Keep parentheses of SequenceExpression for ExportDefaultDeclaration (#7491)

* Fix export default `SequenceExpression`

* Add more parser

* Add change log

* Fix  logic

* Rename that function

* Add a branch

changelog_unreleased/javascript/pr-7491.md

@@ -0,0 +1,15 @@
+#### Keep parentheses of `SequenceExpression` for `ExportDefaultDeclaration` ([#7491](https://github.com/prettier/prettier/pull/7491) by [@fisker](https://github.com/fisker))
+
+Remove parentheses of `SequenceExpression` breaks `ExportDefaultDeclaration`.
+
+<!-- prettier-ignore -->
+```jsx
+// Input
+export default (1, 2);
+
+// Prettier stable
+export default 1, 2;
+
+// Prettier master
+export default (1, 2);
+```

src/language-js/needs-parens.js

@@ -172,11 +172,15 @@ function needsParens(path, options) {
     return true;
   }
 
-  // `export default function` or `export default class` can't be followed by
-  // anything after. So an expression like `export default (function(){}).toString()`
-  // needs to be followed by a parentheses
   if (parent.type === "ExportDefaultDeclaration") {
-    return shouldWrapFunctionForExportDefault(path, options);
+    return (
+      // `export default function` or `export default class` can't be followed by
+      // anything after. So an expression like `export default (function(){}).toString()`
+      // needs to be followed by a parentheses
+      shouldWrapFunctionForExportDefault(path, options) ||
+      // `export default (foo, bar)` also needs parentheses
+      node.type === "SequenceExpression"
+    );
   }
 
   if (parent.type === "Decorator" && parent.expression === node) {

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

@@ -0,0 +1,16 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`export-default.js 1`] = `
+====================================options=====================================
+parsers: ["flow", "babel", "flow", "typescript"]
+printWidth: 80
+                                                                                | printWidth
+=====================================input======================================
+export default (1,
+2);
+
+=====================================output=====================================
+export default (1, 2);
+
+================================================================================
+`;

tests/sequence_parentheses/export-default.js

@@ -0,0 +1,2 @@
+export default (1,
+2);

tests/sequence_parentheses/jsfmt.spec.js

@@ -0,0 +1 @@
+run_spec(__dirname, ["flow", "babel", "flow", "typescript"]);