Display signature xmldoc for implementation symbol when implementatio…

…n xmldoc is missing. (#14711)

src/Compiler/Checking/SignatureConformance.fs

@@ -322,6 +322,7 @@ type Checker(g, amap, denv, remapInfo: SignatureRepackageInfo, checkingSig) =
             // Propagate defn location information from implementation to signature . 
             sigVal.SetOtherRange (implVal.Range, true)
             implVal.SetOtherRange (sigVal.Range, false)
+            implVal.SetOtherXmlDoc(sigVal.XmlDoc)
 
             let mk_err denv f = ValueNotContained(denv, infoReader, implModRef, implVal, sigVal, f)
             let err denv f = errorR(mk_err denv f); false

src/Compiler/TypedTree/TypedTree.fs

@@ -2545,7 +2545,10 @@ type ValOptionalData =
 
       /// XML documentation attached to a value.
       /// MUTABILITY: for unpickle linkage
-      mutable val_xmldoc: XmlDoc 
+      mutable val_xmldoc: XmlDoc
+
+      /// the signature xml doc for an item in an implementation file.
+      mutable val_other_xmldoc : XmlDoc option
 
       /// Is the value actually an instance method/property/event that augments 
       /// a type, and if so what name does it take in the IL?
@@ -2601,6 +2604,7 @@ type Val =
           val_repr_info_for_display = None
           val_access = TAccess []
           val_xmldoc = XmlDoc.Empty
+          val_other_xmldoc = None
           val_member_info = None
           val_declaring_entity = ParentNone
           val_xmldocsig = String.Empty
@@ -2835,7 +2839,13 @@ type Val =
     /// Get the declared documentation for the value
     member x.XmlDoc =
         match x.val_opt_data with
-        | Some optData -> optData.val_xmldoc
+        | Some optData ->
+            if not optData.val_xmldoc.IsEmpty then
+                optData.val_xmldoc
+            else
+                match optData.val_other_xmldoc with
+                | Some xmlDoc -> xmlDoc
+                | None -> XmlDoc.Empty
         | _ -> XmlDoc.Empty
 
     ///Get the signature for the value's XML documentation
@@ -3065,6 +3075,11 @@ type Val =
         | Some optData -> optData.val_other_range <- Some m
         | _ -> x.val_opt_data <- Some { Val.NewEmptyValOptData() with val_other_range = Some m }
 
+    member x.SetOtherXmlDoc xmlDoc =
+        match x.val_opt_data with
+        | Some optData -> optData.val_other_xmldoc <- Some xmlDoc
+        | _ -> x.val_opt_data <- Some { Val.NewEmptyValOptData() with val_other_xmldoc = Some xmlDoc }
+
     member x.SetDeclaringEntity parent = 
         match x.val_opt_data with
         | Some optData -> optData.val_declaring_entity <- parent
@@ -3119,6 +3134,7 @@ type Val =
                        val_repr_info = tg.val_repr_info
                        val_access = tg.val_access
                        val_xmldoc = tg.val_xmldoc
+                       val_other_xmldoc = tg.val_other_xmldoc
                        val_member_info = tg.val_member_info
                        val_declaring_entity = tg.val_declaring_entity
                        val_xmldocsig = tg.val_xmldocsig

src/Compiler/TypedTree/TypedTree.fsi

@@ -1820,6 +1820,9 @@ type ValOptionalData =
         /// MUTABILITY: for unpickle linkage
         mutable val_xmldoc: XmlDoc
 
+        /// the signature xml doc for an item in an implementation file.
+        mutable val_other_xmldoc: XmlDoc option
+
         /// Is the value actually an instance method/property/event that augments
         /// a type, type if so what name does it take in the IL?
         /// MUTABILITY: for unpickle linkage
@@ -1913,6 +1916,8 @@ type Val =
 
     member SetOtherRange: m: (range * bool) -> unit
 
+    member SetOtherXmlDoc: xmlDoc: XmlDoc -> unit
+
     member SetType: ty: TType -> unit
 
     member SetValDefn: val_defn: Expr -> unit

src/Compiler/TypedTree/TypedTreePickle.fs

@@ -2262,6 +2262,7 @@ and u_ValData st =
                      val_const            = x14
                      val_access           = x13
                      val_xmldoc           = defaultArg x15 XmlDoc.Empty
+                     val_other_xmldoc     = None
                      val_member_info      = x8
                      val_declaring_entity = x13b
                      val_xmldocsig        = x12

tests/FSharp.Compiler.Service.Tests/FSharp.Compiler.Service.Tests.fsproj

@@ -186,6 +186,7 @@
     <Compile Include="..\service\PrettyNaming.fs">
       <Link>PrettyNaming.fs</Link>
     </Compile>
+    <Compile Include="TooltipTests.fs" />
     <Compile Include="..\service\Program.fs">
       <Link>Program.fs</Link>
     </Compile>

tests/FSharp.Compiler.Service.Tests/TooltipTests.fs

@@ -0,0 +1,68 @@
+module FSharp.Compiler.Service.Tests.TooltipTests
+
+#nowarn "57"
+
+open FSharp.Compiler.CodeAnalysis
+open FSharp.Compiler.Service.Tests.Common
+open FSharp.Compiler.Text
+open FSharp.Compiler.Tokenization
+open FSharp.Compiler.EditorServices
+open FSharp.Compiler.Symbols
+open NUnit.Framework
+
+[<Test>]
+let ``Display XML doc of signature file if implementation doesn't have one`` () =
+    let files =
+        Map.ofArray
+            [| "A.fsi",
+               SourceText.ofString
+                   """
+module Foo
+
+/// Great XML doc comment
+val bar: a: int -> b: int -> int
+"""
+
+               "A.fs",
+               SourceText.ofString
+                   """
+module Foo
+
+// No XML doc here because the signature file has one right?
+let bar a b = a - b
+""" |]
+
+    let documentSource fileName = Map.tryFind fileName files
+
+    let projectOptions =
+        let _, projectOptions = mkTestFileAndOptions "" Array.empty
+
+        { projectOptions with
+            SourceFiles = [| "A.fsi"; "A.fs" |] }
+
+    let checker =
+        FSharpChecker.Create(documentSource = DocumentSource.Custom documentSource)
+
+    let checkResult =
+        checker.ParseAndCheckFileInProject("A.fs", 0, Map.find "A.fs" files, projectOptions)
+        |> Async.RunImmediate
+
+    match checkResult with
+    | _, FSharpCheckFileAnswer.Succeeded(checkResults) ->
+        let barSymbol = findSymbolByName "bar" checkResults
+
+        match barSymbol with
+        | :? FSharpMemberOrFunctionOrValue as mfv -> Assert.True mfv.HasSignatureFile
+        | _ -> Assert.Fail "Expected to find a symbol FSharpMemberOrFunctionOrValue that HasSignatureFile"
+
+        // Get the tooltip for `bar` in the implementation file
+        let (ToolTipText tooltipElements) =
+            checkResults.GetToolTip(4, 4, "let bar a b = a - b", [ "bar" ], FSharpTokenTag.Identifier)
+
+        match tooltipElements with
+        | [ ToolTipElement.Group [ element ] ] ->
+            match element.XmlDoc with
+            | FSharpXmlDoc.FromXmlText xmlDoc -> Assert.True xmlDoc.NonEmpty
+            | xmlDoc -> Assert.Fail $"Expected FSharpXmlDoc.FromXmlText, got {xmlDoc}"
+        | elements -> Assert.Fail $"Expected a single tooltip group element, got {elements}"
+    | _ -> Assert.Fail "Expected checking to succeed."