[Question] How to extract argument from generic type?

[adi-doorloop]

It's either a brain fart or an actual issue.

export type MutableStep1Dto = MutableDto<Step1Dto, "userType" | "propertyTypes">;

I want to extract the second argument of MutableDto to count the union members. I tried walking the nodes but it just doesn't yield the expected types as seen in the AST viewer, see https://ts-ast-viewer.com/#code/FAUwHgDg9gTgLgAjgTwiBBZArnAhgIwBsQBlOECANgBE4oEBeTHA42qAHjIproBoEAIiwBnEDAAqqEIIQAfIRBhQ08ZFLQjBAPgDcQA.

[markandrus]

import { Project } from 'ts-morph'

const project = new Project()

const sourceFile = project.createSourceFile('test.ts', `\
export type MutableStep1Dto = MutableDto<Step1Dto, "userType" | "propertyTypes">;
`)

const tyNode = sourceFile
  .getTypeAliases()[0]
  .getTypeNodeOrThrow()
  .getTypeArguments()[1]

console.log(tyNode.getText())

// "userType" | "propertyTypes"

[adi-doorloop]

Thanks. Creating a source file seems a bit wild for this purpose.