[swift-evolution] [Review] SE-0182 - String Newline Escaping

[John Holdsworth]

As this review winds down it seems fair to say the response has been generally
favourable with some reservations about whether this should be applied to single
line strings as well. I’d include single line strings myself for consistency with multi-
line and with other languages myself but that isn’t the focus of this proposal.

There has also been some discussion about whether escaping the last newline should
be an error or ignored. For me this highlights that the final newline should be included
in the literal and could therefore be escaped when you want one without a newline at
the end which may or may not be the common use case as has been discussed before.

let text = """
    Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod \
    tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, \
    quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.\
    """

let endsWithNewline = """
    Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod
    tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam,
    quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
    """

While multi-line strings would loose their pleasing symmetry from SE-0168 where initial
and final newlines are stripped I'd argue in response that text is generally asymmetric
with files generally having no newline at the start and a newline at the end. I can see
the arguments for both decisions though and could live with either.

-John
 
> On 14 Jul 2017, at 18:17, Jordan Rose via swift-evolution <swift-evolution at swift.org> wrote:
> 
> 
> 
>> On Jul 14, 2017, at 10:00, Alex Blewitt <alblue at apple.com <mailto:alblue at apple.com>> wrote:
>> 
>>> On 13 Jul 2017, at 23:14, David Hart via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>>> 
>>>> 
>>>> On 14 Jul 2017, at 00:21, Jordan Rose <jordan_rose at apple.com <mailto:jordan_rose at apple.com>> wrote:
>>>> 
>>>> [Proposal: https://github.com/apple/swift-evolution/blob/master/proposals/0182-newline-escape-in-strings.md <https://github.com/apple/swift-evolution/blob/master/proposals/0182-newline-escape-in-strings.md>]
>>>> 
>>>> This is a tiny, tiny point amidst the broader discussions others are having, but
>>>> 
>>>>> 	• All whitespace characters between \ and the newline are disregarded.
>>>> 
>>>> Why? Why bother allowing whitespace characters between \ and the newline?
>>> 
>>> The reasoning is to be consistent with trailing whitespace in the rest of the code: to leave that to a linter instead. Or to see it differently, even with whitespace between \ and the newline, the programmer’s intent is still clear. Why generate an error?
>> 
>> For the same reason that code allows (e.g.) a comment at the end of the line; you wouldn't expect (newline continuation) (comment) to mean the same thing as if generic whitespace were added at the end. The convention in other languages is that \ immediately precedes the line feed to indicate a continuation, not that an orphan \ is valid on its own.
>> 
>> The reason that \(newline) is valid while \(otherchar)(newline) isn't is because \ immediately precedes another character that it is escaping, and it's possible that \(space) would have a meaning in the future, whereas \(newline) won't.
> 
> I agree with Alex on this, although I would be happy to make it a warning rather than an error so that it doesn't block compilation.
> 
> The point about comments is also significant: we previously said that comments should generally be treated like whitespace (SE-0037 <https://github.com/apple/swift-evolution/blob/master/proposals/0037-clarify-comments-and-operators.md>). This is a little different because it's still inside the string literal, but it's probably worth explicitly stating "we're still inside a string literal; you can't just put comments after the backslash".
> 
> Jordan
> 
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