Could you please clarify why does the change need?

This change reflects the cmdlets actual defined attributes.

Prior to this PR they would report as having "Medium" impact when querying the attribute's set ConfirmImpact as that is the default value, despite not implementing ShouldProcess in the first place nor declaring support for it.

This is primarily a change in how this value reports when SupportsShouldProcess is not set to true for a given command, in the interest of visibility for the actual effective ConfirmImpact level of a cmdlet.

All changes from Medium to None are reflective of this. The only cmdlets that had an actual effective ConfirmImpact change are those that have been changed to Low per committee decision, and are all listed in the PR description.

It is my hope that by making plain the true effective implementations of ShouldProcess support in cmdlets and the effective ConfirmImpact values here that we can have a concrete reference point to look at and check which cmdlets should have ShouldProcess support and do not, or have an inappropriate ConfirmImpact value.

Thanks! Please add this to the PR description.

This would cause inconsistency between cmdlet and advanced function. Say for the below function, I will see the ConfirmImpact value to be medium.

function Get-Something
{
    [CmdletBinding(SupportShouldProcess = true)]
    param()
    ...
}

From the committee review:

Should also consider changing default for Get- cmdlets to low if not specified.

I suggest we don't do this, so all Get command will return None for ConfirmImpact unless the command declares ConfirmImpact itself.

Yeah, we should probably avoid disparity between cmdlets and advanced functions if we can.

I read the committee's comment there as "we should consider making Get- cmdlets return Low for ConfirmImpact if and only if SupportsShouldProcess = true and they do not specify a ConfirmImpact explicitly." -- maybe I was misinterpreting a bit?

And that's what this does. Technically it would always set Get cmdlets to Low internally, but nothing will ever register it unless SupportsShouldProcess = true thanks to the gated getter I added.

That said -- should I revert this to avoid disparity between cmdlets and advanced functions, or is there something I could do to mirror this effect for advanced functions named as Get-*?

The committee's comment is "we should consider ..." and we did consider it 😄 However, doing so will cause disparity between cmdlets and advanced functions, and there doesn't seem to be a simple way to make advanced functions do the same, as there is no way to know the verb within CmdletBindingAttribute.
I'm not sure what is the right trade-off in this case -- revert this change so Get-x cmdlets with SupportsShouldProcess = true shows Medium if ConfirmImpact is not specified? or accept the disparity between cmdlets and advanced functions?

@SteveL-MSFT @BrucePay @JamesWTruher @joeyaiello Can you please weigh in?

there doesn't seem to be a simple way to make advanced functions do the same, as there is no way to know the verb within CmdletBindingAttribute.

I think it is enough to indicate in the documentation that is the default for advanced functions and that it is necessary to explicitly indicate ConfirmImpact for Get verb. We could enhance ScriptAnalyzer too. Also we don't break advanced functions and user experience.

Indeed. I think this change makes sense... but I'm not entirely sure this is the appropriate time to apply such a change. Of course, in an ideal world, cmdlet authors would just specify their own ConfirmImpact in every case, and I would generally think that should be the recommendation anyway.

I'd hope this is just a general catch-all for the occasional circumstance where it's omitted... but it may well have a wider impact than I'm thinking, so I would love to hear from the other team members as well. 🙂

@PowerShell/powershell-committee re-reviewed the issue and agrees NOT to change the default

@vexx32 given the new comment from committee review #8157 (comment), can you please revert the following changes?

if (VerbName == VerbsCommon.Get)
{
    ConfirmImpact = ConfirmImpact.Low;
}

I'll take care of it tomorrow. 🙂