Circular references just output [object Object], in need of expert assistance

[adamscybot]

I am writing a custom emitter that outputs TypeSpec to Zod schemas. It's been fantastic and I've got off the ground in less than a day. However, now I need to deal with circular references.

There is some documentation around this, but with that documentation in mind I simply can not figure out why the circular references will not resolve.

I based my emitter closely on the test TS emitter. Theres a lot of noise in my emitter impl, and I've since realised actually, this base test emitter suffers from the same problem -- so no surprise mine does too.

Using the above emitter, with a circular input like:

model Test {
    hello: Test2;
}

model Test2 {
    hi2: Test;
}

You'll get something like:

[object Object]

export interface Test  {
   hello: Test2
}

So let's use that as a toy. Why don't the circular references resolve? The emitter uses code throughout, which I believe should mean it all happens automatically. What needs to change in this example emitter to make it work?

Edit

Now I feel its worth noting I added this to my emitter and also the TS example emitter to get it to work:

programContext(program: Program): Context {
    const sourceFile = this.emitter.createSourceFile("schemas.ts");
    return {
      scope: sourceFile.globalScope,
    };
  }

And then $onemit:

import { EmitContext, emitFile, resolvePath } from "@typespec/compiler";
import { TypeScriptInterfaceEmitter } from "./zod-emitter.js";

export async function $onEmit(context: EmitContext) {
  const emitter = context.getAssetEmitter(TypeScriptInterfaceEmitter);

  emitter.emitProgram({ emitTypeSpecNamespace: false });
  await emitter.writeOutput();
}

Possibly I have not setup the $onemit correct and the scope is messed up. But I also couldnt see how that should be done.

[adamscybot]

I dont know why, but changing the $onEmit to the following and removing programContext which I added to the emitter class) makes it work:

import { EmitContext } from "@typespec/compiler";
import { TsZodSchemaEmitter } from "./zod-emitter.js";
import {
  AssetEmitter,
  createAssetEmitter,
} from "@typespec/compiler/emitter-framework";

export async function $onEmit(context: EmitContext) {
  class SingleFileEmitter extends TsZodSchemaEmitter {
    programContext() {
      const outputFile = emitter.createSourceFile("output.ts");
      return { scope: outputFile.globalScope };
    }
  }
  const emitter: AssetEmitter<string> = createAssetEmitter(
    context.program,
    SingleFileEmitter,
    {
      emitterOutputDir: context.program.compilerOptions.outputDir!,
      options: {},
    } as any
  );
  emitter.emitProgram();
  await emitter.writeOutput();
}

Im not sure what the difference is practically, but magic happened!

There is a remaining issue relating to circular references of a different kind, but I will open another discussion for that If I can not figure it out.

[bterlson]

Hmm I don't understand why SingleFileEmitter would work and your previous one wouldn't considering the implementation of programContext is identical. This seems like a bug. I will investigate at some point, but given that you are unblocked, this may not happen soon!

Excited to see the Zod emitter though!! Definitely post on discussions and/or in discord when you're ready to show it off!

[adamscybot]

Yeh! I think now i've found an actual (?) possibly related circular reference issue, which may or may not be related to this. I'm just trying to get minimal repro and will post a new discussion since it is a more granular case.

[adamscybot]

Yep, nope! On this particular variation its a clearly a me problem as the base TS test emitter does not suffer from it. I will now go and touch grass before tackling that!