[tests] Fix a few nullability issues in cecil-tests and the .NET test…

…s. (xamarin#17095)

Also make any nullability warnings show up as errors.

tests/cecil-tests/cecil-tests.csproj

@@ -6,6 +6,7 @@
     <AssemblyName>cecil-tests</AssemblyName>
     <LangVersion>latest</LangVersion>
     <Nullable>enable</Nullable>
+    <WarningsAsErrors>Nullable</WarningsAsErrors>
   </PropertyGroup>
   <ItemGroup>
     <Reference Include="System" />

tests/dotnet/UnitTests/DotNetUnitTests.csproj

@@ -3,6 +3,8 @@
 		<TargetFramework>net$(BundledNETCoreAppTargetFrameworkVersion)</TargetFramework>
 		<IsPackable>false</IsPackable>
 		<DefineConstants>$(DefineConstants);NET;TESTS</DefineConstants>
+		<Nullable>enable</Nullable>
+		<WarningsAsErrors>Nullable</WarningsAsErrors>
 	</PropertyGroup>
 
 	<ItemGroup>

tests/dotnet/UnitTests/PartialAppManifestTest.cs

@@ -17,7 +17,7 @@ public void Build (ApplePlatform platform, string runtimeIdentifiers)
 			DotNet.AssertBuild (project_path, properties);
 
 			var infoPlistPath = GetInfoPListPath (platform, appPath);
-			var infoPlist = PDictionary.FromFile (infoPlistPath);
+			var infoPlist = PDictionary.FromFile (infoPlistPath)!;
 			Assert.AreEqual ("com.xamarin.mypartialappmanifestapp", infoPlist.GetString ("CFBundleIdentifier").Value, "CFBundleIdentifier");
 			Assert.AreEqual ("MyPartialAppManifestApp", infoPlist.GetString ("CFBundleDisplayName").Value, "CFBundleDisplayName");
 			Assert.AreEqual ("3.14", infoPlist.GetString ("CFBundleVersion").Value, "CFBundleVersion");

