Fix two crashes from unguarded calls into the optional Rich dependency

CHANGELOG.md

@@ -15,6 +15,14 @@ You can find our backwards-compatibility policy [here](https://github.com/hynek/
 
 ## [Unreleased](https://github.com/hynek/structlog/compare/26.1.0...HEAD)
 
+### Fixed
+
+- `structlog.tracebacks.to_repr()` no longer lets exceptions raised by Rich's own object introspection propagate and break exception logging; it now falls back to the non-Rich algorithm instead.
+  [#655](https://github.com/hynek/structlog/issues/655)
+
+- `structlog.dev.RichTracebackFormatter` no longer crashes with a `TypeError` on older versions of Rich (before 13.1.0) that don't support the *locals_hide_dunder* / *locals_hide_sunder* arguments.
+  [#576](https://github.com/hynek/structlog/issues/576)
+
 
 ## [26.1.0](https://github.com/hynek/structlog/compare/25.5.0...26.1.0) - 2026-06-06
 

src/structlog/dev.py

@@ -11,6 +11,7 @@
 
 from __future__ import annotations
 
+import inspect
 import sys
 import warnings
 
@@ -52,6 +53,15 @@
     from rich.traceback import Traceback
 except ImportError:
     rich = None  # type: ignore[assignment]
+else:
+    # Older versions of Rich don't support all keyword arguments we'd like to
+    # pass to Traceback.from_exception() (e.g., locals_hide_dunder /
+    # locals_hide_sunder were only added in Rich 13.1.0). Only pass the ones
+    # that are actually supported by the installed version so that structlog
+    # keeps working with a wide range of Rich versions.
+    _RICH_TRACEBACK_FROM_EXCEPTION_PARAMS = frozenset(
+        inspect.signature(Traceback.from_exception).parameters
+    )
 
 __all__ = [
     "ConsoleRenderer",
@@ -445,21 +455,28 @@ def __call__(self, sio: TextIO, exc_info: ExcInfo) -> None:
         console = Console(
             file=sio, color_system=self.color_system, width=self.width
         )
-        tb = Traceback.from_exception(
-            *exc_info,
-            show_locals=self.show_locals,
-            max_frames=self.max_frames,
-            theme=self.theme,
-            word_wrap=self.word_wrap,
-            extra_lines=self.extra_lines,
-            width=self.width,
-            indent_guides=self.indent_guides,
-            locals_max_length=self.locals_max_length,
-            locals_max_string=self.locals_max_string,
-            locals_hide_dunder=self.locals_hide_dunder,
-            locals_hide_sunder=self.locals_hide_sunder,
-            suppress=self.suppress,
-        )
+        kwargs: dict[str, Any] = {
+            "show_locals": self.show_locals,
+            "max_frames": self.max_frames,
+            "theme": self.theme,
+            "word_wrap": self.word_wrap,
+            "extra_lines": self.extra_lines,
+            "width": self.width,
+            "indent_guides": self.indent_guides,
+            "locals_max_length": self.locals_max_length,
+            "locals_max_string": self.locals_max_string,
+            "locals_hide_dunder": self.locals_hide_dunder,
+            "locals_hide_sunder": self.locals_hide_sunder,
+            "suppress": self.suppress,
+        }
+        # Drop kwargs that the installed Rich version doesn't support yet
+        # (see _RICH_TRACEBACK_FROM_EXCEPTION_PARAMS above).
+        kwargs = {
+            k: v
+            for k, v in kwargs.items()
+            if k in _RICH_TRACEBACK_FROM_EXCEPTION_PARAMS
+        }
+        tb = Traceback.from_exception(*exc_info, **kwargs)
         if hasattr(tb, "code_width"):
             # `code_width` requires `rich>=13.8.0`
             tb.code_width = self.code_width

