Making auto indentation work

As noted in spike https://github.com/microsoft/vscode-python/issues/8669

There are three approaches to solve this:

1. VSCode Language Configuration

VSCode provides OnEnterRules and indentationRules which dedents/indents the block given the previous line matches the regex. But regexes can’t be used to cover every case, and the current rules are not powerful enough. https://github.com/microsoft/vscode/issues/66235 Also sometimes just knowledge of previous line is not sufficient to make a decision on the indent.

2. On-type indenting

When editor.formatOnType is set to true, one can intervene in between when a user types and indent accordingly. We currently use this in onEnterFormatter.ts and other places. We can use this to cover all the cases one by one. But on-type formatting is not enabled by default nor is very popular (and enables a slew of formatting rules other than cursor alignment), so forcing users to enable on-type formatting as a whole would be good to avoid.

3. Add a key binding for enter

We can add something like

"keybindings": [
    {
        "command": "<Command key>",
        "key": "enter",
        "when": "editorTextFocus && editorLangId == python"
    }
],

(may need more modifying)

and use that to intervene. This way we don’t need to have editor.formatOnType enabled. However we need to keep in mind that in this case we’re responsible for cursor alignment after the user presses enter, otherwise cursor would stay where it is.

As there is no progress on vscode upstream issues related to 1., ~going with 3. makes the most sense at this point.~

https://github.com/kbrose/vsc-python-indent/blob/master/src/indent.ts seems like a wonderful place to take help from. It covers most cases (https://github.com/microsoft/vscode-python/issues/481) we currently have open issues for and is well documented. We can use npm package python-indent-parser similarly to the way @kbrose does.

Also another thing to note here is that having both language configuration and key bindings can override each other sometimes. So we should be moving away from regexes when we solve work items for this.

EDIT: We’ve decided to go with 2.

Work items

• Turn on editor.formatOnType to true by default when using python language.
• Modify onEnterFormatter.ts to support only indenting. (onTypeIndenting)
• Move languageConfiguration.ts to .json.
• ~Cut down regexes in language configuration so that it doesn’t conflict with onTypeIndenting.~
• Rules in languageConfiguration.ts may conflict with onTypeIndenting. If you can identify such conflicts, turn off rules in languageConfiguration.ts when editor.formatOnType is set to true.
• Look into how https://github.com/kbrose/vsc-python-indent/blob/master/src/indent.ts solves each of these issues. I’ve verified it works fine for most of these. https://github.com/microsoft/vscode-python/issues/481 (function call) https://github.com/microsoft/vscode-python/issues/684 (meta issue) https://github.com/microsoft/vscode-python/issues/1314 (tests) https://github.com/microsoft/vscode-python/issues/7344 (async for and async with) https://github.com/microsoft/vscode-python/issues/6886 (moving a line breaks things) https://github.com/microsoft/vscode-python/issues/3284 (trailing slash) https://github.com/microsoft/vscode-python/issues/16105 which was introduced when we removed the onEnterFormatter.ts when onType formatting is on.

Note we also do dedenting when user presses semi-colon : https://github.com/Microsoft/vscode-python/blob/3c7bb774519ebf5aed91f90e10c7b8dd0fc567ec/src/client/typeFormatters/blockFormatProvider.ts#L25 Make sure these does not conflict with what Kbrose’s extension is doing.

[karrtikr]

@J-Fields If you browse through the mentioned issues, we used to have indentationRules, and it caused a few bugs, so we decided to remove it. Also I am not sure if we can override their effect with formatOnType, i.e I am not sure what happens when rules conflict.

As indentationRules don’t support every indentation scenario, we can try adding indentationRules after all the other work is done.

[kbrose]

I have not personally noticed any misbehaving on that front. The only issue I’ve received about unexpected behavior related to overriding Enter was related to the vim plugin, which I resolved here.