Predictive IntelliSense

Reference issue: RFC#687

Predictive IntelliSense is an addition to the interactive experience to assist in command discovery and accelerate full command execution. This enables new and experienced users of PowerShell to discover, edit, and execute full commands based on matching predictions from the users history or additional provider.

Tab Completion has accelerated the success of both new and experienced PowerShell users. New users get the benefit of discovery; seeing available cmdlets and parameters as options while interactively typing. Experienced users receive the benefit of acceleration; typing less while using the <tab> key to quickly complete a command.

The increasing amount of technology translates to an increase in cmdlets and full command complexity. Predictive IntelliSense is an addition to the concept of Tab Completion; helping the user discover, build and edit full commands based on the users history or additional plugins.

The proposal is to add Predictive IntelliSense and enhancements for MenuComplete/Dynamic Help to the users interactive experience.

Predictive IntelliSense Protoype maybe found on PSGallery.

Proposed technical implementation details

1. Predictive IntelliSense displays a best match command completion from command history. The prediction may change if a better match is found as the user types additional information. The predicted command may be accepted, edited, or ignored. It may be possible to support additional predictive providers.

1. Predictions are searchable and may be edited. Additional key bindings may be added to the users Profile as in the example below:

Set-PSReadLineKeyHandler -Key "Ctrl+d" -Function MenuComplete
Set-PSReadLineKeyHandler -Key "Ctrl+f" -Function ForwardWord
Set-PSReadLineKeyHandler -Key "Ctrl+b" -Function BackwardWord
Set-PSReadLineKeyHandler -Key "Ctrl+z" -Function Undo
Set-PSReadLineKeyHandler -Key UpArrow -Function HistorySearchBackward
Set-PSReadLineKeyHandler -Key DownArrow -Function HistorySearchForward

1. Predictions are searchable based on the current cursor position.

• Searching history from cmdlet verb.

• Searching histroy from cmdlet noun.

• Searching history from parameter.

1. Predictions may be edited by stepping-through the parameters and arguments.

• Moving forward and backward using additional key bindings.

• Note: Changing the parameter/argument, changes the prediction.

1. MenuComplete/Dynamic Help is a current feature of PSReadLine. When combined with Predictive IntelliSense, MenuComplete provides additonal discovery and help information.

• MenuComplete providing cmdlet discovery and help.

• MenuComplete providing parameter discovery and help.

Open discussion items:

• Should the number of lines displayed for MenuComplete be restricted and what should that restriction be?
• Should an interactive cursor-based scroll bar for paging be included?
• What should the content of Dynamic Help include?

1. Full cmdlet help is accessible using a key binding to access the help in a virtual terminal. An additional key binding will return the user from the virtual terminal to the previous screen.

1. Predictive IntelliSense Accessibility is managed through the users profile.

Set-PSReadLineOption -Colors @{ Prediction = '#8A0303'}
Set-PSReadLineOption -Colors @{ Prediction = '#2F7004'}

Multiple color code values are supported currently in PSReadLine.

Examples of different color code values:

Set-PSReadLineOption -Colors @{ Prediction = 'DarkRed'}
 # Use a ConsoleColor enum
Set-PSReadLineOption -Colors @{ Prediction = [ConsoleColor]::DarkRed}
 # 24 bit color escape sequence
Set-PSReadLineOption -Colors @{ Prediction = "$([char]0x1b)[38;5;100m"}
 # RGB value
Set-PSReadLineOption -Colors @{ Prediction = "#8181f7"}

1. Predictive IntelliSense Extensibility

It may be possible to support 1st party and 3rd party predictive plugins.

[TylerLeonhardt]

One other thing about the Dynamic Help feature… the PowerShell extension has been providing this experience for a while (see the box on the right):

It’s called the completionItem/resolve request as a part of the language server protocol.

The idea here is… for a completion, give me more details about it… but only send the request for more details when it is highlighted.

However, the PowerShell extension goes a step further to provide syntax as you’re typing parameters too:

VS Code decided it was a good idea to separate this into it’s own request called the Signature Help Request.

There are a lot of learning from the PowerShell extension and LSP that can be leveraged in the design of the features outlined here. Please consider them in the design.

[rdhar]

Looking at #687, it looks like some progress has been made with the following:

# Search auto-completion from history
Set-PSReadLineOption -HistorySearchCursorMovesToEnd
Set-PSReadLineKeyHandler -Key UpArrow -Function HistorySearchBackward
Set-PSReadLineKeyHandler -Key DownArrow -Function HistorySearchForward

# Show auto-complete predictions from history
Set-PSReadLineOption -ShowToolTips
Set-PSReadLineOption -PredictionSource history
Get-PSReadLineOption | ForEach-Object predictionsource

That said, still nowhere near as feature-rich as PowerShell’s VS Code extension.