input type for the "brand")

Am I doing something wrong?
Thank you in advance.

[MichalLytek]

In GraphQL, input objects have a separate type in the system because object types can contain fields that express circular references or references to interfaces and unions, neither of which are appropriate for use as input arguments.

That's why TypeGraphQL doesn't have a dedicated mechanism to reuse or convert object types to input types automatically.
You should keep them separated as they represent two different things in GraphQL. The @InputType('BrandInput') is just an unofficial workaround for the simplest cases and for developers who are aware of the limitation.

Here, BrandInput is useless, cause for creating a new Brand, I'm gonna use my own input, CreateBrandInput.

You should put the @InputType decorator on the Product entity, not Brand, if you create your own input type.
And if you use the explicit buildSchema -> resolvers approach, all the not used types are omitted from the schema, so the BrandInput should not appear in the schema.

[SirMishaa]

But why does it need to convert object types to input types? Input Type is used only for mutation, no?

Why can't I only have my own input type like this ?:

// -- dto/create-brand.input.ts
import { Field, InputType } from '@nestjs/graphql';
import { Product } from '@domain/product/model/product.entity';

@InputType()
export class CreateBrandInput {
  @Field(() => String)
  name!: string;

  @Field(() => [Product], { nullable: 'itemsAndList' })
  products?: Array<Product>;
}

I'm using the code first approach, schema are automatically built using the GraphQLModule from @nestjs/graphql :

GraphQLModule.forRoot({
      debug: true,
      playground: true,
      autoSchemaFile: path.join(process.cwd(), 'src/schema.gql'),
      sortSchema: true,
}),

export class AppModule {}

The @inputType('BrandInput') is just an unofficial workaround for the simplest cases and for developers who are aware of the limitation.

In my case, I don't want it, is there any way to remove it using the code first approach? It look like I have to put @InputType at top of my entities since I have relation between them.

[MichalLytek]

I'm using the code first approach, schema are automatically built using the GraphQLModule from @nestjs/graphql :

Please ask on a proper repo:
https://github.com/nestjs/graphql
NestJS has forked TypeGraphQL so I don't provide any support for NestJS GraphQL.