IOS Linker fixes inside Xamarin.Forms

[PureWeen]

Description of Change

• Removes the Preserve Attribute from the Xamarin.Forms SDK
• Removing the Preserve Attribute will have little to no effect until this change [prototype][linker] Do not mark NSObject subclasses from Xamarin.Forms.* assemblies xamarin-macios#7165 makes it into Xamarin.iOS SDK
• Ironically the RenderWith attribute causes all the renderers to not link out. I've ran this branch against the UI tests and all the UI Tests pass with this change. We'll want to test this change against the Forms Samples and really basic projects to make sure full linking doesn't break those projects.
• Add Linker Safe Attribute so that (Assembly-level attributed used to inform MonoTouch's linker that this assembly can be safely linked, regardless of the system linker settings.)

This won't really cause anything to get linked out of the forms platform dll but it sets up the library so that some day maybe it can. It also let's us start testing this against our UI tests and master nightlies to make sure everything still works

Issues Resolved

• Partially fixes ITMS-90809: Deprecated API Usage - Apple will stop accepting submissions of apps that use UIWebView APIs #7323

Platforms Affected

• iOS

Testing Procedure

• pull down the nuget, installed the Xamarin.ios sdk here [prototype][linker] Do not mark NSObject subclasses from Xamarin.Forms.* assemblies xamarin-macios#7165 turn on full linking, and make sure projects all still run

PR Checklist

• Targets the correct branch
• Tests are passing (or failures are unrelated)

[jfversluis]

Tried it, everything still seems to work. Yay!

[jfversluis]

Changes look good, build failed, looked like a fluke, I've triggered them again

[DanielGramsJTL]

Coming from #7323: Which Xamarin.Forms version will include this fix? Many thanks in advance!

[jfversluis]

@DanielGramsJTL I've update the issue

[zhsyedabbas]

Updated Xamarin Forms to v4.4.0.991265.
But when building the project the Xamarin.Forms.Platform.iOS.dll still references the UIWebView
I can see the dll was built and signed on dec10, 12:29 am.

Here's a screenshot from ILSpy

I can see the file has been updated here (https://github.com/xamarin/Xamarin.Forms/blob/master/Xamarin.Forms.Platform.iOS/Renderers/RefreshViewRenderer.cs), but isn't available in the build?.

Thanks

[PureWeen]

@zhsyedabbas this PR will show up in 4.5

I want to heavily emphasize that this PR will have zero effect on the warning about using UIWebView until changes are made to the Xamarin.iOS SDK

Which is another reason this PR is targeting master because it's currently irrelevant to have any of these code changes

[moustafashaban]

@PureWeen I am on 4.5.0.187-pre2
but I am still getting an email from Apple:

ITMS-90809: Deprecated API Usage - Apple will stop accepting submissions of apps that use UIWebView APIs

[DanielGramsJTL]

Hi there! I am bulding Xamarin.Forms 4.5.0.187-pre2 with Xamarin.iOS 13.10.0.17 and --optimize=experimental-xforms-product-type. The linker is set to SdkOnly.

When i launch the app, it crashes with an exception saying "Default constructor not found for type Xamarin.Forms.Platform.iOS.BoxRenderer". I am using BoxView, but only in xaml.

I saw in the code that the BoxRenderer does not have a default constructor with [Preserve(Conditional = true)].

Is there a way to tell the linker to keep the BoxRenderer? Many thanks in advance!

[chrisparkeronline]

I am still getting the email as well. It is not hindering them accepting my app at this point.

[DanielGramsJTL]

Hi there! I am bulding Xamarin.Forms 4.5.0.187-pre2 with Xamarin.iOS 13.10.0.17 and --optimize=experimental-xforms-product-type. The linker is set to SdkOnly.

When i launch the app, it crashes with an exception saying "Default constructor not found for type Xamarin.Forms.Platform.iOS.BoxRenderer". I am using BoxView, but only in xaml.

I saw in the code that the BoxRenderer does not have a default constructor with [Preserve(Conditional = true)].

Is there a way to tell the linker to keep the BoxRenderer? Many thanks in advance!

Just in case, anybody has the same problem: I solved it by adding
[assembly: Preserve(typeof(BoxRenderer), AllMembers = true)]
to AppDelegate.

Btw, after updating i do not get the warning mail from Apple anymore.