feat(Handler/Completion): Support markdown description in resolve

Signed-off-by: Adam Tao <[email protected]>

Author: tcx4c70

src/Common/Conversions.fs

@@ -2,6 +2,7 @@ namespace CSharpLanguageServer.Common
 
 open System
 open Microsoft.CodeAnalysis
+open Microsoft.CodeAnalysis.Completion
 open Microsoft.CodeAnalysis.Text
 open Ionide.LanguageServerProtocol.Types
 open FSharpPlus
@@ -205,3 +206,25 @@ module CompletionContext =
             | CompletionTriggerKind.TriggerCharacter -> Option.map Completion.CompletionTrigger.CreateInsertionTrigger ctx.TriggerCharacter
             | _ -> None)
         |> Option.defaultValue (Completion.CompletionTrigger.Invoke)
+
+
+module CompletionDescription =
+    let toMarkdownString (description: CompletionDescription) : string =
+        description.TaggedParts
+        |> Seq.map (fun taggedText ->
+            // WTF, if the developers of Roslyn don't want users to use TaggedText, why they set TaggedText to public?
+            // If they indeed want users to use it, why they set lots of imported fields to internal?
+            match taggedText.Tag with
+            // TODO: Support code block?
+            | "CodeBlockStart"   -> "`` " + taggedText.Text
+            | "CodeBlockEnd"     -> " ``" + taggedText.Text
+            | TextTags.LineBreak -> "\n\n"
+            | _                  -> taggedText.Text)
+        |> String.concat ""
+
+    let toDocumentation (description: CompletionDescription) : Documentation =
+        Documentation.Markup { Kind = MarkupKind.Markdown; Value = toMarkdownString description }
+
+
+module Documentation =
+    let fromCompletionDescription = CompletionDescription.toDocumentation

src/Handlers/Completion.fs

@@ -136,6 +136,5 @@ module Completion =
                 completionService.GetDescriptionAsync(doc, cachedItem, ct)
                 |> map Option.ofObj
                 |> Async.AwaitTask
-            // TODO: make the doc as a markdown string instead of a plain text
-            return { item with Documentation = description |> map (fun x -> Documentation.String x.Text) } |> success
+            return { item with Documentation = description |> map Documentation.fromCompletionDescription } |> success
     }