Bug in URI.isUri() that fails thing type comparison

[enagic]

• VSCode Version: 1.53.0
• OS Version: macOS 11.1

Steps to Reproduce:

1. Create custom URI class that implements the default URI
2. Pass in the custom URI into URI.isUri(myCustomUri) and it returns false

Background

This is a proposed fix for monaco-editor.

If a model is created using a custom URI, it will fail the URI.isUri() check because it "tries" to check thing against various possible types, but it will fail at fsPath.

class URI {
    static isUri(thing) {
        if (thing instanceof URI) {
            return true;
        }
        if (!thing) {
            return false;
        }
        return typeof thing.authority === 'string'
            && typeof thing.fragment === 'string'
            && typeof thing.path === 'string'
            && typeof thing.query === 'string'
            && typeof thing.scheme === 'string'
            && typeof thing.fsPath === 'function' // this guy right here should be 'string'
            && typeof thing.with === 'function'
            && typeof thing.toString === 'function';
    }
}

The side-effect is that markerService behaves a bit weird and shows markers for all resources, not just for a particular resource/URI.

Example:

class MyUri implements Uri {
  ...
  // rest of class to satisfy TS
  ...
}

const myUri = MyUri.parse('foo://example.com:8042/over/there');

// Note:
// - myUri is _not_ an instanceof Uri
// - typeof myUri.fsPath === 'string', not 'function'

const model = editor.createModel('', 'plaintext', myUri);
const { resource } = model;

// `resourceMarkers` ends up returning all markers of `markerService._data`,
// not just the resource's markers because `DataResourceMap.values()`
// fails the `URI.isUri()` check.
const resourceMarkers = markerService.read({ resource });

Does this issue occur when all extensions are disabled?: Yes

[jrieken]

Indeed. Nice find.