Invalid generated ScalarConfig type for flow types

[emmenko]

Describe the bug
The generated ScalarConfig are invalid for flow types.

To Reproduce
Given a scalar type (e.g. DateTime), a DateTimeScalarType is generated of kind interface. However, the GraphQLScalarTypeConfig flow type from graphql is a type, which makes it impossible to extend as an interface.

For TypeScript, the GraphQLScalarTypeConfig is an interface, which makes it extendible, but not for FlowType.

Expected behavior
I wonder what the purpose of this ScalarConfig is in the first place. Is it really necessary to have? I tried to find some explanations in the commit history but the only things I found are:

• Resolvers for unions, interfaces and directives #910
• Flow plugins #917 (specifically bab23e5)
• ad07eaf (but the commit didn't have any useful explanation on what the problem was)

I am also unsure on how the GraphQLScalarTypeConfig can be "extended". Being a type, it's not really possible to do, even with intersections, especially given that the name property is literal.

Example: https://flow.org/try/#0PQKgBAAgZgNg9gdzCYAoVAXAngBwKZgDiATgIY4AWAigDIDKAxqTKcQCq54DCcAdlAEsA5mAC8YAN4AfML1IBbPAC4wAZwzEBvEVIC+AbkycwAEVIY8bAYsbNWPfsLFEylWrZbtODwSIBkkrIKymAA5GYWVoqhYAboAG6sYIkwAK4hEZbWeB72fL7OEqhgQYoqoQD8FaEANKgGQA

Environment:

• OS: macOS
• Codegen: latest version 0.18.0
• Node: 11

---

Maybe I'm doing something wrong or I'm missing something. It would be good to understand the reasons for having that and what are we supposed to do about it.

Many thanks! 🙏

[dotansimha]

Hi @emmenko ! Thank you for reporting it.

The right way to do it in flow is to use spread, like that:

type DateTimeScalarConfig = { ...GraphQLScalarTypeConfig, name: 'DateTime' };

I fixed it in this PR: #1520

[dotansimha]

Fix available in 1.0.2.

[emmenko]

The right way to do it in flow is to use spread

Ah good to know! Thanks a lot for the fix 🚀