From 83825983fcd1c7ca97c4919cb78048d30100cc44 Mon Sep 17 00:00:00 2001
From: Evan Scott <glitterbyte@gmail.com>
Date: Thu, 26 Jan 2017 12:35:34 -0500
Subject: [PATCH] Patch dangerfile to only do use strict checks on non-es
 modules (#2709)

ES modules are strict mode by default, so the check should look
for use of "import"/"export" to determine if flagging is required.
---
 dangerfile.js | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/dangerfile.js b/dangerfile.js
index 7dce213b5b7d..244dff3d72f5 100644
--- a/dangerfile.js
+++ b/dangerfile.js
@@ -86,11 +86,15 @@ const noFlowFiles = newJsFiles
 
 raiseIssueAboutPaths(warn, noFlowFiles, '@flow');
 
+// based on assumptions from https://github.com/nodejs/node/wiki/ES6-Module-Detection-in-Node
+// basically it needs to contain at least one line with import or export at the
+// beginning of it, followed by a space; any content thereafter doesn't matter
+const esModuleRegex = /^(import|export)\s/g;
 
-// Ensure the use of 'use strict'; on all files
+// Ensure the use of 'use strict' on all non-ES module files
 const noStrictFiles = newJsFiles.filter(filepath => {
   const content = fs.readFileSync(filepath).toString();
-  return !includes(content, 'use strict');
+  return !esModuleRegex.test(content) && !includes(content, 'use strict');
 });
 
 raiseIssueAboutPaths(fail, noStrictFiles, "'use strict'");