fix(grainfmt): Print comments found between comma-separated data statements (#1430)

Author: marcusroberts

compiler/src/formatting/format.re

@@ -3742,19 +3742,37 @@ let data_print =
       ~comments: list(Parsetree.comment),
       datas: list((Parsetree.export_flag, Parsetree.data_declaration)),
     ) => {
+  let previous_data: ref(option(Parsetree.data_declaration)) = ref(None);
   Doc.join(
     ~sep=Doc.concat([Doc.comma, Doc.hardLine]),
     List.map(
       data => {
         let (expt, decl: Parsetree.data_declaration) = data;
 
+        let leading_comments =
+          switch (previous_data^) {
+          | None => []
+          | Some(prev) =>
+            Comment_utils.get_comments_between_locations(
+              ~loc1=prev.pdata_loc,
+              ~loc2=decl.pdata_loc,
+              comments,
+            )
+          };
+
+        let leading_comment_docs =
+          Comment_utils.new_comments_to_docs(leading_comments);
+
         let data_comments =
           Comment_utils.get_comments_inside_location(
             ~location=decl.pdata_loc,
             comments,
           );
 
+        previous_data := Some(decl);
+
         Doc.concat([
+          leading_comment_docs,
           switch ((expt: Asttypes.export_flag)) {
           | Nonexported => Doc.nil
           | Exported => Doc.text("export ")

compiler/test/formatter_inputs/data_docs.gr

@@ -0,0 +1,23 @@
+enum EventType {
+  Enter,
+  Exit,
+},
+/**
+ *   An event is the start or end of a token amongst other events.
+ *   Tokens can “contain” other tokens, even though they are stored in a flat
+ *   list, through `enter`ing before them, and `exit`ing after them.
+ */
+type Event = (EventType, Token, TokenizeContext),
+/**
+ *   Another event is the start or end of a token amongst other events.
+ *   Tokens can “contain” other tokens, even though they are stored in a flat
+ *   list, through `enter`ing before them, and `exit`ing after them.
+ */
+
+
+enum EventType2 {
+  Enter2,
+  Exit2,
+},
+// line comment
+type Event2 = (EventType2, Token, TokenizeContext)

compiler/test/formatter_outputs/data_docs.gr

@@ -0,0 +1,21 @@
+enum EventType {
+  Enter,
+  Exit,
+},
+/**
+ *   An event is the start or end of a token amongst other events.
+ *   Tokens can “contain” other tokens, even though they are stored in a flat
+ *   list, through `enter`ing before them, and `exit`ing after them.
+ */
+type Event = (EventType, Token, TokenizeContext),
+/**
+ *   Another event is the start or end of a token amongst other events.
+ *   Tokens can “contain” other tokens, even though they are stored in a flat
+ *   list, through `enter`ing before them, and `exit`ing after them.
+ */
+enum EventType2 {
+  Enter2,
+  Exit2,
+},
+// line comment
+type Event2 = (EventType2, Token, TokenizeContext)

compiler/test/suites/formatter.re

@@ -48,5 +48,6 @@ describe("formatter", ({test, testSkip}) => {
   assertFormatOutput("rationals", "rationals");
   assertFormatOutput("constraints", "constraints");
   assertFormatOutput("only_comments", "only_comments");
+  assertFormatOutput("data_docs", "data_docs");
   assertFormatOutput("custom_operators", "custom_operators");
 });