Author: Alex Gaynor <[email protected]>
Branch:
Changeset: r59598:9c039c92f0fa
Date: 2012-12-27 14:43 -0800
http://bitbucket.org/pypy/pypy/changeset/9c039c92f0fa/
Log: Merged in nbtaylor/pypy/improved_ebnfparse_error (pull request #103:
better message for ebnf empty production error)
diff --git a/pypy/rlib/parsing/ebnfparse.py b/pypy/rlib/parsing/ebnfparse.py
--- a/pypy/rlib/parsing/ebnfparse.py
+++ b/pypy/rlib/parsing/ebnfparse.py
@@ -246,9 +246,10 @@
real_expansions.append(expansion)
real_changes.append(change)
continue
- assert n != len(expansion), (
- "currently an expansion needs at least one"
- "symbol that always has to occur")
+ if n == len(expansion):
+ raise ValueError("Rule %r's expansion needs "
+ "at least one symbol with >0 repetitions"
+ % rule.nonterminal)
slices = []
start = 0
for i, (maybe, symbol) in enumerate(
diff --git a/pypy/rlib/parsing/test/test_ebnfparse.py
b/pypy/rlib/parsing/test/test_ebnfparse.py
--- a/pypy/rlib/parsing/test/test_ebnfparse.py
+++ b/pypy/rlib/parsing/test/test_ebnfparse.py
@@ -318,7 +318,7 @@
""")
excinfo = py.test.raises(ValueError, make_parse_function, regexs, rules)
assert "primari" in str(excinfo.value)
-
+
def test_starred_star():
regexs, rules, ToAST = parse_ebnf("""
IGNORE: " ";
@@ -470,3 +470,11 @@
t = ToAST().transform(t)
assert len(t.children) == 6
excinfo = py.test.raises(ParseError, parse, "a")
+
+def test_zero_repetition_production():
+ grammar = """
+IGNORE: " ";
+foo: "A"?;
+"""
+ excinfo = py.test.raises(ValueError, parse_ebnf, grammar)
+ assert "foo" in str(excinfo.value)
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