Unexpected Behavior with Group-Object with ScriptBlock

Question

I'm trying to use Group-Object to group a list of objects based on a custom computation. A very simplified example is the following:

$groupedProjects = 1..10 | %{
    [PSCustomObject]@{
        ErrorMessage = if ($_ % 2) { 'SomeError' } else { '' } 
    }
} | Group-Object -Property { if ($_.ErrorMessage) { 'Failed' } else { 'Successful' } } -AsHashTable

$successGroup = $groupedProjects['Successful'] 
# $successGroup is null here instead of a list with the integers.

The problem is that the groups are not keyed by the string but by something else instead - not sure I really understand the problem.

PS: Using a script block is shown in the documentation in this manner:

1..35 | Group-Object -Property {$_ % 2},{$_ % 3}

so I'd assume the idea is valid - using integers instead of strings also works as intended. If there's a better way to do the above I'm all ears though.

Interesting. There is a larger discussion about this here: https://stackoverflow.com/questions/28190053/group-object-diffencies-with-or-without-code-block — Zerqent, May 23 '18 at 11:26
You're using an implicit foreach in your group call with that scriptblock for a property... why? — Maximilian Burszley, May 23 '18 at 12:48
You're also not passing any non-even numbers to your group call in the first place. You lack an else block in `ErrorMessage=` — Maximilian Burszley, May 23 '18 at 12:50
@TheIncorrigle The missing else for the ErrorMessage was too much simplified, I'll fix it. Not sure what you mean with implicit foreach in the group-object script block. I'm using the script block for the property because I need a custom group property - how would you do it? — Voo, May 23 '18 at 14:28

score 2 · Accepted Answer · edited May 25 '18 at 20:28

2

The other posters are correct that the problem is with the key being stored as a PSObject but there is a build-in solution for this: use the -AsString switch along with -AsHashTable. This will force the key to be stored as a string.

I've opened an issue on GitHub for this bug.

edited May 25 '18 at 20:28

mklement0

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answered May 23 '18 at 23:32

Bruce Payette

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Unexpected Behavior with Group-Object with ScriptBlock

1 Answers1