New-PSFormatXML - handle empty property values

[scriptingstudio]

This is "unusual" way of object prototype creating which I often exploit.

$obj = '' | select-object <properties>
$obj.PSOBject.TypeNames.Insert(0,<FormatName>)
$obj | New-PSFormatXML -FormatType table -path <path>

You cannot call a method on a null-valued expression.
+ $Member.value.tostring().length
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [], RuntimeException
    + FullyQualifiedErrorId : InvokeMethodOnNull

It is method .tostring() that throws error in line 195.
This happens because of property values are NULL. To avoid this a property value should be tested for $null.
It can be done like this (quick fix):

$len = if (-not $Member.value) {0} else {$Member.value.tostring().length}
$longest = $len, $member.name.length | Sort-Object | Select-Object -last 1

[jdhitsolutions]

That's not how the command is designed. It needs a sample property with values so it can make a best guess for column widths. Are you asking for better error handling or do you want to be able to pass an object with a null or empty property value?

[scriptingstudio]

I want to say that values are not important when I create new format because I have property names, so yes, property values should be tested. Am I correct and clear to express?

[scriptingstudio]

Error handling not important I believe

[jdhitsolutions]

Without property values, this defeats the function's design and intent. All you need to do is insert some placeholder values.

$o = '' | Select-Object -Property Name,Size,Color
$o.name="foo"
$o.size= 123
$o.color="blue"
$o | new-psformatxml -Typename MyObject -Path c:\work\foo.format.ps1xml

I have to think about this a bit more.

[scriptingstudio]

I did it but it implies much typing of useless information.
Anyway I use my "fix" for myself. And I am gonna learn the function engine. This function is very useful. Thanks.

[jdhitsolutions]

Your technique, while it works, is not really the best approach. Especially when scripting. At the very least, you are better off creating a hashtable and then using New-Object. Or learn how to use the [pscustomobject] type accelerator. The Select-Object trick was something we needed in early versions of PowerShell.

[scriptingstudio]

Yes, you are absolutely right and I am aware of all ways of object creation. I choose the safest and fastest way in every particular case.

[scriptingstudio]

BTW the same error can be repro with

new-object psobject -Property @{a=$null;b=$null}

[jdhitsolutions]

Yes. And that is by a design you are asking to be changed.

[scriptingstudio]

If my comments are not practical/useful the issue can be closed.

[jdhitsolutions]

I appreciate the feedback. What you want is an ability to generate the format file like this:

'' | Select-Object -Property Name,Size,Date,Count,Age | new-psformatxml -Typename myThing -Path c:\work\mything.format.ps1xml

I can't fault this approach. I actually needed to better handle input objects which might have had one empty value. I used to work around it by using a different reference object. But now I'll handle empty property values. This change will be available in v2.25.0.

[jdhitsolutions]

Update to v2.25.0 and see if this works better for you.