(GH-17) Create assembly loader to support dynamic addins

Author: AdmiringWorm

Cake.Issues.Recipe/Content/loader/AddinData.cake

@@ -0,0 +1,159 @@
+using System.Reflection;
+using Cake.Core.Annotations;
+
+public abstract class AddinData
+{
+    protected AddinData(ICakeContext context, string packageName, string packageVersion, string assemblyName = null)
+    {
+        this.Initialize(context, packageName, packageVersion, assemblyName);
+    }
+
+    public Assembly AddinAssembly { get; private set; }
+    public IEnumerable<Type> DeclaredEnums { get; private set; }
+    public IEnumerable<MethodInfo> DefinedAliases { get; private set; }
+    public IEnumerable<TypeInfo> DefinedClasses { get; private set; }
+    public IEnumerable<MethodInfo> DefinedMethods { get; private set; }
+
+    protected void Initialize(ICakeContext context, string packageName, string packageVersion, string assemblyName = null)
+    {
+        if (string.IsNullOrEmpty(assemblyName))
+        {
+            assemblyName = packageName;
+        }
+        
+        var assembly = LoadAddinAssembly(context, packageName, packageVersion, assemblyName);
+
+        if (assembly is null)
+        {
+            return;
+        }
+
+        AddinAssembly = assembly;
+
+        var declaredEnums = new List<Type>();
+        var definedClasses = new List<TypeInfo>();
+
+        foreach (var ti in assembly.DefinedTypes.Where(ti => ti.IsPublic))
+        {
+            if (ti.IsEnum)
+            {
+                declaredEnums.Add(ti.AsType());
+                EnumerationFound(context, ti.AsType());
+            }
+            else if(ti.IsClass && (!ti.IsAbstract || ti.IsStatic()) && !ti.IsGenericTypeDefinition)
+            {
+                definedClasses.Add(ti);
+                ClassFound(context, ti);
+                ParseClass(context, ti);
+            }
+        }
+
+        DeclaredEnums = declaredEnums;
+        DefinedClasses = definedClasses;
+    }
+
+    protected virtual void AliasFound(ICakeContext context, MethodInfo method)
+    {
+    }
+
+    protected virtual void ClassFound(ICakeContext context, TypeInfo classTypeInfo)
+    {
+    }
+
+    protected void ParseClass(ICakeContext context, TypeInfo classTypeInfo)
+    {
+        var aliases = new List<MethodInfo>();
+        var methods = new List<MethodInfo>();
+
+        foreach (var mi in classTypeInfo.DeclaredMethods.Where(i => i.IsPublic))
+        {
+            if (mi.GetCustomAttribute<CakeMethodAliasAttribute>() != null)
+            {
+                aliases.Add(mi);
+                AliasFound(context, mi);
+            }
+            else
+            {
+                methods.Add(mi);
+                MethodFound(context, mi);
+            }
+        }
+
+        DefinedAliases = aliases;
+        DefinedMethods = methods;
+    }
+
+    protected virtual void EnumerationFound(ICakeContext context, Type enumType)
+    {
+    }
+
+    protected virtual void MethodFound(ICakeContext context, MethodInfo method)
+    {
+    }
+
+    private static Assembly LoadAddinAssembly(ICakeContext context, string packageName, string packageVersion, string assemblyName)
+    {
+        var dllPath = GetAssemblyPath(context, packageName, packageVersion, assemblyName);
+
+        if (dllPath is null)
+        {
+            var script = $"#tool nuget:?package={packageName}&version={packageVersion}&prerelease";
+            var tempFile = Guid.NewGuid() + ".cake";
+
+            System.IO.File.WriteAllText(tempFile, script);
+
+            try
+            {
+                context.CakeExecuteScript(tempFile);
+            }
+            finally
+            {
+                if (context.FileExists(tempFile))
+                {
+                    context.DeleteFile(tempFile);
+                }
+            }
+        }
+
+        dllPath = GetAssemblyPath(context, packageName, packageVersion, assemblyName);
+
+        if (dllPath is null)
+        {
+            context.Warning("Unable to find path to the {0} package assembly!", packageName);
+            return null;
+        }
+
+        var assembly = Assembly.LoadFrom(dllPath.FullPath);
+        return assembly;
+    }
+
+    private static FilePath GetAssemblyPath(ICakeContext context, string packageName, string packageVersion, string assemblyName)
+    {
+        FilePath dllPath = null;
+        const string pathFormat = "{0}.{1}/**/{2}*/{3}.dll";
+
+        var possibleFrameworks = new List<String>();
+
+        if (context.Environment.Runtime.IsCoreClr)
+        {
+            possibleFrameworks.Add("netcoreapp");
+            possibleFrameworks.Add("net4"); // TODO: Remove this after debugging
+        }
+        else
+        {
+            possibleFrameworks.Add("net4");
+        }
+        possibleFrameworks.Add("netstandard");
+
+        foreach (var framework in possibleFrameworks)
+        {
+            dllPath = context.Tools.Resolve(string.Format(pathFormat, packageName, packageVersion, framework, assemblyName));
+            if (dllPath is null)
+                dllPath = context.Tools.Resolve(string.Format(pathFormat, packageName, "*", framework, assemblyName));
+            if (dllPath is object)
+                break;
+        }
+
+        return dllPath;
+    }
+}

Cake.Issues.Recipe/Content/loader/loader.cake

@@ -0,0 +1 @@
+#load ./AddinData.cake