fix(signature): avoid generating signatures

Avoid generating signatures if no signatures are specified.

tartufo/scanner.py

@@ -425,9 +425,13 @@ def signature_is_excluded(self, blob: str, file_path: str) -> bool:
         :param blob: The piece of data which is being scanned
         :param file_path: The path and file name for the data being scanned
         """
+        excluded_signatures = self.excluded_signatures
+        if len(excluded_signatures) == 0:
+            return False
+
         return (
             blob
-            in self.excluded_signatures  # Signatures themselves pop up as entropy matches
+            in excluded_signatures  # Signatures themselves pop up as entropy matches
             or util.generate_signature(blob, file_path) in self.excluded_signatures
         )
 

tests/test_base_scanner.py

@@ -322,6 +322,13 @@ def test_rule_patterns_with_rule_patterns_syntax_issue(self):
 
 
 class SignatureTests(ScannerTestCase):
+    @mock.patch("tartufo.util.generate_signature")
+    def test_no_signatures_should_not_generate_signature(self, mock_signature: mock.MagicMock):
+        test_scanner = TestScanner(self.options)
+        self.options.exclude_signatures = ()
+        mock_signature.assert_not_called()
+        self.assertFalse(test_scanner.signature_is_excluded("bar", "blah"))
+
     @mock.patch("tartufo.util.generate_signature")
     def test_matched_signatures_are_excluded(self, mock_signature: mock.MagicMock):
         mock_signature.return_value = "foo"