(dsc): Export ignores `--input` filter for `Repository` and `PSResourceList` on DSC 3.3.* or above

Start by inspecting the manifest command and ExportOperation, focusing on how the export input is passed from stdin. Reproduce the issue with the two commands shown for Repository and PSResourceList, then verify that each returns only the PSGallery instance rather than every item.

Prerequisites

• Write a descriptive title.
• Make sure you are able to repro it on the latest released version
• Search the existing issues.

Steps to reproduce

As a user, I want dsc resource export --input to honour the filter I pass, so that I can export the resources of one repository or a single repository by name instead of everything on the machine.

Since DSC 3.3.0, export receives the filter instance on stdin when --input (or properties in a configuration) is given. Both manifests declare "input": "stdin" for export, but the manifest command does not pipe $Input to the script and ExportOperation never reads $stdinput, so the filter is silently discarded and the full list is returned.

dsc resource export -r Microsoft.PowerShell.PSResourceGet/PSResourceList --input '{"repositoryName":"PSGallery"}'
dsc resource export -r Microsoft.PowerShell.PSResourceGet/Repository --input '{"name":"PSGallery"}'

Expected behavior

The first command returns one PSResourceList instance for PSGallery, whereas the second command returns one Repository instance for PSGallery.

Actual behavior

Both commands return every repository / every resource list on the machine, identical to running export without --input. No warning is emitted.

Error details

Environment data

Directory: C:\Program Files\PowerShell\Modules

ModuleType Version    PreRelease Name                                PSEdition ExportedCommands
---------- -------    ---------- ----                                --------- ----------------
Binary     1.3.0      preview1   Microsoft.PowerShell.PSResourceGet  Core,Desk {Compress-PSResource, Find-PSResource, …
Binary     1.2.0      preview5   Microsoft.PowerShell.PSResourceGet  Core,Desk {Compress-PSResource, Find-PSResource, …

    Directory: C:\program files\powershell\7\Modules

ModuleType Version    PreRelease Name                                PSEdition ExportedCommands
---------- -------    ---------- ----                                --------- ----------------
Binary     1.2.0                 Microsoft.PowerShell.PSResourceGet  Core,Desk {Compress-PSResource, Find-PSResource, …

Key   : PSVersion
Value : 7.6.6
Name  : PSVersion


Key   : PSEdition
Value : Core
Name  : PSEdition


Key   : GitCommitId
Value : 7.6.6
Name  : GitCommitId


Key   : OS
Value : Microsoft Windows 10.0.26200
Name  : OS


Key   : Platform
Value : Win32NT
Name  : Platform


Key   : PSCompatibleVersions
Value : {1.0, 2.0, 3.0, 4.0…}
Name  : PSCompatibleVersions


Key   : PSRemotingProtocolVersion
Value : 2.4
Name  : PSRemotingProtocolVersion


Key   : SerializationVersion
Value : 1.1.0.1
Name  : SerializationVersion


Key   : WSManStackVersion
Value : 3.0
Name  : WSManStackVersion

Visuals

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