An ArgumentCompleter script block returning no results should not result in falling back to the default tab-completion behavior

[mklement0]

Currently, if you attach an ArgumentCompleterAttribute to a parameter and its script block happens to return no completions, tab completion falls back to the default behavior, i.e., completion of item names in the current location (which, in a filesystem location, cycles through the names of all files and directories in the current directory).

However, it makes more sense to not complete in this event, given that the intended completions may be unrelated to provider items altogether.

Steps to reproduce

Assume that the current location is a filesystem location and that no *.ext files are present.

function foo {
  param(
    [ArgumentCompleter({
      Get-ChildItem -Name *.ext
    })]
    [string] $Bar
  )

  $Bar
}

foo # <-- press TAB here

Expected behavior

A no-op: given that the argument-completer script block outputs no completions, nothing should happen.

Actual behavior

Tab completion falls back to the default behavior and cycles through the names of all files and subdirectories in the current dir.

Environment data

Written as of:

PowerShell Core v6.1.0-preview.3

[Betoz]

Attaching ArgumentCompletions attribute with empty string as the only tab completion value, i.e. [ArgumentCompletions('')], in addition to ArgumentCompleter attribute, results in no completion when ArgumentCompleter script block returns no completions.

I agree with it making more sense to not complete when ArgumentCompleter script block returns no completions, or at least to handling the return of empty string as a valid completion, like it does for the ArgumentCompletions attribute.

Maybe it is a design decision to use ArgumentCompletions for static completions in the case of ArgumentCompleter script block returning no completions?
If so, I would like this information in the about_functions_argument_completion documentation, e.g.

Hey! You can block tab completion with [ArgumentCompletions('')].

Note that the ArgumentCompletions attribute was introduced in PowerShell 6.0.

I confirmed usage of [ArgumentCompletions('')] to work with PowerShell 7.1.2, and to not work with 5.1 (breaks, because not supported).

[microsoft-github-policy-service]

This issue has not had any activity in 6 months, if this is a bug please try to reproduce on the latest version of PowerShell and reopen a new issue and reference this issue if this is still a blocker for you.

[microsoft-github-policy-service]

This issue has not had any activity in 6 months, if this is a bug please try to reproduce on the latest version of PowerShell and reopen a new issue and reference this issue if this is still a blocker for you.

[microsoft-github-policy-service]

This issue has not had any activity in 6 months, if this is a bug please try to reproduce on the latest version of PowerShell and reopen a new issue and reference this issue if this is still a blocker for you.

[microsoft-github-policy-service]

This issue has been marked as "No Activity" as there has been no activity for 6 months. It has been closed for housekeeping purposes.