Tooltips for hints (#15127)

* WIP: Tooltips for hints

* casing

* Actually, tooltips

* Update HintTestFramework.fs

* Simplify async

Author: psfinaki

vsintegration/src/FSharp.Editor/Hints/Hints.fs

@@ -2,6 +2,8 @@
 
 namespace Microsoft.VisualStudio.FSharp.Editor.Hints
 
+open System.Threading
+open Microsoft.CodeAnalysis
 open FSharp.Compiler.Text
 
 module Hints =
@@ -17,6 +19,7 @@ module Hints =
             Kind: HintKind
             Range: range
             Parts: TaggedText list
+            GetTooltip: Document -> Async<TaggedText list>
         }
 
     let serialize kind =

vsintegration/src/FSharp.Editor/Hints/InlineParameterNameHints.fs

@@ -12,18 +12,47 @@ open Hints
 
 type InlineParameterNameHints(parseResults: FSharpParseFileResults) =
 
+    let getTooltip (symbol: FSharpSymbol) _ =
+        async {
+            // This brings little value as of now. Basically just discerns fields from parameters
+            // and fills the tooltip bubble which otherwise looks like a visual glitch.
+            //
+            // Now, we could add some type information here, like C# does, for example:
+            // (parameter) int number
+            //
+            // This would work for simple cases but can get weird in more complex ones.
+            // Consider this code:
+            //
+            // let rev list = list |> List.rev
+            // let reversed = rev [ 42 ]
+            //
+            // With the trivial implementation, the tooltip for hint before [ 42 ] will look like:
+            // parameter 'a list list
+            //
+            // Arguably, this can look confusing.
+            // Hence, I wouldn't add type info to the text until we have some coloring plugged in here.
+            //
+            // Some alignment with C# also needs to be kept in mind,
+            // e.g. taking the type in braces would be opposite to what C# does which can be confusing.
+            let text = symbol.ToString()
+
+            return [ TaggedText(TextTag.Text, text) ]
+        }
+
     let getParameterHint (range: range, parameter: FSharpParameter) =
         {
             Kind = HintKind.ParameterNameHint
             Range = range.StartRange
             Parts = [ TaggedText(TextTag.Text, $"{parameter.DisplayName} = ") ]
+            GetTooltip = getTooltip parameter
         }
 
     let getFieldHint (range: range, field: FSharpField) =
         {
             Kind = HintKind.ParameterNameHint
             Range = range.StartRange
             Parts = [ TaggedText(TextTag.Text, $"{field.Name} = ") ]
+            GetTooltip = getTooltip field
         }
 
     let parameterNameExists (parameter: FSharpParameter) = parameter.DisplayName <> ""

vsintegration/src/FSharp.Editor/Hints/InlineReturnTypeHints.fs

@@ -19,13 +19,21 @@ type InlineReturnTypeHints(parseFileResults: FSharpParseFileResults, symbol: FSh
                 TaggedText(TextTag.Space, " ")
             ])
 
+    let getTooltip _ =
+        async {
+            let typeAsString = symbol.ReturnParameter.Type.TypeDefinition.ToString()
+            let text = $"type {typeAsString}"
+            return [ TaggedText(TextTag.Text, text) ]
+        }
+
     let getHint symbolUse range =
         getHintParts symbolUse
         |> Option.map (fun parts ->
             {
                 Kind = HintKind.ReturnTypeHint
                 Range = range
                 Parts = parts
+                GetTooltip = getTooltip
             })
 
     let isValidForHint (symbol: FSharpMemberOrFunctionOrValue) = symbol.IsFunction

vsintegration/src/FSharp.Editor/Hints/InlineTypeHints.fs

@@ -21,11 +21,29 @@ type InlineTypeHints(parseResults: FSharpParseFileResults, symbol: FSharpMemberO
         // not sure when this can happen
         | None -> []
 
