first commit

backend/app/dataset/rules/python/concurrency.py

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+"""AST-level concurrency safety injection for Python."""
+
+import ast
+from typing import Optional
+
+from app.dataset.rules.base import Mutation, MutationRule
+
+
+class ConcurrencyRule(MutationRule):
+    """Remove a threading.Lock.acquire/release pair to introduce race condition.
+
+    Uses `ast` to find a with-statement using a lock and replaces it with the
+    bare body, removing synchronization.
+    """
+
+    name = "concurrency"
+    language = "python"
+    defect_type = "concurrency_issue"
+
+    def detect_and_mutate(self, source: str, filename: str = "") -> Optional[Mutation]:
+        try:
+            tree = ast.parse(source)
+        except SyntaxError:
+            return None
+
+        for node in ast.walk(tree):
+            if not isinstance(node, ast.With):
+                continue
+            first_item = node.items[0]
+            ctx = first_item.context_expr
+            if isinstance(ctx, ast.Call) and isinstance(ctx.func, ast.Attribute) and ctx.func.attr == "acquire":
+                start = node.lineno
+                end = getattr(node, "end_lineno", node.lineno) or node.lineno
+                lines = source.splitlines(keepends=True)
+                body = lines[start:end]
+                dedented = []
+                for line in body[1:]:
+                    if line.startswith("    "):
+                        dedented.append(line[4:])
+                    else:
+                        dedented.append(line)
+                mutated = "".join(lines[: start - 1] + dedented + lines[end:])
+                return Mutation(
+                    defect_type=self.defect_type,
+                    language=self.language,
+                    line_start=start,
+                    line_end=end,
+                    mutated_source=mutated,
+                    reference_fix="Restore `with lock:` to protect the critical section.",
+                    description="Removed lock acquisition, exposing a race condition.",
+                )
+        return None