[Eventgrid] Improve error message when providing wrong authentication

[rakshith91]

Upon providing wrong key for authentication during publisher client, we get

UnboundLocalError: local variable 'authentication_policy' referenced before assignment on providing wrong credential in the publisher client

This message must improve - perhaps start with insisting on providing an AzureKeyCredential?

[lmazuel]

Can you paste a full example with the full stacktrace of this?

[rakshith91]

Can you paste a full example with the full stacktrace of this?

>>> e  = EventGridPublisherClient("https://rakshith-eg.westus-1.eventgrid.azure.net/api/events", "dsf")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Users\Administrator\Documents\Workspace\azure-sdk-for-python\envtrace\lib\site-packages\azure\eventgrid\_publisher_client.py", line 75, in __init__
    policies=EventGridPublisherClient._policies(credential, **kwargs),
  File "C:\Users\Administrator\Documents\Workspace\azure-sdk-for-python\envtrace\lib\site-packages\azure\eventgrid\_publisher_client.py", line 82, in _policies
    auth_policy = _get_authentication_policy(credential)
  File "C:\Users\Administrator\Documents\Workspace\azure-sdk-for-python\envtrace\lib\site-packages\azure\eventgrid\_helpers.py", line 87, in _get_authentication_policy
    return authentication_policy
UnboundLocalError: local variable 'authentication_policy' referenced before assignment

[lmazuel]

That's a bug in this code:

azure-sdk-for-python/sdk/eventgrid/azure-eventgrid/azure/eventgrid/_helpers.py

Lines 77 to 87 in c2dea16

	def _get_authentication_policy(credential):
	if credential is None:
	raise ValueError("Parameter 'self._credential' must not be None.")
	if isinstance(credential, AzureKeyCredential):
	authentication_policy = AzureKeyCredentialPolicy(credential=credential, name=constants.EVENTGRID_KEY_HEADER)
	if isinstance(credential, EventGridSharedAccessSignatureCredential):
	authentication_policy = EventGridSharedAccessSignatureCredentialPolicy(
	credential=credential,
	name=constants.EVENTGRID_TOKEN_HEADER
	)
	return authentication_policy

If all if are wrong, we reach a return on an undeclared variable.

Correct code:

def _get_authentication_policy(credential):
    if credential is None:
        raise ValueError("Parameter 'self._credential' must not be None.")
    if isinstance(credential, AzureKeyCredential):
        return AzureKeyCredentialPolicy(credential=credential, name=constants.EVENTGRID_KEY_HEADER)
    if isinstance(credential, EventGridSharedAccessSignatureCredential):
        return EventGridSharedAccessSignatureCredentialPolicy(
            credential=credential,
            name=constants.EVENTGRID_TOKEN_HEADER
        )
    raise ValueError("The provided credential should be an instance of EventGridSharedAccessSignatureCredentialPolicy or AzureKeyCredentialPolicy")