Implement spread array printer

Author: shulhi

jscomp/syntax/src/res_core.ml

@@ -4006,8 +4006,9 @@ and parseArrayExp p =
   let collectExprs = function 
     | [], Some spread, _startPos, _endPos -> [spread]
     | exprs, Some spread, _startPos, _endPos -> (
-      let els = Ast_helper.Exp.array ~loc exprs
-      in [els; spread])
+      let els = Ast_helper.Exp.array ~loc exprs in
+      let _spread_expr = {spread with Parsetree.pexp_attributes = [spreadAttr]} in
+      [els; spread])
     | exprs, None, _startPos, _endPos -> (
       let els = Ast_helper.Exp.array ~loc exprs
       in [els])

jscomp/syntax/src/res_parsetree_viewer.ml

@@ -104,6 +104,11 @@ let hasAwaitAttribute attrs =
       | _ -> false)
     attrs
 
+let collectArrayExpressions expr =
+  match expr.pexp_desc with
+  | Pexp_array exprs -> (exprs, None)
+  | _ -> ([], Some expr)
+
 let collectListExpressions expr =
   let rec collect acc expr =
     match expr.pexp_desc with
@@ -678,6 +683,17 @@ let isSpreadBeltListConcat expr =
     hasSpreadAttr expr.pexp_attributes
   | _ -> false
 
+let isSpreadBeltArrayConcat expr =
+  match expr.pexp_desc with
+  | Pexp_ident
+      {
+        txt =
+          Longident.Ldot
+            (Longident.Ldot (Longident.Lident "Belt", "Array"), "concatMany");
+      } ->
+    hasSpreadAttr expr.pexp_attributes
+  | _ -> false
+
 (* Blue | Red | Green -> [Blue; Red; Green] *)
 let collectOrPatternChain pat =
   let rec loop pattern chain =

jscomp/syntax/src/res_parsetree_viewer.mli

@@ -46,6 +46,10 @@ val collectIfExpressions :
   (Location.t * ifConditionKind * Parsetree.expression) list
   * Parsetree.expression option
 
+val collectArrayExpressions :
+  Parsetree.expression ->
+  Parsetree.expression list * Parsetree.expression option
+
 val collectListExpressions :
   Parsetree.expression ->
   Parsetree.expression list * Parsetree.expression option
@@ -142,6 +146,8 @@ val hasTemplateLiteralAttr : Parsetree.attributes -> bool
 
 val isSpreadBeltListConcat : Parsetree.expression -> bool
 
+val isSpreadBeltArrayConcat : Parsetree.expression -> bool
+
 val collectOrPatternChain : Parsetree.pattern -> Parsetree.pattern list
 
 val processBracesAttr :

jscomp/syntax/src/res_printer.ml

@@ -3046,6 +3046,9 @@ and printExpression ~state (e : Parsetree.expression) cmtTbl =
                Doc.rbrace;
              ])
       | extension -> printExtension ~state ~atModuleLvl:false extension cmtTbl)
+    | Pexp_apply (e, [(Nolabel, {pexp_desc = Pexp_array subLists})])
+      when ParsetreeViewer.isSpreadBeltArrayConcat e ->
+      printBeltArrayConcatApply ~state subLists cmtTbl
     | Pexp_apply (e, [(Nolabel, {pexp_desc = Pexp_array subLists})])
       when ParsetreeViewer.isSpreadBeltListConcat e ->
       printBeltListConcatApply ~state subLists cmtTbl
@@ -3813,6 +3816,61 @@ and printBinaryExpression ~state (expr : Parsetree.expression) cmtTbl =
          ])
   | _ -> Doc.nil
 
+and printBeltArrayConcatApply ~state subLists cmtTbl =
+  let makeSpreadDoc commaBeforeSpread = function
+    | Some expr ->
+      Doc.concat
+        [
+          commaBeforeSpread;
+          Doc.dotdotdot;
+          (let doc = printExpressionWithComments ~state expr cmtTbl in
+           match Parens.expr expr with
+           | Parens.Parenthesized -> addParens doc
+           | Braced braces -> printBraces doc expr braces
+           | Nothing -> doc);
+        ]
+    | None -> Doc.nil
+  in
+  let makeSubListDoc (expressions, spread) =
+    let commaBeforeSpread =
+      match expressions with
+      | [] -> Doc.nil
+      | _ -> Doc.concat [Doc.text ","; Doc.line]
+    in
+    let spreadDoc = makeSpreadDoc commaBeforeSpread spread in
+    Doc.concat
+      [
+        Doc.join
+          ~sep:(Doc.concat [Doc.text ","; Doc.line])
+          (List.map
+             (fun expr ->
+               let doc = printExpressionWithComments ~state expr cmtTbl in
+               match Parens.expr expr with
+               | Parens.Parenthesized -> addParens doc
+               | Braced braces -> printBraces doc expr braces
+               | Nothing -> doc)
+             expressions);
+        spreadDoc;
+      ]
+  in
+  Doc.group
+    (Doc.concat
+       [
+         Doc.lbracket;
+         Doc.indent
+           (Doc.concat
+              [
+                Doc.softLine;
+                Doc.join
+                  ~sep:(Doc.concat [Doc.text ","; Doc.line])
+                  (List.map makeSubListDoc
+                     (List.map ParsetreeViewer.collectArrayExpressions subLists));
+              ]);
+         Doc.trailingComma;
+         Doc.softLine;
+         Doc.rbracket;
+       ])
+
 and printBeltListConcatApply ~state subLists cmtTbl =
   let makeSpreadDoc commaBeforeSpread = function
     | Some expr ->