TypeScript Error: TS2345 [ERROR]: Argument of type 'string | URL' is not assignable to parameter of type 'string'.

Issue

Setup:

• deno 1.2.0
• v8 8.5.216
• typescript 3.9.2
• opine main at 2295ba25be8320e0a3adfb5fe9d53477b02d1650

(Also checked with the latest v0.18.0)

Details

When running my program:

// mod.ts
import {opine} from "https://deno.land/x/opine@main/mod.ts";

const app = opine();

app.get('/', (req, res) => {
    res.send('Hello Deno Land 🦕');
});

app.listen(3000);
console.log("running at htpss://localhost:3000");

with the command: deno run mod.ts

I get the following error:

error: TS2345 [ERROR]: Argument of type 'string | URL' is not assignable to parameter of type 'string'.
  Type 'URL' is not assignable to type 'string'.
  return new URL(url).pathname
                 ~~~
    at https://deno.land/std@0.60.0/path/win32.ts:917:18

TS2345 [ERROR]: Argument of type 'string | URL' is not assignable to parameter of type 'string'.
  Type 'URL' is not assignable to type 'string'.
  return new URL(url).pathname;
                 ~~~
    at https://deno.land/std@0.60.0/path/posix.ts:438:18

TS2345 [ERROR]: Argument of type 'string | URL' is not assignable to parameter of type 'string'.
  Type 'URL' is not assignable to type 'string'.
  return new URL(url).pathname
                 ~~~
    at https://deno.land/std@0.58.0/path/win32.ts:917:18

TS2345 [ERROR]: Argument of type 'string | URL' is not assignable to parameter of type 'string'.
  Type 'URL' is not assignable to type 'string'.
  return new URL(url).pathname;
                 ~~~
    at https://deno.land/std@0.58.0/path/posix.ts:438:18

TS2345 [ERROR]: Argument of type 'ParsedURL' is not assignable to parameter of type 'string'.
    const loc = encodeUrl(new URL(originalUrl).toString());
                                  ~~~~~~~~~~~
    at https://deno.land/x/opine@main/src/middleware/serveStatic.ts:227:35

Found 5 errors.

I’ve traced the issue to these two lines:

https://github.com/asos-craigmorten/opine/blob/2295ba25be8320e0a3adfb5fe9d53477b02d1650/src/middleware/serveStatic.ts#L227

https://github.com/asos-craigmorten/opine/blob/2295ba25be8320e0a3adfb5fe9d53477b02d1650/src/utils/parseUrl.ts#L70

I believe this is an error in type and should be addressed. I cannot run my program at this time. Let me know if you agree this is the issue and I can try to implement a fix.

[KaKi87]

Hello, I’m experiencing this issue using Opine 0.25.0 on Deno 1.4.2 ? Thanks

[asos-craigmorten]

Thanks for raising this @srepollock!

Having followed the issue on GitHub and Discord, and reading the changelog I still managed to overlook this 🤦

Relevant issues / PRs:

• https://github.com/denoland/deno/pull/5521
• https://github.com/denoland/deno/pull/5564
• https://github.com/denoland/deno/pull/6653

It’s annoying that it deviates from what browsers / node allow, but the Deno team are aiming to write to WHATWG spec.

Should be simple enough to fix, we just need to cast to string as the URL constructor no longer accepts a URL as the first parameter.