Could not detect any platforms from 'XCODE10' / 'XCODE11'

Description

Starting v4.5.0, Xamarin.Forms added 2 new folders in their NuGet packages, under the folder build, named XCODE10 and XCODE11.

When installing this package with Paket, the following warnings appear:

Xamarin.Forms 4.5.0.495 unzipped to /Users/timothelariviere/Git/GitHub/Fabulous/packages/androidapp/Xamarin.Forms
Could not detect any platforms from 'XCODE10' in '/Users/timothelariviere/Git/GitHub/Fabulous/packages/androidapp/Xamarin.Forms/build/XCODE10/Xamarin.Forms.Platform.iOS.dll', please tell the package authors
Could not detect any platforms from 'XCODE10' in '/Users/timothelariviere/Git/GitHub/Fabulous/packages/androidapp/Xamarin.Forms/build/XCODE10/Xamarin.Forms.Platform.macOS.dll', please tell the package authors
Could not detect any platforms from 'XCODE10' in '/Users/timothelariviere/Git/GitHub/Fabulous/packages/androidapp/Xamarin.Forms/build/XCODE10/Xamarin.Forms.Platform.iOS.pdb', please tell the package authors
Could not detect any platforms from 'XCODE11' in '/Users/timothelariviere/Git/GitHub/Fabulous/packages/androidapp/Xamarin.Forms/build/XCODE11/Xamarin.Forms.Platform.iOS.dll', please tell the package authors
Could not detect any platforms from 'XCODE11' in '/Users/timothelariviere/Git/GitHub/Fabulous/packages/androidapp/Xamarin.Forms/build/XCODE11/Xamarin.Forms.Platform.macOS.dll', please tell the package authors
Could not detect any platforms from 'XCODE11' in '/Users/timothelariviere/Git/GitHub/Fabulous/packages/androidapp/Xamarin.Forms/build/XCODE11/Xamarin.Forms.Platform.iOS.pdb', please tell the package authors
Could not detect any platforms from 'XCODE10' in '/Users/timothelariviere/Git/GitHub/Fabulous/packages/androidapp/Xamarin.Forms/build/XCODE10/Xamarin.Forms.Platform.iOS.dll', please tell the package authors
Could not detect any platforms from 'XCODE10' in '/Users/timothelariviere/Git/GitHub/Fabulous/packages/androidapp/Xamarin.Forms/build/XCODE10/Xamarin.Forms.Platform.macOS.dll', please tell the package authors
Could not detect any platforms from 'XCODE10' in '/Users/timothelariviere/Git/GitHub/Fabulous/packages/androidapp/Xamarin.Forms/build/XCODE10/Xamarin.Forms.Platform.iOS.pdb', please tell the package authors
Could not detect any platforms from 'XCODE11' in '/Users/timothelariviere/Git/GitHub/Fabulous/packages/androidapp/Xamarin.Forms/build/XCODE11/Xamarin.Forms.Platform.iOS.dll', please tell the package authors
Could not detect any platforms from 'XCODE11' in '/Users/timothelariviere/Git/GitHub/Fabulous/packages/androidapp/Xamarin.Forms/build/XCODE11/Xamarin.Forms.Platform.macOS.dll', please tell the package authors
Could not detect any platforms from 'XCODE11' in '/Users/timothelariviere/Git/GitHub/Fabulous/packages/androidapp/Xamarin.Forms/build/XCODE11/Xamarin.Forms.Platform.iOS.pdb', please tell the package authors

Repro steps

1. Add a reference to Xamarin.Forms 4.5.0.495

nuget Xamarin.Forms 4.5.0.495

1. Run paket install

2. Warnings about XCODE10 and XCODE11 should appear (see example above)

Expected behavior

I’m not exactly sure what these warnings mean, but I would expect no warning at all.

Actual behavior

Warnings are appearing.

Known workarounds

No workaround known.

[vshapenko]

@forki , if we look into the srtucture of directory build, we will see the following:

• Xamarin.Forms.props -Xamarin.Forms.targets -Xamarin.Forms.Default.props -Xamarin.Forms.Default.targets MonoAndroid10
  net46
  netstandard2.0
  XCODE10
  XCODE11\

We need to put <packagename>.props at the beginning of project file, put <packagename>.targets to the end of project file. But before we do this, we should scan folders for props and targets for tfm related files, i.e. there may be <tfm>/<packagename>.props, which we should take instead root props file. Important: Only props and targets should be taken, neither dll or other one. Name of file should match the package name. P.,S. There can be a buildMultitarget directory in package :

MSBuild .props and .targets files for cross-framework targeting can be placed in the \buildMultiTargeting folder. During package installation, NuGet adds the corresponding <Import> elements to the project file with the condition, that the target framework is not set (the MSBuild property $(TargetFramework) must be empty).

P.S.S https://docs.microsoft.com/en-us/nuget/create-packages/creating-a-package#from-a-convention-based-working-directory is more detailed and full information about possible folder names and their behaviour.

[TimLariviere]

@forki I confirm that the warnings disappeared with 6.0.0-alpha027.

For the props/targets, Xamarin.Forms requires to import both build\Xamarin.Forms.props and build\Xamarin.Forms.targets (inside Xamarin.Forms NuGet package) in order to compile. It’s these files that import the dlls from the XCODE10/XCODE11 folders.

Note that build\Xamarin.Forms.DefaultItems.props is imported by build\Xamarin.Forms.props, same with targets. So I guess a props/targets file inside the build folder with the same name as the package is meant to be imported by default?