EXOTenantAllowBlockListItems: Resource not being compared correctly

[ricmestre]

Description of the issue

@FabienTschanz Hi, I have a customer with tons of policies for this resource and when using Assert-M365DSCBlueprint for looking for drifts there are a lot of them, looking at the list looks like there's seems to be some cache problem because it's comparing apples to oranges as in it's referring some drifts as values that are in the tenant but actually are values for other resources (with different keys) of the same type that are in that very same blueprint.

This is very sensitive and I cannot paste it here with REDACTED info without actually showing real data, please ping me on LinkedIn and I'll share those resources with you.

Microsoft 365 DSC Version

1.26.311.1

Which workloads are affected

Exchange Online

The DSC configuration

Ping me on LinkedIn

Verbose logs showing the problem

N/A

Environment Information + PowerShell Version

Win11/PS5.1

[FabienTschanz]

Found the issue. The EXOTenantAllowBlockListItems resource is the only resource that uses three mandatory parameters. Since Get-DscResource does not differentiate between Required and Key parameters (it just uses IsMandatory, which both types correspond to), and the delta report engine only checks at most two keys, it always determines the wrong resources. Not sure how to fix this without having to combine the schema definition and the output of Get-DscResource. Or we make the Action parameter of the resource not even required but just a Write property. However, when creating a new item, it is still required to be set.

[FabienTschanz]

Nvm, found a way to deal with it. Not pretty, but it works. PR was updated.

[ricmestre]

Yuck! It sure doesn't look pretty lol but hey if it works...

        if ($Resource.ResourceName -eq 'EXOTenantAllowBlockListItems')
        {
            $mandatoryParameters = $mandatoryParameters | Where-Object Name -NE 'Action' # Action is not a key property but still mandatory
        }

[FabienTschanz]

Yeah, it's really ugly, but hey. If the information isn't there beforehand, we have to store it somewhere else.