Improve transformer error handling

PFERD/__main__.py

@@ -7,6 +7,7 @@ from .cli import PARSER, load_default_section
 from .config import Config, ConfigDumpError, ConfigLoadError, ConfigOptionError
 from .logging import log
 from .pferd import Pferd
+from .transformer import RuleParseError
 from .version import NAME, VERSION
 
 
@@ -122,6 +123,10 @@ def main() -> None:
         log.unlock()
         log.error(str(e))
         exit(1)
+    except RuleParseError as e:
+        log.unlock()
+        e.pretty_print()
+        exit(1)
     except KeyboardInterrupt:
         log.unlock()
         log.explain_topic("Interrupted, exiting immediately")

PFERD/transformer.py

@@ -6,10 +6,11 @@
 import ast
 import re
 from abc import ABC, abstractmethod
-from dataclasses import dataclass
 from pathlib import PurePath
 from typing import Dict, Optional, Union
 
+from .logging import log
+
 
 class Rule(ABC):
     @abstractmethod
@@ -122,16 +123,18 @@ class ReRule(Rule):
         return False
 
 
-@dataclass
+class RuleParseError(Exception):
-class RuleParseException(Exception):
+    def __init__(self, line: "Line", reason: str):
-    line: "Line"
+        super().__init__(f"Error in rule on line {line.line_nr}, column {line.index}: {reason}")
-    reason: str
+
+        self.line = line
+        self.reason = reason
 
     def pretty_print(self) -> None:
-        print(f"Error parsing rule on line {self.line.line_nr}:")
+        log.error(f"Error parsing rule on line {self.line.line_nr}:")
-        print(self.line.line)
+        log.error_contd(self.line.line)
         spaces = " " * self.line.index
-        print(f"{spaces}^--- {self.reason}")
+        log.error_contd(f"{spaces}^--- {self.reason}")
 
 
 class Line:
@@ -170,7 +173,7 @@ class Line:
             if self.get() == char:
                 self.advance()
             else:
-                raise RuleParseException(self, f"Expected {char!r}")
+                raise RuleParseError(self, f"Expected {char!r}")
 
 
 QUOTATION_MARKS = {'"', "'"}
@@ -186,7 +189,7 @@ def parse_string_literal(line: Line) -> str:
     if quotation_mark not in QUOTATION_MARKS:
         # This should never happen as long as this function is only called from
         # parse_string.
-        raise RuleParseException(line, "Invalid quotation mark")
+        raise RuleParseError(line, "Invalid quotation mark")
     line.advance()
 
     while c := line.get():
@@ -204,7 +207,7 @@ def parse_string_literal(line: Line) -> str:
         else:
             line.advance()
 
-    raise RuleParseException(line, "Expected end of string literal")
+    raise RuleParseError(line, "Expected end of string literal")
 
 
 def parse_until_space_or_eol(line: Line) -> str:
@@ -235,12 +238,12 @@ def parse_arrow(line: Line) -> str:
     while True:
         c = line.get()
         if not c:
-            raise RuleParseException(line, "Expected rest of arrow")
+            raise RuleParseError(line, "Expected rest of arrow")
         elif c == "-":
             line.advance()
             c = line.get()
             if not c:
-                raise RuleParseException(line, "Expected rest of arrow")
+                raise RuleParseError(line, "Expected rest of arrow")
             elif c == ">":
                 line.advance()
                 break  # End of arrow
@@ -267,7 +270,7 @@ def parse_rule(line: Line) -> Rule:
     left = parse_string(line)
     if isinstance(left, bool):
         line.index = leftindex
-        raise RuleParseException(line, "Left side can't be '!'")
+        raise RuleParseError(line, "Left side can't be '!'")
 
     # Parse arrow
     parse_whitespace(line)
@@ -301,7 +304,7 @@ def parse_rule(line: Line) -> Rule:
         return NameRule(ReRule(left, right))
     else:
         line.index = arrowindex + 1  # For nicer error message
-        raise RuleParseException(line, "Invalid arrow name")
+        raise RuleParseError(line, "Invalid arrow name")
 
 
 class Transformer: