$(DefineConstants) is based off of $(TargetFramework) and may be inconsistent with actual referenced assemblies

[jonpryor]

Apple platform

iOS

Framework version

net9.0-*

Affected platform version

.NET 10

Description

The set of #defines present within $(DefineConstants) is consistent with $(TargetFramework), and may be inconsistent with the actual assembly used to build the project.

Steps to Reproduce

Context: dfb9a22

Commit dfb9a22 updated WKUIDelegate.RunJavaScriptTextInputPanel() to be obsolete. However, this obsoletion was only visible on iOS 26.0 assemblies, not on iOS 18.0 assemblies; in iOS 18.0, this method is not obsolete.

When building an "unversioned" target framework, the latest reference assembly is used, which may differ from what was actually intended.

Create a new ioslib project:

dotnet new ioslib -n myioslib

Update $(TargetFramework)=net9.0-ios18.0 ("fixed"):

diff --git a/myioslib.csproj b/myioslib.csproj
index c62adc2..0853df5 100644
--- a/myioslib.csproj
+++ b/myioslib.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFramework>net10.0-ios</TargetFramework>
+    <TargetFramework>net9.0-ios18.0</TargetFramework>
     <Nullable>enable</Nullable>
     <ImplicitUsings>true</ImplicitUsings>

Add the following MyWKUIDelegate type to the project:

diff --git a/Class1.cs b/Class1.cs
index 648114f..5f8dbae 100644
--- a/Class1.cs
+++ b/Class1.cs
@@ -1,4 +1,14 @@
+using WebKit;
+
 namespace myioslib;
 
-public class Class1 {
+public class Class1
+{
+}
+
+class MyWKUIDelegate : WKUIDelegate
+{
+    public override void RunJavaScriptTextInputPanel(WKWebView webView, string prompt, string? defaultText, WKFrameInfo frame, Action<string> completionHandler)
+    {
+    }
 }

Build the project:

% dotnet build -bl

No warnings are generated.

Update $(TargetFramework)=net9.0-ios ("floating"):

diff --git a/myioslib.csproj b/myioslib.csproj
index c62adc2..1e1a6ca 100644
--- a/myioslib.csproj
+++ b/myioslib.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFramework>net10.0-ios</TargetFramework>
+    <TargetFramework>net9.0-ios</TargetFramework>
     <Nullable>enable</Nullable>
     <ImplicitUsings>true</ImplicitUsings>

Build the project:

% dotnet build -bl
Restore complete (0.7s)
    info NETSDK1057: You are using a preview version of .NET. See: https://aka.ms/dotnet-support-policy
  myioslib net9.0-ios succeeded with 1 warning(s) (1.5s) → bin/Debug/net9.0-ios/myioslib.dll
    …/myioslib/Class1.cs(11,26): warning CS0672: Member 'MyWKUIDelegate.RunJavaScriptTextInputPanel(WKWebView, string, string?, WKFrameInfo, Action<string>)' overrides obsolete member 'WKUIDelegate.RunJavaScriptTextInputPanel(WKWebView, string, string?, WKFrameInfo, Action<string>)'. Add the Obsolete attribute to 'MyWKUIDelegate.RunJavaScriptTextInputPanel(WKWebView, string, string?, WKFrameInfo, Action<string>)'.

Build succeeded with 1 warning(s) in 2.5s

Supposedly, net9.0-ios should be an alias for net9.0-ios18.0, but it isn't: net9.0-ios18.0 builds with no warnings, while net9.0-ios emits a warning!

Why?

If you look at the Diagnostic output from the builds, and look at the Task "Csc" section for Task Parameter: References=, the net9.0-ios18.0 build has:

$HOME/.nuget/packages/microsoft.ios.ref.net9.0_18.0/18.0.9617/ref/net9.0/Microsoft.iOS.dll
        AssemblyName=Microsoft.iOS
        AssemblyVersion=18.0.0.0
        CopyLocal=false
        ExternallyResolved=true
        FileVersion=0.0.0.0
        FrameworkReferenceName=Microsoft.iOS
        FrameworkReferenceVersion=18.0.9617
        FusionName=Microsoft.iOS, Version=18.0.0.0, Culture=neutral, PublicKeyToken=84e04ff9cfb79065
        NuGetPackageId=Microsoft.iOS.Ref.net9.0_18.0
        NuGetPackageVersion=18.0.9617
        OriginalItemSpec=$HOME/.nuget/packages/microsoft.ios.ref.net9.0_18.0/18.0.9617/ref/net9.0/Microsoft.iOS.dll
        Private=false
        PublicKeyToken=84e04ff9cfb79065
        ReferenceAssembly=$HOME/.nuget/packages/microsoft.ios.ref.net9.0_18.0/18.0.9617/ref/net9.0/Microsoft.iOS.dll
        ReferenceSourceTarget=ResolveAssemblyReference
        ResolvedFrom={RawFileName}
        Version=

While the net9.0-ios (floating) build has:

