Display issue with hashtable: only the first field is shown and if it's null it looks like it's empty #19354

cnotin · 2023-03-16T20:06:10Z

Prerequisites

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Refer to Differences between Windows PowerShell 5.1 and PowerShell.

Steps to reproduce

Run these commands:

@{ id = "id"; KeyCredentials = @(@{ Key = $null; DisplayName = "CN=MyServicePrincipalCert"})} | select KeyCredentials
@{ id = "id"; KeyCredentials = @(@{ Key = "Test Key"; DisplayName = "CN=MyServicePrincipalCert"})} | select KeyCredentials

In the first command output, it looks like the KeyCredentials is empty whereas it isn't. I think it's because it shows its first field, Key, which is $null
But this is surprising in my opinion, and it led me to thinking there was a bug in the Microsoft Graph PowerShell SDK whereas there wasn't any: microsoftgraph/msgraph-sdk-powershell#1849

The second command is a more normal case, and its output looks more natural to me.

Expected behavior

PS C:\> @{ id = "id"; KeyCredentials = @(@{ Key = $null; DisplayName = "CN=MyServicePrincipalCert"})} | select KeyCredentials

KeyCredentials
--------------
{$null}
# or perhaps:
# Key = $null; DisplayName = "CN=MyServicePrincipalCert"
# or even the second field considering the first one is $null:
# DisplayName = "CN=MyServicePrincipalCert"

PS C:\> @{ id = "id"; KeyCredentials = @(@{ Key = "Test Key"; DisplayName = "CN=MyServicePrincipalCert"})} | select KeyCredentials

KeyCredentials
--------------
{Test Key}

Actual behavior

PS C:\> @{ id = "id"; KeyCredentials = @(@{ Key = $null; DisplayName = "CN=MyServicePrincipalCert"})} | select KeyCredentials

KeyCredentials
--------------
{}
# this {} is surprising to me. Is the array empty? Is there nothing? No! There's something

PS C:\> @{ id = "id"; KeyCredentials = @(@{ Key = "Test Key"; DisplayName = "CN=MyServicePrincipalCert"})} | select KeyCredentials

KeyCredentials
--------------
{Test Key}

Workaround

Instead of using | select, if I access the property directly the hashtable output is clearer:

PS C:\> $Object1 = New-object psobject -Property @{ id = "id"; KeyCredentials = @(@{ Key = $null; DisplayName = "CN=MyServicePrincipalCert"})}
PS C:\> $object1.KeyCredentials

Name                           Value
----                           -----
DisplayName                    CN=MyServicePrincipalCert
Key

Error details

None

Environment data

PS C:\> $PSVersionTable

Name                           Value
----                           -----
PSVersion                      7.4.0-preview.1
PSEdition                      Core
GitCommitId                    7.4.0-preview.1
OS                             Microsoft Windows 10.0.19045
Platform                       Win32NT
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0…}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0

Visuals

No response

The text was updated successfully, but these errors were encountered:

mklement0 · 2023-03-16T23:45:48Z

Conceptually related:

$null should be indicated by a blank line, especially when within an array #17683

I haven't looked at the source code, but it appears that there is hard-coded logic in the formatting system for properties whose array elements happen to be of type [hashtable]: they are rendered by the value of an entry whose key is 'Key', if present, and otherwise by the value of whatever happens to be the first entry in the (inherently unordered) hash table.

By contrast, [ordered] hashtables and [System.Collections.Generic.Dictionary[T1, T2]] instances (unhelpfully) stringify by their type name (i.e. they are rendered with .ToString()).

cnotin added the Needs-Triage The issue is new and needs to be triaged by a work group. label Mar 16, 2023

SteveL-MSFT added the WG-Engine-Format label Mar 20, 2023

vexx32 added the Issue-Enhancement the issue is more of a feature request than a bug label Mar 20, 2023

vexx32 assigned SeeminglyScience Mar 20, 2023

Display issue with hashtable: only the first field is shown and if it's null it looks like it's empty #19354

Display issue with hashtable: only the first field is shown and if it's null it looks like it's empty #19354

cnotin commented Mar 16, 2023 •

edited

mklement0 commented Mar 16, 2023

Display issue with hashtable: only the first field is shown and if it's null it looks like it's empty #19354

Display issue with hashtable: only the first field is shown and if it's null it looks like it's empty #19354

Comments

cnotin commented Mar 16, 2023 • edited

Prerequisites

Steps to reproduce

Expected behavior

Actual behavior

Workaround

Error details

Environment data

Visuals

mklement0 commented Mar 16, 2023

cnotin commented Mar 16, 2023 •

edited