fix: include decorators in TreeSitter fragments and use chunk for gaps

- Fix TreeSitterStrategy to detect decorated_definition nodes and map
  them to function/class based on the inner definition
- Change gap fragments from kind="module" to kind="chunk" since they
  are arbitrary code chunks, not complete modules
- Update test to expect chunk instead of module for gap fragments

Author: nikolay-e

src/treemapper/diffctx/fragments.py

@@ -366,7 +366,7 @@ def _extract_definitions(
         end = node.end_point[0] + 1
 
         if node.type in definition_types:
-            kind = self._node_type_to_kind(node.type)
+            kind = self._node_type_to_kind(node.type, node)
 
             if (kind, end) in added_ends:
                 for child in node.children:
@@ -392,7 +392,14 @@ def _extract_definitions(
         for child in node.children:
             self._extract_definitions(child, code_bytes, path, lines, definition_types, fragments, covered, added_ends)
 
-    def _node_type_to_kind(self, node_type: str) -> str:
+    def _node_type_to_kind(self, node_type: str, node: Node | None = None) -> str:
+        if node_type == "decorated_definition" and node is not None:
+            for child in node.children:
+                if child.type in {"function_definition", "async_function_definition"}:
+                    return "function"
+                if child.type == "class_definition":
+                    return "class"
+            return "function"
         if "function" in node_type or "method" in node_type:
             return "function"
         if "class" in node_type:
@@ -460,7 +467,7 @@ def _create_gap_fragments(self, path: Path, lines: list[str], covered: list[tupl
             fragments.append(
                 Fragment(
                     id=FragmentId(path=path, start_line=start, end_line=end),
-                    kind="module",
+                    kind="chunk",
                     content=snippet,
                     identifiers=extract_identifiers(snippet, profile="code"),
                 )
@@ -607,7 +614,7 @@ def _create_gap_fragments(self, path: Path, lines: list[str], covered: list[tupl
             fragments.append(
                 Fragment(
                     id=FragmentId(path=path, start_line=start, end_line=end),
-                    kind="module",
+                    kind="chunk",
                     content=snippet,
                     identifiers=extract_identifiers(snippet, profile="code"),
                 )

tests/test_diff_fragments_regression.py

@@ -199,12 +199,12 @@ def main():
 
         fragments = fragment_file(file_path, code)
 
-        module_frags = [f for f in fragments if f.kind == "module"]
-        assert len(module_frags) >= 1
+        chunk_frags = [f for f in fragments if f.kind == "chunk"]
+        assert len(chunk_frags) >= 1
 
-        module_frag = module_frags[0]
-        assert "import os" in module_frag.content
-        assert "CONFIG_PATH" in module_frag.content
+        chunk_frag = chunk_frags[0]
+        assert "import os" in chunk_frag.content
+        assert "CONFIG_PATH" in chunk_frag.content
 
     def test_frag_py_021_module_gap_between_definitions(self, tmp_path):
         code = """\