Refine grammar to avoid too much backtracking

In order to provide useful error messages, the grammar had to be more
strict and not backtract too far from where the problem actually is.

learnbot_dsl/learnbotCode/Parser.py

@@ -213,8 +213,8 @@ def used_vars(self):
     + Suppress(DOT)
     + IDENTIFIER
     + OPAR
-    + Group(Optional(delimitedList(OPERATION)))
-    + CPAR
+    - Group(Optional(delimitedList(OPERATION)))
+    - CPAR
 ).setParseAction(Call)
 
 """-----------------SIMPLECALL-------------------------"""
@@ -239,8 +239,8 @@ def used_vars(self):
 SIMPLECALL = Group(
         IDENTIFIER
         + OPAR
-        + Group(Optional(delimitedList(OPERATION)))
-        + CPAR
+        - Group(Optional(delimitedList(OPERATION)))
+        - CPAR
     ).setParseAction(SimpleCall)
 
 """-----------------OPERACIONES---------------------"""
@@ -355,7 +355,7 @@ def used_vars(self):
     INDENT
     + IDENTIFIER
     + (ASSIGN | PLUA | MINA | DIVA | MULA)
-    + OPERATION
+    - OPERATION
 ).setParseAction(Var)
 
 """-----------------LINEA---------------------------"""
@@ -454,26 +454,26 @@ def used_vars(self):
 ELSEIF << (
     INDENT
     + Suppress(Literal('elif'))
-    + OPERATION
-    + COLON
-    + LINES
+    - OPERATION
+    - COLON
+    - LINES
 ).setParseAction(ElseIf)
 
 ELSE << (
     INDENT
     + Suppress(Literal('else'))
-    + COLON
-    + LINES
+    - COLON
+    - LINES
 ).setParseAction(Else)
 
 IF = (
     INDENT
     + Suppress(Literal('if'))
-    + OPERATION
-    + COLON
-    + LINES
-    + Group(ZeroOrMore(ELSEIF) + Optional(ELSE))
-    + END
+    - OPERATION
+    - COLON
+    - LINES
+    - Group(ZeroOrMore(ELSEIF) + Optional(ELSE))
+    - END
 ).setParseAction(If)
 
 """-----------------LOOP----------------------------"""
@@ -509,10 +509,10 @@ def used_vars(self):
 BLOQUEWHILE = (
     INDENT
     + Suppress(Literal('while'))
-    + OPERATION
-    + COLON
-    + LINES
-    + END
+    - OPERATION
+    - COLON
+    - LINES
+    - END
 ).setParseAction(While)
 
 """-----------------WHEN+CONDICION------------------"""
@@ -577,14 +577,14 @@ def to_python(self, gen, *_):
 BLOQUEWHENCOND = (
     INDENT
     + Suppress(Literal('when'))
-    + IDENTIFIER
-    + Optional(
+    - IDENTIFIER
+    - Optional(
         Suppress(ASSIGN)
-        + OPERATION
+        - OPERATION
     )
-    + COLON
-    + LINES
-    + END
+    - COLON
+    - LINES
+    - END
 ).setParseAction(When)
 
 """-----------------ACTIVATE-CONDITION----------------"""
@@ -654,12 +654,12 @@ def used_vars(self):
 
 DEF = (
     Suppress(Literal('def'))
-    + IDENTIFIER
-    + OPAR
-    + CPAR
-    + COLON
-    + LINES
-    + END
+    - IDENTIFIER
+    - OPAR
+    - CPAR
+    - COLON
+    - LINES
+    - END
 ).setParseAction(Def)
 
 """-----------------IMPORT----------------------------"""
@@ -701,9 +701,9 @@ def used_vars(self):
 
 MAIN = (
     Suppress(Literal('main'))
-    + COLON
-    + LINES
-    + END
+    - COLON
+    - LINES
+    - END
 ).setParseAction(Main)
 
 class Program(Node):
@@ -731,9 +731,9 @@ def used_vars(self):
 
 LB = (
     Group(ZeroOrMore(IMPORT))
-    + Group(ZeroOrMore(LINE))
-    + Group(ZeroOrMore(DEF))
-    + Group(MAIN | ZeroOrMore(BLOQUEWHENCOND))
+    - Group(ZeroOrMore(LINE))
+    - Group(ZeroOrMore(DEF))
+    - Group(MAIN | ZeroOrMore(BLOQUEWHENCOND))
 ).setParseAction(Program)
 
 LB.ignore(pythonStyleComment)
@@ -850,8 +850,7 @@ def parserLearntBotCodeOnlyUserFuntion(code):
     text = ""
     # TODO: check for errors
     try:
-        _, tree = Parser.parse_str(code)
-
+        tree = Parser.parse_str(code)
         text = PythonGenerator.generate(tree)
     except Exception as e:
         traceback.print_exc()
@@ -882,7 +881,7 @@ def parserLearntBotCode(inputFile, outputFile, client_name):
         errors.append({
             'level': 'error',
             'message': "Parse error",
-            'from': (output.lineno, output.col),
+            'from': (e.lineno, e.col),
             'to': None,
         })
 
@@ -909,7 +908,7 @@ def parserLearntBotCodeFromCode(code, name_client):
         errors.append({
             'level': 'error',
             'message': "Parse error",
-            'from': (output.lineno, output.col),
+            'from': (e.lineno, e.col),
             'to': None,
         })
 
@@ -918,6 +917,7 @@ def parserLearntBotCodeFromCode(code, name_client):
 if __name__ == "__main__":
     textprueba = """
 
+?
 x = None
 sum = None
 result = None
@@ -975,7 +975,7 @@ def foo():
         print()
         print(PythonGenerator.generate(tree))
         print()
-    except ParseException as pe:
+    except Exception as pe:
         print(pe.line)
         print(' ' * (pe.col - 1) + '^')
         print(pe)