Subscription "NameOfSubscription" must select only one top level field when using addTypenameSelectionDocumentTransform and generating code for subscription

[Sojaner]

Which packages are impacted by your issue?

@graphql-codegen/client-preset

Describe the bug

The __typename should not be added to the root node of a subscription when using addTypenameSelectionDocumentTransform with documentTransforms since a single root node is expected and the code generator fails because of that

Your Example Website or App

https://github.com/Sojaner/graphql-code-generator-issue-sandbox-template

Steps to Reproduce the Bug or Issue

1. Clone the issue-sandbox-template repo
2. Install packages using yarn
3. yarn generate (Test without the addTypenameSelectionDocumentTransform - Works fine)
4. yarn generate --add-typenames (Test with the addTypenameSelectionDocumentTransform - This will fail)
5. yarn generate --add-fixed-typenames (Test with the patched addTypenameSelectionDocumentTransform - Works fine)

Expected behavior

Generating types from all types of documents should work when using the addTypenameSelectionDocumentTransform document transformer, but currently, the subscription types will cause an error and fail the code generation.

Platform

• OS: Windows
• NodeJS: 20.11.1
• graphql version: N/A
• @graphql-codegen/client-preset version: 4.2.4

Codegen Config File

import { CodegenConfig } from "@graphql-codegen/cli";
import { addTypenameSelectionDocumentTransform } from "@graphql-codegen/client-preset";

const config: CodegenConfig = {
  schema: "schema.graphql",
  documents: "document.graphql",
  generates: {
    "types.ts": { plugins: ["typescript", "typescript-operations"], documentTransforms: [ addTypenameSelectionDocumentTransform] },
  },
};

export default config;