feat(devtools-connect): make dns lookup configurable COMPASS-9793 (#602)

Author: nbbeeken

packages/devtools-connect/.depcheckrc

@@ -8,5 +8,6 @@ ignores:
  # this is explicitly called as a dependency to make sure that is bootstrapped
  # before mongodb-runner, since it is required via mongodb
  - '@mongodb-js/saslprep'
+ - 'ts-node' # used by mocha
 ignore-patterns:
  - 'dist'

packages/devtools-connect/package.json

@@ -36,7 +36,7 @@
     "depcheck": "depcheck",
     "check": "npm run typecheck && npm run lint && npm run depcheck",
     "check-ci": "npm run check",
-    "testonly": "nyc mocha --colors -r ts-node/register src/**/*.spec.ts",
+    "testonly": "nyc mocha --colors --register ts-node/register src/**/*.spec.ts",
     "test": "npm run lint && npm run compile && npm run testonly",
     "test-cov": "nyc -x \"**/*.spec.*\" --reporter=lcov --reporter=text --reporter=html npm run test",
     "test-watch": "npm run test -- --watch",

packages/devtools-connect/src/connect.spec.ts

@@ -412,6 +412,30 @@ describe('devtools connect', function () {
       expect(result.client).to.equal(mClient);
     });
 
+    it('allows lookup to be configured', async function () {
+      const uri = 'localhost:27017';
+      const mClient = stubConstructor(FakeMongoClient);
+      const mClientType = sinon.stub().returns(mClient);
+      mClient.connect.onFirstCall().resolves(mClient);
+      const lookupSpy = sinon.spy();
+      await connectMongoClient(
+        uri,
+        { ...defaultOpts, useSystemCA: false, lookup: lookupSpy },
+        bus,
+        mClientType as any,
+      );
+
+      // get options passed to mongo client
+      const finalClientOptions = mClientType.getCalls()[0].args[1];
+      expect(finalClientOptions.lookup).to.not.equal(lookupSpy); // lookup is always wrapped
+      finalClientOptions.lookup('localhost', 27017, () => {}); // invoke it the way it would be by net/tls
+      expect(lookupSpy.getCalls()).to.have.lengthOf(1); // verify our input lookup was called instead of the dns package
+      expect(lookupSpy.getCalls()[0].args[1]).to.have.property(
+        'verbatim',
+        false,
+      ); // but we still always set verbatim to false
+    });
+
     describe('retryable TLS errors', function () {
       it('retries TLS errors without system CA integration enabled -- MongoClient error', async function () {
         const uri = 'localhost:27017';

packages/devtools-connect/src/connect.ts

@@ -588,10 +588,15 @@ async function connectMongoClientImpl({
       ca ? { ca } : {},
     );
 
+    const customLookup = mongoClientOptions.lookup;
     // Adopt dns result order changes with Node v18 that affected the VSCode extension VSCODE-458.
     // Refs https://github.com/microsoft/vscode/issues/189805
     mongoClientOptions.lookup = (hostname, options, callback) => {
-      return dns.lookup(hostname, { verbatim: false, ...options }, callback);
+      return (customLookup ?? dns.lookup)(
+        hostname,
+        { verbatim: false, ...options },
+        callback,
+      );
     };
 
     delete (mongoClientOptions as any).useSystemCA; // can be removed once no product uses this anymore