CSharpLanguageServer.Handlers.DocumentFormatting: rewrite in a more functional approach

Author: razzmatazz

src/CSharpLanguageServer/Handlers/DocumentFormatting.fs

@@ -5,26 +5,29 @@ open Ionide.LanguageServerProtocol.Types
 open Ionide.LanguageServerProtocol.JsonRpc
 
 open CSharpLanguageServer.State
+open CSharpLanguageServer.Util
 open CSharpLanguageServer.Roslyn.Document
 
 [<RequireQualifiedAccess>]
-module DocumentFormatting =
-    let provider (clientCapabilities: ClientCapabilities) : U2<bool, DocumentFormattingOptions> option =
-        Some(U2.C1 true)
 
-    let handle (context: ServerRequestContext) (p: DocumentFormattingParams) : AsyncLspResult<TextEdit[] option> = async {
-        let lspFormattingOptions =
-            if context.State.Settings.ApplyFormattingOptions then
-                Some p.Options
-            else
-                None
+module DocumentFormatting =
+    let provider (_cc: ClientCapabilities) : U2<bool, DocumentFormattingOptions> option = Some(U2.C1 true)
 
-        match context.GetUserDocument p.TextDocument.Uri with
-        | None -> return None |> LspResult.success
-        | Some doc ->
-            let! ct = Async.CancellationToken
-            let! options = getDocumentFormattingOptionSet doc lspFormattingOptions
-            let! newDoc = Formatter.FormatAsync(doc, options, cancellationToken = ct) |> Async.AwaitTask
-            let! textEdits = getDocumentDiffAsLspTextEdits newDoc doc
-            return textEdits |> Some |> LspResult.success
+    let formatDocument lspFormattingOptions doc : Async<TextEdit array option> = async {
+        let! ct = Async.CancellationToken
+        let! options = getDocumentFormattingOptionSet doc lspFormattingOptions
+        let! newDoc = Formatter.FormatAsync(doc, options, cancellationToken = ct) |> Async.AwaitTask
+        let! textEdits = getDocumentDiffAsLspTextEdits newDoc doc
+        return textEdits |> Some
     }
+
+    let handle (context: ServerRequestContext) (p: DocumentFormattingParams) : AsyncLspResult<TextEdit[] option> =
+        let formatDocument =
+            p.Options
+            |> context.State.Settings.GetEffectiveFormattingOptions
+            |> formatDocument
+
+        context.GetUserDocument p.TextDocument.Uri
+        |> async.Return
+        |> Async.bindOption formatDocument
+        |> Async.map LspResult.success

src/CSharpLanguageServer/Types.fs

@@ -11,6 +11,12 @@ type ServerSettings =
       ApplyFormattingOptions: bool
       DebugMode: bool }
 
+    member this.GetEffectiveFormattingOptions options =
+        if this.ApplyFormattingOptions then
+            Some options
+        else
+            None
+
     static member Default: ServerSettings =
         { SolutionPath = None
           LogLevel = LogLevel.Information

src/CSharpLanguageServer/Util.fs

@@ -103,6 +103,11 @@ module Async =
     let map f computation =
         async.Bind(computation, f >> async.Return)
 
+    let bindOption f computation =
+        async.Bind(computation, fun v -> match v with
+                                         | Some v -> f v
+                                         | None -> async.Return None)
+
 module Map =
     let union map1 map2 =
         Map.fold (fun acc key value -> Map.add key value acc) map1 map2