update pretty printer to print line comments while forcing multiline

comments for lists that break `IfNeed`ed

Author: dxu

src/reason_pprint_ast.ml

@@ -1215,12 +1215,21 @@ let smallestLeadingSpaces strs =
   in
   smallestLeadingSpaces 99999 strs
 
-let formatItemComment (str, commLoc) =
+(*
+  forceMultiline should be set to true in cases where the comment
+  is part of a list that could potentially break to prevent inline
+  comments from being rendered as line comments
+*)
+let formatItemComment ?(forceMultiline=false) (str, commLoc) =
   let commLines = Str.split_delim (Str.regexp "\n") ("/*" ^ str ^ "*/") in
   match commLines with
   | [] -> easyAtom ""
   | [hd] ->
-    makeEasyList ~inline:(true, true) ~postSpace:true ~preSpace:true ~indent:0 ~break:IfNeed [easyAtom hd]
+    if forceMultiline then
+      makeEasyList ~inline:(true, true) ~postSpace:true ~preSpace:true ~indent:0 ~break:IfNeed [easyAtom hd]
+    (* caveat: single line comment . *)
+    else
+      makeEasyList ~inline:(true, true) ~postSpace:true ~preSpace:true ~indent:0 ~break:IfNeed [easyAtom ("//" ^ str)]
   | zero::one::tl ->
     let lineZero = List.nth commLines 0 in
     let lineOne = List.nth commLines 1 in
@@ -1240,7 +1249,7 @@ let formatItemComment (str, commLoc) =
     (* Use the Str module for regex splitting *)
     makeEasyList ~inline:(true, true) ~indent:0 ~break:Always_rec (List.map easyAtom lines)
 
-let formatComments comms = List.map formatItemComment comms
+let formatComments ?(forceMultiline=false) comms = List.map (formatItemComment ~forceMultiline:forceMultiline) comms
 
 let convertIsListyToIsSequencey isListyImpl =
   let rec isSequencey layoutNode = match layoutNode with
@@ -1279,7 +1288,16 @@ let rec interleaveComments listConfig layoutListItems comments =
         | _ -> ([], layoutToEasyFormatAndSurplus hd comments)
       in
       let (recItems, recUnconsumedComms) = interleaveComments listConfig tl unconsumedComms in
-      let easyComments = List.map (fun c -> Comment (formatItemComment c)) itemComments in
+      let easyComments = match listConfig.break with
+        (*
+         * If the comment is part of a list that isn't meant to break, or potentially might not break,
+         * we need to force it to be a multiline string due to interleaving
+         *)
+        | IfNeed | Never ->
+          List.map (fun c -> Comment (formatItemComment ~forceMultiline:true c)) itemComments
+        | _ ->
+          List.map (fun c -> Comment (formatItemComment ~forceMultiline:false c)) itemComments
+      in
       (List.concat [easyComments; [Item easyItem]; recItems], recUnconsumedComms)
 
 and attach listConfig ~useSep easyItem = match (listConfig.sep, listConfig.preSpace, listConfig.postSpace) with
@@ -1343,10 +1361,20 @@ and layoutToEasyFormatAndSurplus layoutNode comments = match layoutNode with
           listConfig
           [subLayout]
           afterStart in
-      match (beforeStart, items, listConfig.wrap) with
-        | (_, [], _) -> raise (NotPossible "No items")
-        | ([], [singleItem], ("", "")) -> (singleItem, unconsumed)
-        | (leadingComms, items, _) -> (
+      match (beforeStart, items, listConfig.wrap, listConfig.break) with
+        | (_, [], _, _) -> raise (NotPossible "No items")
+        | ([], [singleItem], ("", ""), _) -> (singleItem, unconsumed)
+        (*
+         * If the comment is part of a list that isn't meant to break, or potentially might not break,
+         * we need to force it to be a multiline string due to interleaving
+         *)
+        | (leadingComms, items, _, IfNeed) | (leadingComms, items, _, Never)-> (
+          easyListWithConfig
+            listConfig
+            (List.concat [formatComments ~forceMultiline:true leadingComms; items;]),
+          unconsumed
+          )
+        | (leadingComms, items, _, _) -> (
           easyListWithConfig
             listConfig
             (List.concat [formatComments leadingComms; items;]),