Undo/Cancel Completion Key Handler

The issue points to Completion.cs and the TabCompleteNext call path; start by reading that entry point alongside CompleteImpl and the vi completion entry points mentioned. Done means Ctrl+e restores the original line and cursor after repeated forward or backward completion in the supported vi modes, while leaving ordinary editing unaffected.

Prerequisites

• Write a descriptive title.

Description of the new feature/enhancement

Like vim, it would be nice to be able to ctrl+e to cancel all the previous completions. If one gets three tabs into a completion cycle, it can be annoying to have to realize your search space is too wide and have to undo many times to get back to the initial text to be completed.

Proposed technical implementation details (optional)

Playing with the below naive implementation. Problems are tracking the "is completing" state and movement of the cursor during completions.

    & {
        $psrlTabState = [PSCustomObject]@{
            OriginalLine     = $null
            OriginalCursor   = 0
            CompletedLine    = $null
            CompletedCursor  = 0
        }
    
        $tabHandlerSb = {
           param($key, $arg)
    
            $line = $null
            $cursor = 0
    
            [Microsoft.PowerShell.PSConsoleReadLine]::GetBufferState(
                [ref]$line,
                [ref]$cursor
            )
    
            if (
                $null -eq $psrlTabState.CompletedLine -or
                $line -cne $psrlTabState.CompletedLine -or
                $cursor -ne $psrlTabState.CompletedCursor
            )
            {
                $psrlTabState.OriginalLine = $line
                $psrlTabState.OriginalCursor = $cursor
            }
    
            [Microsoft.PowerShell.PSConsoleReadLine]::TabCompleteNext($key, $arg)
    
            [Microsoft.PowerShell.PSConsoleReadLine]::GetBufferState(
                [ref]$line,
                [ref]$cursor
            )
    
            $psrlTabState.CompletedLine = $line
            $psrlTabState.CompletedCursor = $cursor
        }.GetNewClosure()
        $viTabHandlerSb = {
           param($key, $arg)
    
            $line = $null
            $cursor = 0
    
            [Microsoft.PowerShell.PSConsoleReadLine]::GetBufferState(
                [ref]$line,
                [ref]$cursor
            )
    
            if (
                $null -eq $psrlTabState.CompletedLine -or
                $line -cne $psrlTabState.CompletedLine -or
                $cursor -ne $psrlTabState.CompletedCursor
            )
            {
                $psrlTabState.OriginalLine = $line
                $psrlTabState.OriginalCursor = $cursor
            }
    
            [Microsoft.PowerShell.PSConsoleReadLine]::ViTabCompleteNext($key, $arg)
    
            [Microsoft.PowerShell.PSConsoleReadLine]::GetBufferState(
                [ref]$line,
                [ref]$cursor
            )
    
            $psrlTabState.CompletedLine = $line
            $psrlTabState.CompletedCursor = $cursor
        }.GetNewClosure()
        $prevTabHandlerSb = {
           param($key, $arg)
    
            $line = $null
            $cursor = 0
    
            [Microsoft.PowerShell.PSConsoleReadLine]::GetBufferState(
                [ref]$line,
                [ref]$cursor
            )
    
            if (
                $null -eq $psrlTabState.CompletedLine -or
                $line -cne $psrlTabState.CompletedLine -or
                $cursor -ne $psrlTabState.CompletedCursor
            )
            {
                $psrlTabState.OriginalLine = $line
                $psrlTabState.OriginalCursor = $cursor
            }
    
            [Microsoft.PowerShell.PSConsoleReadLine]::TabCompletePrevious($key, $arg)
    
            [Microsoft.PowerShell.PSConsoleReadLine]::GetBufferState(
                [ref]$line,
                [ref]$cursor
            )
    
            $psrlTabState.CompletedLine = $line
            $psrlTabState.CompletedCursor = $cursor
        }.GetNewClosure()
        $viPrevTabHandlerSb = {
           param($key, $arg)
    
