Apollo GraphQL Error: Query root type must be provided

GraphQL must have at least one @Query() to be considered valid. So maybe only need add any Query to your Resolver code will be helpful. Ex:

export class FooResolver {

  @Query(() => String)
  sayHello(): string {
    return 'Hello World!';
  }
}

This error throws when your schema stiching/definitions are incorrect. Please check the check your root schema definitions

https://www.advancedgraphql.com/content/schema-stitching

I was having the same issue while using graphql-codegen.

my codegen.yml is

overwrite: true
schema: "http://localhost:3001/graphql"
documents: "src/app/graphql/*.graphql"
generates:
  src/generated/graphql.ts:
    plugins:
      - typescript
      - typescript-operations
      - typescript-apollo-angular

The issue was coming when I used the plugin typescript-apollo-angular.

I'm using Nodejs with graphql as backend.

The issue got resolved when I renamed the type RootQuery -> Query and RootMutation -> Mutation in backend schema.

Before

type RootQuery {
  _empty: String  
}

type RootMutation {
  _empty: String
}

schema {
    query: RootQuery
    mutation: RootMutation
}

After

type Query {
  _empty: String  
}

type Mutation {
  _empty: String
}

schema {
    query: Query
    mutation: Mutation
}

I ended up reverting back to a previous version of the codebase and reapplied my modifications manually and it works now. The only thing I can think of is I ran npm update which updated apollo-angular from 1.8.3 to 1.10.0.

EDIT Here is my code:

codegen.yml (used to generate code from npm command):

overwrite: true
schema: "https://to_end_point/Prod/api/v1/GraphQL"
documents: "src/**/*.graphql"
generates:
  src/generated/graphql.ts:
    plugins:
      - "typescript"
      - "typescript-operations"
      - "typescript-apollo-angular"
  ./graphql.schema.json:
    plugins:
      - "introspection"

After reverting back to a previous version of Angular code then re-applying my code modifications, GraphQl code generation worked again. The only thing I can think of which could have caused this issue was when I ran npm update. Below is a screenshot of before/after of package.json: