Make the block comment work in Python (and other languages without block comments)

[krassowski]

Problem

• CodeMirror does not implement block comment for Python language which means executing block comment shortcut is no-op in Python and users think it is broken
• Python does not define block comment syntax, although """ is de facto standard substitute as blessed by BDFL
• we want to keep separate block and line comments shortcuts for users using languages which do have as separate block comments

Proposed Solution

Either or both:

• (a) use pythonLanguage.data.of({commentTokens: ...}) to add """ as block comment for Python - this only helps for Python
• (b) replace uses of toggleBlockComment with a composite command which tries to run toggleBlockComment first and toggleComment second if the former did not succeed (or check if language data have commentTokens.block defined)

Additional context

See discussion in upstream issue codemirror/dev#1372 - upstream will not include that command nor the """ syntax for Python so it is up to JupyterLab to implement it.

[krassowski]

These lines would need to be modified for (b):

jupyterlab/packages/codemirror-extension/src/commands.ts

Lines 81 to 90 in 2dd8f4e

	caption: trans.__(
	'Toggles block commends in languages which support it (e.g. C, JavaScript)'
	),
	execute: () => {
	const view = findEditorView();
	if (!view) {
	return;
	}
	toggleBlockComment(view);
	},

[krassowski]

These lines would need to be modified for (a):

jupyterlab/packages/codemirror/src/language.ts

Lines 476 to 495 in 2dd8f4e

	const m = await import('@codemirror/lang-python');
	return new LanguageSupport(
	m.pythonLanguage,
	pythonBuiltin(m.pythonLanguage)
	);
	}
	},
	{
	name: 'ipython',
	displayName: trans.__('ipython'),
	mime: 'text/x-ipython',
	async load() {
	// FIXME Restore '?' operator - using the default python LanguageSupport allows
	// to activate feature such as code folding.
	// return Promise.resolve(legacy(mkPython({ singleOperators: /\?/ })));
	const m = await import('@codemirror/lang-python');
	return new LanguageSupport(
	m.pythonLanguage,
	pythonBuiltin(m.pythonLanguage)
	);

[krassowski]

Some research is needed on (a) - what other other IDEs do? Do they use """ syntax for block comment, or do they fall back to multiple # ?

[smbrett]

Hi I would like to work on this issue.

[krassowski]

Please do!