Weird Type From OpenAPI when Using AnyOf for Nullability

[graham-iheart]

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• 1. The issue provides a reproduction available on
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Please make sure Mesh package versions under package.json matches yours.

• 2. A failing test has been provided
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---

Describe the bug

To Reproduce Steps to reproduce the behavior:

• Include a property in a component schema that looks something like this:

{
  "anyOf": [
    {"type": "string"},
    {"type": "null"}
  ]
}

• The following type gets generated:

type Property @join__type(graph: GRAPH)  {
  String: String @resolveRoot(subgraph: "Graph") 
  Void: Void @resolveRoot(subgraph: "Graph") 
}

Reproduction Codesandbox
Expected behavior

I would expect it to generate a nullable scalar type.

Environment:

• OS: MacOS 15.6
• "@graphql-hive/gateway": "^1.16.3",
• "@graphql-mesh/compose-cli": "^1.4.12",
• "@graphql-mesh/types": "^0.104.7",
• "@graphql-mesh/utils": "^0.104.7",
• "@omnigraph/openapi": "^0.109.14",
• "graphql": "^16.11.0
• NodeJS: 24.4.0

Additional context

I'm happy to send in a fix for this if you could just point me in the right direction in the codebase.

[graham-iheart]

I also noticed that this happens on input types as well, it just gives it a type of JSON.