Provide more descriptive error message when there is a duplicate line…

… to be parsed (#539)

netutils/config/parser.py

@@ -621,7 +621,14 @@ def _update_same_line_children_configs(self) -> None:
         new_config_lines: t.List[ConfigLine] = []
         for line in self.config_lines:
             if line in self.same_line_children:
-                previous_line = new_config_lines[-1]
+                try:
+                    previous_line = new_config_lines[-1]
+                except IndexError as error:
+                    raise IndexError(
+                        f"This error is likely from a duplicate line detected at the line `{line.config_line}`, "
+                        "see https://netutils.readthedocs.io/en/latest/dev/dev_config/#duplicate-line-detection "
+                        f"for more details.\nOriginal Error: {error}"
+                    )
                 previous_config_line = previous_line.config_line
                 current_parents = previous_line.parents + (previous_config_line,)
                 line = ConfigLine(line.config_line, current_parents)

tests/unit/test_parser.py

@@ -68,3 +68,14 @@ def test_incorrect_banner_ios():
     )
     with pytest.raises(ValueError):
         compliance.parser_map["cisco_ios"](banner_cfg).config_lines  # pylint: disable=expression-not-assigned
+
+
+def test_duplicate_line():
+    logging = (
+        "!\n"
+        "snmp-server community <<REPLACED>> RO SNMP_ACL_RO\n"
+        "snmp-server community <<REPLACED>> RO SNMP_ACL_RO\n"
+        "snmp-server community <<REPLACED>> RW SNMP_ACL_RW\n"
+    )
+    with pytest.raises(IndexError, match=r".*This error is likely from a duplicate line detected.*"):
+        compliance.parser_map["cisco_ios"](logging).config_lines  # pylint: disable=expression-not-assigned