[issue1030] translator: Improve PDDL error reporting.

We have substantially extended the PDDL syntax checks in the translator. Many PDDL errors are now diagnosed much better and lead to a meaningful error message and exit code where previously they would trigger failed assertions or be silently accepted with unclear semantics.

src/translate/pddl/tasks.py

@@ -68,15 +68,22 @@ def dump(self):
             for axiom in self.axioms:
                 axiom.dump()
 
+
+REQUIREMENT_LABELS = [
+    ":strips", ":adl", ":typing", ":negation", ":equality",
+    ":negative-preconditions", ":disjunctive-preconditions",
+    ":existential-preconditions", ":universal-preconditions",
+    ":quantified-preconditions", ":conditional-effects",
+    ":derived-predicates", ":action-costs"
+]
+
+
 class Requirements:
     def __init__(self, requirements: List[str]):
         self.requirements = requirements
         for req in requirements:
-            assert req in (
-              ":strips", ":adl", ":typing", ":negation", ":equality",
-              ":negative-preconditions", ":disjunctive-preconditions",
-              ":existential-preconditions", ":universal-preconditions",
-              ":quantified-preconditions", ":conditional-effects",
-              ":derived-predicates", ":action-costs"), req
+            if req not in REQUIREMENT_LABELS:
+                raise ValueError(f"Invalid requirement. Got: {req}\n"
+                                 f"Expected: {', '.join(REQUIREMENT_LABELS)}")
     def __str__(self):
         return ", ".join(self.requirements)

src/translate/pddl_parser/__init__.py

@@ -1 +1,2 @@
+from .parse_error import ParseError
 from .pddl_file import open

src/translate/pddl_parser/lisp_parser.py

@@ -1,20 +1,18 @@
-__all__ = ["ParseError", "parse_nested_list"]
+__all__ = ["parse_nested_list"]
 
-class ParseError(Exception):
-    def __init__(self, value):
-        self.value = value
-    def __str__(self):
-        return self.value
+from .parse_error import ParseError
 
 # Basic functions for parsing PDDL (Lisp) files.
 def parse_nested_list(input_file):
     tokens = tokenize(input_file)
     next_token = next(tokens)
     if next_token != "(":
-        raise ParseError("Expected '(', got %s." % next_token)
+        raise ParseError(f"Expected '(', got '{next_token}'.")
     result = list(parse_list_aux(tokens))
-    for tok in tokens:  # Check that generator is exhausted.
-        raise ParseError("Unexpected token: %s." % tok)
+    remaining_tokens = list(tokens)
+    if remaining_tokens:
+        raise ParseError(f"Tokens remaining after parsing: "
+                         f"{' '.join(remaining_tokens)}")
     return result
 
 def tokenize(input):
@@ -23,8 +21,7 @@ def tokenize(input):
         try:
             line.encode("ascii")
         except UnicodeEncodeError:
-            raise ParseError("Non-ASCII character outside comment: %s" %
-                             line[0:-1])
+            raise ParseError(f"Non-ASCII character outside comment: {line[0:-1]}")
         line = line.replace("(", " ( ").replace(")", " ) ").replace("?", " ?")
         for token in line.split():
             yield token.lower()

src/translate/pddl_parser/parse_error.py

@@ -0,0 +1,2 @@
+class ParseError(Exception):
+    pass