Adding Predictive IntelliSense to PowerShell VSCode Extension

Adding Predictive IntelliSense to PowerShell VSCode Extension

Summary of new feature

Predictive IntelliSense is an addition to the concept of tab completion that assists the user in
successfully completing commands. This enables new and experienced users of PowerShell to discover,
edit, and execute full commands based on matching predictions from the users history and additional
domain specific plugins such as
Az.Tools.Predictor.

PowerShell users would benefit from predictions in VSCode Terminal (PowerShell Integrated Console)
and Editor:

• PowerShell users with previous cmdlet experience receive suggestions from history and additional
  plugins, accelerating the time to command completion. Historical predictions come from the users
  PSReadLine history of completed commands, allowing them to quickly accept the prediction.

• PowerShell users without previous cmdlet experience receive guided suggestions from plugin
  predictors like Az.Tools.Predictor to help successfully complete the command. These plugins may
  provide a range of guided assistance in the form of complete commands or suggesting parameters and
  arguments.

Terminal

Terminal (PowerShell Integrated Console), should have the same features as PowerShell (shell) with
predictions as described in this
blog.

This includes InLineView and ListView for predictions, switchable with F2 key.

• Example of InLineView in PowerShell Integrated Console:

• Example of ListView in PowerShell Integrated Console:

Editor

Displaying predictions in the editor could be similar to IntelliCode for Visual Studio described
here.

When the user begins to type a cmdlet, a prediction using InLineView appears above other cmdlet
names. A star indicates that the suggestion comes from a predictor, followed by the InLineView
prediction, followed by the prediction source.

After the cmdlet name, when the user types dash (-) to begin a parameter, the first suggestion pair
(parameter and argument) is displayed along with the prediction source. As the user continues to
type the next parameter with a dash, the next suggestion pair is displayed until the prediction is
complete.

In the above example, the Az.Tools.Predictor will suggest the parameter and argument based on:

• Examples - Ml-based plugins may learn the most common uses of a cmdlet from documentation examples.
• Reuse - If the parameter and argument pair has been previously typed within the current session,
  the predictor will supply the previously typed argument.
• Syntax - If no examples or history is available, the predictor will display the parameter with the
  Object type for the argument.

Enabling/Disabling

Predictions are enabled and disabled using the Set-PSReadLineOption -PredictionSource <argument>
and may be stored in the users profile. Accepted values for the argument are None, History,
HistoryAndPlugin.

Configuring a predictor

Customizing prediction color, keybindings, and additional plugins is accomplished through PSReadLine
Set-PSReadLineOption and Set-PSReadLineKeyHandler cmdlets. Custom settings may be stored in the
users profile.

No source files, tests, or entry points are named. Start by breaking down the Terminal and Editor requirements, then review how the extension integrates with PSReadLine prediction settings and predictor plugins; done means supported history/plugin predictions, views, configuration, and keybindings work as described.