[typing] Add DefaultAzureCredential to allowed types for credentials in KeyVaultClient

[Søren Skov Eriksen (soer7022)]

Description

The current typing for KeyVaultClient does not match the steps described in current documentation: here

I have added the DefaultAzureCredential from azure.identity based on the current recommended steps from the documentation.

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• The pull request does not introduce [breaking changes]
• CHANGELOG is updated for new features, bug fixes or other significant changes.
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[Deleted user (ghost)]

Thank you for your contribution soer7022! We will review the pull request and get back to you soon.

[Laia Patiño (laiapat)]

Hi Søren Skov Eriksen (@soer7022), thank you for opening a PR and contributing to the SDK!

In this instance though, I believe the current typing is correct. Key Vault clients (and other clients in the SDK) don't necessarily require azure-identity credentials. They accept any credential that supports the TokenCredential protocol, which does include the DefaultAzureCredential, but also includes other azure-identity credentials and even custom credentials (some examples). So, TokenCredential is used as the credential type here and elsewhere 🙂

Do you think the documentation should be more clear about that? And/or is there a type checker that raised an error when providing a DefaultAzureCredential to a Key Vault client? If so, that might be something we'd want to find a fix for.

[Søren Skov Eriksen (soer7022)]

Hi @mccoyp, thank you for the detailed reply 😄

The main reason that I made this pull request is due to PyCharm flagging it as a incorrect type:

Is my fix the right fix? Or should we look into making something more general?

[Laia Patiño (laiapat)]

Søren Skov Eriksen (@soer7022) Thank you for providing context about the issue! That's the first time I've seen an IDE raise a concern with the typing, and suggests that there's something we can do to make the protocol implementation more clear to Python (and users).

I can't reproduce the PyCharm warning on my end unfortunately -- I'm using a Python 3.10.0 interpreter on PyCharm Community Edition 2021.1.3. Could I know what interpreter and PyCharm version you're using?

If you don't mind, I'd like to continue this discussion on #25175, an issue I opened to track this. It would be great if you could continue to help us to fix this! If not, that's no problem -- I appreciate that you brought this to our attention 🙂

I'm going to close this PR though, since the solution should come from the credential definition and/or the TokenCredential protocol definition.

[Søren Skov Eriksen (soer7022)]

Thank you! I will add further details and comments on the issue