[webview_flutter_wkwebview] `-[WKPreferences javaScriptEnabled]` is deprecated in iOS 14

[jmagman]

webview_flutter_wkwebview is using an API that was deprecated in iOS 14. Use an @availability check to use the non-deprecated property, and fall back to the old one on < 14.

  [[self preferencesForIdentifier:identifier] setJavaScriptEnabled:enabled.boolValue];

https://github.com/flutter/packages/blob/c90dd9834ebfd3d9b06f5f99dae1dd7652de6053/packages/webview_flutter/webview_flutter_wkwebview/ios/Classes/FWFPreferencesHostApi.m#L44

Deprecation says Use WKWebpagePreferences.allowsContentJavaScript to disable content JavaScript on a per-navigation basis. I don't think WKWebpagePreferences is currently created in the plugin.

FWFPreferencesHostApi.m:44:47: error: 'setJavaScriptEnabled:' is deprecated: first deprecated in iOS 14.0 - Use WKWebpagePreferences.allowsContentJavaScript to disable content JavaScript on a per-navigation basis [-Werror,-Wdeprecated-declarations]
  [[self preferencesForIdentifier:identifier] setJavaScriptEnabled:enabled.boolValue];
                                              ^
In module 'WebKit' imported from FWFPreferencesHostApi.h:6:
WKPreferences.h:92:28: note: property 'javaScriptEnabled' is declared deprecated here
@property (nonatomic) BOOL javaScriptEnabled API_DEPRECATED("Use WKWebpagePreferences.allowsContentJavaScript to disable content JavaScript on a per-navigation basis", macos(10.10, 11.0), ios(8.0, 14.0));

You can see this by running:

$ dart run script/tool/bin/flutter_plugin_tools.dart xcode-analyze "--ios-min-version=14.0" --ios

    args: ["xcode-analyze", "--ios", "--ios-min-version=14.0"]

https://github.com/flutter/packages/blob/c90dd9834ebfd3d9b06f5f99dae1dd7652de6053/.ci/targets/ios_platform_tests.yaml#L15

[stuartmorgan-g]

See discussion in #128714 about how we might go about addressing this in the current Dart/native mirroring structure.

[jmagman]

@bparrishMines @stuartmorgan Is there some way we can unblock this so we can increase the xcode-analyze minimum version? Should I exclude webview_flutter_wkwebview from that check?
flutter/packages#7431

[stuartmorgan-g]

We don't have to remove the whole plugin to unblock the check, we could just #pragma-suppress the specific warning if it's blocking us.

[jmagman]

Oh right... 🤦‍♀️