onEnterRules should be multi-line aware

[kghose]

Use case: microsoft/vscode-cpptools#2072
Steps to Reproduce:

Type the following text in a .cpp file

a = a
    * b;

Then hit enter at the end of the line to begin a new line. You'll get

a = a
    * b;
    * 

This is not expected behavior in this context. This is perhaps expected when in the middle of a multiline decorated comment but not otherwise.

This does not happen in an unsaved file, a file with no extension, .txt extension etc. and does not happen if the cpptools extension is disabled and happens when it is re-enabled.

[aeschli]

The CPP extension sets onEnterRules like TypeScript:

onEnterRules: [
		{
			// e.g. /** | */
			beforeText: /^\s*\/\*\*(?!\/)([^\*]|\*(?!\/))*$/,
			afterText: /^\s*\*\/$/,
			action: { indentAction: IndentAction.IndentOutdent, appendText: ' * ' }
		}, {
			// e.g. /** ...|
			beforeText: /^\s*\/\*\*(?!\/)([^\*]|\*(?!\/))*$/,
			action: { indentAction: IndentAction.None, appendText: ' * ' }
		}, {
			// e.g.  * ...|
			beforeText: /^(\t|[ ])*[ ]\*([ ]([^\*]|\*(?!\/))*)?$/,
			action: { indentAction: IndentAction.None, appendText: '* ' }
		}, 

Looks like the last rule matches here and causes the observed behavior.

[bobbrow]

The user wants to keep the last rule when inside a multiline comment, but from what I understand the beforeText can only match a single line, so it appears that there's no way for us to write a rule that can detect whether we're in a multiline comment or not (e.g. by looking at the previous line).