src/structlog/tracebacks.py

@@ -153,29 +153,37 @@ def to_repr(
        implementation.
     """
     if use_rich and rich is not None:
-        # Let rich render the repr if it is available.
-        # It produces much better results for containers and dataclasses/attrs.
-        obj_repr = rich.pretty.traverse(
-            obj, max_length=max_length, max_string=max_string
-        ).render()
-    else:
-        # Generate a (truncated) repr if rich is not available.
-        # Handle str/bytes differently to get better results for truncated
-        # representations.  Also catch all errors, similarly to "safe_str()".
         try:
-            if isinstance(obj, (str, bytes)):
-                if max_string is not None and len(obj) > max_string:
-                    truncated = len(obj) - max_string
-                    obj_repr = f"{obj[:max_string]!r}+{truncated}"
-                else:
-                    obj_repr = repr(obj)
+            # Let rich render the repr if it is available.
+            # It produces much better results for containers and
+            # dataclasses/attrs.
+            return rich.pretty.traverse(
+                obj, max_length=max_length, max_string=max_string
+            ).render()
+        except Exception:  # noqa: BLE001, S110
+            # Rich's introspection can raise on objects it doesn't expect
+            # (e.g. ones with unusual attribute access), which would
+            # otherwise break exception logging entirely. Fall back to the
+            # manual algorithm below instead.
+            pass
+
+    # Generate a (truncated) repr if rich is not available, or failed above.
+    # Handle str/bytes differently to get better results for truncated
+    # representations.  Also catch all errors, similarly to "safe_str()".
+    try:
+        if isinstance(obj, (str, bytes)):
+            if max_string is not None and len(obj) > max_string:
+                truncated = len(obj) - max_string
+                obj_repr = f"{obj[:max_string]!r}+{truncated}"
             else:
                 obj_repr = repr(obj)
-                if max_string is not None and len(obj_repr) > max_string:
-                    truncated = len(obj_repr) - max_string
-                    obj_repr = f"{obj_repr[:max_string]!r}+{truncated}"
-        except Exception as error:  # noqa: BLE001
-            obj_repr = f"<repr-error {str(error)!r}>"
+        else:
+            obj_repr = repr(obj)
+            if max_string is not None and len(obj_repr) > max_string:
+                truncated = len(obj_repr) - max_string
+                obj_repr = f"{obj_repr[:max_string]!r}+{truncated}"
+    except Exception as error:  # noqa: BLE001
+        obj_repr = f"<repr-error {str(error)!r}>"
 
     return obj_repr
 

tests/test_dev.py

@@ -841,6 +841,36 @@ def test_code_width_support(self, sio, code_width_support):
         if code_width_support:
             assert tb.code_width == 88
 
+    def test_old_rich_missing_locals_hide_params(self, sio, monkeypatch):
+        """
+        If the installed Rich version doesn't support the
+        locals_hide_dunder / locals_hide_sunder keyword arguments (added in
+        Rich 13.1.0), they are silently omitted from the call to
+        Traceback.from_exception() instead of raising a TypeError (#576).
+        """
+        from rich.traceback import Trace
+
+        monkeypatch.setattr(
+            dev,
+            "_RICH_TRACEBACK_FROM_EXCEPTION_PARAMS",
+            dev._RICH_TRACEBACK_FROM_EXCEPTION_PARAMS
+            - {"locals_hide_dunder", "locals_hide_sunder"},
+        )
+
+        tb = mock.Mock(spec=dev.Traceback(Trace([])))
+        tb.__rich_console__.return_value = "for Python 3.8 compatibility"
+
+        with mock.patch.object(
+            dev.Traceback, "from_exception", return_value=tb
+        ) as factory:
+            try:
+                0 / 0
+            except ZeroDivisionError:
+                dev.rich_traceback(sio, sys.exc_info())
+
+        assert "locals_hide_dunder" not in factory.call_args.kwargs
+        assert "locals_hide_sunder" not in factory.call_args.kwargs
+
 
 @pytest.mark.skipif(
     dev.better_exceptions is None, reason="Needs better-exceptions."

tests/test_tracebacks.py

@@ -133,6 +133,26 @@ def __repr__(self) -> str:
     assert "<repr-error 'BAAM!'>" == tracebacks.to_repr(Baam())
 
 
+def test_to_repr_rich_error(monkeypatch: pytest.MonkeyPatch) -> None:
+    """
+    "to_repr()" falls back to the non-Rich algorithm if Rich's own
+    introspection raises an exception instead of propagating it (#655).
+    """
+    try:
+        import rich
+        import rich.pretty
+    except ImportError:
+        pytest.skip(reason="rich not installed")
+
+    def boom(*args: Any, **kwargs: Any) -> Any:
+        raise AttributeError("'Baam' object has no attribute 'x'")
+
+    monkeypatch.setattr(tracebacks, "rich", rich)
+    monkeypatch.setattr(rich.pretty, "traverse", boom)
+
+    assert "'spam'" == tracebacks.to_repr("spam")
+
+
 def test_simple_exception():
     """
     Tracebacks are parsed for simple, single exceptions.