Fix Mac build to use UnixName Custom Build Task

_system_name and _system_type are not available by default in the
environment.  Use new UnixName Custom Build Task to conditionally
build Mac unit tests instead of depending on _system_name.

Define new build/platform.targets that can be used to create
system-specific definitions for conditional compilation.

Author: chrisvire

Palaso.Tests/Palaso.Tests.csproj

@@ -198,9 +198,6 @@
     <ErrorReport>prompt</ErrorReport>
     <CodeAnalysisRuleSet>MinimumRecommendedRules.ruleset</CodeAnalysisRuleSet>
   </PropertyGroup>
-  <PropertyGroup Condition= " '$(_system_name)' != '' ">
-    <DefineConstants>$(DefineConstants);SYSTEM_$(_system_name)</DefineConstants>
-  </PropertyGroup>
   <ItemGroup>
     <Reference Include="System" />
     <Reference Include="System.Core" />
@@ -346,6 +343,7 @@
     </BootstrapperPackage>
   </ItemGroup>
   <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
+  <Import Project="..\build\platform.targets" />
   <!-- To modify your build process, add your task inside one of the targets below and uncomment it.
 	   Other similar extension points exist, see Microsoft.Common.targets.
   <Target Name="BeforeBuild">

Palaso.Tests/PlatformUtilities/PlatformTests.cs

@@ -4,25 +4,6 @@
 using NUnit.Framework;
 using Palaso.PlatformUtilities;
 
-// For code shipped with products, please try to use runtime checks to select code to run.
-// There are cases that require compile-time conditionals (e.g. when testing the runtime or
-// referencing platform specific imported assemblies like MonoMac.dll).  In this case, do
-// The following:
-// 1) include the following PropertyGroup in the .csproj after all of the DefineConstants
-//    elements.  [Note: _system_name and _system_type are defined by xbuild in later 
-//    versions of Mono.  We tested with Mono 3.12 that comes with Xamarin Studio for 
-//    Mac.  To verify, add /verbosity:diag to xbuild command-line. YMMV.]
-//
-// <PropertyGroup Condition= " '$(_system_name)' != '' ">
-//   <DefineConstants>$(DefineConstants);SYSTEM_$(_system_name)</DefineConstants>
-// </PropertyGroup>
-//
-// 2) In code use a conditional based on the desired platform.
-// 
-// #if SYSTEM_OSX
-// using MonoMac.Foundation;
-// #endif
-
 namespace Palaso.Tests.PlatformUtilities
 {
 	[TestFixture]
@@ -56,7 +37,7 @@ public void IsDotnet_Net()
 			Assert.That(Platform.IsDotNet, Is.True);
 		}
 
-#if SYSTEM_OSX
+#if SYSTEM_MAC
 		[Test]
 		public void IsLinux_Mac()
 		{
@@ -78,7 +59,7 @@ public void IsLinux_Windows()
 			Assert.That(Platform.IsLinux, Is.False);
 		}
 
-#if SYSTEM_OSX
+#if SYSTEM_MAC
 		[Test]
 		public void IsWindows_Mac()
 		{
@@ -100,7 +81,7 @@ public void IsWindows_Windows()
 			Assert.That(Platform.IsWindows, Is.True);
 		}
 
-#if SYSTEM_OSX
+#if SYSTEM_MAC
 		[Test]
 		public void IsMac_Mac()
 		{
@@ -122,7 +103,7 @@ public void IsMac_Windows()
 			Assert.That(Platform.IsMac, Is.False);
 		}
 
-#if SYSTEM_OSX
+#if SYSTEM_MAC
 		[Test]
 		public void IsUnix_Mac()
 		{

build/Palaso.BuildTasks.dll

@@ -0,0 +1,35 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<!--
+Include this file at the end of a csproj file (just before the
+include of Microsoft.CSharp.targets) to add system-specific defines
+for conditional compilation.
+Example: libpalaso/Palaso.Tests/Palaso.Tests.csproj
+
+These constants will be defined:
+SYSTEM_UNIX - should be compiled on Linux and Mac
+SYSTEM_MAC - should only be compiled on Mac (e.g. Unit Tests specific to Mac)
+SYSTEM_LINUX - should only be compiled on Linux
+
+In csproj file:
+<Include Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
+<Include Project="..\build\platform.targets" />
+
+To use in C# code:
+#if SYSTEM_MAC
+/* code that should only be compiled on Mac */
+#endif
+-->
+<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <UsingTask TaskName="UnixName" AssemblyFile="Palaso.BuildTasks.dll" />
+  <Target Name="BeforeBuild">
+    <UnixName>
+      <Output TaskParameter="Value" PropertyName="UNIX_NAME" />
+    </UnixName>
+    <PropertyGroup>
+      <DefineConstants Condition="'$(OS)' == 'Unix'">$(DefineConstants);SYSTEM_UNIX</DefineConstants>
+      <DefineConstants Condition="'$(UNIX_NAME)' == 'Darwin'">$(DefineConstants);SYSTEM_MAC</DefineConstants>
+      <DefineConstants Condition="'$(UNIX_NAME)' == 'Linux'">$(DefineConstants);SYSTEM_LINUX</DefineConstants>
+    </PropertyGroup>
+  </Target>
+</Project>
+