Powershell Select-Object: Executing native commands in calculated property - powershell

Question

I'm trying to create a report file which lists all files in my Git repository with these columns:
Name
Size
Last Modified
Git Commit
The first 3 are no problem:
gci -File -Recurse | Select-Object -Property #{
label = 'Size(KB)'
expr = { [string]::Format("{0:0.00}", $_.Length/1KB) }
}, LastWriteTime, FullName
However, retrieving the git commit requires running Git, a native command.
I've tried, among others:
gci -File -Recurse | Select-Object -Property #{
label = 'Git commit'
expr = { Invoke-Expression "git log -1 --format:format=`"%s`" -- $($_.FullName)" }
},
#{
label = 'Size(KB)'
expr = { [string]::Format("{0:0.00}", $_.Length/1KB) }
}, LastWriteTime, FullName
But it just gets stuck.
Does anyone know how to do this??
P.S.
All the flags and options to Git doesn't matter for the manner of sake, I just copied what I already did.

Answer 1

As #mklement0 suggested in the comments, the issue was just that your formatting for the --format command was off just enough to cause a problem.
You had:
--format:format="%s" # won't work
--format=format:"%s" # works
So to fix it, we just swap in the right format, giving us this command with the output below.
gci -File | Select-Object -Property #{
label = 'Git commit'
expr = { Invoke-Expression "git log -1 --format=format:`"%s`" $($_.Name)" }
},
#{
label = 'Size(KB)'
expr = { [string]::Format("{0:0.00}", $_.Length/1KB) }
}, LastWriteTime, FullName
Git commit Size(KB) LastWriteTime FullName
---------- -------- ------------- --------
applied gitingore 6.07 5/11/2020 11:22:06 AM C:\git\ClientFaux\.gitignore
cleanin up layout 1.40 10/9/2020 3:20:33 PM C:\git\ClientFaux\ClientFaux.sln
Create LICENSE (#25) 34.98 7/13/2020 9:55:00 AM C:\git\ClientFaux\LICENSE
Update README.md (#27) 3.37 7/13/2020 9:55:00 AM C:\git\ClientFaux\README.md
31.13 7/13/2020 9:55:27 AM C:\git\ClientFaux\UpgradeLog.htm

Answer 2

FoxDeploy's helpful answer contains the crucial pointer, but let me offer a (corrected) PowerShell-idiomatic reformulation of your code.
Get-ChildItem -File -Recurse | Select-Object -Property #{
label = 'Git commit'
expr = { git log -1 --format=format:%s -- $_.FullName }
},
#{
label = 'Size(KB)'
expr = { '{0:0.00}' -f ($_.Length/1KB) }
}, LastWriteTime, FullName
Note:
Invoke-Expression should generally be avoided; definitely don't use it to invoke an external program or PowerShell script, so the above uses direct invocation of git.
As mentioned, --format:format="%s" is syntactically incorrect and should be --format=format:"%s" (I've omitted the " above, which PowerShell would strip behind the scenes anyway).
-f, the format operator, is used as the PowerShell-idiomatic alternative to directly calling the underlying .NET API, System.String.Format.
Calling native executables in calculated properties:
Generally, note that there's nothing fundamentally special about calling native executables from the expression script block ({ ... }) of a calculated property.
Specifically, the following considerations apply:
In PowerShell, stdout output from native executables is invariably converted to text ([string] instances). If the output comprises multiple lines, the property values becomes a (regular [object[]]) array containing strings.
If the native executable produces no stdout output, the value of the property is "nothing", i.e. the so-called "Automation Null" value ([System.Management.Automation.Internal.AutomationNull]::Value) that in most context behaves like $null.
Any stderr output from the native executable is quietly discarded. (Analogously, errors from PowerShell commands or expressions in expression script blocks are quietly ignored.)
Therefore, in order to troubleshoot an expression script block, execute it stand-alone, via a ForEach-Object command (whose built-in alias is %), so as to surface any errors; e.g.:
# Uses broken `git` syntax; note the resulting error message.
PS> (Get-ChildItem -File)[0] | % { git log -1 --format:format=%s -- $_.FullName }
fatal: unrecognized argument: --format:format=%s
As for what you tried:
Because your git command was syntactically incorrect, git only produced stderr output, which PowerShell then ignored, as explained above.
Thus, your Git commit properties ended up containing "nothing", which simply renders blank in output formatting.