Scan assembly for mutations

Mutannot/Program.fs

@@ -1,13 +1,77 @@
 open System
 open System.IO
+open System.Reflection
+open System.Runtime.InteropServices
 open Fli
 
+type MutationCase = { TestName: string; Id: string }
+
+let ensureBuilt projectPath =
+    cli {
+        Exec "dotnet"
+        Arguments [ "build"; projectPath ]
+        Output(new StreamWriter(Console.OpenStandardOutput()))
+    }
+    |> Command.execute
+    |> Output.throwIfErrored
+    |> ignore
+
+let getAssemblyPath projectPath =
+    cli {
+        Exec "dotnet"
+        Arguments [ "msbuild"; projectPath; "--getProperty:TargetPath" ]
+    }
+    |> Command.execute
+    |> Output.toText
+
+let getMetadataLoadContext (assemblyPath: string) =
+    // This allows us to inspect assemblies regardless of the platform that they were built for
+    // https://learn.microsoft.com/en-us/dotnet/standard/assembly/inspect-contents-using-metadataloadcontext
+    let assemblyDir = Path.GetDirectoryName assemblyPath
+
+    let pathAssemblyResolver =
+        [ yield assemblyPath
+          yield! Directory.EnumerateFiles(assemblyDir, "*.dll")
+          yield! Directory.EnumerateFiles(assemblyDir, "*.exe")
+          yield! Directory.GetFiles(RuntimeEnvironment.GetRuntimeDirectory(), "*.dll") ]
+        |> PathAssemblyResolver
+
+    new MetadataLoadContext(pathAssemblyResolver, typeof<obj>.Assembly.GetName().Name)
+
+let getMutationCases projectPath =
+    ensureBuilt projectPath
+
+    let assemblyPath = getAssemblyPath projectPath
+
+    use metadataLoadContext = getMetadataLoadContext assemblyPath
+
+    let assemblyTypes =
+        assemblyPath |> metadataLoadContext.LoadFromAssemblyPath |> _.GetTypes()
+
+    let assemblyMethods =
+        assemblyTypes
+        |> Seq.collect _.GetMethods(BindingFlags.Public ||| BindingFlags.Instance)
+
+    assemblyMethods
+    |> Seq.collect (fun m ->
+        m.GetCustomAttributesData()
+        |> Seq.choose (fun attr ->
+            match attr.AttributeType.FullName with
+            | "Mutannot.MutationCaseAttribute" ->
+                Some
+                    { TestName = $"{m.DeclaringType.FullName}.{m.Name}"
+                      Id = attr.ConstructorArguments[0].Value :?> string }
+            | _ -> None))
+    |> Seq.toList
+
 [<EntryPoint>]
 let main argv =
     if argv.Length <> 1 then
         eprintfn "Usage: mutannot <path/to/project.csproj|fsproj>"
         exit 1
 
+    let projectPath = argv[0]
+
     let gitState =
         cli {
             Exec "git"
@@ -20,13 +84,7 @@ let main argv =
         eprintfn "Uncommitted changes. Refusing to run."
         exit 2
 
-    cli {
-        Exec "dotnet"
-        Arguments [ "build"; argv[0] ]
-        Output(new StreamWriter(Console.OpenStandardOutput()))
-    }
-    |> Command.execute
-    |> Output.throwIfErrored
-    |> ignore
+    for mutationCase in getMutationCases projectPath do
+        printfn "%s" <| mutationCase.ToString()
 
     0