mongodb-connection-string-url: 'get protocol' called on an object that is not a valid instance of URL (regression on main, blocks mongodb connect) #11139

On current main, constructing a mongodb-connection-string-url ConnectionString throws whatwg-url's brand-check error. That makes new MongoClient(uri) fail before any socket I/O, so mongodb 7.5.0 can no longer connect. This is a regression: on d8f24f1 the same fixture, with #11113 (#11043) and #11130 (#11111/#11106) applied, connected and completed ping. It now fails at startup, with or without #11113 applied.

Repro

package.json:

{
  "dependencies": { "mongodb": "7.5.0" },
  "perry": {
    "compilePackages": ["mongodb", "bson", "mongodb-connection-string-url", "@mongodb-js/saslprep", "whatwg-url", "sparse-bitfield", "memory-pager", "tr46", "webidl-conversions", "punycode"],
    "allow": { "compilePackages": ["mongodb", "bson", "mongodb-connection-string-url", "@mongodb-js/saslprep", "whatwg-url", "sparse-bitfield", "memory-pager", "tr46", "webidl-conversions", "punycode"] }
  }
}

url.ts:

const { URL: WURL } = require("whatwg-url");
function tryIt(label: string, f: () => unknown) {
  try { console.log(label, f()); } catch (e: any) { console.log(label, "THROWS", e.message); }
}
tryIt("direct", () => new WURL("mongodb://h/db").protocol);
class Sub extends WURL {}
tryIt("subclass", () => new Sub("mongodb://h/db").protocol);
const CS = require("mongodb-connection-string-url").default;
tryIt("ConnectionString", () => new CS("mongodb://127.0.0.1:27243/db").protocol);

Node 26.5.1 (whatwg-url 14.2.0, mongodb-connection-string-url 7.0.2):

direct mongodb:
subclass mongodb:
ConnectionString mongodb:

Perry main 784ed8e (v0.5.1649) + #11130, perry-dev, Linux x64:

direct mongodb:
subclass mongodb:
ConnectionString THROWS 'get protocol' called on an object that is not a valid instance of URL.

The error text comes from whatwg-url's generated URL.js wrapper (exports.is(esValue) fails). The ConnectionString instance is not seen as a URL wrapper, so the object that super(...) returned presumably lost its implSymbol own property, or its prototype link.

What does not reproduce it

All of these pass on the same build, written as user TypeScript against the compiled whatwg-url:

• plain URL
• class Sub extends URL {}
• class Sub2 extends Sub { constructor(u) { super(u) } }
• ConnectionString's two distinctive traits, alone and together: a class field _hosts;, and super(...) called inside try { … } catch

So the trigger appears to need the package's own compiled-JS class, inside its CommonJS module wrapper: class URLWithoutHost extends whatwg_url_1.URL {} and then class ConnectionString extends URLWithoutHost { _hosts; constructor(uri, options = {}) { …; try { super(…) } catch (err) { … } } } (lib/index.js, lines 73–130).

Range

Good: d8f24f1 + #11105 + #11113 + #11130; the fixture connected and ran ping. Bad: 784ed8e (merge trains 264–266). Not bisected.