Extend FS25 codefix to allow generating match cases from scratch (#1309)

src/FsAutoComplete.Core/UnionPatternMatchCaseGenerator.fs

@@ -211,6 +211,19 @@ let private tryFindPatternMatchExprInParsedInput (pos: Position) (parsedInput: P
             | _ -> None
           else
             None)
+        |> Option.orElseWith (fun () ->
+          if synMatchClauseList.IsEmpty then
+            match debugPoint with
+            | DebugPointAtBinding.Yes range ->
+              { MatchWithOrFunctionRange = range
+                Expr = matchExpr
+                Clauses = [] }
+              |> Some
+            | _ -> None
+          else
+            None
+
+        )
 
       | SynExpr.App(_exprAtomicFlag, _isInfix, synExpr1, synExpr2, _range) ->
         List.tryPick walkExpr [ synExpr1; synExpr2 ]
@@ -496,20 +509,24 @@ let tryFindCaseInsertionParamsAtPos (codeGenService: ICodeGenerationService) pos
       let! insertionParams = tryFindInsertionParams codeGenService document patMatchExpr
       return patMatchExpr, insertionParams
     else
-      return! None
+      return
+        patMatchExpr,
+        { InsertionPos = patMatchExpr.Expr.Range.End
+          IndentColumn = patMatchExpr.Expr.Range.Start.Column }
   }
 
 let tryFindUnionDefinitionFromPos (codeGenService: ICodeGenerationService) pos document =
   asyncOption {
-    let! patMatchExpr, insertionParams = tryFindCaseInsertionParamsAtPos codeGenService pos document
     let! _, symbolUse = codeGenService.GetSymbolAndUseAtPositionOfKind(document.FullName, pos, SymbolKind.Ident)
+    let! patMatchExpr, insertionParams = tryFindCaseInsertionParamsAtPos codeGenService pos document
 
 
     let! superficialTypeDefinition =
       asyncOption {
         let! symbolUse = symbolUse
 
         match symbolUse.Symbol with
+        | SymbolPatterns.MemberFunctionOrValue(mfv) -> return Some mfv.FullType.TypeDefinition
         | SymbolPatterns.UnionCase(case) when case.ReturnType.HasTypeDefinition ->
           return Some case.ReturnType.TypeDefinition
         | SymbolPatterns.FSharpEntity(entity, _, _) -> return Some entity

src/FsAutoComplete/CodeFixes/GenerateUnionCases.fs

@@ -18,22 +18,47 @@ let fix
   (getTextReplacements: unit -> Map<string, string>)
   =
   Run.ifDiagnosticByCode (Set.ofList [ "25" ]) (fun diagnostic codeActionParams ->
+    let getCasePosFromCaseLine (lines: IFSACSourceText) (fcsRange: FcsRange) =
+      result {
+        let! nextLine = lines.NextLine fcsRange.Start |> Result.ofOption (fun _ -> "no next line")
+
+        let! caseLine = lines.GetLine(nextLine) |> Result.ofOption (fun _ -> "No case line")
+
+        let! caseCol =
+          match caseLine.IndexOf('|') with
+          | -1 -> Error "Invalid case line"
+          | idx -> Ok(uint32 idx + 3u) // Find column of first case in pattern matching
+
+        let casePos =
+          { Line = uint32 nextLine.Line - 1u
+            Character = caseCol }
+
+        return casePos
+      }
+
+    let getCasePosFromMatch (lines: IFSACSourceText) (fcsRange: FcsRange) =
+      result {
+        let! matchLine = lines.GetLine fcsRange.Start |> Result.ofOption (fun _ -> "no current line")
+        let caseCol = matchLine.IndexOf("match")
+
+        let casePos =
+          { Line = uint32 fcsRange.Start.Line - 1u
+            Character = uint32 caseCol + 7u }
+
+        return casePos
+      }
+
     asyncResult {
-      let fileName = codeActionParams.TextDocument.GetFilePath() |> Utils.normalizePath
+      let fileName = codeActionParams.TextDocument.GetFilePath() |> normalizePath
 
       let! lines = getFileLines fileName
       // try to find the first case already written
       let fcsRange = protocolRangeToRange (FSharp.UMX.UMX.untag fileName) diagnostic.Range
 
-      let! nextLine = lines.NextLine fcsRange.Start |> Result.ofOption (fun _ -> "no next line")
-
-      let! caseLine = lines.GetLine(nextLine) |> Result.ofOption (fun _ -> "No case line")
-
-      let caseCol = uint32 (caseLine.IndexOf('|')) + 3u // Find column of first case in pattern matching
 
-      let casePos =
-        { Line = uint32 nextLine.Line - 1u
-          Character = caseCol }
+      let! casePos =
+        (getCasePosFromCaseLine lines fcsRange)
+        |> Result.orElseWith (fun _ -> getCasePosFromMatch lines fcsRange)
 
       let casePosFCS = protocolPosToPos casePos
 

test/FsAutoComplete.Tests.Lsp/CodeFixTests/Tests.fs

@@ -2100,7 +2100,7 @@ let private generateUnionCasesTests state =
   serverTestList (nameof GenerateUnionCases) state config None (fun server ->
     [ let _selectCodeFix = CodeFix.withTitle GenerateUnionCases.title
 
-      testCaseAsync "can generate match cases for a simple DU"
+      testCaseAsync "can generate match cases for a simple DU with one case"
       <| CodeFix.check
         server
         """
@@ -2122,6 +2122,29 @@ let private generateUnionCasesTests state =
         | A -> ()
         | B -> failwith "---"
         | C -> failwith "---"
+        """
+
+      testCaseAsync "can generate match cases for a simple DU without cases"
+      <| CodeFix.check
+        server
+        """
+        type Letter = A | B | C
+
+        let char = A
+
+        match $0char with
+        """
+        (Diagnostics.expectCode "25")
+        (CodeFix.withTitle GenerateUnionCases.title)
+        """
+        type Letter = A | B | C
+
+        let char = A
+
+        match char with
+        | A -> failwith "---"
+        | B -> failwith "---"
+        | C -> failwith "---"
         """ ])
 
 let private makeDeclarationMutableTests state =
@@ -2724,6 +2747,7 @@ let private replaceWithSuggestionTests state =
       let validateDiags (diags: Diagnostic[]) =
         Diagnostics.expectCode "39" diags
         let messages = diags |> Array.map (fun d -> d.Message) |> String.concat "\n"
+
         Expect.exists
           diags
           (fun (d: Diagnostic) -> d.Message.Contains "Maybe you want one of the following:")
@@ -3175,8 +3199,8 @@ let private removePatternArgumentTests state =
           | B = 2
 
         do
-	        let (E.A x$0) = E.A
-	        ()
+          let (E.A x$0) = E.A
+          ()
         """
         (Diagnostics.expectCode "3191")
         selectCodeFix
@@ -3186,8 +3210,8 @@ let private removePatternArgumentTests state =
           | B = 2
 
         do
-	        let (E.A) = E.A
-	        ()
+          let (E.A) = E.A
+          ()
         """
 
       testCaseAsync "Local literal constant pattern qualified parameter"