[Key Vault] Handle missing inner certificate operation error (#41965)

* Handle missing inner certificate operation error

* Use public attributes in test

Author: mccoyp

sdk/keyvault/azure-keyvault-certificates/CHANGELOG.md

@@ -10,6 +10,9 @@
 
 - When creating a certificate with an unknown issuer, `CertificateClient.(begin_)create_certificate` now returns a
   `CertificateOperation` instead of `None`
+- When a certificate operation's error doesn't have an inner error, `CertificateOperationError` will be correctly
+  serialized instead of raising an exception
+  ([Azure/azure-cli #31764](https://github.com/Azure/azure-cli/issues/31764))
 
 ### Other Changes
 

sdk/keyvault/azure-keyvault-certificates/azure/keyvault/certificates/_models.py

@@ -86,10 +86,10 @@ class CertificateOperationError(object):
     :param str code: The error code.
     :param str message: The error message.
     :param inner_error: The error object itself
-    :type inner_error: ~azure.keyvault.certificates.CertificateOperationError
+    :type inner_error: ~azure.keyvault.certificates.CertificateOperationError or None
     """
 
-    def __init__(self, code: str, message: str, inner_error: "CertificateOperationError") -> None:
+    def __init__(self, code: str, message: str, inner_error: "Optional[CertificateOperationError]") -> None:
         self._code = code
         self._message = message
         self._inner_error = inner_error
@@ -102,7 +102,7 @@ def _from_error_bundle(cls, error_bundle: models.KeyVaultErrorError) -> "Certifi
         return cls(
             code=error_bundle.code,  # type: ignore
             message=error_bundle.message,  # type: ignore
-            inner_error=cls._from_error_bundle(error_bundle.inner_error),  # type: ignore
+            inner_error=cls._from_error_bundle(error_bundle.inner_error) if error_bundle.inner_error else None,
         )
 
     @property
@@ -124,11 +124,11 @@ def message(self) -> str:
         return self._message
 
     @property
-    def inner_error(self) -> "CertificateOperationError":
+    def inner_error(self) -> "Optional[CertificateOperationError]":
         """The error itself.
 
         :returns: The error itself.
-        :rtype: ~azure.keyvault.certificates.CertificateOperationError
+        :rtype: ~azure.keyvault.certificates.CertificateOperationError or None
         """
         return self._inner_error
 

sdk/keyvault/azure-keyvault-certificates/tests/test_certificates_client.py

@@ -31,6 +31,10 @@
     WellKnownIssuerNames,
 )
 from azure.keyvault.certificates._client import NO_SAN_OR_SUBJECT
+from azure.keyvault.certificates._generated.models import (
+    CertificateOperation as _CertificateOperation,
+    KeyVaultErrorError,
+)
 from azure.keyvault.certificates._shared.client_base import DEFAULT_VERSION
 import pytest
 
@@ -834,3 +838,14 @@ def test_thumbprint_hex():
         x509_thumbprint=b"v\xe1\x81\x9f\xad\xf0jU\xefK\x12j.\xf7C\xc2\xba\xe8\xa1Q",
     )
     assert "76E1819FADF06A55EF4B126A2EF743C2BAE8A151" in str(properties)
+
+
+def test_certificate_operation_empty_inner_error():
+    """Ensure a CertificateOperation can be serialized when the generated model has no inner error.
+    See https://github.com/Azure/azure-cli/issues/31764.
+    """
+    error = KeyVaultErrorError(code="500", message="Bad Request", inner_error=None)
+    generated_operation = _CertificateOperation(error=error)
+    operation = CertificateOperation._from_certificate_operation_bundle(generated_operation)
+    assert operation.error
+    assert operation.error.inner_error is None