Regex Literal Pitch v2 #187

hamishknight · 2022-02-25T16:05:44Z

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Documentation/Evolution/DelimiterSyntax.md

…or support.

hamishknight · 2022-03-21T13:44:08Z

I vote for insisting on raw syntax here. Every little heuristic like this is a strike against elegance. It's something that every editor will have to deal with. Raw literals are an obvious extension, and are probably easier to implement.

Yeah, I think I agree. I guess it ultimately depends on what the raw syntax rules regarding backslash end up being, if they end up treating backslashes as literal, we may not want to recommend raw syntax, as that would require changing any escape sequences written. We would likely want the user to use the alternative spellings e.g (?<...>) instead.

However even if this is not something we support, I still feel there is some value in the compiler at least implementing the heuristic, as it only impacts invalid code, and allows us to effectively emit a diagnostic with a fix-it to change the regex. Though I don't have a good sense of how common the (?'...') syntax is in the wild.

A quick pass to flip `/.../` out of the alternatives and into the main syntax. Still needs a bunch of work. Also add some commentary on a regex with `]` as the starting character.

…n. Split out Proposed solution from Detailed design. Parallelize the structure a bit better.

More details and word smithing.

milseman · 2022-04-09T00:57:05Z

Documentation/Evolution/DelimiterSyntax.md

+
+### Named typed captures
+
+Regex literals have their capture types statically determined by the capture groups present. This follows the same inference behavior as [the DSL][regex-dsl], and is explored in more detail in *[Strongly Typed Captures][strongly-typed-captures]*. One aspect of this that is currently unique to the literal is the ability to infer labeled tuple elements for named capture groups. For example:


Strongly typed captures isn't a proposal itself. Should we link the DSL proposal or else talk about it more here?

We do link the DSL here ([the DSL][regex-dsl]), should it be used as the main reference for the typed capture behavior? I was hesitant to talk more about typed captures here, as there's quite a bit to cover, and I believe most of it is shared behavior with the DSL. But maybe an overview would be reasonable?

Documentation/Evolution/DelimiterSyntax.md

Co-authored-by: Michael Ilseman <[email protected]>

hamishknight · 2022-04-11T09:57:17Z

Documentation/Evolution/DelimiterSyntax.md

+
+```swift
+let regex = #/
+  /usr/lib/modules/ # Prefix


Note this is a slightly different regex to the single-line version as it includes a / at the start, we probably ought to be consistent, what do you think? I mainly avoided it in the single-line version as GitHub syntax colors it as a comment 😬

Any extra slashes are unintentional and the natural outcome of using slash as both part of a delimiter and an interior character.

It's interesting that #//usr/local/# and #/user/local//# would sensibly be lexed as comments by source tools. That's a downside of / we should mention too. I suppose the workaround is to escape the slash if it's at the very beginning or end, which is another little wrinkle that #/.../# doesn't alleviate.

hamishknight · 2022-04-11T09:58:59Z

Documentation/Evolution/DelimiterSyntax.md

+
+### Extended delimiters `#/.../#`, `##/.../##`
+
+Backslashes may be used to write forward slashes within the regex literal, e.g `/foo\/bar/`. However, this can be quite syntactically noisy and confusing. To avoid this, a regex literal may be surrounded by an arbitrary number of balanced octothorpes. This changes the delimiter of the literal, and therefore allows the use of forward slashes without escaping. For example:


We call # a pound symbol elsewhere in the proposal, should we be consistent?

FWIW Unicode calls it "number sign", which is less confusable with £ (whose official name is "POUND SIGN"). How does "number sign" consistently sound? Even in the US, we don't dial numbers that often anymore, so I expect "pound sign" to have limited life span, especially in the era of hashtags.

Sounds good to me!

Updated to use "number sign", though a couple of occurrences were phrased as "number of ...", which sounded a bit awkward, so I changed those to use the # character directly.

Standardize on "number signs" for mentions of `#` (though a couple of them read better as just the character). Also change the multi-line example to not include a `/` at the start, which matches the single-line version.

airspeedswift · 2022-04-12T18:29:49Z

This is looking good, the only things I think might want tweaking:

I would spend less time on comments. It's a challenge, but not a major one
I think it's worth acknowledging in the alternatives considered that in some communities such as Perl, the / syntax has become less popular.

- Add Source Compatibility section - Condense comment syntax ambiguity section - Mention `/.../` being less popular in some communities

And remove the old version of the pitch.

hamishknight · 2022-04-13T17:36:04Z

@swift-ci please test

hamishknight requested a review from milseman February 25, 2022 16:07

hamishknight mentioned this pull request Feb 25, 2022

Pitch and Proposal Status #107

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milseman reviewed Feb 28, 2022

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hamishknight force-pushed the delimiter-syntax branch from 4afdabf to 77cbb0e Compare March 18, 2022 17:55

Add DelimiterSyntax.md

381a3c7

hamishknight force-pushed the delimiter-syntax branch from 77cbb0e to 381a3c7 Compare March 18, 2022 17:57

DaveEwing added 2 commits March 19, 2022 23:34

Expand on parsing issues with / as delimited. Add a note about edit…

c79f457

…or support.

