Command Explorer lists multiple commands with the same name

[corbob]

System Details

System Details Output

### VSCode version: 1.31.0-insider 28e7467661d67c05c3662ff900ee1984f7e2fbcc x64
(node:27697) [DEP0005] DeprecationWarning: Buffer() is deprecated due to security and usability issues. Please use the Buffer.alloc(), Buffer.allocUnsafe(), or Buffer.from() methods instead.

### VSCode extensions:
DavidAnson.vscode-markdownlint@0.23.0
EditorConfig.EditorConfig@0.12.6
eg2.tslint@1.0.42
ms-vscode.csharp@1.17.1
ms-vscode.PowerShell@1.10.2
msjsdiag.debugger-for-chrome@4.11.1


### PSES version: 1.10.2.0

### PowerShell version:

Name                           Value
----                           -----
PSVersion                      6.1.1
PSEdition                      Core
GitCommitId                    6.1.1
OS                             Linux 4.9.0-8-amd64 #1 SMP Debian 4.9.130-2 (2018-10-27)
Platform                       Unix
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0...}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0

Issue Description

While working on an enhancement to the Command Explorer, I noticed a number of command names showed up twice. I also noted that they didn't duplicate in pwsh at the terminal. It appears they are being duplicated when you have multiple versions of the same module (in my case I have versions 1.6.7 and 2.0.3 of PowerShellGet installed).

I ran the command Microsoft.PowerShell.Core\Get-Command -CommandType @("Function","Cmdlet","ExternalScript") | Microsoft.PowerShell.Utility\Select-Object -Property @("Name","ModuleName") | Microsoft.PowerShell.Utility\Sort-Object -Property Name and I don't see the double commands.

Expected Behaviour

When refreshing the Command Explorer, should return a single instance of each command.

Actual Behaviour

Getting duplicate commands:

Attached Logs

logs.zip

[corbob]

I've done a bit more thinking on this, and it appears that this is the same thing that Show-Command does:

Given that it's the same behavior, would it still be classified as a bug?

[iricigor]

Problem comes from old PowerShell command discovery logic. If Get-Command is run without -Name filter it will find all versions of the same commands. On the other hand, if you specify -Name it will show only 1 version of command and import module. If you repeat first search, it will now find only 1 version of the command, as the module is imported now.

Here is an example with one command from Pester module:

PS C:\> (Get-Command | ? Name -eq AfterAll).Count
# 4
PS C:\> (Get-Command AfterAll).Count
# 1
PS C:\> (Get-Command | ? Name -eq AfterAll).Count
# 1

PowerShell ISE has the same bug. On initial load it also displays multiple commands. But, as it has standard workflow to import module for which you need more info, it quickly recovers itself and this bug is not so visible.

[corbob]

I was looking through some of the issues for Command Explorer, and it occurred to me that this could easily be "fixed" by piping through Select-Object -Unique... Naturally, I tested this in the most scientific way possible...

Based on this entirely scientific testing 🤪 this isn't a promising idea for a feature that already struggles with performance issues (to prove it wasn't a 1-off, I have run the second command again and it was 43 seconds this time). I haven't tried if we filter it on the vscode side in TypeScript. We could also try filtering down to unique in the C# before we return to vscode...

Might also just be a tradeoff we have to make to duplicate commands as opposed to taking the (potentially) massive performance hit of filtering them out.

[iricigor]

I presume that points to issues with Select -Unique implementation. Using Linq in these commands in my tests shows minimal speed penalty (3%) compared to the first command:

Duration CommandLine
-------- -----------
4.749    Get-Command | Sort-Object Name
4.914    [Linq.Enumerable]::Distinct([string[]]((Get-Command).Name)) | Sort-Object