fix: reject malformed brace globs

Fixes #1690

Co-Authored-By: OpenAI Codex <noreply@openai.com>

CHANGELOG.md

@@ -38,6 +38,7 @@ Status of the `main` branch. Changes prior to the next official version change w
   - Fix: Use LSP-compliant line splitting ("\n", "\r\n" and "\r" can define line breaks); previously only "\n" considered
   - Fix: Apply consistent line splitting across tools, uniformly applying the LSP splitting semantics; 
     affects `search_text` used by `search_for_pattern` tool (reported in #1684)
+  - Fix: glob pattern expansion in `expand_braces` did not terminate with empty or unbalanced braces #1690
 
 * CLI:
   - Fix `--project-from-cwd` hijacking git worktrees nested under a Serena project. `find_project_root`

src/serena/util/text_utils.py

@@ -216,18 +216,22 @@ def expand_braces(pattern: str) -> list[str]:
     Handles multiple brace sets as well.
     """
     patterns = [pattern]
-    while any("{" in p for p in patterns):
+    while any("{" in p or "}" in p for p in patterns):
         new_patterns = []
         for p in patterns:
-            match = re.search(r"\{([^{}]+)\}", p)
+            match = re.search(r"\{([^{}]*)\}", p)
             if match:
+                options_expr = match.group(1)
+                if not options_expr:
+                    raise ValueError(f"Invalid glob brace expression in {pattern!r}: empty braces are not allowed")
+
                 prefix = p[: match.start()]
                 suffix = p[match.end() :]
-                options = match.group(1).split(",")
+                options = options_expr.split(",")
                 for option in options:
                     new_patterns.append(f"{prefix}{option}{suffix}")
             else:
-                new_patterns.append(p)
+                raise ValueError(f"Invalid glob brace expression in {pattern!r}: unmatched brace")
         patterns = new_patterns
     return patterns
 

test/serena/test_text_utils.py

@@ -606,6 +606,21 @@ class TestExpandBraces:
 
         assert sorted(expand_braces(pattern)) == sorted(expected)
 
+    @pytest.mark.parametrize(
+        "pattern",
+        [
+            "src/{}.py",
+            "src/{utils,models",
+            "src/utils,models}.py",
+        ],
+    )
+    def test_expand_braces_rejects_malformed_braces(self, pattern):
+        """Malformed brace globs should fail instead of looping forever."""
+        from serena.util.text_utils import expand_braces
+
+        with pytest.raises(ValueError, match="Invalid glob brace expression"):
+            expand_braces(pattern)
+
 
 class TestMultiFileContentReplacer:
     FILES = [