fix: keep the Error object an exception is built from

SCIMException.from_error() rebuilt the status and the scimType from the
exception class, so everything it has no class for was lost: a 429
status came back as 400, and a vendor specific scimType came back empty.
to_error() now gives back the object it was built from.

A client turning a server error into an exception and back into an HTTP
response no longer changes the status the server sent.

Author: azmeuk

doc/changelog.rst

@@ -1,6 +1,17 @@
 Changelog
 =========
 
+[Unreleased]
+------------
+
+Fixed
+^^^^^
+- :meth:`~scim2_models.SCIMException.from_error` keeps the :class:`~scim2_models.Error`
+  object it is built from, and :meth:`~scim2_models.SCIMException.to_error` gives it back.
+  The status and the scimType a server sent used to be replaced by the ones of the
+  exception class, which dropped everything it has no class for, such as a ``429`` status
+  or a vendor specific scimType.
+
 [0.8.0] - 2026-09-20
 --------------------
 

scim2_models/exceptions.py

@@ -39,6 +39,7 @@ def __init__(
         self.context = context
         self._detail = detail
         self.scim_ctx = scim_ctx
+        self._error: Error | None = None
         super().__init__(detail or self._default_detail)
 
     @property
@@ -47,9 +48,16 @@ def detail(self) -> str:
         return self._detail or self._default_detail
 
     def to_error(self) -> "Error":
-        """Convert this exception to a SCIM Error response object."""
+        """Convert this exception to a SCIM Error response object.
+
+        Exceptions built by :meth:`~scim2_models.SCIMException.from_error` return
+        the very object they were built from.
+        """
         from .messages.error import Error
 
+        if self._error is not None:
+            return self._error
+
         return Error(
             status=self.status,
             scim_type=self.scim_type or None,
@@ -70,6 +78,11 @@ def from_error(
     ) -> "SCIMException":
         """Create an exception from a SCIM Error object.
 
+        The error object is kept as-is, and
+        :meth:`~scim2_models.SCIMException.to_error` gives it back. This matters for
+        the values no exception class describes, such as a ``429`` status or a
+        vendor specific scimType.
+
         :param error: The SCIM Error object to convert.
         :param scim_ctx: The SCIM context in which the exception occurred.
         :return: The appropriate SCIMException subclass instance.
@@ -80,7 +93,13 @@ def from_error(
             raise TypeError(f"Expected Error, got {type(error).__name__}")
 
         exception_class = _SCIM_TYPE_TO_EXCEPTION.get(error.scim_type or "", cls)
-        return exception_class(detail=error.detail, scim_ctx=scim_ctx)
+        exc = exception_class(detail=error.detail, scim_ctx=scim_ctx)
+        exc._error = error
+        if error.status is not None:
+            exc.status = error.status
+        if error.scim_type:
+            exc.scim_type = error.scim_type
+        return exc
 
 
 class InvalidFilterException(SCIMException):

tests/test_exceptions.py

@@ -471,3 +471,25 @@ def test_from_error_without_scim_ctx():
     exc = SCIMException.from_error(error)
     assert isinstance(exc, InvalidFilterException)
     assert exc.scim_ctx is None
+
+
+def test_from_error_keeps_the_error_object():
+    """to_error() gives back the very object from_error() was built from."""
+    error = Error(status=404, detail="Resource unknown not found")
+    exc = SCIMException.from_error(error)
+    assert exc.to_error() is error
+
+
+def test_from_error_keeps_what_no_exception_class_describes():
+    """from_error() keeps a status and a scimType that match no exception class."""
+    error = Error(status=429, scim_type="tooManyRequests", detail="Slow down")
+    exc = SCIMException.from_error(error)
+    assert exc.status == 429
+    assert exc.scim_type == "tooManyRequests"
+
+
+def test_from_error_without_status():
+    """from_error() keeps the class status when the Error object carries none."""
+    error = Error(scim_type="uniqueness", detail="Duplicate userName")
+    exc = SCIMException.from_error(error)
+    assert exc.status == 409