Change raw string literal syntax: `[#]"` represents single-line string and `[#]'''` represents block string #1360

SlaterLatiao · 2022-06-30T22:54:44Z

Requiring """ to only be used for block string can avoid confusions.
Update: Use " for simple string literals and ''' for block string literals.

proposals/p1360.md

jonmeow · 2022-07-01T23:03:51Z

I want to note, another thing we sometimes do is edit the design in the same PR as the proposal. i.e., to edit string_literals.md and make corresponding adjustments for this proposal. That can be considered a substitution for "details", as the design is what people are typically referring to. It may make sense to do here when you respond to my prior comments.

…tion.

jonmeow

See comment -- there is still a miscommunication on how to handle simple block string literals.

This reverts commit 60bbf51.

This reverts commit 5f55689.

This reverts commit 060900e.

…plementation." This reverts commit 2fb548c.

jonmeow

Basically LGTM on my end, just a little more example tuning.

docs/design/lexical_conventions/string_literals.md

LGTM, but leaving approval for lead

lexi-nadia · 2022-07-25T20:45:34Z

I'm not sure what the scope of this PR is (maybe it's narrower than i'm getting at), but could the alternatives section be updated to describe the current C++ behavior? If we're discarding that -- which doesn't have this problem -- it seems worth stating why.

SlaterLatiao · 2022-07-26T23:37:07Z

Discussed C++ and Swift behaviors in alternatives section.

docs/design/lexical_conventions/string_literals.md

proposals/p1360.md

Co-authored-by: Richard Smith <[email protected]>

…le literals with ``. Co-authored-by: Richard Smith <[email protected]>

chandlerc · 2022-08-04T01:02:52Z

proposals/p1360.md

+[easy to read, understand, and write](/docs/project/goals.md#code-that-is-easy-to-read-understand-and-write),
+because it avoids confusion on the type of certain string literals.
+
+## Alternatives considered


I think there are other alternatives we should at least document here...

We could allow a non-escape based disambiguation that focuses on making the opening marker not ambiguous between single-line and block. I can imagine two ways of doing this.

a) We could allow some non-quote marker after the open quote similar to C++. Either #"(")"# or #"#"#"# come to mind.

b) We could use different quotes in various ways that allow: #'"'#.

b1) /#+'/ could be an additional way to start a single line string literal, without removing anything

b2) /#+'/ could always start a single line string literal, and /#+" could always start a block string literal

These all seem to have problems though that should be covered in the alternatives considered.

(a) IMO hurts readability and makes it harder to adddress a complaint of a collision by adding a(nother) set of #s around the contents. The first time, you'd have to modify things more than that. It also loses the visual connection of the "s surrounding the quoted-text.

(b) Adds a lot of complexity no matter how we slice it, and doesn't fully remove a lurking surprise in the lexical structure.

Fundamentally, (a), (b), (c) this proposal, and (d) the status quo are moving around where there is a surprise, but not eliminating it.

The source of the surprise is that the introducing syntax for single line string literals in a prefix of multiline string literals, including in the raw case. The result is that we don't know which we're seeing until its too late to avoid surprises.

But there is yet another alternative, suggested @zygoloid after I gave a long series of bad suggestions, let's call it (e).

In (e), we change block string literals to always use ''', never """. Everything else stays the same. If/when we have character literals of any form, we reject '', when we see '' we know the next character must be ' and it is a block string literal. Raw block string literals are #+'''. Etc. Python already allows ''' as well, although it is rarely used to my knowledge.

With (e), #"""# is the same as "\"" and doesn't require anything to recognize. You can even write #""""A python string here!""""#.

For teaching, this even seems nice -- its a "triply quoted" string instead of a "triple-double quoted" string. ;]

WDYT? Both @zygoloid and I quite like this, but we should check with @KateGregory as well.

Just FYI, seems all leads are happy here and haven't heard huge concerns. It is a bit inventive, but I think folks are roughly comfortable so let's consider the path forward.

Per discussion, I believe the intent is to also disallow """ (triple double quote), rather than interpreting it as two string literals. This would help reduce the confusion with Python (where ''' is supported, but """ is recommended under PEP 257).

Of course, #""" is still a confusability issue -- but I think it sounds like the leads want to support that use-case?

