Fix auto-tracing Python 3.12 ParamSpec syntax (#1247)

Author: alexmojaki

logfire/_internal/ast_utils.py

@@ -2,7 +2,7 @@
 
 import ast
 from dataclasses import dataclass
-from typing import cast
+from typing import Any, cast
 
 from opentelemetry.util import types as otel_types
 
@@ -104,19 +104,10 @@ def rewrite_function(self, node: ast.FunctionDef | ast.AsyncFunctionDef, qualnam
         )
         new_body.append(span)
 
-        return ast.fix_missing_locations(
-            ast.copy_location(
-                type(node)(  # type: ignore
-                    name=node.name,
-                    args=node.args,
-                    body=new_body,
-                    decorator_list=node.decorator_list,
-                    returns=node.returns,
-                    type_comment=node.type_comment,
-                ),
-                node,
-            )
-        )
+        kwargs: dict[str, Any] = {name: getattr(node, name, None) for name in node._fields}
+        kwargs['body'] = new_body
+        new_node = type(node)(**kwargs)
+        return ast.fix_missing_locations(ast.copy_location(new_node, node))
 
     def logfire_method_call_node(self, node: ast.FunctionDef | ast.AsyncFunctionDef, qualname: str) -> ast.Call:
         raise NotImplementedError()

pyproject.toml

@@ -216,7 +216,7 @@ include = ["/README.md", "CHANGELOG.md", "/Makefile", "/logfire", "/tests"]
 # https://beta.ruff.rs/docs/configuration/
 [tool.ruff]
 line-length = 120
-extend-exclude = ["logfire-api/logfire_api/*"]
+extend-exclude = ["logfire-api/logfire_api/*", "tests/auto_trace_samples/param_spec.py"]
 
 [tool.ruff.lint]
 extend-select = [

tests/auto_trace_samples/param_spec.py

@@ -0,0 +1,2 @@
+def check_param_spec_syntax[**P](*args: P.args, **kwargs: P.kwargs):
+    return args, kwargs

tests/test_auto_trace.py

@@ -185,6 +185,11 @@ def test_auto_trace_sample(exporter: TestExporter) -> None:
         ]
     )
 
+    if sys.version_info >= (3, 12):
+        from tests.auto_trace_samples import param_spec
+
+        assert param_spec.check_param_spec_syntax(1, 2, a=3, b=4) == ((1, 2), {'a': 3, 'b': 4})  # type: ignore
+
 
 def test_check_already_imported() -> None:
     # Check that nothing gets imported during this test,