fix(firestore): honour Settings.ssl when building the API endpoint

packages/google_cloud_firestore/lib/src/firestore.dart

@@ -138,9 +138,12 @@ class Settings {
   /// set this to 'localhost:8080' (or your emulator's host:port).
   final String? host;
 
-  /// Whether to use SSL when connecting.
+  /// Whether to connect over HTTPS.
   ///
-  /// Defaults to true. Set to false when using the emulator.
+  /// Defaults to `true`. Set it to `false` alongside [host] to reach a plain
+  /// HTTP endpoint, such as a locally running emulator.
+  ///
+  /// Ignored when `FIRESTORE_EMULATOR_HOST` is set, which always uses HTTP.
   final bool ssl;
 
   /// The credential to use for authentication.

packages/google_cloud_firestore/lib/src/firestore_http_client.dart

@@ -172,8 +172,15 @@ class FirestoreHttpClient {
     return discovered != null ? (_cachedProjectId = discovered) : null;
   }
 
-  /// Gets the Firestore API host URL based on emulator configuration.
-  Uri get _firestoreApiHost {
+  /// Gets the Firestore API host URL.
+  ///
+  /// `FIRESTORE_EMULATOR_HOST` takes precedence over [Settings.host], since it
+  /// is the documented way to redirect the SDK at an emulator. Otherwise the
+  /// scheme follows [Settings.ssl], which lets a custom [Settings.host] be
+  /// reached over plain HTTP.
+  @internal
+  @visibleForTesting
+  Uri get firestoreApiHost {
     final emulatorHost = Environment.getFirestoreEmulatorHost(
       _settings.environmentOverride,
     );
@@ -182,7 +189,8 @@ class FirestoreHttpClient {
       return Uri.http(emulatorHost, '/');
     }
 
-    return Uri.https(_settings.host ?? 'firestore.googleapis.com', '/');
+    final host = _settings.host ?? 'firestore.googleapis.com';
+    return _settings.ssl ? Uri.https(host, '/') : Uri.http(host, '/');
   }
 
   /// Checks if the Firestore emulator is enabled via environment variable.
@@ -242,7 +250,7 @@ class FirestoreHttpClient {
     Future<R> Function(firestore_v1.Firestore api, String projectId) fn,
   ) => _run(
     (client, projectId) => fn(
-      firestore_v1.Firestore(client: client, endPoint: _firestoreApiHost),
+      firestore_v1.Firestore(client: client, endPoint: firestoreApiHost),
       projectId,
     ),
   );

packages/google_cloud_firestore/test/firestore_api_host_test.dart

@@ -0,0 +1,88 @@
+// Copyright 2026 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import 'package:google_cloud_firestore/google_cloud_firestore.dart';
+import 'package:google_cloud_firestore/src/environment.dart';
+import 'package:google_cloud_firestore/src/firestore_http_client.dart';
+import 'package:test/test.dart';
+
+/// Builds a client for host resolution only; no request is ever sent.
+///
+/// [Settings.environmentOverride] is always supplied so the ambient
+/// `FIRESTORE_EMULATOR_HOST` cannot leak into these expectations.
+FirestoreHttpClient _clientFor({
+  String? host,
+  bool ssl = true,
+  Map<String, String> environment = const {},
+}) {
+  return FirestoreHttpClient(
+    credential: Credential.fromApplicationDefaultCredentials(),
+    settings: Settings(
+      projectId: 'test-project',
+      host: host,
+      ssl: ssl,
+      environmentOverride: environment,
+    ),
+  );
+}
+
+void main() {
+  group('firestoreApiHost', () {
+    test('defaults to the production endpoint over HTTPS', () {
+      final uri = _clientFor().firestoreApiHost;
+
+      expect(uri.scheme, 'https');
+      expect(uri.host, 'firestore.googleapis.com');
+    });
+
+    test('uses HTTPS for a custom host when ssl is true', () {
+      final uri = _clientFor(host: 'example.test:8080').firestoreApiHost;
+
+      expect(uri.scheme, 'https');
+      expect(uri.host, 'example.test');
+      expect(uri.port, 8080);
+    });
+
+    test('uses HTTP for a custom host when ssl is false', () {
+      final uri = _clientFor(
+        host: '127.0.0.1:8080',
+        ssl: false,
+      ).firestoreApiHost;
+
+      expect(uri.scheme, 'http');
+      expect(uri.host, '127.0.0.1');
+      expect(uri.port, 8080);
+    });
+
+    test('uses HTTP against the default host when ssl is false', () {
+      final uri = _clientFor(ssl: false).firestoreApiHost;
+
+      expect(uri.scheme, 'http');
+      expect(uri.host, 'firestore.googleapis.com');
+    });
+
+    test('FIRESTORE_EMULATOR_HOST wins over host and ssl', () {
+      final uri = _clientFor(
+        host: 'example.test:9090',
+        environment: const {
+          Environment.firestoreEmulatorHost: '127.0.0.1:8080',
+        },
+      ).firestoreApiHost;
+
+      expect(uri.scheme, 'http');
+      expect(uri.host, '127.0.0.1');
+      expect(uri.port, 8080);
+    });
+  });
+}