Firestore: Enable auto-detection of long-polling networking mode

.changeset/long-lemons-change.md

@@ -0,0 +1,6 @@
+---
+'@firebase/firestore': minor
+'firebase': minor
+---
+
+Enabled long-polling networking mode auto detection by default. It can be explicitly disabled by setting `FirestoreSettings.experimentalForceLongPolling` to `false`.

docs-devsite/firestore_.firestoresettings.md

@@ -23,7 +23,7 @@ export declare interface FirestoreSettings
 |  Property | Type | Description |
 |  --- | --- | --- |
 |  [cacheSizeBytes](./firestore_.firestoresettings.md#firestoresettingscachesizebytes) | number | NOTE: This field will be deprecated in a future major release. Use <code>cache</code> field instead to specify cache size, and other cache configurations.<!-- -->An approximate cache size threshold for the on-disk data. If the cache grows beyond this size, Firestore will start removing data that hasn't been recently used. The size is not a guarantee that the cache will stay below that size, only that if the cache exceeds the given size, cleanup will be attempted.<!-- -->The default value is 40 MB. The threshold must be set to at least 1 MB, and can be set to <code>CACHE_SIZE_UNLIMITED</code> to disable garbage collection. |
-|  [experimentalAutoDetectLongPolling](./firestore_.firestoresettings.md#firestoresettingsexperimentalautodetectlongpolling) | boolean | Configures the SDK's underlying transport (WebChannel) to automatically detect if long-polling should be used. This is very similar to <code>experimentalForceLongPolling</code>, but only uses long-polling if required.<!-- -->This setting will likely be enabled by default in future releases and cannot be combined with <code>experimentalForceLongPolling</code>. |
+|  [experimentalAutoDetectLongPolling](./firestore_.firestoresettings.md#firestoresettingsexperimentalautodetectlongpolling) | boolean | Configures the SDK's underlying transport (WebChannel) to automatically detect if long-polling should be used. This is very similar to <code>experimentalForceLongPolling</code>, but only uses long-polling if required.<!-- -->After having had a default value of <code>false</code> since its inception in 2019, the default value of this setting was changed in mid-2023 to <code>true</code>. That is, auto-detection of long polling is now enabled by default. To disable it, set this setting to <code>false</code>, and please open a GitHub issue to share the problems that motivated you disabling long-polling auto-detection. |
 |  [experimentalForceLongPolling](./firestore_.firestoresettings.md#firestoresettingsexperimentalforcelongpolling) | boolean | Forces the SDK’s underlying network transport (WebChannel) to use long-polling. Each response from the backend will be closed immediately after the backend sends data (by default responses are kept open in case the backend has more data to send). This avoids incompatibility issues with certain proxies, antivirus software, etc. that incorrectly buffer traffic indefinitely. Use of this option will cause some performance degradation though.<!-- -->This setting cannot be used with <code>experimentalAutoDetectLongPolling</code> and may be removed in a future release. If you find yourself using it to work around a specific network reliability issue, please tell us about it in https://github.com/firebase/firebase-js-sdk/issues/1674. |
 |  [host](./firestore_.firestoresettings.md#firestoresettingshost) | string | The hostname to connect to. |
 |  [ignoreUndefinedProperties](./firestore_.firestoresettings.md#firestoresettingsignoreundefinedproperties) | boolean | Whether to skip nested properties that are set to <code>undefined</code> during object serialization. If set to <code>true</code>, these properties are skipped and not written to Firestore. If set to <code>false</code> or omitted, the SDK throws an exception when it encounters properties of type <code>undefined</code>. |
@@ -48,7 +48,7 @@ cacheSizeBytes?: number;
 
 Configures the SDK's underlying transport (WebChannel) to automatically detect if long-polling should be used. This is very similar to `experimentalForceLongPolling`<!-- -->, but only uses long-polling if required.
 
-This setting will likely be enabled by default in future releases and cannot be combined with `experimentalForceLongPolling`<!-- -->.
+After having had a default value of `false` since its inception in 2019, the default value of this setting was changed in mid-2023 to `true`<!-- -->. That is, auto-detection of long polling is now enabled by default. To disable it, set this setting to `false`<!-- -->, and please open a GitHub issue to share the problems that motivated you disabling long-polling auto-detection.
 
 <b>Signature:</b>
 

packages/firestore/src/api/settings.ts

@@ -88,8 +88,11 @@ export interface FirestoreSettings extends LiteSettings {
    * detect if long-polling should be used. This is very similar to
    * `experimentalForceLongPolling`, but only uses long-polling if required.
    *
-   * This setting will likely be enabled by default in future releases and
-   * cannot be combined with `experimentalForceLongPolling`.
+   * After having had a default value of `false` since its inception in 2019,
+   * the default value of this setting was changed in mid-2023 to `true`. That
+   * is, auto-detection of long polling is now enabled by default. To disable
+   * it, set this setting to `false`, and please open a GitHub issue to share
+   * the problems that motivated you disabling long-polling auto-detection.
    */
   experimentalAutoDetectLongPolling?: boolean;
 }

packages/firestore/src/lite-api/settings.ts

@@ -29,7 +29,7 @@ import { validateIsNotUsedTogether } from '../util/input_validation';
 export const DEFAULT_HOST = 'firestore.googleapis.com';
 export const DEFAULT_SSL = true;
 
-const DEFAULT_AUTO_DETECT_LONG_POLLING = false;
+const DEFAULT_AUTO_DETECT_LONG_POLLING = true;
 
 /**
  * Specifies custom configurations for your Cloud Firestore instance.

packages/firestore/test/unit/api/database.test.ts

@@ -279,10 +279,10 @@ describe('Settings', () => {
     );
   });
 
-  it('long polling should be disabled by default', () => {
+  it('long polling should be in auto-detect mode by default', () => {
     // Use a new instance of Firestore in order to configure settings.
     const db = newTestFirestore();
-    expect(db._getSettings().experimentalAutoDetectLongPolling).to.be.false;
+    expect(db._getSettings().experimentalAutoDetectLongPolling).to.be.true;
     expect(db._getSettings().experimentalForceLongPolling).to.be.false;
   });
 
@@ -306,13 +306,13 @@ describe('Settings', () => {
     expect(db._getSettings().experimentalForceLongPolling).to.be.false;
   });
 
-  it('long polling should be disabled if force=false', () => {
+  it('long polling should be in auto-detect mode if force=false', () => {
     // Use a new instance of Firestore in order to configure settings.
     const db = newTestFirestore();
     db._setSettings({
       experimentalForceLongPolling: false
     });
-    expect(db._getSettings().experimentalAutoDetectLongPolling).to.be.false;
+    expect(db._getSettings().experimentalAutoDetectLongPolling).to.be.true;
     expect(db._getSettings().experimentalForceLongPolling).to.be.false;
   });