Just to note, I think it'd be good to go through the discussed options and some advantages and disadvantages of each in the alternatives. If you're trying to find a good example of how to do this, something like the alternatives from one of these:

Explicitly calling out advantages and disadvantages:
https://github.com/carbon-language/carbon-lang/blob/trunk/proposals/p0257.md#alternatives-considered

Using prose to talk about options, but a separate section for each significant option:
https://github.com/carbon-language/carbon-lang/blob/trunk/proposals/p0722.md#alternatives-considered

Added discussed options to the alternatives.

zygoloid

Looks good to me.

docs/design/lexical_conventions/string_literals.md

zygoloid

Leads are happy with this.

SlaterLatiao added the proposal A proposal label Jun 30, 2022

SlaterLatiao requested a review from a team June 30, 2022 22:54

Filling out template with PR 1360

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SlaterLatiao force-pushed the raw_string_literal_proposal branch from b741148 to bb43d88 Compare June 30, 2022 22:54

SlaterLatiao changed the title ~~Change raw string literal syntax~~ Change raw string literal syntax: enforcing """ to be block string Jun 30, 2022

SlaterLatiao added 2 commits June 30, 2022 17:25

Update p1360.md

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SlaterLatiao changed the title ~~Change raw string literal syntax: enforcing """ to be block string~~ Change raw string literal syntax: requiring """ to only be used for block strings Jul 1, 2022

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SlaterLatiao added the proposal rfc Proposal with request-for-comment sent out label Jul 1, 2022

SlaterLatiao marked this pull request as ready for review July 1, 2022 00:31

Updated with pre-commit.

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Updated with corrected understanding of current design and implementa…

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…tion.

Updated title.

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SlaterLatiao changed the title ~~Change raw string literal syntax: requiring """ to only be used for block strings~~ Change raw string literal syntax: block strings start with [#]+""" and [#]+""" only used for block strings Jul 7, 2022

Updated string literals design.

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Updated proposal with modified design doc and corrected links.

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Revert "Updated proposal with modified design doc and corrected links."

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Revert "Updated string literals design."

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…plementation." This reverts commit 2fb548c.

Updated proposal on simple block string literals.

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Minor change.

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SlaterLatiao changed the title ~~Change raw string literal syntax: block strings start with [#]+""" and [#]+""" only used for block strings~~ Change raw string literal syntax: [#]*""" always starts a block string Jul 11, 2022

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Addressed PR comments.

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SlaterLatiao requested a review from jonmeow July 21, 2022 05:09

jonmeow mentioned this pull request Jul 25, 2022

triple-quoted strings issue #1644

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jonmeow mentioned this pull request Jul 25, 2022

Implementation of raw string literal corner case. #1358

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Updated Alternatives with C++ and Swift.

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SlaterLatiao mentioned this pull request Jul 26, 2022

Implement block string literals to start with """ #1757

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Co-authored-by: Richard Smith <[email protected]>

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…le literals with ``. Co-authored-by: Richard Smith <[email protected]>

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SlaterLatiao changed the title ~~Change raw string literal syntax: [#]*""" always starts a block string~~ Change raw string literal syntax: [#]\*" represents single-line string and [#]\*''' represents block string Aug 8, 2022

SlaterLatiao changed the title ~~Change raw string literal syntax: [#]\*" represents single-line string and [#]\*''' represents block string~~ Change raw string literal syntax: [#]*" represents single-line string and [#]*''' represents block string Aug 8, 2022

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Missed " -> ' update.

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zygoloid mentioned this pull request Aug 25, 2022

consider requiring that """ can only be used when starting a block string literal #1359

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etalian mentioned this pull request Aug 27, 2022

Explorer does not support current block string literal syntax #2121

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zygoloid mentioned this pull request Sep 1, 2022

Revisit the set of disallowed characters in a file type indicator #2140

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chandlerc added the documentation An issue or proposed change to our documentation label Jan 13, 2023

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Making # free #3498

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Change raw string literal syntax: `[#]"` represents single-line string and `[#]'''` represents block string #1360

Change raw string literal syntax: `[#]"` represents single-line string and `[#]'''` represents block string #1360

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Change raw string literal syntax: [#]*" represents single-line string and [#]*''' represents block string #1360

Change raw string literal syntax: [#]*" represents single-line string and [#]*''' represents block string #1360

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Change raw string literal syntax: `[#]"` represents single-line string and `[#]'''` represents block string #1360

Change raw string literal syntax: `[#]"` represents single-line string and `[#]'''` represents block string #1360

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