fix(cli): reject an open range missing its end instead of scanning zero targets

tests/test_patterns.py

@@ -186,6 +186,13 @@ def test_error_unclosed_brace():
         list(expand_patterns("test[a]{1-3"))
 
 
+def test_error_open_range_missing_end():
+    """"{2-}" consumes the dash and finds no end: same error class as "{-2}",
+    not a silent expansion to zero permutations."""
+    with pytest.raises(ValueError, match="range end"):
+        list(expand_patterns("test[a-c]{2-}"))
+
+
 def test_error_lone_open_bracket():
     with pytest.raises(ValueError):
         list(expand_patterns("["))

user_scanner/core/patterns.py

@@ -98,7 +98,12 @@ def _parse_lenset(lexer: Lexer) -> Set[int]:
                 lexer.next()
                 rhs = lexer.parse_number()
 
-                if lhs is not None and rhs is not None:
+                # "{2-}" consumed the dash but has no end: erroring matches
+                # "{-2}", while skipping silently expands to zero permutations
+                # and the scan runs on no targets without a word.
+                if rhs is None:
+                    raise ValueError('Missing range end after "-" in lenset')
+                if lhs is not None:
                     for i in range(lhs, rhs + 1):
                         lenset.add(i)
             elif lhs is not None: