Benjamin Gruenbaum (2015-06-13T18:39:39.000Z)
d at domenic.me (2015-06-16T16:55:30.381Z)
On Sat, Jun 13, 2015 at 9:07 PM, Mark S. Miller <erights at google.com> wrote: > On Sat, Jun 13, 2015 at 9:17 AM, Domenic Denicola <d at domenic.me> wrote: > >> All of these should be building on top of RegExp.escape :P >> > > It's funny how, by considering it as leading to a proposal, I quickly saw > deep flaws that I was previously missing. > > That was a big part of making a proposal out of it - to find these things :) > the overall result does not do this. For example: > > const data = ':x'; > const rebad = RegExp.tag`(?${data})`; > console.log(rebad.test('x')); // true > > is nonsense. Since the RegExp grammar can be extended per platform, the > same argument that says we should have the platform provide RegExp.escape > says we should have the platform provide RegExp.tag -- so that they can > conisistently reflect these platform extensions. > > This is a good point, I considered whether or not `-` should be included for a similar reason. I think it is reasonable to only include syntax identifiers and expect users to deal with parts of patterns of more than one characters themselves (by wrapping the string with `()` in the constructor). This is what every other language does practically. That said - I'm very open to allowing implementations to escape _more_ than `SyntaxCharacter` in their implementations and to even recommend that they do so in such a way that is consistent with their regular expressions. What do you think about doing that? I'm also open to `.tag` wrapping with `()` to avoid these issues but I'm not sure if we have a way in JavaScript to not make a capturing group out of it. > * Now that we have modules, I would like to see us stop having each > proposal for new functionality come at the price of further global > namespace pollution. I would like to see us transition towards having most > new std library entry points be provided by std modules. I understand why > we haven't yet, but something needs to go first. > > I think that doing this should be an eventual target but I don't think adding a single much-asked-for static function to the RegExp function would be a good place to start. I think the committee first needs to agree about how this form of modularisation should be done - there are much bigger targets first and I would not like to see this proposal tied and held back by that (useful) goal. > * ES6 made RegExp subclassable with most methods delegating to a common > @exec method, so that a subclass only needs to consistently override a > small number of things to stay consistent. Neither RegExpSubclass.escape > nor RegExpSubclass.tag can be derived from aRegExpSubclass[@exec]. Because > of the first bullet, RegExpSubclass.tag also cannot be derived from > RegExpSubclass.escape. But having RegExpSubclass.escape delegating to > RegExpSubclass.tag seem weird. > > Right but it makes sense that `escape` does not play in this game since it is a static method that takes a string argument - I'm not sure how it could use @exec. > * The instanceof below prevents this polyfill from working cross-frame. > Also, when doing RegExpSubclass1.tag`xx${aRegExpSubclass2}yy`, where > RegExpSubclass2.source produces a regexp grammar string that > RegExpSubclass1 does not understand, I have no idea what the composition > should do other than reject with an error. But what if the strings happen > to be mutually valid but with conflicting meaning between these subclasses? This is hacky, but in my code I just did `argument.exec ? treatAsRegExp : treatAsString`.