Graphql-code-generator: Double // @flow comment added to generated file

[FezVrasta]

Describe the bug

Hi, when I enable flow and flow-operations plugins at the same time, two // @flow headers are added to the graphql.js file.

To Reproduce
Steps to reproduce the behavior:

I tried to edit the template but it doesn't seem to work with the Flow plugins.

https://codesandbox.io/s/wizardly-paper-wsqgl?file=/document.graphql

1. My GraphQL schema:

Not relevant for the issue

1. My GraphQL operations:

Not relevant for the issue

1. My codegen.yml config file:

overwrite: true
schema: 'allSchema.graphql'
generates:
  ./src/generated/graphql.js:
    documents: 'queries/*.js'
    plugins:
      - flow
      - flow-operations

Expected behavior

Environment:

• OS: macOS Catalina
• @graphql-codegen/flow: same as codesandbox
• @graphql-codegen/flow-operations: same as codesandbox
• NodeJS: 14.5.0

Additional context

[dotansimha]

I think this was introduced in: https://github.com/dotansimha/graphql-code-generator/pull/4609
Does it's breaking anything @FezVrasta ? or it's just semantics?

[FezVrasta]

It errors in my create-react-app project

[dotansimha]

@FezVrasta build error or lint error? As far as I can tell, the Flow compiler works perfectly fine with that...

[FezVrasta]

When the double comment is present, I also get a bunch of other errors on any file that imports from it, because it doesn't recognize the types.

Cannot use CreateAddendumMutationVariables as a type. A name can be used as a type only if it refers to a type,
interface, class, or enum definition. To get the type of a non-class value, use typeof. [value-as-type]

[sam-rad]

Having the the same issue. This is where flow throws:

| MultipleFlowAttributes ->
  [
    text "Unexpected ";
    code "@flow";
    text " declaration. Only one per ";
    text "file is allowed.";
  ]

[sam-rad]

What if we remove // @flow prepend from flow operations since flow plugin already has it?

[dotansimha]

Fixed in @graphql-codegen/[email protected].