Use simple diff to output xform result.

Author: cristianoc

analysis/src/Xform.ml

@@ -111,11 +111,40 @@ let parse ~filename =
   in
   (structure, print)
 
+let diff ~filename ~newContents =
+  match Files.readFile ~filename with
+  | None -> assert false
+  | Some oldContents ->
+    let rec findFirstLineDifferent n old new_ =
+      match (old, new_) with
+      | old1 :: oldRest, new1 :: newRest ->
+        if old1 = new1 then findFirstLineDifferent (n + 1) oldRest newRest
+        else (n, old, new_)
+      | _ -> (n, old, new_)
+    in
+    let oldLines = String.split_on_char '\n' oldContents in
+    let newLines = String.split_on_char '\n' newContents in
+    let firstLineDifferent, old, new_ =
+      findFirstLineDifferent 0 oldLines newLines
+    in
+    let firstLineR, _oldR, newR =
+      findFirstLineDifferent 0 (List.rev old) (List.rev new_)
+    in
+    let lastLineEqual = firstLineDifferent + List.length old - firstLineR in
+    let newLines = List.rev newR in
+    (firstLineDifferent, lastLineEqual, newLines)
+
 let command ~path ~pos =
   if Filename.check_suffix path ".res" then
     let structure, print = parse ~filename:path in
     match IfThenElse.xform ~pos structure with
     | None -> ()
     | Some newStructure ->
       let formatted = print newStructure in
-      Printf.printf "Hit IfThenElse. Formatted:\n%s" formatted
+      let firstLineDifferent, lastLineEqual, newLines =
+        diff ~filename:path ~newContents:formatted
+      in
+      Printf.printf
+        "Hit IfThenElse firstLineDifferent:%d lastLineEqual:%d newLines:\n%s\n"
+        firstLineDifferent lastLineEqual
+        (newLines |> String.concat "\n")

analysis/tests/src/expected/Xform.res.txt

@@ -1,36 +1,13 @@
 Xform tests/src/Xform.res 6:5
-Hit IfThenElse. Formatted:
-type kind = First | Second | Third
-type r = {name: string, age: int}
-
-let ret = _ => assert false
-let kind = assert false
-
+Hit IfThenElse firstLineDifferent:6 lastLineEqual:11 newLines:
 switch kind {
 | First =>
   // ^xfm
   ret("First")
 | _ => ret("Not First")
-}
-
-#kind("First", {name: "abc", age: 3}) != kind ? ret("Not First") : ret("First")
-//             ^xfm
 
 Xform tests/src/Xform.res 13:15
-Hit IfThenElse. Formatted:
-type kind = First | Second | Third
-type r = {name: string, age: int}
-
-let ret = _ => assert false
-let kind = assert false
-
-if kind == First {
-  // ^xfm
-  ret("First")
-} else {
-  ret("Not First")
-}
-
+Hit IfThenElse firstLineDifferent:13 lastLineEqual:15 newLines:
 switch kind {
 | #kind("First", {name: "abc", age: 3}) => ret("First")
 //             ^xfm