462: Fix disappearing comments in nested Ppat_or (#508)

Author: cknitt

src/res_comments_table.ml

@@ -1682,22 +1682,13 @@ and walkExprArgument (_argLabel, expr) t comments =
         recordRows
         t
         comments
-    | Ppat_or (pattern1, pattern2) ->
-      let (beforePattern1, insidePattern1, afterPattern1) =
-        partitionByLoc comments pattern1.ppat_loc
-      in
-      attach t.leading pattern1.ppat_loc beforePattern1;
-      walkPattern pattern1 t insidePattern1;
-      let (afterPattern1, rest) =
-        partitionAdjacentTrailing pattern1.ppat_loc afterPattern1
-      in
-      attach t.trailing pattern1.ppat_loc afterPattern1;
-      let (beforePattern2, insidePattern2, afterPattern2) =
-        partitionByLoc rest pattern2.ppat_loc
-      in
-      attach t.leading pattern2.ppat_loc beforePattern2;
-      walkPattern pattern2 t insidePattern2;
-      attach t.trailing pattern2.ppat_loc afterPattern2
+    | Ppat_or _->
+      walkList
+        ~getLoc: (fun pattern -> pattern.Parsetree.ppat_loc)
+        ~walkNode: (fun pattern -> walkPattern pattern)
+        (Res_parsetree_viewer.collectOrPatternChain pat)
+        t
+        comments
     | Ppat_constraint (pattern, typ) ->
       let (beforePattern, insidePattern, afterPattern) =
         partitionByLoc comments pattern.ppat_loc

tests/printer/comments/expected/pattern.res.txt

@@ -59,7 +59,21 @@ let /* before */ {
 
 // Ppat_or
 let /* b1 */ Blue /* b2 */ | /* c1 */ Red /* c2 */ = color
-let /* b1 */ Blue /* b2 */ | /* c1 */ Red | /* d1 */ Green /* d2 */ = color
+let /* b1 */ Blue /* b2 */ | /* c1 */ Red /* c2 */ | /* d1 */ Green /* d2 */ = color
+
+// #462: Comments in nested Ppat_or must not disappear.
+// (comment positions not optimal yet because `|` has no AST location)
+let _ = switch "anything" {
+// above 1
+| "1"
+| // below 1
+"2"
+| // below 2
+"3"
+| // below 3
+_ => "4"
+// below 4
+}
 
 // Ppat_constraint
 let /* c0 */ number /* c1 */: /* c2 */ int /* c3 */ = 123

tests/printer/comments/pattern.res

@@ -58,6 +58,20 @@ let /* before */ {
 let /* b1 */ Blue /* b2 */ | /* c1 */ Red /* c2 */ = color
 let /* b1 */ Blue /* b2 */ | /* c1 */ Red /* c2 */ | /* d1 */ Green /* d2 */ = color
 
+// #462: Comments in nested Ppat_or must not disappear.
+// (comment positions not optimal yet because `|` has no AST location)
+let _ = switch "anything" {
+// above 1
+| "1"
+// below 1
+| "2"
+// below 2
+| "3"
+// below 3
+| _ => "4"
+// below 4
+}
+
 // Ppat_constraint
 let /* c0 */ number /* c1 */: /* c2 */ int /* c3 */ = 123