typescript-transform-rtti

This transformer emits runtime type information (RTTI) about typescript types.

There's currently just one intrinsic function that emits an array of values about literal unions and const enums, see rtti.d.ts.

rtti.literalsOf<>()

An intrinsic function that gets replaced with a unique set of values about literal unions and const enums per type argument. Don't rely on a particular order.

This is useful for runtime validation of values, e.g. using zod.

export const enum StringBasedEnum {
    one = "1",
    two = "2",
}
z.enum(rtti.literalsOf<StringBasedEnum>() /* << replaced with ["1", "2"] */);

// mixed types:
type Another = "6" | 7;
const literals = rtti.literalsOf<
    StringBasedEnum | Another | "eight" | 5
>(); /* << replaced with ["1", "2", "6", 7, "eight", 5] */

Generic type rtti.LiteralsOf<> for declaration files (.d.ts)

Emitting the literals (rtti.literalsOf<>() preserves the exact type as inferred by the compiler in your .d.ts files. In case you want to flatten out your literals type-wise, e.g. get rid of const enums in declaration files, you need to set up a separate transformer in your tsconfig.json for .d.ts files.

This will rewrite generics like rtti.LiteralsOf<Foo> into a literal union type in your .d.ts files.

Installation

Use it alongside with typescript and ts-patch as a dev dependency, e.g.

$ npm install typescript-transform-rtti --save-dev

Add it as a plugin in your tsconfig.json:

    "compilerOptions": {
        //...
        "plugins": [{
            "transform": "typescript-transform-rtti"
            // extra options for renaming
            // `rtti` or `literalsOf` here
        }, { // .d.ts: the below only when you need to rewrite your .d.ts via rtti.LiteralsOf<>
            "transform": "typescript-transform-rtti",
            "afterDeclarations": true
            // extra options for renaming
            // `rtti` or `TypeLiteralsOf` here
        }]
    },
    "include": [
        //...
        // Integrate the def file for rtti.*:
        // Copy and tweak to your needs if you change
        // `namespace` or `literalsOf` resp. `TypeLiteralsOf`.
        "./node_modules/typescript-transform-rtti/rtti.d.ts"
    ]

You can customize the transformer with the following options:

• namespace?: string -- Namespace to use for intrinsics, defaults to "rtti".
• literalsOf?: string -- Function name for literals to detect, defaults to "literalsOf".