Exclude iOS Safari < 10.0 and Android < 4.4 when checking isAvailable() to enable persistence (#1703)

Author: Brian Chen

packages/firestore/src/local/simple_db.ts

@@ -162,10 +162,20 @@ export class SimpleDb {
     // ua = 'Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML,
     // like Gecko) Chrome/39.0.2171.71 Safari/537.36 Edge/12.0';
 
+    // iOS Safari: Disable for users running iOS version < 10.
+    const iOSVersion = SimpleDb.getIOSVersion(ua);
+    const isUnsupportedIOS = 0 < iOSVersion && iOSVersion < 10;
+
+    // Android browser: Disable for userse running version < 4.5.
+    const androidVersion = SimpleDb.getAndroidVersion(ua);
+    const isUnsupportedAndroid = 0 < androidVersion && androidVersion < 4.5;
+
     if (
       ua.indexOf('MSIE ') > 0 ||
       ua.indexOf('Trident/') > 0 ||
-      ua.indexOf('Edge/') > 0
+      ua.indexOf('Edge/') > 0 ||
+      isUnsupportedIOS ||
+      isUnsupportedAndroid
     ) {
       return false;
     } else {
@@ -181,6 +191,27 @@ export class SimpleDb {
     return txn.store<KeyType, ValueType>(store);
   }
 
+  // visible for testing
+  /** Parse User Agent to determine iOS version. Returns -1 if not found. */
+  static getIOSVersion(ua: string): number {
+    const iOSVersionRegex = ua.match(/i(?:phone|pad|pod) os ([\d_]+)/i);
+    const version = iOSVersionRegex ? iOSVersionRegex[1].split('_')[0] : '-1';
+    return Number(version);
+  }
+
+  // visible for testing
+  /** Parse User Agent to determine Android version. Returns -1 if not found. */
+  static getAndroidVersion(ua: string): number {
+    const androidVersionRegex = ua.match(/Android ([\d.]+)/i);
+    const version = androidVersionRegex
+      ? androidVersionRegex[1]
+          .split('.')
+          .slice(0, 2)
+          .join('.')
+      : '-1';
+    return Number(version);
+  }
+
   constructor(private db: IDBDatabase) {}
 
   runTransaction<T>(

packages/firestore/test/unit/local/simple_db.test.ts

@@ -121,6 +121,22 @@ describe('SimpleDb', () => {
 
   after(() => SimpleDb.delete(dbName));
 
+  it('regex test', () => {
+    const iPhoneSafariAgent =
+      'Mozilla/5.0 (iPhone; CPU iPhone OS 10_14_4 like Mac OS X)' +
+      ' AppleWebKit/600.1.4 (KHTML, like Gecko) Version/8.0 Mobile/12B411' +
+      ' Safari/600.1.4';
+    const iPadSafariAgent =
+      'Mozilla/5.0 (iPad; CPU iPad OS 9_0 like Mac OS X) AppleWebKit/601.1.46 (KHTML, like Gecko)' +
+      ' Version/9.0 Mobile/13A344 Safari/601';
+    const androidAgent =
+      'Mozilla/5.0 (Linux; U; Android 2.2.1; fr-fr; Desire HD Build/FRG83D)' +
+      ' AppleWebKit/533.1 (KHTML, like Gecko) Version/4.0 Mobile Safari/533.1';
+    expect(SimpleDb.getIOSVersion(iPhoneSafariAgent)).to.equal(10);
+    expect(SimpleDb.getIOSVersion(iPadSafariAgent)).to.equal(9);
+    expect(SimpleDb.getAndroidVersion(androidAgent)).to.equal(2.2);
+  });
+
   it('can get', async () => {
     await runTransaction(store => {
       return store