Add .NET 5.0 support

While we're at it, clean up the conditional compliation constants and dependencies:
- Define `SPAN_NATIVE` on all platforms _except_ `net45` and `netstandard2.0` (so it's defined automatically on new .NET versions)
- Only add `System.Memory` dependency on `net45` and `netstandard2.0`.
- Fix `NATIVE_SPAN` typo
- Remove obsolete `NETCORE` preprocessor variable.

plist-cil.benchmark/plist-cil.benchmark.csproj

@@ -2,12 +2,12 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>netcoreapp2.1</TargetFramework>
+    <TargetFramework>net5.0</TargetFramework>
     <RootNamespace>Claunia.PropertyList.Benchmark</RootNamespace>
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="BenchmarkDotNet" Version="0.10.14" />
+    <PackageReference Include="BenchmarkDotNet" Version="0.12.1" />
   </ItemGroup>
 
   <ItemGroup>

plist-cil.test/NSNumberTests.cs

@@ -110,8 +110,6 @@ namespace plistcil.test
         // The value being used comes seen in a real property list:
         // <key>TimeZoneOffsetFromUTC</key>
         // <real>7200.000000</real>
-
-        #if !NETCORE
         [Fact]
         [UseCulture("en-US")]
         public static void ParseNumberEnTest()
@@ -156,7 +154,6 @@ namespace plistcil.test
             Assert.True(number.isReal());
             Assert.Equal(7200d, number.ToDouble());
         }
-#endif
 
         public static IEnumerable<object[]> StringConstructorTestData()
         {

plist-cil.test/plist-cil.test.csproj

@@ -1,19 +1,15 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>netcoreapp2.0</TargetFramework>
+    <TargetFramework>net5.0</TargetFramework>
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.7.2" />
-    <PackageReference Include="xunit" Version="2.3.1" />
-    <PackageReference Include="xunit.runner.visualstudio" Version="2.3.1" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.9.4" />
+    <PackageReference Include="xunit" Version="2.4.1" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.4.3" />
   </ItemGroup>
 
-  <PropertyGroup Condition="'$(TargetFramework)' == 'netcoreapp1.0'">
-    <DefineConstants>NETCOREAPP1_0;NETCORE</DefineConstants>
-  </PropertyGroup>
-
   <ItemGroup>
     <ProjectReference Include="..\plist-cil\plist-cil.csproj" />
   </ItemGroup>

plist-cil/BinaryPropertyListWriter.cs

@@ -355,10 +355,10 @@ namespace Claunia.PropertyList
 
         internal void Write(Span<byte> bytes)
         {
-            #if SPAN_NATIVE
+            #if NATIVE_SPAN
             outStream.Write(bytes);
             count += bytes.Length;
-#else
+            #else
             Write(bytes.ToArray());
             #endif
         }

plist-cil/plist-cil.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>net45;netcoreapp2.0;netstandard2.0;netcoreapp2.1;netcoreapp2.2;netcoreapp3.0;netcoreapp3.1</TargetFrameworks>
+    <TargetFrameworks>net45;netstandard2.0;netcoreapp2.1;netcoreapp3.1;net5.0</TargetFrameworks>
     <VersionPrefix>2.1</VersionPrefix>
     <Authors>Natalia Portillo</Authors>
     <Company>Claunia.com</Company>
@@ -37,11 +37,7 @@ Use invariant culture to format NSDate.</PackageReleaseNotes>
     <DefineConstants>TRACE;DEBUG</DefineConstants>
   </PropertyGroup>
   
-  <PropertyGroup Condition="$(TargetFramework.StartsWith('netcoreapp')) Or $(TargetFramework.StartsWith('netstandard'))">
-    <DefineConstants>$(DefineConstants);NETCORE</DefineConstants>
-  </PropertyGroup>
-
-  <PropertyGroup Condition="'$(TargetFramework)' == 'netcoreapp2.1' Or '$(TargetFramework)' == 'netcoreapp2.2' Or $(TargetFramework.StartsWith('netcoreapp.3.'))">
+  <PropertyGroup Condition=" '$(TargetFramework)' != 'net45' AND '$(TargetFramework)' != 'netstandard2.0'">
     <DefineConstants>$(DefineConstants);NATIVE_SPAN</DefineConstants>
   </PropertyGroup>
 
@@ -49,8 +45,8 @@ Use invariant culture to format NSDate.</PackageReleaseNotes>
     <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.0.0" PrivateAssets="All" />
   </ItemGroup>
 
-  <ItemGroup Condition="'$(TargetFramework)' != 'netcoreapp2.1'">
-    <PackageReference Include="System.Memory" Version="4.5.0" />
+  <ItemGroup Condition=" '$(TargetFramework)' == 'net45' OR '$(TargetFramework)' == 'netstandard2.0' ">
+    <PackageReference Include="System.Memory" Version="4.5.4" />
   </ItemGroup>
 
   <ItemGroup>