tests/dotnet/UnitTests/ProjectTest.cs

@@ -28,7 +28,7 @@ public void BuildMySingleView (string runtimeIdentifier)
 			AssertThatLinkerExecuted (result);
 			AssertAppContents (platform, appPath);
 			var infoPlistPath = Path.Combine (appPath, "Info.plist");
-			var infoPlist = PDictionary.FromFile (infoPlistPath);
+			var infoPlist = PDictionary.FromFile (infoPlistPath)!;
 			Assert.AreEqual ("com.xamarin.mysingletitle", infoPlist.GetString ("CFBundleIdentifier").Value, "CFBundleIdentifier");
 			Assert.AreEqual ("MySingleTitle", infoPlist.GetString ("CFBundleDisplayName").Value, "CFBundleDisplayName");
 			Assert.AreEqual ("3.14", infoPlist.GetString ("CFBundleVersion").Value, "CFBundleVersion");
@@ -83,7 +83,7 @@ public void BuildMyCatalystApp (string runtimeIdentifier)
 			AssertThatLinkerExecuted (result);
 			AssertAppContents (platform, appPath);
 			var infoPlistPath = Path.Combine (appPath, "Contents", "Info.plist");
-			var infoPlist = PDictionary.FromFile (infoPlistPath);
+			var infoPlist = PDictionary.FromFile (infoPlistPath)!;
 			Assert.AreEqual ("com.xamarin.mycatalystapp", infoPlist.GetString ("CFBundleIdentifier").Value, "CFBundleIdentifier");
 			Assert.AreEqual ("MyCatalystApp", infoPlist.GetString ("CFBundleDisplayName").Value, "CFBundleDisplayName");
 			Assert.AreEqual ("3.14", infoPlist.GetString ("CFBundleVersion").Value, "CFBundleVersion");
@@ -326,7 +326,7 @@ public void BuildFatApp (ApplePlatform platform, string runtimeIdentifiers)
 			AssertThatLinkerExecuted (result);
 			var infoPlistPath = GetInfoPListPath (platform, appPath);
 			Assert.That (infoPlistPath, Does.Exist, "Info.plist");
-			var infoPlist = PDictionary.FromFile (infoPlistPath);
+			var infoPlist = PDictionary.FromFile (infoPlistPath)!;
 			Assert.AreEqual ("com.xamarin.mysimpleapp", infoPlist.GetString ("CFBundleIdentifier").Value, "CFBundleIdentifier");
 			Assert.AreEqual ("MySimpleApp", infoPlist.GetString ("CFBundleDisplayName").Value, "CFBundleDisplayName");
 			Assert.AreEqual ("3.14", infoPlist.GetString ("CFBundleVersion").Value, "CFBundleVersion");
@@ -357,7 +357,7 @@ public void BuildFatMonoTouchTest (ApplePlatform platform, string runtimeIdentif
 			var appPath = Path.Combine (Path.GetDirectoryName (project_path)!, "bin", "Debug", platform.ToFramework (), "monotouchtest.app");
 			var infoPlistPath = GetInfoPListPath (platform, appPath);
 			Assert.That (infoPlistPath, Does.Exist, "Info.plist");
-			var infoPlist = PDictionary.FromFile (infoPlistPath);
+			var infoPlist = PDictionary.FromFile (infoPlistPath)!;
 			Assert.AreEqual ("com.xamarin.monotouch-test", infoPlist.GetString ("CFBundleIdentifier").Value, "CFBundleIdentifier");
 			Assert.AreEqual ("MonoTouchTest", infoPlist.GetString ("CFBundleDisplayName").Value, "CFBundleDisplayName");
 		}
@@ -577,7 +577,7 @@ public void BuildCoreCLR (ApplePlatform platform, string runtimeIdentifiers)
 			AssertThatLinkerExecuted (rv);
 			var infoPlistPath = GetInfoPListPath (platform, appPath);
 			Assert.That (infoPlistPath, Does.Exist, "Info.plist");
-			var infoPlist = PDictionary.FromFile (infoPlistPath);
+			var infoPlist = PDictionary.FromFile (infoPlistPath)!;
 			Assert.AreEqual ("com.xamarin.mysimpleapp", infoPlist.GetString ("CFBundleIdentifier").Value, "CFBundleIdentifier");
 			Assert.AreEqual ("MySimpleApp", infoPlist.GetString ("CFBundleDisplayName").Value, "CFBundleDisplayName");
 			Assert.AreEqual ("3.14", infoPlist.GetString ("CFBundleVersion").Value, "CFBundleVersion");
@@ -689,7 +689,7 @@ public void AppWithResources (ApplePlatform platform, string runtimeIdentifiers)
 			Assert.That (fontBFile, Does.Exist, "B.otf existence");
 			Assert.That (fontCFile, Does.Exist, "C.ttf existence");
 
-			var plist = PDictionary.FromFile (GetInfoPListPath (platform, appPath));
+			var plist = PDictionary.FromFile (GetInfoPListPath (platform, appPath))!;
 			switch (platform) {
 			case ApplePlatform.iOS:
 			case ApplePlatform.TVOS:
@@ -974,7 +974,7 @@ public void BuildNet6_0App (ApplePlatform platform, string runtimeIdentifiers)
 			AssertThatLinkerExecuted (result);
 			var infoPlistPath = GetInfoPListPath (platform, appPath);
 			Assert.That (infoPlistPath, Does.Exist, "Info.plist");
-			var infoPlist = PDictionary.FromFile (infoPlistPath);
+			var infoPlist = PDictionary.FromFile (infoPlistPath)!;
 			Assert.AreEqual ("com.xamarin.mysimpleapp", infoPlist.GetString ("CFBundleIdentifier").Value, "CFBundleIdentifier");
 			Assert.AreEqual ("MySimpleApp", infoPlist.GetString ("CFBundleDisplayName").Value, "CFBundleDisplayName");
 			Assert.AreEqual ("6.0", infoPlist.GetString ("CFBundleVersion").Value, "CFBundleVersion");

tests/dotnet/UnitTests/TestBaseClass.cs

@@ -389,7 +389,7 @@ protected bool TryGetEntitlements (string nativeExecutable, [NotNullWhen (true)]
 			Assert.AreEqual (0, rv, $"'codesign {string.Join (" ", args)}' failed:\n{codesignOutput}");
 			if (File.Exists (entitlementsPath)) {
 				entitlements = PDictionary.FromFile (entitlementsPath);
-				return true;
+				return entitlements is not null;
 			}
 			entitlements = null;
 			return false;