Command not found should suggest how to install like in bash

[lzybkr]

Steps to reproduce

Run a command that's not installed on your Linux machine, e.g. dtrace.

Expected behavior

jasonsh@jasonsh-ubd02:~$ dtrace
The program 'dtrace' is currently not installed. You can install it by typing:
sudo apt-get install systemtap-sdt-dev

Actual behavior

PS> dtrace                                                                                                               
dtrace : The term 'dtrace' is not recognized as the name of a cmdlet, function, script file, or operable program. Check 
the spelling of the name, or if a path was included, verify that the path is correct and try again.
At line:1 char:1
+ dtrace
+ ~~~~~~

Environment data

PS /home/jasonsh> $PSVersionTable                                                                                        

Name                           Value                                                                                    
----                           -----                                                                                    
PSVersion                      6.0.0-alpha                                                                              
PSEdition                      Core                                                                                     
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0...}                                                                  
BuildVersion                   3.0.0.0                                                                                  
GitCommitId                    v6.0.0-alpha.9                                                                           
CLRVersion                                                                                                              
WSManStackVersion              3.0                                                                                      
PSRemotingProtocolVersion      2.3                                                                                      
SerializationVersion           1.1.0.1                                                                                  


PS /home/jasonsh> uname -v                                                                                               
#49~14.04.1-Ubuntu SMP Wed Jun 29 20:22:11 UTC 2016

[rkeithhill]

That would be nice! Is there some repo/registry that maintains the mapping of "command to pkg name" for the various Linux distro's, as well as the pkg mgr to use (apt-get vs yum vs Install-Module)?

[nerdshark]

This isn't built-in bash functionality; it's normally defined as an error-handler callback (for error 127) in one of the system-wide shell profiles (probably in /etc/bashrc, /etc/profile, or /etc/profile.d/*).

Keith Hill (@rkeithhill) It's not likely. Distros that support this kind of functionality generally do two or three things:

• maintain a database of files owned by installed packages;
• provide downloadable databases of repositories' package contents;
• and provide an online, searchable database of package contents.

I don't think that using or maintaining an unofficial, centralized database of command-to-package mappings or package contents for multiple versions of multiple distros is the right approach. Instead, I think that Powershell should provide relevant error-handler hook points (or use existing ones) in the command loop and let Powershell packagers write callbacks tailored to their specific OS/package manager combination. This is in line with the existing practice above, and should require minimal effort to maintain.

[SteveL-MSFT]

Need some api in PSGallery to enable this

[BrucePay]

I think that Powershell should provide relevant error-handler hook points (or use existing ones) in the command loop

FYI: there's been a "command not found" action available in PowerShell since version 3.

$executioncontext.InvokeCommand.CommandNotFoundAction = { 
    param ($e, $e2)  

   $e2.StopSearch = $true
   $e2.CommandScriptblock = {
       Write-Verbose -Verbose ` 
          "Look for a module containing the command '$e somewhere"}.GetNewClosure()
    }
}

[BrucePay]

It turns out that the gallery does give you a way to look up modules containing a command Find-Module -Command. So adding that to the hook code, you get something like this:

$ExecutionContext.InvokeCommand.CommandNotFoundAction = {
    param ($n, $e)

    $e.StopSearch = $true
    $e.CommandScriptBlock = {
        Write-Host -ForegroundColor Yellow `
            -Verbose "Command '$n' was not found; searching on-line for modules with this command"
        $result = Find-Module -Command $n
        if ($result)
        {
            $result | Out-String | Write-Host -ForegroundColor Yellow
        }
        else
        {
            Write-Host -ForegroundColor Yellow "No matching modules were found."
        }
    }.GetNewClosure()
}

The response from the gallery can be a bit slow, but you can always cancel the lookup with ctrl-C.

[SteveL-MSFT]

Opened https://github.com/PowerShell/PowerShellGet/issues/287, if they can get the perf down to 100ms or less, I think we can add this capability into PSCore6 (but probably need to have it timeout after 250ms to not impact the interactive experience)