Add support for printing optional catch binding (#2570)

src/parser-babylon.js

@@ -23,7 +23,8 @@ function parse(text, parsers, opts) {
       "functionSent",
       "dynamicImport",
       "numericSeparator",
-      "importMeta"
+      "importMeta",
+      "optionalCatchBinding"
     ]
   };
 

src/printer.js

@@ -1552,9 +1552,8 @@ function genericPrintNoParens(path, options, print, args) {
       ]);
     case "CatchClause":
       return concat([
-        "catch (",
-        path.call(print, "param"),
-        ") ",
+        "catch ",
+        n.param ? concat(["(", path.call(print, "param"), ") "]) : "",
         path.call(print, "body")
       ]);
     case "ThrowStatement":

tests/optional_catch_binding/__snapshots__/jsfmt.spec.js.snap

@@ -0,0 +1,19 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`optional_catch_binding.js 1`] = `
+try {
+
+}
+catch {
+
+}
+finally {
+
+}
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+try {
+} catch {
+} finally {
+}
+
+`;

tests/optional_catch_binding/jsfmt.spec.js

@@ -0,0 +1 @@
+run_spec(__dirname, { parser: "babylon" });

tests/optional_catch_binding/optional_catch_binding.js

@@ -0,0 +1,9 @@
+try {
+
+}
+catch {
+
+}
+finally {
+
+}