            $line = $null
            $cursor = 0
    
            [Microsoft.PowerShell.PSConsoleReadLine]::GetBufferState(
                [ref]$line,
                [ref]$cursor
            )
    
            if (
                $null -eq $psrlTabState.CompletedLine -or
                $line -cne $psrlTabState.CompletedLine -or
                $cursor -ne $psrlTabState.CompletedCursor
            )
            {
                $psrlTabState.OriginalLine = $line
                $psrlTabState.OriginalCursor = $cursor
            }
    
            [Microsoft.PowerShell.PSConsoleReadLine]::ViTabCompletePrevious($key, $arg)
    
            [Microsoft.PowerShell.PSConsoleReadLine]::GetBufferState(
                [ref]$line,
                [ref]$cursor
            )
    
            $psrlTabState.CompletedLine = $line
            $psrlTabState.CompletedCursor = $cursor
        }.GetNewClosure()
    
        $cancelCompHandlerSb = {
            $line = $null
            $cursor = 0
    
            [Microsoft.PowerShell.PSConsoleReadLine]::GetBufferState(
                [ref]$line,
                [ref]$cursor
            )
    
            if (
                $null -ne $psrlTabState.CompletedLine -and
                $line -ceq $psrlTabState.CompletedLine -and
                $cursor -eq $psrlTabState.CompletedCursor
            )
            {
                [Microsoft.PowerShell.PSConsoleReadLine]::Replace(
                    0,
                    $line.Length,
                    $psrlTabState.OriginalLine
                )
    
                [Microsoft.PowerShell.PSConsoleReadLine]::SetCursorPosition(
                    $psrlTabState.OriginalCursor
                )
            }
    
            $psrlTabState.OriginalLine = $null
            $psrlTabState.OriginalCursor = 0
            $psrlTabState.CompletedLine = $null
            $psrlTabState.CompletedCursor = 0
        }.GetNewClosure()
    
        Set-PSReadLineKeyHandler -Chord 'Tab' -ViMode 'Insert' -ScriptBlock $viTabHandlerSb -BriefDescription 'ViTabCompleteNextSaveState' -Description 'Match ViTabCompleteNext functionality and save state for CancelCompletion'
        Set-PSReadLineKeyHandler -Chord 'Tab' -ViMode 'Command' -ScriptBlock $tabHandlerSb -BriefDescription 'TabCompleteNextSaveState' -Description 'Match TabCompleteNext functionality and save state for CancelCompletion'
        Set-PSReadLineKeyHandler -Chord 'Shift+Tab' -ViMode 'Insert' -ScriptBlock $viPrevTabHandlerSb -BriefDescription 'ViTabCompletePreviousSaveState' -Description 'Match ViTabCompletePrevious functionality and save state for CancelCompletion'
        Set-PSReadLineKeyHandler -Chord 'Shift+Tab' -ViMode 'Command' -ScriptBlock $prevTabHandlerSb -BriefDescription 'TabCompletePreviousSaveState' -Description 'Match TabCompletePrevious functionality and save state for CancelCompletion'
        Set-PSReadLineKeyHandler -Chord 'Ctrl+e' -ViMode 'Insert' -ScriptBlock $cancelCompHandlerSb -BriefDescription 'CancelCompletion' -Description 'Revert and undo all of the previous completions. Relies on SaveState suffixed key handlers.'
    }

EDIT 1 : Better code implementation handling vi mode. Apparently TabCompleteNext doesn't handle VI mode like Complete or MenuComplete.

EDIT 2: Curious why TabCompleteNext doesn't have the same call stack and call CompleteImpl.

EDIT 3: Updated the script with finalized version which properly takes in account the Vi related tab complete next. I'm using chezmoi template on [scriptblock] and they are all the same accept for the *TabComplete* method they call. Now maybe there is some way to handle it with the ConsoleKeyInfo passed in to reduce the duplication. I just solved with an embedded golang template.