`[String!]!` is translating to typescript type `Array<Scalars['String']> | Scalars['String']`

Issue workflow progress

Progress of the issue based on the Contributor Workflow

• 1. The issue provides a reproduction available on GitHub, Stackblitz or CodeSandbox

Link to codesandbox: https://codesandbox.io/s/hardcore-tdd-q7uyd1?file=/types.ts

• 2. A failing test has been provided
• 3. A local solution has been provided
• 4. A pull request is pending review

---

Describe the bug

The graphql type [String!]!, i.e., a non-nullable array of non-nullable strings, is converted to Array<Scalars['String']> | Scalars['String'] rather than only Array<Scalars['String']>.

To Reproduce Steps to reproduce the behavior:

1. My GraphQL schema:

type ProjectCreateMutation {
    response: String!
    message: String!
}

type Mutation {
    createProject(
        description: String!
        name: String!
        subtitle: String!
        tags: [String]!
    ): ProjectCreateMutation
}

type Query {
    getMessage: String
}

1. My GraphQL operations:

mutation createNewProject(
  $description: String!
  $name: String!
  $subtitle: String!
  $tags: [String!]!
  ) {
  createProject(
      description: $description
      name: $name
      subtitle: $subtitle
      tags: $tags
  ) {
      response
      message
  }
}

1. My codegen.yml config file:

overwrite: true
schema: schema.graphql
documents: document.ts
generates:
  types.ts:
    plugins:
      - typescript
      - typescript-operations

Expected behavior

[String!]! should be converted to Array<Scalars['String']>

Environment:

• OS: Linux (PopOS)
• @graphql-codegen/...:

{
  "dependencies": {
      "@graphql-codegen/cli": "2.6.2",
      "@graphql-codegen/typescript": "2.4.11",
      "@graphql-codegen/typescript-graphql-files-modules": "2.1.1",
      "@graphql-codegen/typescript-operations": "2.4.0",
      "graphql-request": "^4.3.0",
      "graphql": "^16.5.0"
  }
}

• NodeJS: v16.14.2

Additional context

[falkenhawk]

I believe this is expected, because of input coercion for lists: https://spec.graphql.org/June2018/#sec-Type-System.List

[ardatan]

I think we can close this issue then 😃