Fix UseIdenticalMandatoryParametersForDSC rule logic

[kapilmb]

Resolves #596

This PR also fixes the violation extent of the rule, which prior to this would mark the entire script. This prevented rule suppression from working when the suppression attribute was placed inside a function.

[daviwil]

Looks great man, nice work!

[daviwil]

Always a good thing to do!

[kapilmb]

Thanks @daviwil

[mbreakey3]

I would remove the 'that are also the keys in the corresponding mof file.' While this is usually true, sometimes there are mandatory parameters that aren't keys.

[kapilmb]

But isn't the rule supposed to look for identical mandatory parameters in Get/Test/Set functions only if they are present as keys in the mof file?

[kapilmb]

According to this, the rule should be looking for all the properties in the mof file.

All three functions must take a parameter set that is identical to the set of properties defined in the MOF schema that you created for your resource. In this document, this set of properties is referred to as the “resource properties.”

It appears I had the wrong understanding about the rule :(. Guess I need to update the logic then, because the current logic only looks for keys that defined as identical mandatory parameters.

[mbreakey3]

Yeah, sorry about the confusion. It's a little confusing

[kapilmb]

Oh no worries.
So, I went through some of the script based resources and this is what I have found out:

• If a parameter is declared as mandatory in get-targetresource, then it has to be mandatory in the corresponding set and test functions.
• If a field is declared with attributes Key or Required in a mof file, then it should present as mandatory parameter in get/set/test functions.
• set and test functions should have identical mandatory parameters.

Is that correct?

[kapilmb]

The last point should be: set and test functions should have identical parameters regardless of whether they are mandatory or not.

[mbreakey3]

Yes - except the last point is a little misleading. Set and Test functions should have all identical parameters, not just mandatory.

Also the first point should read: If a parameter is declared as mandatory in any of Get/Set/Test then it should be a mandatory parameter in all of Get/Set/Test

[kapilmb]

Got it. Thanks!

[mbreakey3]

I would modify this example as such:

Wrong

function Get-TargetResource
{
    [CmdletBinding()]
    param
    (
        [Parameter(Mandatory = $true)]
        [ValidateNotNullOrEmpty()]
        [String]
        $Message
    )
}

function Set-TargetResource
{
    [CmdletBinding()]
    param
    (
        [Parameter(Mandatory = $true)]
        [ValidateNotNullOrEmpty()]
        [String]
        $Message,

        [Parameter(Mandatory = $true)]
        [ValidateNotNullOrEmpty()]
        [String]
        $Name
    )
}

function Test-TargetResource
{
    [CmdletBinding()]
    param
    (
        [Parameter(Mandatory = $true)]
        [ValidateNotNullOrEmpty()]
        [String]
        $Message,

        [Parameter(Mandatory = $true)]
        [ValidateNotNullOrEmpty()]
        [String]
        $Name
    )
}

Correct

function Get-TargetResource
{
    [CmdletBinding()]
    param
    (
        [Parameter(Mandatory = $true)]
        [ValidateNotNullOrEmpty()]
        [String]
        $Message,

        [Parameter(Mandatory = $true)]
        [ValidateNotNullOrEmpty()]
        [String]
        $Name
    )
}

function Set-TargetResource
{
    [CmdletBinding()]
    param
    (
        [Parameter(Mandatory = $true)]
        [ValidateNotNullOrEmpty()]
        [String]
        $Message,

        [Parameter(Mandatory = $true)]
        [ValidateNotNullOrEmpty()]
        [String]
        $Name
    )
}

function Test-TargetResource
{
    [CmdletBinding()]
    param
    (
        [Parameter(Mandatory = $true)]
        [ValidateNotNullOrEmpty()]
        [String]
        $Message,

        [Parameter(Mandatory = $true)]
        [ValidateNotNullOrEmpty()]
        [String]
        $Name
    )
}

Because this is most often what we see people doing wrong.