Is it possible to auto convert camelCase to snake_case when using the schema generator?

[keith-miller]

Hello! We are currently using Graphql Kotlin (thanks for this, btw) to develop a replacement server for Hasura. Currently Hasura uses the snake_case database column names in it's responses. We were wondering if it is possible to tell the schema generate to do this conversion for us, since our field names are camelCase in the code. If not it's not a big deal since we can use @GraphQLName to set the names, but it would be a nice to have.

Thanks

[smyrick]

You could accomplish this with the schema generator hooks:

class MyHooks : SchemaGeneratorHooks {
  fun willAddGraphQLTypeToSchema(type: KType, generatedType: GraphQLType): GraphQLType  {
    if (generatedType is GraphQLNamedType  && isSnakeCase(generatedType.name)) {
      // rebuild the type with new name here
    }

    return generatedType
  }
}

[keith-miller]

You just made my day. Thanks!

[keith-miller]

Hmm, that worked to replace the schema, but using the new snake_case fields in the query returns

"message": "The field at path '/item_types/returning[0]/game_item_type_id' was declared as a non null type, but the code involved in retrieving data has wrongly returned a null value.  The graphql specification requires that the parent field be set to null, or if that is non nullable that it bubble up null to its parent and so on. The non-nullable type is 'String' within parent type 'item_type'"

Code I'm using:

    override fun willAddGraphQLTypeToSchema(type: KType, generatedType: GraphQLType): GraphQLType {
        if(generatedType is GraphQLNamedType) {
            return when (generatedType) {
                is GraphQLObjectType -> {
                    GraphQLObjectType.Builder(generatedType)
                        .name(CaseFormat.LOWER_CAMEL.to(CaseFormat.LOWER_UNDERSCORE, generatedType.name))
                        .replaceFields(convertFieldDefinitions(generatedType.fieldDefinitions))
                        .build()
                }
                is GraphQLEnumType -> {
                    GraphQLEnumType.Builder(generatedType)
                        .name(CaseFormat.LOWER_CAMEL.to(CaseFormat.LOWER_UNDERSCORE, generatedType.name))
                        .build()
                }
                is GraphQLInputObjectType -> {
                    GraphQLInputObjectType.Builder(generatedType)
                        .name(CaseFormat.LOWER_CAMEL.to(CaseFormat.LOWER_UNDERSCORE, generatedType.name))
                        .replaceFields(convertInputObjectFields(generatedType.fields))
                        .build()
                }
                else -> {
                    generatedType
                }
            }
        }

        return generatedType
    }

    private fun convertFieldDefinitions(fields: List<GraphQLFieldDefinition>): List<GraphQLFieldDefinition> {
        return fields.map { field ->
            if(field.name.contains("_")) {
                field
            } else {
                GraphQLFieldDefinition.Builder(field)
                    .name(CaseFormat.LOWER_CAMEL.to(CaseFormat.LOWER_UNDERSCORE, field.name))
                    .build()
            }
        }
    }

    private fun convertInputObjectFields(fields: List<GraphQLInputObjectField>): List<GraphQLInputObjectField> {
        return fields.map { field ->
            if(field.name.contains("_")) {
                field
            } else {
                GraphQLInputObjectField.Builder(field)
                    .name(CaseFormat.LOWER_CAMEL.to(CaseFormat.LOWER_UNDERSCORE, field.name))
                    .build()
            }
        }
    }

[smyrick]

I think you have to check for nullable types in the first block. is GraphQLNonNull