Fixed AttributeError when formatting unpickled TBEs from an unpatched process

Fixes #144.

Author: agronholm

CHANGES.rst

@@ -3,6 +3,13 @@ Version history
 
 This library adheres to `Semantic Versioning 2.0 <http://semver.org/>`_.
 
+**UNRELEASED**
+
+- Fixed ``AttributeError: 'TracebackException' object has no attribute 'exceptions'``
+  when formatting unpickled TBEs from another Python process which did not apply the
+  ``exceptiongroup`` patches
+  (`#144 <https://github.com/agronholm/exceptiongroup/issues/144>`_)
+
 **1.3.0**
 
 - Added ``**kwargs`` to function and method signatures as appropriate to match the

src/exceptiongroup/_formatting.py

@@ -241,7 +241,7 @@ def format(self, *, chain=True, _ctx=None, **kwargs):
         for msg, exc in reversed(output):
             if msg is not None:
                 yield from _ctx.emit(msg)
-            if exc.exceptions is None:
+            if getattr(exc, "exceptions", None) is None:
                 if exc.stack:
                     yield from _ctx.emit("Traceback (most recent call last):\n")
                     yield from _ctx.emit(exc.stack.format())
@@ -332,12 +332,13 @@ def format_exception_only(self, **kwargs):
         else:
             yield from traceback_exception_original_format_exception_only(self)
 
-        if isinstance(self.__notes__, collections.abc.Sequence):
-            for note in self.__notes__:
+        notes = getattr(self, "__notes__", None)
+        if isinstance(notes, collections.abc.Sequence):
+            for note in notes:
                 note = _safe_string(note, "note")
                 yield from [line + "\n" for line in note.split("\n")]
-        elif self.__notes__ is not None:
-            yield _safe_string(self.__notes__, "__notes__", func=repr)
+        elif notes is not None:
+            yield _safe_string(notes, "__notes__", func=repr)
 
 
 traceback_exception_original_format = traceback.TracebackException.format

tests/dummyscript.py

@@ -0,0 +1,12 @@
+# This script exists solely for test_unpatched_tracebackexception_format()
+import pickle
+import sys
+import traceback
+
+assert "exceptiongroup" not in sys.modules, "exceptiongroup was already imported"
+
+try:
+    raise ValueError("hello")
+except ValueError as exc:
+    tbe = traceback.TracebackException(type(exc), exc, exc.__traceback__)
+    sys.stdout.buffer.write(pickle.dumps(tbe, protocol=pickle.HIGHEST_PROTOCOL))

tests/test_formatting.py

@@ -1,5 +1,8 @@
+import pickle
+import subprocess
 import sys
 import traceback
+from pathlib import Path
 from typing import NoReturn
 from urllib.error import HTTPError
 
@@ -55,6 +58,22 @@ def old_argstyle(request: SubRequest) -> bool:
     return request.param
 
 
+@pytest.mark.skipif(
+    sys.version_info >= (3, 11),
+    reason="The failure only occurs on Python 3.10 and earlier",
+)
+def test_unpatched_tracebackexception_format():
+    dummy_script_path = Path(__file__).parent / "dummyscript.py"
+    process = subprocess.run(
+        [sys.executable, str(dummy_script_path)], capture_output=True
+    )
+    tbe = pickle.loads(process.stdout)
+    assert not hasattr(tbe, "exceptions")
+    assert not hasattr(tbe, "__notes__")
+    formatted = tbe.format()
+    "".join(formatted)
+
+
 def test_exceptionhook(capsys: CaptureFixture) -> None:
     try:
         raise_excgroup()