Improve statement parsing: clear diagnostics, paren validation

brian2/parsing/statements.py

@@ -3,23 +3,29 @@
     Combine,
     Optional,
     ParseException,
+    ParseSyntaxException,
     Regex,
     Suppress,
     Word,
     alphas,
     nums,
+    restOfLine,
 )
 
 from brian2.utils.caching import cached
 
 VARIABLE = Word(f"{alphas}_", f"{alphas + nums}_").set_results_name("variable")
 
-OP = Regex(r"(\+|\-|\*|/|//|%|\*\*|>>|<<|&|\^|\|)?=").set_results_name("operation")
+OP = (
+    Regex(r"(\+|\-|\*|/|//|%|\*\*|>>|<<|&|\^|\|)?=")
+    .set_results_name("operation")
+    .set_name("assignment operator")
+)
 EXPR = Combine(
     CharsNotIn("=", min=1, max=1) + Optional(CharsNotIn("#"))
 ).set_results_name("expression")
-COMMENT = Optional(CharsNotIn("#")).set_results_name("comment")
-STATEMENT = VARIABLE + OP + EXPR + Optional(Suppress("#") + COMMENT)
+COMMENT = restOfLine.set_results_name("comment")
+STATEMENT = VARIABLE - OP - EXPR + Optional(Suppress("#") + COMMENT)
 
 
 @cached
@@ -49,20 +55,26 @@ def parse_statement(code):
     """
     try:
         parsed = STATEMENT.parse_string(code, parseAll=True)
-    except ParseException as p_exc:
+    except (ParseException, ParseSyntaxException) as p_exc:
         raise ValueError(
-            "Parsing the statement failed: \n"
+            f"Parsing the statement failed: {p_exc.msg}\n"
             + str(p_exc.line)
             + "\n"
             + " " * (p_exc.column - 1)
             + "^\n"
-            + str(p_exc)
+            + f"(line {p_exc.lineno}, col {p_exc.column})"
         ) from p_exc
-    parsed_statement = (
-        parsed["variable"].strip(),
-        parsed["operation"],
-        parsed["expression"].strip(),
-        parsed.get("comment", "").strip(),
-    )
 
-    return parsed_statement
+    var = parsed["variable"].strip()
+    op = parsed["operation"]
+    expr = parsed["expression"].strip()
+    comment = parsed.get("comment", "").strip()
+
+    if expr.count("(") != expr.count(")"):
+        raise ValueError(
+            f"Unbalanced parentheses in expression: '{expr}'\n"
+            f"{code}\n"
+            f"{' ' * code.find(expr)}{'^' * len(expr)}"
+        )
+
+    return var, op, expr, comment

brian2/tests/test_codegen.py

@@ -502,13 +502,25 @@ def test_automatic_augmented_assignments():
         "x[0] = 3",
         "dx/dt = -v / tau",
         "v == 3*mV",
+        "v = (5 + 3",
+        "v = 5 + 3)",
     ],
 )
 def test_incorrect_statements(s):
     with pytest.raises(ValueError):
         parse_statement(s)
 
 
+@pytest.mark.codegen_independent
+def test_parse_statement_comments():
+    s = "v = 1.0 # some # comment"
+    var, op, expr, comment = parse_statement(s)
+    assert var == "v"
+    assert op == "="
+    assert expr == "1.0"
+    assert comment == "some # comment"
+
+
 def test_clear_cache():
     target = prefs.codegen.target
     if target == "numpy":