Fix issue where printing nested pipe discards await (#688)

Author: cristianoc

CHANGELOG.md

@@ -42,6 +42,7 @@
 - Fix issue where the formatter would delete `async` in a function with labelled arguments.
 - Fix several printing issues with `async` including an infinite loop https://github.com/rescript-lang/syntax/pull/680
 - Fix issue where certain JSX expressions would be formatted differenctly in compiler 10.1.0-rc.1 https://github.com/rescript-lang/syntax/issues/675
+- Fix issue where printing nested pipe discards await https://github.com/rescript-lang/syntax/issues/687
 
 #### :eyeglasses: Spec Compliance
 

src/res_printer.ml

@@ -3604,14 +3604,29 @@ and printBinaryExpression ~customLayout (expr : Parsetree.expression) cmtTbl =
               | [] -> doc
               | _ -> addParens doc
             in
+            let isAwait =
+              ParsetreeViewer.hasAwaitAttribute expr.pexp_attributes
+            in
             let doc =
-              Doc.concat
-                [
-                  leftPrinted;
-                  printBinaryOperator ~inlineRhs:false operator;
-                  rightPrinted;
-                ]
+              if isAwait then
+                Doc.concat
+                  [
+                    Doc.text "await ";
+                    Doc.lparen;
+                    leftPrinted;
+                    printBinaryOperator ~inlineRhs:false operator;
+                    rightPrinted;
+                    Doc.rparen;
+                  ]
+              else
+                Doc.concat
+                  [
+                    leftPrinted;
+                    printBinaryOperator ~inlineRhs:false operator;
+                    rightPrinted;
+                  ]
             in
+
             let doc =
               if (not isLhs) && Parens.rhsBinaryExprOperand operator expr then
                 Doc.concat [Doc.lparen; doc; Doc.rparen]

tests/printer/expr/asyncAwait.res

@@ -96,3 +96,6 @@ let f11 = (. ~x) => (. ~y) => 3
 
 let f12 = @a (@b x) => 3
 let f13 = @a @b (~x) => 3
+
+let aw = (await (server->start))->foo
+let aw = (@foo (server->start))->foo

tests/printer/expr/expected/asyncAwait.res.txt

@@ -118,3 +118,6 @@ let f11 = (. ~x) => (. ~y) => 3
 
 let f12 = @a x => 3
 let f13 = (@a @b ~x) => 3
+
+let aw = await (server->start)->foo
+let aw = @foo (server->start)->foo