Add actions for executing code

[jmcphers]

Intent

Make it possible to create keybindings that run code in Positron. This feature has been requested frequently by both private beta and internal beta users.

Addresses #2375
Addresses #2661

Approach

There are two new commands here; they have arguments and semantics that are different enough to warrant the bifurcation.

workbench.action.executeCode.console - executes code as if the user typed it. This is useful for keybindings that are used more like macros.

workbench.action.executeCode.silently - executes code silently. This is useful for code that is run for its side effects (e.g. making API calls).

Both commands accept an argument object that can specify langId and code fields. They can also accept just a plain string as an argument, in which case the code will be run in whatever console happens to be active.

QA Notes

Here is an example keybinding to start playing with this:

    {
        "key": "Alt+Shift+E",
        "command": "workbench.action.executeCode.console",
        "description": "Print Elbereth",
        "when": "editorTextFocus",
        "args": {
            "langId": "python", 
            "code": "print('Elbereth')",
            "focus": true
        }
    }

Try:

• executing silently and observing side effects (note that many side effects are not visible until you run something else in the console since that's when most kernels check for changes)
• specifying the args as a plain string

[lionel-]

That's going to be so useful!

[lionel-]

Doc: This action executes code immediately after the currently running command (if any) has finished. It has priority over the queue of pending console inputs from the user but still needs to wait until the current command is finished, which might take a long time.

Any output (messages, warnings, or errors) generated by this command is discarded silently instead of being shown in the console.

[jennybc]

I'm playing with this now and want to leave a few more notes for test driving:

1. Open the Command Palette.
2. Type "Open Keyboard Shortcuts" and select "Open Keyboard Shortcuts (JSON)". Make sure to not accidentally open the JSON for the default keyboard shortcuts (ask me how I know).
3. Paste the keybinding snippet above at the end of the list (for me it's the only entry at this point), making sure it's comma-separated from the previous entries.

I am also in some unhappy state w.r.t. Python right now and the above snippet works simply by substituting 'r' for 'python' in langId. Important to note the when clause that it only fires when an editor is focused.

[jennybc]

I just had a lovely time with this:

{
        "key": "Cmd+Shift+R",
        "command": "workbench.action.executeCode.console",
        "when": "editorTextFocus",
        "args": {
            "langId": "r",
            "code": "reprex::reprex_selection()",
            "focus": true
        }
    }

This gives me an experience similar to what I enjoy in RStudio, where (1) reprex::reprex_selection() has to be registered as an addin, so that I can (2) customize a keybinding for it.

[jennybc]

Possibly silly example, but this works for an active R console (didn't try Python due to unhappy situation mentioned above):

{
        "key": "Cmd+Shift+H",
        "command": "workbench.action.executeCode.console",
        "when": "editorTextFocus",
        "args": "1 + 1"
}

[jennybc]

Here's a good example for experiencing workbench.action.executeCode.silently (but also probably a terrible example of code that you would want to use this for):

{
        "key": "Cmd+Shift+J",
        "command": "workbench.action.executeCode.silently",
        "when": "editorTextFocus",
        "args": {
            "langId": "r",
            "code": "options(digits = 2)"
        }
}

Here's me printing pi before and after invoking the keyboard shortcut:

> pi
[1] 3.141593
> pi
[1] 3.1

[jennybc]

A few straightforward experiments worked and I think this is great!

Because of the example I chose (messing with significant digits), I used the "Restart console" button in the R console, which dutifully restarted the console. But now when I invoke the keyboard shortcut (Cmd + Shift + J, in the case of that example), I see this

But there is definitely an active R console. The other keybindings are still working, which suggests the problem is specific to workbench.action.executeCode.silently.

[jmcphers]

But there is definitely an active R console.

I spent some time trying to reproduce this and found that this is a bug in the code that tracks console sessions; fixed in 7b08b7b.