Line terminators

http://www.ecma-international.org/ecma-262/7.0/index.html#sec-line-terminators

Code Point	Unicode Name	Abbreviation
U+000A	LINE FEED (LF)	<LF>
U+000D	CARRIAGE RETURN (CR)	<CR>
U+2028	LINE SEPARATOR	<LS>
U+2029	PARAGRAPH SEPARATOR	<PS>

…

 LineTerminatorSequence::
    <LF>
    <CR>[lookahead ≠ <LF>]
    <LS>
    <PS>
    <CR><LF>

(In practice these days, everyone uses \n/<LF> except Windows which uses \r\n/<CR><LF>.)

It seems like prettier sometimes assumes that \n/<LF> is the only newline. We need to grep through the code base and fix those cases.

A question is how it should be fixed. Use utility functions everywhere? It’s easy to forget, though, and add new places of .indexOf('\n') and similar in the future. Another idea is to replace all other newlines before parsing: text.replace(/\r\n|[\r\u2028\u2029]/g, '\n').

EDIT: No we cannot replace all line terminal sequences before parsing. That would change the contents of template literals and multiline strings.

[vjeux]

I don’t think that we should handle anything except for \r and \r\n. For those two, we should have good support, if something is broken, please report an error and we’ll fix it. The big things are:

• Detecting new lines: https://github.com/jlongster/prettier/blob/master/src/util.js#L167
• Printing line endings is based on the type of the first one on the file: https://github.com/jlongster/prettier/blob/master/index.js#L12
• We have places like shebang where do manually deal with it: https://github.com/jlongster/prettier/blob/master/index.js#L67

Looks like there’s a few places where we only consider \n in the printer https://github.com/jlongster/prettier/blob/master/src/printer.js that we need to fix (search for \n)

[lydell]

Just for future reference:

Normalizing \r, \u2028 and \u2029 to either \n or \r\n is a thing that prettier could do, but I guess it’s not worth it.

This statement is wrong. prettier already does exactly this normalization. And it leaves all line terminator characters inside strings alone as it should.