Client generation: Scalar for BigDecimal

[huehnerlady]

HI,

after being able to generate a client with the help provided here We now run into the issue, that we use java.math.BigDecimal in our GraphQL Schema, created with com.expediagroup:graphql-kotlin-schema-generator. We rely here on a central mode, which unfortunately is made out of Groovy classes (We currently have the main lanuage as groovy, but I try to introduce kotlin more and more), so changing BigDecimal is not possible.

In the Schema we can see the Scalar:

"Built-in java.math.BigDecimal"
scalar BigDecimal

But when using the graphql-kotlin client generator we end up with that type being just String. I could find a generated class:

/**
 * Built-in java.math.BigDecimal
 */
public typealias BigDecimal = String

Then I tried to use a customScalar:

    customScalars.add(GraphQLScalar("BigDecimal", "java.math.BigDecimal", "my.package.BigDecimalConverter"))

This seems to create a wrapper class though:

/**
 * Built-in java.math.BigDecimal
 */
public data class BigDecimal(
  public val value: java.math.BigDecimal
) {
  @JsonValue
  public fun rawValue() = converter.toJson(value)

  public companion object {
    public val converter: BigDecimalConverter = BigDecimalConverter()

    @JsonCreator
    @JvmStatic
    public fun create(rawValue: Any) = BigDecimal(converter.toScalar(rawValue))
  }
}

So again that is not the behaviour we want.

When I manually change the type alias to be java.math.BigDecimal it all works as expected. So can I somehow say in the config, that I just want a type alias? I was hoping the Comment would help there, as it is generated by graphql-kotlin, but that seems not to be enough?

Thanks for your help 🙂

[dariuszkuc]

Hello 👋
Per GraphQL spec all all GraphQL scalars are representable as strings and while servers can use more appropriate primitives, clients have no knowledge what custom scalars represent. Since all scalars have to be representable as strings that is also the common default for all custom scalars. To keep logic simple and consistent, currently we don't support providing custom type aliases for custom scalars and always rely on the explicit converter to handle de-/serialization.

I'm thinking we could potentially support it by allowing to specify something like GraphQLScalarTypeAlias and default GraphQLScalar (with the converter).

[huehnerlady]

That sounds very promising, many thanks for looking into this for us ❤️

[dariuszkuc]

@huehnerlady we released the change in 5.0.0-alpha.2

[huehnerlady]

@dariuszkuc great, thank you so much for your help. I have to say I am very glad that we use your library as I feel the support and the responsiveness is absolutely amazing ❤️

As we use that in production unfortunately all I can do with an alpha version is test it, but not use it. Do you have an estimate when you plan to release version 5?

[smyrick]

@dariuszkuc I don't have any major features left that need to get in. GraphQL Java is getting ready to release v17 so we could wait for that https://github.com/graphql-java/graphql-java/releases

[huehnerlady]

@dariuszkuc @smyrick any update on when you plan to release 5.0? :)