Custom Type Run time type checking issue not working

[anu1097]

I have a use case where I want to ensure my custom types are respected during run time as well. I would have written custom checks myself but Typescript's String Literal Types are not available during run time.

I am posting my code sample and generated code with ts-runtime library -

My Code -

type UploadMediaPayload = {
    abc: string
}

type analyticsEvent = {
  'Upload Media': UploadMediaPayload
}

function sampleFunction<Key extends keyof analyticsEvent>(evtName: Key, evtData: analyticsEvent[Key]){
    console.log(evtName, evtData);
}

const getData = () =>
  Promise.resolve({
      key: "key",
      value: "value"
  });
 
// usage (1)
getData()
  .then(data => {
    const {key, value} = data;
    sampleFunction(<keyof analyticsEvent>key, <UploadMediaPayload><unknown>value);
  });

getData();

sampleFunction("Upload Media", {abc: "abc"});
let key, value;
sampleFunction(key, value);

Generated Code

import t from "ts-runtime/lib";
const UploadMediaPayload = t.type("UploadMediaPayload", t.object(t.property("abc", t.string())));
const analyticsEvent = t.type("analyticsEvent", t.object(t.property("pload Medi", t.ref(UploadMediaPayload))));
function sampleFunction(evtName, evtData) {
    const Key = t.typeParameter("Key", t.any());
    let _evtNameType = t.flowInto(Key);
    let _evtDataType = t.any();
    t.param("evtName", _evtNameType).assert(evtName);
    t.param("evtData", _evtDataType).assert(evtData);
    console.log(evtName, evtData);
}
t.annotate(sampleFunction, t.function(fn => {
    const Key = fn.typeParameter("Key", t.any());
    return [t.param("evtName", t.flowInto(Key)), t.param("evtData", t.any()), t.return(t.any())];
}));
const getData = t.annotate(() => {
    return Promise.resolve({
        key: "key",
        value: "value"
    });
}, t.function(t.return(t.any())));
// usage (1)
getData()
    .then(t.annotate((data) => {
    const { key, value } = data;
    sampleFunction(key, value);
}, t.function(t.param("data", t.any()), t.return(t.any()))));
getData();
sampleFunction("Upload Media", { abc: "abc" });
let key, value;
sampleFunction(key, value);

analyticsEvent is not referred in the generated code. What do I have to make it work ?

[fabiandev]

Types constructed with keyof are not implemented in ts-runtime at this point:

ts-runtime/src/factory.ts

Lines 135 to 144 in 963e9d8

	case ts.SyntaxKind.MappedType:
	// type Readonly<T> = {
	// readonly [P in keyof T]: T[P];
	// }
	case ts.SyntaxKind.IndexedAccessType:
	// function getProperty<T, K extends keyof T>(o: T, name: K): T[K] {
	// return o[name]; // o[name] is of type T[K]
	// }
	case ts.SyntaxKind.TypeOperator:
	// let a: keyof MyClass;

You should see warnings that reflections could not be found when generating the code. The runtime type will fall back to any in that case. See your example in the playground.

[anu1097]

Is there a feature statement written somewhere I can try to contribute.
Thanks for replying. I am looking for some solution for this problem checking out other libraries too.

[fabiandev]

There is no documentation around contributing, happy to answer questions though :)

However, please note that this package is a POC and not really intended to be used in production environments, mainly due to the impact on bundle size and execution time. Unfortunately I haven't had time to spend more time on the project to develop it further.

[anu1097]

Cool I'll check out your package to understand better. Then will ask further questions.