fix!: Deprecate(/Remove) scrollView category extension on UIView

[dpogue]

Platforms affected

iOS

Motivation and Context

As mentioned in #1399, this API was added as a compatibility shim at the time we supported both UIWebView and WKWebView, when WKWebView did not expose a public scrollView property. That property was made available in iOS 8, and this extension now risks causing problems due to being applied globally to all UIView subclasses.

Closes #1399.

Description

Deprecate the category extension to expose a scrollView property on all UIView object instances, and remove it entirely from visibility to Swift.

Testing

• Existing tests pass.
• Tested against all core Apache plugins.
• Manually tested that this resolves the issue in Please remove org_apache_cordova_UIView_Extension because it isn't necessary since iOS 8.  #1399 where a Swift UIView subclass defines a scrollView property

Checklist

• I've run the tests to see all new and existing tests pass
• If this Pull Request resolves an issue, I linked to the issue in the text above (and used the correct keyword to close issues using keywords)

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.31%. Comparing base (3a426fd) to head (609170a).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1400   +/-   ##
=======================================
  Coverage   78.31%   78.31%           
=======================================
  Files          16       16           
  Lines        1826     1826           
=======================================
  Hits         1430     1430           
  Misses        396      396           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[dpogue]

This causes issues for the statusbar plugin which relies on this to access the scroll view without knowing the specific type of the web view implementation.

So putting this on hold for the moment.

[dpogue]

Status Bar plugin is fixed, but this API is used in a number of 3rd party plugins as well... I feel like our only option is going to be deprecation instead of removal (which doesn't actually address the issue that was raised about this) 😞

[jcesarmobile]

I don’t see what’s the problem with introducing a breaking change.
Changing the template to swift is also breaking to some plugins and it’s merged.

[dpogue]

The best short term solution seems to be the following:

• Remove the extension from being visible to Swift code. This solves the problem raised in Please remove org_apache_cordova_UIView_Extension because it isn't necessary since iOS 8.  #1399
  • This breaks any Swift plugins that use this API, but there seem to only be a few and they are not maintained and don't have high download counts
• Mark the Objective C method as deprecated so that existing 3rd party plugins that call it will see warnings
• Prepare to remove this entirely in Cordova iOS 9 as per the deprecation

Re: breaking plugins due to moving the template to Swift, we tested and added compatible headers so that existing plugins should continue working even with the new template. It's possible we missed some edge cases, but we're definitely trying to keep existing plugins working (with lots of noisy deprecation warnings)

[erisu]

LGTM

I tested and confirmed that Obj-C based plugins with self.webView.scrollView will continue to work as expected and displays the deprecation warning.

Swift based plugins will need to update to continue working, which is expected.

var webViewScrollView: UIScrollView? {
    let scrollViewSelector = NSSelectorFromString("scrollView")
    
    if webView.responds(to: scrollViewSelector) {
        return webView.perform(scrollViewSelector)?.takeUnretainedValue() as? UIScrollView
    }
    
    return nil
}

[dpogue]

The equivalent Objective C code would be (copied from the statusbar plugin):

- (UIScrollView *)webViewScrollView
{
    SEL scrollViewSelector = NSSelectorFromString(@"scrollView");

    if ([self.webView respondsToSelector:scrollViewSelector]) {
        return ((id (*)(id, SEL))objc_msgSend)(self.webView, scrollViewSelector);
    }

    return nil;
}