feat(android): polyfill applicationNameForUserAgent on Android (#707)

android/src/main/java/com/reactnativecommunity/webview/RNCWebViewManager.java

 
   protected RNCWebChromeClient mWebChromeClient = null;
   protected boolean mAllowsFullscreenVideo = false;
+  protected @Nullable String mUserAgent = null;
+  protected @Nullable String mUserAgentWithApplicationName = null;
 
   public RNCWebViewManager() {
     mWebViewConfig = new WebViewConfig() {
   @ReactProp(name = "userAgent")
   public void setUserAgent(WebView view, @Nullable String userAgent) {
     if (userAgent != null) {
-      // TODO(8496850): Fix incorrect behavior when property is unset (uA == null)
-      view.getSettings().setUserAgentString(userAgent);
+      mUserAgent = userAgent;
+    } else {
+      mUserAgent = null;
+    }
+    this.setUserAgentString(view);
+  }
+
+  @ReactProp(name = "applicationNameForUserAgent")
+  public void setApplicationNameForUserAgent(WebView view, @Nullable String applicationName) {
+    if(applicationName != null) {
+      if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) {
+        String defaultUserAgent = WebSettings.getDefaultUserAgent(view.getContext());
+        mUserAgentWithApplicationName = defaultUserAgent + " " + applicationName;
+      }
+    } else {
+      mUserAgentWithApplicationName = null;
+    }
+    this.setUserAgentString(view);
+  }
+
+  protected void setUserAgentString(WebView view) {
+    if(mUserAgent != null) {
+      view.getSettings().setUserAgentString(mUserAgent);
+    } else if(mUserAgentWithApplicationName != null) {
+      view.getSettings().setUserAgentString(mUserAgentWithApplicationName);
+    } else if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) {
+      // handle unsets of `userAgent` prop as long as device is >= API 17
+      view.getSettings().setUserAgentString(WebSettings.getDefaultUserAgent(view.getContext()));
     }
   }
 

docs/Reference.md

 
 ### `applicationNameForUserAgent`
 
-Append to the existing user-agent. Available on iOS WKWebView only. Setting `userAgent` will override this.
+Append to the existing user-agent. This will only work for iOS if you are using WKWebView, not UIWebView. Setting `userAgent` will override this.
 
 | Type   | Required | Platform      |
 | ------ | -------- | ------------- |
-| string | No       | iOS WKWebView |
+| string | No       | Android, iOS WKWebView |
+
+```jsx
+<WebView
+  source={{ uri: 'https://facebook.github.io/react-native' }}
+  applicationNameForUserAgent={"DemoApp/1.1.0"}
+/>
+// Resulting User-Agent will look like:
+// Mozilla/5.0 (Linux; Android 8.1.0; Android SDK built for x86 Build/OSM1.180201.021; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/61.0.3163.98 Mobile Safari/537.36 DemoApp/1.1.0
+// Mozilla/5.0 (iPhone; CPU iPhone OS 12_2 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Mobile/15E148 DemoApp/1.1.0
+```
 
 ### `allowsFullscreenVideo`
 

src/WebViewTypes.ts

   // eslint-disable-next-line @typescript-eslint/no-explicit-any
   source: any;
   userAgent?: string;
+  /**
+   * Append to the existing user-agent. Overriden if `userAgent` is set.
+   */
+  applicationNameForUserAgent?: string;
 }
 
 export interface AndroidNativeWebViewProps extends CommonNativeWebViewProps {
    */
   useSharedProcessPool?: boolean;
 
-  /**
-   * Append to the existing user-agent. Overriden if `userAgent` is set.
-   * @platform ios
-   */
-  applicationNameForUserAgent?: string;
-
   /**
    * The custom user agent string.
    */