Fix traversal project loading by correcting IsTraversal and DesignTimeCapable active patterns

Author: TheAngryByrd

src/Ionide.ProjInfo/Library.fs

@@ -1,4 +1,4 @@
-namespace Ionide.ProjInfo
+namespace Ionide.ProjInfo
 
 open System
 open System.Collections.Generic
@@ -358,16 +358,25 @@ module ProjectLoader =
         | Other of ProjectInstance
 
     let (|IsTraversal|_|) (p: ProjectInstance) =
-        match p.GetProperty "IsTraversal" with
-        | null -> None
-        | p when Boolean.TryParse(p.EvaluatedValue) = (true, false) -> None
-        | _ -> Some()
+        let prop = p.GetProperty "IsTraversal"
+        if isNull prop then
+            None
+        else
+            match Boolean.TryParse(prop.EvaluatedValue) with
+            | true, true -> Some()
+            | _ -> None
 
     let (|DesignTimeCapable|_|) (targets: string seq) (p: ProjectInstance) =
-        if Seq.forall p.Targets.ContainsKey targets then
-            Some()
+        // https://github.com/dotnet/project-system/blob/main/docs/design-time-builds.md#diagnosing-design-time-builds
+        let designTimeBuildTargets = p.GetProperty "DesignTimeBuildTargets"
+        if not (isNull designTimeBuildTargets) && not (String.IsNullOrWhiteSpace designTimeBuildTargets.EvaluatedValue) then
+             Some()
         else
-            None
+            let missing = targets |> Seq.filter (fun t -> not (p.Targets.ContainsKey t)) |> Seq.toList
+            if List.isEmpty missing then
+                Some()
+            else
+                None
 
     let internal projectLoaderLogger = lazy (LogProvider.getLoggerByName "ProjectLoader")
 
@@ -437,7 +446,7 @@ module ProjectLoader =
             member this.Parameters: string = ""
 
             member this.Parameters
-                with set (v: string): unit = printfn "v"
+                with set (v: string): unit = ()
 
             member this.Shutdown() : unit = ()
             member this.Verbosity: LoggerVerbosity = LoggerVerbosity.Detailed
@@ -655,10 +664,7 @@ module ProjectLoader =
                 "CoreCompile"
             |]
         else
-            [|
-                yield! designTimeBuildTargetsCore
-                "DispatchToInnerBuilds"
-            |]
+            designTimeBuildTargetsCore
 
     let setLegacyMsbuildProperties isOldStyleProjFile =
         match LegacyFrameworkDiscovery.msbuildBinary.Value with