Using hyphen/dash parameter produces "Cannot process argument because the value of argument “name” is not valid"

Using the latest PowerShell 6.2.2:

C:\Test>pwsh -File Test.ps1 -
C:\Test\Test.ps1 : Cannot process argument because the value of argument "name" is not valid. Change the value of the "name" argument and run the operation again.
+ CategoryInfo          : InvalidArgument: (:) [Test.ps1], PSArgumentException
+ FullyQualifiedErrorId : Argument,Test.ps1

The Test.ps1 is simple

echo "foo"

The error does not make any sense to me. I suspect it’s a bug in command-line parsing.

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PowerShell 5.1 also processes the dash strangely (although it manifests differently): What does hyphen/dash parameter mean to PowerShell?

PowerShell 2.0 works as expected.

[mklement0]

@martinprikryl

The problem exists in Windows PowerShell and (no longer) in PowerShell Core as of the current preview (Core 7.0.0-preview.3). I do see it in 6.2.2, though (not sure what the policy re fixes is there).

I’m not sure how likely back-porting of fixes to Windows PowerShell is at this point, but you can also report the issue at Windows PowerShell UserVoice

As for a workaround: use -Command instead of -File; while that changes the semantics of how the command line is parsed, in simple cases such as this one it should be fine:

C:\> pwsh -Command ./Test.ps1 -  # note the "./" - should work in both WinPS and PS Core

Note the ./, because using -Command (-c) makes PowerShell parse the arguments as if they were PowerShell code, and the usual restrictions re executing scripts by filename only apply.

If your script file path needed quoting, you’d have to use enclosing and nested quoting and prepend &; e.g.:

C:\> pwsh -Command "& \"./Test.ps1\" -"

[iSazonov]

I guess we haven’t direct commit for the issue, it was a side effect from adding new parameters. So it is not easy backport the change.