Rewrite that Editor Considerations paragraph.

731292e

hamishknight and others added 18 commits March 21, 2022 14:03

Change single quote constructs to be invalid

1049276

Elaborate on starting character limitations

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Elaborate on comma case

7074cfb

grammar

945219e

Add comma disambiguation

d1d0d57

Update comma disambiguation

bcebfc6

Flip pitch to /.../ as the main syntax

1c2b7ad

A quick pass to flip `/.../` out of the alternatives and into the main syntax. Still needs a bunch of work. Also add some commentary on a regex with `]` as the starting character.

Update alternatives considered

e841184

Fix headings

be7a802

Tweak phrasing

06c2b28

Small tweaks

91a93a8

Tweak

c0e3bef

Flesh things out a bit more. Initial bits for the Intro and Motivatio…

298092c

…n. Split out Proposed solution from Detailed design. Parallelize the structure a bit better.

Expand out disclosure triangles, and other tweaks

1ebefa1

Generalize discussion on language mode

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Expand some prose

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Update to also pitch #/.../#

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Add DSL example

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hamishknight force-pushed the delimiter-syntax branch from dbd02ad to 35d9132 Compare March 28, 2022 20:18

hamishknight added 2 commits March 29, 2022 12:32

Rejig motivation/solution

f99dadb

Expand on typed captures

eed1b24

hamishknight changed the title ~~Delimiter Syntax Pitch~~ Regex Literal Pitch v2 Mar 29, 2022

hamishknight added 7 commits March 29, 2022 20:31

Generalize language mode

7ad4037

Add multi-line mode

f4ef0c2

Update pitch

addfbfd

Clarify upgrade path

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Update typed captures section + other tweaks

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Author links

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Updated extended delimiter section

8da68d3

hamishknight marked this pull request as ready for review April 8, 2022 21:52

Update delimiter proposal

9d0cf04

More details and word smithing.

milseman reviewed Apr 9, 2022

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Documentation/Evolution/DelimiterSyntax.md Outdated Show resolved Hide resolved

hamishknight and others added 2 commits April 11, 2022 10:43

Update Documentation/Evolution/DelimiterSyntax.md

720c10c

Co-authored-by: Michael Ilseman <[email protected]>

Clarify backslash rule

c045e21

hamishknight commented Apr 11, 2022

View reviewed changes

Minor tweaks

e31262d

Standardize on "number signs" for mentions of `#` (though a couple of them read better as just the character). Also change the multi-line example to not include a `/` at the start, which matches the single-line version.

hamishknight added 2 commits April 12, 2022 21:15

Update pitch

bf7702f

- Add Source Compatibility section - Condense comment syntax ambiguity section - Mention `/.../` being less popular in some communities

Rename DelimiterSyntax.md -> RegexLiterals.md

9c8a116

And remove the old version of the pitch.

hamishknight merged commit 0338178 into swiftlang:main Apr 13, 2022

hamishknight deleted the delimiter-syntax branch April 13, 2022 17:56

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Regex Literal Pitch v2 #187

Regex Literal Pitch v2 #187

hamishknight commented Feb 25, 2022

hamishknight commented Mar 21, 2022

milseman Apr 9, 2022

hamishknight Apr 11, 2022

hamishknight Apr 11, 2022

milseman Apr 11, 2022

hamishknight Apr 11, 2022

milseman Apr 11, 2022

hamishknight Apr 11, 2022

hamishknight Apr 11, 2022

airspeedswift commented Apr 12, 2022

hamishknight commented Apr 13, 2022


		### Named typed captures

		Regex literals have their capture types statically determined by the capture groups present. This follows the same inference behavior as [the DSL][regex-dsl], and is explored in more detail in [Strongly Typed Captures][strongly-typed-captures]. One aspect of this that is currently unique to the literal is the ability to infer labeled tuple elements for named capture groups. For example:


		### Extended delimiters `#/.../#`, `##/.../##`

		Backslashes may be used to write forward slashes within the regex literal, e.g `/foo\/bar/`. However, this can be quite syntactically noisy and confusing. To avoid this, a regex literal may be surrounded by an arbitrary number of balanced octothorpes. This changes the delimiter of the literal, and therefore allows the use of forward slashes without escaping. For example:

Regex Literal Pitch v2 #187

Regex Literal Pitch v2 #187

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hamishknight commented Feb 25, 2022

hamishknight commented Mar 21, 2022

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airspeedswift commented Apr 12, 2022

hamishknight commented Apr 13, 2022