add to traceback

python · iritkatriel · Dec 3, 2021 · Nov 29, 2021 · Dec 1, 2021 · Dec 1, 2021
commit 8ab5e134e8313e8b401fc0d5f019df19b16ff2e8
diff --git a/Lib/test/test_traceback.py b/Lib/test/test_traceback.py
@@ -1224,6 +1224,19 @@ def test_syntax_error_various_offsets(self):
                 exp = "\n".join(expected)
                 self.assertEqual(exp, err)
 
+    def test_exception_with_note(self):
+        e = ValueError(42)
+        vanilla = self.get_report(e)
+
+        e.__note__ = 'My Note'
+        self.assertEqual(self.get_report(e), vanilla + 'My Note\n')
+
+        e.__note__ = 'Your Note'
+        self.assertEqual(self.get_report(e), vanilla + 'Your Note\n')
+
+        e.__note__ = None
+        self.assertEqual(self.get_report(e), vanilla)
+
     def test_exception_qualname(self):
         class A:
             class B:

diff --git a/Lib/traceback.py b/Lib/traceback.py
@@ -685,6 +685,12 @@ def __init__(self, exc_type, exc_value, exc_traceback, *, limit=None,
         # Capture now to permit freeing resources: only complication is in the
         # unofficial API _format_final_exc_line
         self._str = _some_str(exc_value)
+        if exc_value is not None:
+            self.__note__ = exc_value.__note__
+            assert self.__note__ is None or isinstance(self.__note__, str)
+        else:
+            self.__note__ = None
+
         if exc_type and issubclass(exc_type, SyntaxError):
             # Handle SyntaxError's specially
             self.filename = exc_value.filename
@@ -816,6 +822,8 @@ def format_exception_only(self):
             yield _format_final_exc_line(stype, self._str)
         else:
             yield from self._format_syntax_error(stype)
+        if self.__note__ is not None:
+            yield self.__note__ + "\n"
 
     def _format_syntax_error(self, stype):
         """Format SyntaxError exceptions (internal helper)."""

@@ -1083,6 +1083,25 @@ print_exception(struct exception_print_context *ctx, PyObject *value)
         PyErr_Clear();
     }
     err += PyFile_WriteString("\n", f);
+
+    if (err == 0 && PyExceptionInstance_Check(value)) {
+        _Py_IDENTIFIER(__note__);
+
+        PyObject *note = _PyObject_GetAttrId(value, &PyId___note__);
+        if (note == NULL) {
+            err = -1;
+        }
+        if (err == 0 && PyUnicode_Check(note)) {
+            err = write_indented_margin(ctx, f);
+            if (err == 0) {
+                err = PyFile_WriteObject(note, f, Py_PRINT_RAW);
+            }
+            if (err == 0) {
+                err = PyFile_WriteString("\n", f);
+            }
+        }
+        Py_XDECREF(note);
+    }
     Py_XDECREF(tb);
     Py_DECREF(value);
     /* If an error happened here, don't show it.