$HOME/.nuget/packages/microsoft.ios.ref.net9.0_26.0/26.0.9752/ref/net9.0/Microsoft.iOS.dll
        AssemblyName=Microsoft.iOS
        AssemblyVersion=26.0.0.0
        CopyLocal=false
        ExternallyResolved=true
        FileVersion=0.0.0.0
        FrameworkReferenceName=Microsoft.iOS
        FrameworkReferenceVersion=26.0.9752
        FusionName=Microsoft.iOS, Version=26.0.0.0, Culture=neutral, PublicKeyToken=84e04ff9cfb79065
        NuGetPackageId=Microsoft.iOS.Ref.net9.0_26.0
        NuGetPackageVersion=26.0.9752
        OriginalItemSpec=$HOME/.nuget/packages/microsoft.ios.ref.net9.0_26.0/26.0.9752/ref/net9.0/Microsoft.iOS.dll
        Private=false
        PublicKeyToken=84e04ff9cfb79065
        ReferenceAssembly=$HOME/.nuget/packages/microsoft.ios.ref.net9.0_26.0/26.0.9752/ref/net9.0/Microsoft.iOS.dll
        ReferenceSourceTarget=ResolveAssemblyReference
        ResolvedFrom={RawFileName}
        Version=

In particular, note that %(AssemblyVersion) differs: net9.0-ios18.0 has %(AssemblyVersion)=18.0.0.0, while net9.0-ios has %(AssemblyVersion)=26.0.0.0.

Even though net9.0-ios is supposed to be an alias for net9.0-ios18.0 for library projects, it is using the latest assembly!

Furthermore, $(DefineConstants) for both builds is the same!

Task Parameter:DefineConstants=IOS;MOBILE;UNIFIED;TRACE;DEBUG;NET;NET9_0;NETCOREAPP;IOS;IOS18_0;NET5_0_OR_GREATER;NET6_0_OR_GREATER;NET7_0_OR_GREATER;NET8_0_OR_GREATER;NET9_0_OR_GREATER;NETCOREAPP1_0_OR_GREATER;NETCOREAPP1_1_OR_GREATER;NETCOREAPP2_0_OR_GREATER;NETCOREAPP2_1_OR_GREATER;NETCOREAPP2_2_OR_GREATER;NETCOREAPP3_0_OR_GREATER;NETCOREAPP3_1_OR_GREATER;IOS10_0_OR_GREATER;IOS10_1_OR_GREATER;IOS10_2_OR_GREATER;IOS11_0_OR_GREATER;IOS11_1_OR_GREATER;IOS11_2_OR_GREATER;IOS11_3_OR_GREATER;IOS11_4_OR_GREATER;IOS12_0_OR_GREATER;IOS12_1_OR_GREATER;IOS12_2_OR_GREATER;IOS12_3_OR_GREATER;IOS12_4_OR_GREATER;IOS13_0_OR_GREATER;IOS13_1_OR_GREATER;IOS13_2_OR_GREATER;IOS13_3_OR_GREATER;IOS13_4_OR_GREATER;IOS13_5_OR_GREATER;IOS13_6_OR_GREATER;IOS14_0_OR_GREATER;IOS14_1_OR_GREATER;IOS14_2_OR_GREATER;IOS14_3_OR_GREATER;IOS14_4_OR_GREATER;IOS14_5_OR_GREATER;IOS15_0_OR_GREATER;IOS15_2_OR_GREATER;IOS15_4_OR_GREATER;IOS16_0_OR_GREATER;IOS16_1_OR_GREATER;IOS16_2_OR_GREATER;IOS16_4_OR_GREATER;IOS17_0_OR_GREATER;IOS17_2_OR_GREATER;IOS17_4_OR_GREATER;IOS17_5_OR_GREATER;IOS18_0_OR_GREATER

There is thus no way within C# source code to know which assembly you're building against. This is problematic if you have $(TreatWarningsAsErrors)=true, in which case the warning becomes an error.

Did you find any workaround?

Don't use floating versions. Always use an explicit version.

Build logs

No response

[rolfbjarne]

I can reproduce this.

The problem is in WorkloadManifest.targets:

<ImportGroup Condition=" '$(TargetPlatformIdentifier)' == 'iOS' And '$(UsingAppleNETSdk)' != 'true' And $([MSBuild]::VersionEquals($(TargetFrameworkVersion), '9.0')) And '$(TargetPlatformVersion)' == '18.0'">
	<Import Project="Sdk.props" Sdk="Microsoft.iOS.Sdk.net9.0_18.0" />
	<Import Project="Sdk.props" Sdk="Microsoft.iOS.Windows.Sdk.Aliased.net9.0_18.0" Condition=" $([MSBuild]::IsOSPlatform('windows'))" />
</ImportGroup>

This is supposed to load the 18.0 SDK when TargetPlatformVersion=18.0, but TargetPlatformVersion isn't set yet, so the check fails.

This is also the reason for the lack of 18.1+ constants in DefineConstants: TargetPlatformVersion is set later on, and used to create the list of these constants.

[rolfbjarne]

The workaround is to be explicit about the target platform version in the TargetFramework value:

<TargetFramework>net9.0-ios18.0</TargetFramework>