fix: do not export duplicate keys

Author: joscha

lib/compile-exports.js

@@ -16,10 +16,11 @@ module.exports = function compileExports(result, importItemMatcher, camelCaseKey
     valueAsString = valueAsString.replace(result.importItemRegExpG, importItemMatcher);
     res.push("\t" + JSON.stringify(key) + ": " + valueAsString);
 
-    if (camelCaseKeys === true) {
-      res.push("\t" + JSON.stringify(camelCase(key)) + ": " + valueAsString);
-    } else if (camelCaseKeys === 'dashes') {
-      res.push("\t" + JSON.stringify(dashesCamelCase(key)) + ": " + valueAsString);
+    var targetKey;
+    if (camelCaseKeys === true && (targetKey = camelCase(key)) !== key) {
+      res.push("\t" + JSON.stringify(targetKey) + ": " + valueAsString);
+    } else if (camelCaseKeys === 'dashes' && (targetKey = dashesCamelCase(key)) !== key) {
+      res.push("\t" + JSON.stringify(targetKey) + ": " + valueAsString);
     }
 
     return res;