Prevented hostname from being changed when using BrowserPollConnection w/ emulator

.changeset/fresh-experts-mix.md

@@ -0,0 +1,6 @@
+---
+"@firebase/database-compat": patch
+"@firebase/database": patch
+---
+
+Fixed issue where hostname set by `connectDatabaseEmulator` was being overridden by longpolling response

packages/database-compat/test/database.test.ts

@@ -272,18 +272,26 @@ describe('Database Tests', () => {
   });
 
   it('refFromURL() validates argument', () => {
+    // TODO: Remove all any references
     const db = (firebase as any).database();
     expect(() => {
       const ref = (db as any).refFromURL();
     }).to.throw(/Expects at least 1/);
   });
 
   it('can call useEmulator before use', () => {
-    const db = (firebase as any).database();
+    const db = firebase.database();
     db.useEmulator('localhost', 1234);
+    // Cast as any as _delegate isn't a public property
+    expect((db as any)._delegate._repo.repoInfo_.isUsingEmulator).to.be.true;
     expect(db.ref().toString()).to.equal('http://localhost:1234/');
   });
 
+  it('initializes usingEmulator to false before use', () => {
+    const db = firebase.database();
+    expect((db as any)._delegate._repo.repoInfo_.isUsingEmulator).to.be.false;
+  });
+
   it('cannot call useEmulator after use', () => {
     const db = (firebase as any).database();
 

packages/database/src/api/Database.ts

@@ -95,7 +95,8 @@ function repoManagerApplyEmulatorSettings(
     repo.repoInfo_.webSocketOnly,
     repo.repoInfo_.nodeAdmin,
     repo.repoInfo_.persistenceKey,
-    repo.repoInfo_.includeNamespaceInQueryParams
+    repo.repoInfo_.includeNamespaceInQueryParams,
+    /*isUsingEmulator=*/ true
   );
 
   if (tokenProvider) {

packages/database/src/core/RepoInfo.ts

@@ -45,7 +45,8 @@ export class RepoInfo {
     public readonly webSocketOnly: boolean,
     public readonly nodeAdmin: boolean = false,
     public readonly persistenceKey: string = '',
-    public readonly includeNamespaceInQueryParams: boolean = false
+    public readonly includeNamespaceInQueryParams: boolean = false,
+    public readonly isUsingEmulator: boolean = false
   ) {
     this._host = host.toLowerCase();
     this._domain = this._host.substr(this._host.indexOf('.') + 1);

packages/database/src/realtime/Connection.ts

@@ -337,14 +337,19 @@ export class Connection {
     if (MESSAGE_DATA in controlData) {
       const payload = controlData[MESSAGE_DATA];
       if (cmd === SERVER_HELLO) {
-        this.onHandshake_(
-          payload as {
+        const handshakePayload = {
+          ...(payload as {
             ts: number;
             v: string;
             h: string;
             s: string;
-          }
-        );
+          })
+        };
+        if (this.repoInfo_.isUsingEmulator) {
+          // Upon connecting, the emulator will pass the hostname that it's aware of, but we prefer the user's set hostname via `connectDatabaseEmulator` over what the emulator passes.
+          handshakePayload.h = this.repoInfo_.host;
+        }
+        this.onHandshake_(handshakePayload);
       } else if (cmd === END_TRANSMISSION) {
         this.log_('recvd end transmission on primary');
         this.rx_ = this.secondaryConn_;