+    let getTooltip _ =
+        async {
+            // Done this way because I am not sure if we want to show full-blown types everywhere,
+            // e.g. Microsoft.FSharp.Core.string instead of string.
+            // On the other hand, for user types this could be useful.
+            // Then there should be some smarter algorithm here.
+            let text =
+                if symbol.FullType.HasTypeDefinition then
+                    let typeAsString = symbol.FullType.TypeDefinition.ToString()
+                    $"type {typeAsString}"
+                else
+                    // already includes the word "type"
+                    symbol.FullType.ToString()
+
+            return [ TaggedText(TextTag.Text, text) ]
+        }
+
     let getHint symbol (symbolUse: FSharpSymbolUse) =
         {
             Kind = HintKind.TypeHint
             Range = symbolUse.Range.EndRange
             Parts = getHintParts symbol symbolUse
+            GetTooltip = getTooltip
         }
 
     let isSolved (symbol: FSharpMemberOrFunctionOrValue) =

vsintegration/src/FSharp.Editor/Hints/NativeToRoslynHintConverter.fs

@@ -2,10 +2,14 @@
 
 namespace Microsoft.VisualStudio.FSharp.Editor.Hints
 
+open System
 open System.Collections.Immutable
+open System.Threading
+open System.Threading.Tasks
 open Microsoft.CodeAnalysis.Text
 open Microsoft.CodeAnalysis.ExternalAccess.FSharp.InlineHints
 open Microsoft.VisualStudio.FSharp.Editor
+open Microsoft.CodeAnalysis
 open FSharp.Compiler.Text
 open Hints
 
@@ -21,7 +25,14 @@ module NativeToRoslynHintConverter =
         let text = taggedText.Text
         RoslynTaggedText(tag, text)
 
+    let nativeToRoslynFunc nativeFunc =
+        Func<Document, CancellationToken, Task<ImmutableArray<RoslynTaggedText>>>(fun doc ct ->
+            nativeFunc doc
+            |> Async.map (List.map nativeToRoslynText >> ImmutableArray.CreateRange)
+            |> fun comp -> Async.StartAsTask(comp, cancellationToken = ct))
+
     let convert sourceText hint =
         let span = rangeToSpan hint.Range sourceText
         let displayParts = hint.Parts |> Seq.map nativeToRoslynText
-        FSharpInlineHint(span, displayParts.ToImmutableArray())
+        let getDescription = hint.GetTooltip |> nativeToRoslynFunc
+        FSharpInlineHint(span, displayParts.ToImmutableArray(), getDescription)

vsintegration/tests/FSharp.Editor.Tests/Hints/HintTestFramework.fs

@@ -12,9 +12,13 @@ module HintTestFramework =
 
     // another representation for extra convenience
     type TestHint =
-        { Content: string; Location: int * int }
+        {
+            Content: string
+            Location: int * int
+            Tooltip: string
+        }
 
-    let private convert hint =
+    let private convert (hint, tooltip) =
         let content =
             hint.Parts |> Seq.map (fun hintPart -> hintPart.Text) |> String.concat ""
 
@@ -26,6 +30,7 @@ module HintTestFramework =
         {
             Content = content
             Location = location
+            Tooltip = tooltip
         }
 
     let getFsDocument code =
@@ -57,9 +62,17 @@ module HintTestFramework =
     let getHints (document: Document) hintKinds =
         async {
             let! ct = Async.CancellationToken
+
+            let getTooltip hint =
+                async {
+                    let! roslynTexts = hint.GetTooltip document
+                    return roslynTexts |> Seq.map (fun roslynText -> roslynText.Text) |> String.concat ""
+                }
+
             let! sourceText = document.GetTextAsync ct |> Async.AwaitTask
             let! hints = HintService.getHintsForDocument sourceText document hintKinds "test" ct
-            return hints |> Seq.map convert
+            let! tooltips = hints |> Seq.map getTooltip |> Async.Parallel
+            return tooltips |> Seq.zip hints |> Seq.map convert
         }
         |> Async.RunSynchronously