From 8c66e44db15dd324d44dbbe8ef1f3bafa91825db Mon Sep 17 00:00:00 2001
From: Davy Duperron <yamafaktory@gmail.com>
Date: Sat, 4 Feb 2017 22:16:24 +0100
Subject: [PATCH] Fix use strict as expression statement (#602)

* Add parentheses if node is StringLiteral surrounded by ExpressionStatement :tools:.

* Add new test.

* Update tests to run against Babylon, plus no regression case.

* Split actual test and no regression test in two files.

* Disable Flow till facebook/flow#3234 is merged.
---
 src/fast-path.js                               |  5 +++++
 .../__snapshots__/jsfmt.spec.js.snap           | 18 ++++++++++++++++++
 tests/expression_statement/jsfmt.spec.js       |  2 ++
 tests/expression_statement/no_regression.js    |  2 ++
 tests/expression_statement/use_strict.js       |  2 ++
 5 files changed, 29 insertions(+)
 create mode 100644 tests/expression_statement/__snapshots__/jsfmt.spec.js.snap
 create mode 100755 tests/expression_statement/jsfmt.spec.js
 create mode 100644 tests/expression_statement/no_regression.js
 create mode 100755 tests/expression_statement/use_strict.js

diff --git a/src/fast-path.js b/src/fast-path.js
index 53ef717c..d4dbca3a 100644
--- a/src/fast-path.js
+++ b/src/fast-path.js
@@ -497,6 +497,11 @@ FPp.needsParens = function(assumeExpressionContext) {
         return name === "object" && parent.object === node;
       }
 
+    case "StringLiteral":
+      if (parent.type === "ExpressionStatement") {
+        return true;
+      }
+
     default:
       if (
         parent.type === "NewExpression" &&
diff --git a/tests/expression_statement/__snapshots__/jsfmt.spec.js.snap b/tests/expression_statement/__snapshots__/jsfmt.spec.js.snap
new file mode 100644
index 00000000..54a281bd
--- /dev/null
+++ b/tests/expression_statement/__snapshots__/jsfmt.spec.js.snap
@@ -0,0 +1,18 @@
+exports[`test no_regression.js 1`] = `
+"// Ensure no regression.
+\"use strict\";
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+// Ensure no regression.
+\"use strict\";
+
+"
+`;
+
+exports[`test use_strict.js 1`] = `
+"// Parentheses around expression statement should be preserved in this case.
+(\"use strict\");
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+// Parentheses around expression statement should be preserved in this case.
+(\"use strict\");
+"
+`;
diff --git a/tests/expression_statement/jsfmt.spec.js b/tests/expression_statement/jsfmt.spec.js
new file mode 100755
index 00000000..67caec39
--- /dev/null
+++ b/tests/expression_statement/jsfmt.spec.js
@@ -0,0 +1,2 @@
+// TODO: Re-enable Flow when the following fix is merged facebook/flow#3234.
+run_spec(__dirname, {parser: 'babylon'});
diff --git a/tests/expression_statement/no_regression.js b/tests/expression_statement/no_regression.js
new file mode 100644
index 00000000..8a5e0f44
--- /dev/null
+++ b/tests/expression_statement/no_regression.js
@@ -0,0 +1,2 @@
+// Ensure no regression.
+"use strict";
diff --git a/tests/expression_statement/use_strict.js b/tests/expression_statement/use_strict.js
new file mode 100755
index 00000000..31bce868
--- /dev/null
+++ b/tests/expression_statement/use_strict.js
@@ -0,0 +1,2 @@
+// Parentheses around expression statement should be preserved in this case.
+("use strict");