Fix a bug with whitespace linter

Summary: Fix a MySqlWhitespace linter bug where it matches two whitespace lines too aggressively. We should discard whitespace only lines in the comparison since it is too easy for them to accidentally match

Reviewed By: lth

Differential Revision: D13776064

fbshipit-source-id: 1311a69

arcanist/lint/linter/FacebookMySQLWhitespaceLinter.php

@@ -121,6 +121,19 @@ private function stripWhitespace($str) {
   }
 
   private function differsByWhitespaceOnly($line1, $line2) {
-    return $this->stripWhitespace($line1) === $this->stripWhitespace($line2);
+    if ($line1 === $line2) {
+      // Definitely don't flag two identical lines
+      return false;
+    }
+
+    $stripped_line1 = $this->stripWhitespace($line1);
+    $stripped_line2 = $this->stripWhitespace($line2);
+    if ($stripped_line1 === "" and
+        $stripped_line2 === "") {
+      // Don't want to flag two whitespace only lines by accident
+      return false;
+    }
+
+    return $stripped_line1 === $stripped_line2;
   }
 }