Improve the language discovery heuristics of AssemblyInfoBuilder

Improve how the AssemblyInfoBuilder discovers what language is being compiled
by not looking for an `AssemblyInfo.*` file, but instead finding the first
*.vb og *.cs file and deducing the langauge from there.

Also adds a few more guards and tests for AssemblyInfoBuilder to make it more
robust and easier to understand if it breaks.

Author: asbjornu

src/GitVersionTask.Tests/AssemblyInfoBuilderTests.cs

@@ -1,14 +1,17 @@
 using System;
+using System.Collections.Generic;
 using System.ComponentModel;
 using System.IO;
 using System.Linq;
 using System.Reflection;
 using System.Runtime.CompilerServices;
 using GitVersion;
 using GitVersionCore.Tests;
+using Microsoft.Build.Framework;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp;
 using Microsoft.CodeAnalysis.VisualBasic;
+using NSubstitute;
 using NUnit.Framework;
 using Shouldly;
 
@@ -212,6 +215,36 @@ public void VerifyAssemblyVersion_MajorMinorPatchTag_NugetAssemblyInfo([ValueSou
         VerifyAssemblyVersion(compiler, AssemblyVersioningScheme.MajorMinorPatchTag, "{NugetVersion}");
     }
 
+    [Test]
+    public void GetAssemblyInfoBuilder_Empty_ThrowsWarningException()
+    {
+        var taskItems = Substitute.For<IEnumerable<ITaskItem>>();
+        var exception = Assert.Throws<GitTools.WarningException>(() => AssemblyInfoBuilder.GetAssemblyInfoBuilder(taskItems));
+        exception.Message.ShouldBe("Unable to determine which AssemblyBuilder required to generate GitVersion assembly information");
+    }
+
+    [Test]
+    public void GetAssemblyInfoBuilder_Null_ThrowsArgumentNullException()
+    {
+        var exception = Assert.Throws<ArgumentNullException>(() => AssemblyInfoBuilder.GetAssemblyInfoBuilder(null));
+        exception.ParamName.ShouldBe("compileFiles");
+    }
+
+    [TestCase("Class1.cs", typeof(CSharpAssemblyInfoBuilder))]
+    [TestCase("Class1.vb", typeof(VisualBasicAssemblyInfoBuilder))]
+    [TestCase("AssemblyInfo.cs", typeof(CSharpAssemblyInfoBuilder))]
+    [TestCase("AssemblyInfo.vb", typeof(VisualBasicAssemblyInfoBuilder))]
+    public void GetAssemblyInfoBuilder_ShouldReturnAppropriateAssemblyInfoBuilder(string fileName, Type assemblyInfoBuilderType)
+    {
+        var taskItem = Substitute.For<ITaskItem>();
+        taskItem.ItemSpec.Returns(fileName);
+
+        var assemblyInfoBuilder = AssemblyInfoBuilder.GetAssemblyInfoBuilder(new[] { taskItem });
+
+        assemblyInfoBuilder.ShouldNotBeNull();
+        assemblyInfoBuilder.ShouldBeOfType(assemblyInfoBuilderType);
+    }
+
     static void VerifyAssemblyVersion(ICompiler compiler, AssemblyVersioningScheme avs, string assemblyInformationalFormat = null)
     {
         var semanticVersion = new SemanticVersion

src/GitVersionTask.Tests/GitVersionTask.Tests.csproj

@@ -87,6 +87,10 @@
       <HintPath>..\packages\Newtonsoft.Json.8.0.3\lib\net45\Newtonsoft.Json.dll</HintPath>
       <Private>True</Private>
     </Reference>
+    <Reference Include="NSubstitute, Version=1.10.0.0, Culture=neutral, PublicKeyToken=92dd2e9066daa5ca, processorArchitecture=MSIL">
+      <HintPath>..\packages\NSubstitute.1.10.0.0\lib\net45\NSubstitute.dll</HintPath>
+      <Private>True</Private>
+    </Reference>
     <Reference Include="nunit.core, Version=2.6.4.14350, Culture=neutral, PublicKeyToken=96d09a1eb7f44a77, processorArchitecture=MSIL">
       <HintPath>..\packages\NUnitTestAdapter.2.0.0\lib\nunit.core.dll</HintPath>
       <Private>True</Private>

src/GitVersionTask.Tests/packages.config

@@ -14,6 +14,7 @@
   <package id="Microsoft.Web.Xdt" version="2.1.1" targetFramework="net45" />
   <package id="ModuleInit.Fody" version="1.5.9.0" targetFramework="net45" developmentDependency="true" />
   <package id="Newtonsoft.Json" version="8.0.3" targetFramework="net45" />
+  <package id="NSubstitute" version="1.10.0.0" targetFramework="net45" />
   <package id="NUnit" version="3.2.1" targetFramework="net45" />
   <package id="NUnitTestAdapter" version="2.0.0" targetFramework="net45" />
   <package id="ObjectApproval" version="1.3.0" targetFramework="net45" />

src/GitVersionTask/AssemblyInfoBuilder/AssemblyInfoBuilder.cs

@@ -1,37 +1,44 @@
 using System;
 using System.Collections.Generic;
+using System.IO;
 using System.Linq;
+using GitTools;
 using GitVersion;
 using Microsoft.Build.Framework;
-using System.IO;
-using GitTools;
 
 public abstract class AssemblyInfoBuilder
 {
-    private static readonly Dictionary<string, Type> assemblyInfoBuilders = new Dictionary<string, Type>()
+    private static readonly Dictionary<string, Type> assemblyInfoBuilders = new Dictionary<string, Type>
     {
-        { ".cs", typeof(CSharpAssemblyInfoBuilder) },
-        { ".vb", typeof(VisualBasicAssemblyInfoBuilder) }
+        {".cs", typeof(CSharpAssemblyInfoBuilder)},
+        {".vb", typeof(VisualBasicAssemblyInfoBuilder)}
         // TODO: Missing FSharpAssemblyInfoBuilder
     };
 
+    public abstract string AssemblyInfoExtension { get; }
+
     public static AssemblyInfoBuilder GetAssemblyInfoBuilder(IEnumerable<ITaskItem> compileFiles)
     {
+        if (compileFiles == null)
+        {
+            throw new ArgumentNullException("compileFiles");
+        }
+
         Type builderType;
 
-        var assemblyInfoExtension = compileFiles.Select(x => x.ItemSpec)
-            .Where(compileFile => compileFile.Contains("AssemblyInfo"))
-            .Select(Path.GetExtension).FirstOrDefault();
+        var assemblyInfoExtension = compileFiles
+            .Select(x => x.ItemSpec)
+            .Select(Path.GetExtension)
+            // TODO: While it works, this seems like a bad way to discover the language is being compiled. @asbjornu
+            .FirstOrDefault(extension => assemblyInfoBuilders.ContainsKey(extension.ToLowerInvariant()));
 
-        if (assemblyInfoBuilders.TryGetValue(assemblyInfoExtension, out builderType))
+        if (assemblyInfoExtension != null && assemblyInfoBuilders.TryGetValue(assemblyInfoExtension, out builderType))
         {
             return Activator.CreateInstance(builderType) as AssemblyInfoBuilder;
         }
 
         throw new WarningException("Unable to determine which AssemblyBuilder required to generate GitVersion assembly information");
     }
 
-    public abstract string AssemblyInfoExtension { get; }
-
     public abstract string GetAssemblyInfoText(VersionVariables vars, string rootNamespace);
-}
+}