Fix else keyword not being part of SynIfThenElse range. Fixes #713 (#724

)

src/Fantomas.Tests/IfThenElseTests.fs

@@ -804,4 +804,68 @@ module String =
         if la <> lb then if la > lb then a' else b'
         else if String.length a' < String.length b' then a'
         else b'
+"""
+
+[<Test>]
+let ``second else if where else and if are on separate lines, 713`` () =
+    formatSourceString false """if v1 < v2 then
+    -1
+elif v1 > v2 then
+    1
+else
+    if t1 < t2 then
+        -1
+    elif t1 > t2 then
+        1
+    else
+        0
+"""  config
+    |> prepend newline
+    |> should equal """
+if v1 < v2 then -1
+elif v1 > v2 then 1
+else if t1 < t2 then -1
+elif t1 > t2 then 1
+else 0
+"""
+
+[<Test>]
+let ``newline between else if,  prior by elif`` () =
+    formatSourceString false """
+module String =
+    let merge a b =
+            if la <> lb then
+                if la > lb then a' else b'
+            elif la = lb then a'
+            else
+                if String.length a' < String.length b' then a' else b'
+"""  config
+    |> prepend newline
+    |> should equal """
+module String =
+    let merge a b =
+        if la <> lb then if la > lb then a' else b'
+        elif la = lb then a'
+        else if String.length a' < String.length b' then a'
+        else b'
+"""
+
+[<Test>]
+let ``newline between else if, followed by else if`` () =
+    formatSourceString false """
+module String =
+    let merge a b =
+            if la <> lb then
+                if la > lb then a' else b'
+            else
+                if String.length a' < String.length b' then a' else if String.length a' > String.length b' then b' else b'
+"""  config
+    |> prepend newline
+    |> should equal """
+module String =
+    let merge a b =
+        if la <> lb then if la > lb then a' else b'
+        else if String.length a' < String.length b' then a'
+        else if String.length a' > String.length b' then b'
+        else b'
 """

src/Fantomas/CodePrinter.fs

@@ -1151,46 +1151,38 @@ and genExpr astContext synExpr =
     | ElIf((e1,e2, _, _, _)::es, enOpt) ->
         // https://docs.microsoft.com/en-us/dotnet/fsharp/style-guide/formatting#formatting-if-expressions
         fun ctx ->
-            let elseKeywordRange =
-                ctx.Trivia
-                |> TriviaHelpers.``keyword tokens inside range`` ["IF"; "THEN"; "ELIF"; "ELSE"] synExpr.Range
-                |> fun tokens ->
-                    // skip if .. then and take first else keyword
-                    // ignore if third keyword is elif f.ex.
-
-                    match synExpr with
-                    // elif keyword matches the start of the optional else expression
-                    | SynExpr.IfThenElse(_, _, Some(optionalExprElse), _, _, _, _)
-                        when (List.exists (fun ({ TokenName = tn }: FSharpTokenInfo,t) -> tn = "ELIF" && t.Range.Start = optionalExprElse.Range.Start) tokens) ->
-                        None
-                    // the else keyword is floating between the thenExpression and the optional elseExpression
-                    | SynExpr.IfThenElse(_, exprThen, Some(_), _, _, _, _) ->
-                        let filtered =
-                            tokens
-                            |> List.filter (fun ({ TokenName = tn }, t) -> tn = "ELSE" && RangeHelpers.``range starts after`` exprThen.Range t.Range)
-                            |> List.tryHead
-                            |> Option.map (fun (_,t) -> t.Range)
-                        filtered
-
+            let correctedElifRanges =
+                es
+                |> List.pairwise
+                |> List.map (fun ((_,beforeNode,_,_,_),(_,_,_,_, node)) -> (beforeNode.Range, node.Range))
+                |> fun tail ->
+                    match es with
+                    | (_,_,_,_,hn)::_ -> (e2.Range, hn.Range)::tail
+                    | _ -> tail
+                |> List.indexed
+                |> List.choose(fun (idx, (beforeRange, elseIfRange)) ->
+                    let rangeBetween = mkRange "between" beforeRange.End elseIfRange.Start
+                    let keywordsFoundInBetween = TriviaHelpers.``keyword tokens inside range`` ["ELSE"] rangeBetween ctx.Trivia
+                    match List.tryHead keywordsFoundInBetween with
+                    | Some (_, elseKeyword) ->
+                        (idx, mkRange "else if" elseKeyword.Range.Start elseIfRange.End)
+                        |> Some
                     | _ ->
                         None
+                )
+                |> Map.ofList
 
             let elfis =
-                let lastEsIndex = (List.length es) - 1
                 List.indexed es
                 |> List.map (fun (idx, (elf1, elf2, _, fullRange, _)) ->
-                    if idx = lastEsIndex then
                         // In some scenarios the last else keyword of the 'else if' combination is not included in inner IfThenElse syn expr
                         // f.ex if  a then b else // meh
                         //          if c then d else e
                         let correctedRange =
-                            match elseKeywordRange with
-                            | Some er -> mkRange "else if" er.Start fullRange.End
-                            | None -> fullRange
-                        (elf1, elf2, correctedRange)
-                    else
-                        (elf1, elf2, fullRange)
-            )
+                            Map.tryFind idx correctedElifRanges
+                            |> Option.defaultValue fullRange
+
+                        (elf1, elf2, correctedRange))
 
             let hasElfis = not (List.isEmpty elfis)