How can I automatically syntax check a powershell script file?

Question

I want to write a unit-test for some code which generates a powershell script and then check that the script has valid syntax.

What's a good way to do this without actually executing the script?

A .NET code solution is ideal, but a command line solution that I could use by launching an external process would be good enough.

Related post - [How to do full syntax check of PowerShell script file using the PowerShell cmdlet](https://stackoverflow.com/q/68397836/465053) — RBT, Oct 29 '21 at 06:44

score 27 · Answer 1 · edited Dec 10 '21 at 14:58

27

I stumbled onto Get-Command -syntax 'script.ps1' and found it concise and useful.

ETA from the comment below: This gives a detailed syntax error report, if any; otherwise it shows the calling syntax (parameter list) of the script.

edited Dec 10 '21 at 14:58

NovaDev

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answered Mar 25 '19 at 12:29

Willem M.

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For me, this just produces the name of the scriupt file. – Christoph Apr 29 '19 at 07:53
5

Indeed it does. Now try it on a script that has syntax errors. – Willem M. May 13 '19 at 10:58
11

This gives a detailed syntax error report, if any; otherwise it shows the calling syntax (parameter list) of the script. This is much easier to use for a quick error check than the accepted answer. – royappa Sep 11 '19 at 19:01
4

@royappa: This answer is only useful because of your comment, which has 10 times more information than the answer. +1 for both. – Tobias Knauss Mar 13 '21 at 11:57
This is just entirely awesome. – Hannah Vernon Aug 11 '23 at 22:04

Mathias R. Jessen · Accepted Answer · 2019-04-29T15:27:05.787

You could run your code through the Parser and observe if it raises any errors:

# Empty collection for errors
$Errors = @()

# Define input script
$inputScript = 'Do-Something -Param 1,2,3,'

[void][System.Management.Automation.Language.Parser]::ParseInput($inputScript,[ref]$null,[ref]$Errors)

if($Errors.Count -gt 0){
    Write-Warning 'Errors found'
}

This could easily be turned into a simple function:

function Test-Syntax
{
    [CmdletBinding(DefaultParameterSetName='File')]
    param(
        [Parameter(Mandatory=$true, ParameterSetName='File', Position = 0)]
        [string]$Path, 

        [Parameter(Mandatory=$true, ParameterSetName='String', Position = 0)]
        [string]$Code
    )

    $Errors = @()
    if($PSCmdlet.ParameterSetName -eq 'String'){
        [void][System.Management.Automation.Language.Parser]::ParseInput($Code,[ref]$null,[ref]$Errors)
    } else {
        [void][System.Management.Automation.Language.Parser]::ParseFile($Path,[ref]$null,[ref]$Errors)
    }

    return [bool]($Errors.Count -lt 1)
}

Then use like:

if(Test-Syntax C:\path\to\script.ps1){
    Write-Host 'Script looks good!'
}

This is likely the most direct on-point answer to the question. Mine is more general unit testing. — Matthew Wetmore, Apr 04 '17 at 19:50
If someone could make this answer a bit more dummy proof, I'd appreciate it. Do I understand correctly that the first and the second code are redundant? Or rather: it's the second one I'm supposed to use? — Christoph, Apr 29 '19 at 08:00
Could it be that to use the function, you need the `-path` option? For me only `Test-Syntax -path C:\path\to\script.ps1` seems to work, not `Test-Syntax C:\path\to\script.ps1` — Christoph, Apr 29 '19 at 08:36

Matthew Wetmore · Answer 3 · 2017-04-04T17:39:02.030

PS Script Analyzer is a good place to start at static analysis of your code.

PSScriptAnalyzer provides script analysis and checks for potential code defects in the scripts by applying a group of built-in or customized rules on the scripts being analyzed.

It also integrates with Visual Studio Code.

There are a number of strategies for mocking PowerShell as part of unit tests, and also have a look at Pester.

The Scripting Guy's Unit Testing PowerShell Code With Pester
PowerShellMagazine's Get Started With Pester (PowerShell unit testing framework)

How can I automatically syntax check a powershell script file?

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