schema generator should fail if input types with nullable fields do not define a default value

Discussed in https://github.com/ExpediaGroup/graphql-kotlin/discussions/1525

<div type='discussions-op-text'>

^{Originally posted by Anthonyzou August 22, 2022} With the changes in version 6.2.0 and above, input types that could be nullable did not require a default value.

This code would work before version 6.2.0

@GraphQLDescription("")
data class Book(
    val title: String?
)

Now I get the error No argument provided for a required parameter: parameter #0... unless I change the input type to:

@GraphQLDescription("")
data class Book(
    val title: String? = null
)
```</div>

[samuelAndalon]

we can add more custom logic here https://github.com/ExpediaGroup/graphql-kotlin/blob/master/generator/graphql-kotlin-schema-generator/src/main/kotlin/com/expediagroup/graphql/generator/hooks/SchemaGeneratorHooks.kt#L144

adding this logic when unwrapped is GraphQLInputObjectType

type.jvmErasure.primaryConstructor?.parameters?.forEach { param ->
  if (param.type.isMarkedNullable && !param.isOptional) {
   // just for demo, we can use a custom exception
    throw RuntimeException("${type.jvmErasure.simpleName}.${param.name} is nullable but not optional")
  }
}

@xenomachina i would assume you did it in the didGenerateGraphQLType hook ?

[samuelAndalon]

released https://github.com/ExpediaGroup/graphql-kotlin/releases/tag/6.2.2