Powershell: Bad error message thrown when creating a symbolic link

[daxian-dbw]

Steps to reproduce

## I intend to create a symbolic link `foo` pointing to the directory 'bar'.
## However, I incorrectly specified the target directory path as the argument to `-Path`.
mkdir F:\temp\bar
New-Item -ItemType SymbolicLink -Path F:\temp\bar -Value F:\temp\foo

Expected behavior

Error message should be meaningful and useful

Actual behavior

PS:62> New-Item -ItemType SymbolicLink -Path F:\temp\bar -Value F:\temp\foo
New-Item : NewItemIOError
At line:1 char:1
+ New-Item -ItemType SymbolicLink -Path F:\temp\bar -Value F:\temp\foo
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : ResourceExists: (F:\temp\bar:String) [New-Item], IOException
    + FullyQualifiedErrorId : NewItemIOError,Microsoft.PowerShell.Commands.NewItemCommand

Environment data

> $PSVersionTable
Name                           Value                                                               
----                           -----                                                               
PSVersion                      6.0.0-alpha                                                         
PSEdition                      Core                                                                
BuildVersion                   3.0.0.0                                                             
CLRVersion                                                                                         
GitCommitId                    v6.0.0-alpha.18-54-g3e416fb6422c0c25f63bd0228edd2403ae2c78d4        
OS                             Linux 4.8.0-41-generic #44~16.04.1-Ubuntu SMP Fri Mar 3 17:11:16 ...
Platform                       Unix                                                                
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0...}                                             
PSRemotingProtocolVersion      2.3                                                                 
SerializationVersion           1.1.0.1                                                             
WSManStackVersion              3.0              

[daxian-dbw]

@jeffbi you have a lot experiences related to symbolic link, can you please have a quick look at this issue and see if it's easy to fix?

[jeffbi]

@daxian-dbw Well, the error message is correct, as far as it goes---the name given as the symlink path does already exist.

What would be preferred? We could try to be a little more clever and if we're trying to create a symlink and a) the item on -Path already exists and b) the item on -Value does not, we could do something "git-ish" like:

Item F:\tmp\bar already exists. Did you mean "-Path F:\tmp\foo -Value F:\tmp\bar?"

Not really a prompt, just a hint. Of course we'd probably want to know if target path was given via -Value or -Target and adjust the message accordingly.

Or just a new message specific to symlinks when the path item exists? Either one would be fairly easy.

[iSazonov]

Simple Item F:\tmp\bar already exists looks good in all cases.

[jeffbi]

It looks like this is the one place in the FileSystemProvider.cs code file that an ErrorRecord is being built from a newly-constructed IOException object without going out to FileSystemProviderStrings. It just plugs that ugly, non-localized text into the error:
C# WriteError(new ErrorRecord(new IOException("NewItemIOError"), "NewItemIOError", ErrorCategory.ResourceExists, path));
I think we just need a new message and to change the code to use it.

[jeffbi]

I'd really like to change the error ID from "NewItemIOError" to "SymLinkExists" if for no other reason it will make for better tests. Or would that be a breaking change?

[iSazonov]

It is a breaking change but acceptable and reasonable.

[daxian-dbw]

@jeffbi Thanks for the quick fix!