Make msbuild work on Arm-based Macs

csharp/autobuilder/Semmle.Autobuild.CSharp.Tests/BuildScripts.cs

@@ -145,6 +145,14 @@ namespace Semmle.Autobuild.CSharp.Tests
 
         bool IBuildActions.IsWindows() => IsWindows;
 
+        public bool IsMacOs { get; set; }
+
+        bool IBuildActions.IsMacOs() => IsMacOs;
+
+        public bool IsArm { get; set; }
+
+        bool IBuildActions.IsArm() => IsArm;
+
         public string PathCombine(params string[] parts)
         {
             return string.Join(IsWindows ? '\\' : '/', parts.Where(p => !string.IsNullOrWhiteSpace(p)));

csharp/autobuilder/Semmle.Autobuild.Shared/BuildActions.cs

@@ -7,6 +7,7 @@ using System.Xml;
 using System.Net.Http;
 using System.Diagnostics.CodeAnalysis;
 using System.Threading.Tasks;
+using System.Runtime.InteropServices;
 
 namespace Semmle.Autobuild.Shared
 {
@@ -98,6 +99,18 @@ namespace Semmle.Autobuild.Shared
         /// </summary>
         bool IsWindows();
 
+        /// <summary>
+        /// Gets a value indicating whether we are running on macOS.
+        /// </summary>
+        /// <returns>True if we are running on macOS.</returns>
+        bool IsMacOs();
+
+        /// <summary>
+        /// Gets a value indicating whether we are running on arm.
+        /// </summary>
+        /// <returns>True if we are running on arm.</returns>
+        bool IsArm();
+
         /// <summary>
         /// Combine path segments, Path.Combine().
         /// </summary>
@@ -203,6 +216,12 @@ namespace Semmle.Autobuild.Shared
 
         bool IBuildActions.IsWindows() => Win32.IsWindows();
 
+        bool IBuildActions.IsMacOs() => RuntimeInformation.IsOSPlatform(OSPlatform.OSX);
+
+        bool IBuildActions.IsArm() =>
+            RuntimeInformation.ProcessArchitecture == Architecture.Arm64 ||
+            RuntimeInformation.ProcessArchitecture == Architecture.Arm;
+
         string IBuildActions.PathCombine(params string[] parts) => Path.Combine(parts);
 
         void IBuildActions.WriteAllText(string filename, string contents) => File.WriteAllText(filename, contents);

csharp/autobuilder/Semmle.Autobuild.Shared/MsBuildRule.cs

@@ -1,18 +1,36 @@
 using Semmle.Util.Logging;
+using System;
 using System.Linq;
+using System.Runtime.InteropServices;
 
 namespace Semmle.Autobuild.Shared
 {
+    internal static class MsBuildCommandExtensions
+    {
+        /// <summary>
+        /// Appends a call to msbuild.
+        /// </summary>
+        /// <param name="cmdBuilder"></param>
+        /// <param name="builder"></param>
+        /// <returns></returns>
+        public static CommandBuilder MsBuildCommand(this CommandBuilder cmdBuilder, IAutobuilder<AutobuildOptionsShared> builder)
+        {
+            var isArmMac = builder.Actions.IsMacOs() && builder.Actions.IsArm();
+
+            // mono doesn't ship with `msbuild` on Arm-based Macs, but we can fall back to
+            // msbuild that ships with `dotnet` which can be invoked with `dotnet msbuild`
+            // perhaps we should do this on all platforms?
+            return isArmMac ?
+                cmdBuilder.RunCommand("dotnet").Argument("msbuild") :
+                cmdBuilder.RunCommand("msbuild");
+        }
+    }
+
     /// <summary>
     /// A build rule using msbuild.
     /// </summary>
     public class MsBuildRule : IBuildRule<AutobuildOptionsShared>
     {
-        /// <summary>
-        /// The name of the msbuild command.
-        /// </summary>
-        private const string msBuild = "msbuild";
-
         public BuildScript Analyse(IAutobuilder<AutobuildOptionsShared> builder, bool auto)
         {
             if (!builder.ProjectsOrSolutionsToBuild.Any())
@@ -57,7 +75,7 @@ namespace Semmle.Autobuild.Shared
                             Script;
                     var nugetRestore = GetNugetRestoreScript();
                     var msbuildRestoreCommand = new CommandBuilder(builder.Actions).
-                        RunCommand(msBuild).
+                        MsBuildCommand(builder).
                         Argument("/t:restore").
                         QuoteArgument(projectOrSolution.FullPath);
 
@@ -95,7 +113,7 @@ namespace Semmle.Autobuild.Shared
                     command.RunCommand("set Platform=&& type NUL", quoteExe: false);
                 }
 
-                command.RunCommand(msBuild);
+                command.MsBuildCommand(builder);
                 command.QuoteArgument(projectOrSolution.FullPath);
 
                 var target = builder.Options.MsBuildTarget ?? "rebuild";