Constants are compiled as enums

[Ksisa]

Describe the bug

If I have a value that's a constant on an object, it will get compiled into an anonymous schema. This overcomplicates things by a lot.

Input:

    TradeMessageClient:
      name: Trade Message (client)
      title: Trade Message (client)
      description: A message containing trade data
      payload:
        title: TradePayloadClient
        type: object
        properties:
          operation:
            type: string
            const: Trade
          data:
            $ref: '#/components/schemas/TradeClient'
        additionalProperties: false
        required:
          - operation
          - data

Expected TypeScript output:

interface TradePayloadClient {
  operation: "Trade"
  data: TradeClient;
}

Actual Typescript Output:

interface TradePayloadClient {
  operation: AnonymousSchema_11;
  data: TradeClient;
}
enum AnonymousSchema_11 {
  TRADE = "Trade",
}

Expected C# output:

public class TradePayloadClient
{
    public const string Operation = "Trade";
    public TradeClient? Data { get; set; }
}

Actual C# output:

public class TradePayloadClient
  {
    public AnonymousSchema_11? Operation { get; set; }
    public TradeClient? Data { get; set; }
  }

public enum AnonymousSchema_11
  {
    TRADE
  }

  public static class AnonymousSchema_11Extensions
  {
    public static string? GetValue(this AnonymousSchema_11 enumValue)
    {
      switch (enumValue)
      {
        case AnonymousSchema_11.TRADE: return "Trade";
      }
      return null;
    }

    public static AnonymousSchema_11? ToAnonymousSchema_11(string? value)
    {
      switch (value)
      {
        case "Trade": return AnonymousSchema_11.TRADE;
      }
      return null;
    }
  }

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[jonaslagoni]

@Ksisa try and switch over to the next version, it has this updated 🙂

[Ksisa]

@jonaslagoni for Typescript, I get this, which is invalid

interface TradePayloadClient {
  operation: 'Trade' = 'Trade';
  data: TradeClient;
}

And for C#, it doesn't retain the constant's value

public class TradePayloadClient
{
  public string Operation { get; set; }
  public TradeClient Data { get; set; }
}

[jonaslagoni]

@jonaslagoni for Typescript, I get this, which is invalid

How is that input invalid? 🤔

And for C#, it doesn't retain the constant's value

Yea C# still need a few things

[Ksisa]

@jonaslagoni It's an interface, variables can't be initialized.

[jonaslagoni]

Ahh yea 😅

So it's part of https://github.com/asyncapi/modelina/blob/042b45e38ae6a08c6a3ef7df9feb1a724eb63969/src/generators/typescript/TypeScriptObjectRenderer.ts#L49C70-L49C75 that is called by

modelina/src/generators/typescript/renderers/InterfaceRenderer.ts

Line 29 in 042b45e

return renderer.renderProperty(property);

, so we just need to provide conditional check whether we render for interface or class, and if interface only render the types.

@Ksisa wanna provide a fix for it?

[Ksisa]

Yeah, I can take a look tomorrow evening.

[jonaslagoni]

@Ksisa wanna have a look at the c# generator as well?

It is slightly more complicated than your last PR.

First part is implementing the constant constrainer for C#: https://github.com/asyncapi/modelina/blob/next/src/generators/csharp/constrainer/ConstantConstrainer.ts you can use the TypeScript constant constrainer as a guideline.

Then in the generator, you just need to adapt the property rendering using the .options.const.value value, by altering it here:

modelina/src/generators/csharp/renderers/ClassRenderer.ts

Line 123 in 33c66a4

return `private ${property.property.type} ${property.propertyName}${nullablePropertyEnding};`;

[Ksisa]

@jonaslagoni what is the constant constrainer used for? I can see the Java ConstantConstrainer is identical to the TypeScript one, so I'm tempted to just copy paste it, especially since Java is syntactically very similar to C#.

[github-actions]

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Thank you for your patience ❤️

[jonaslagoni]

@jonaslagoni what is the constant constrainer used for? I can see the Java ConstantConstrainer is identical to the TypeScript one, so I'm tempted to just copy paste it, especially since Java is syntactically very similar to C#.

It renders the constant value in language at hand. Some languages will overlap in that others will be unique. So it's vary possible that the implementation is gonna be the same or very similar between them 🙂

[moritzkalwa]

@jonaslagoni Is const only implemented for strings? 🤔 If so, should there be a check on the property type in the generator so we don't generate junk (e.g. private const double property = undefined)?

[asyncapi-bot]

🎉 This issue has been resolved in version 4.0.0-next.4 🎉

The release is available on:

• npm package (@next dist-tag)
• GitHub release

Your semantic-release bot 📦🚀