On Sun, Feb 12, 2017 at 8:37 PM, Dietmar Planitzer <dplanit...@q.com> wrote:
> I know that private was scoped to files before Swift 3. > > Fileprivate should obviously be removed because it is, like I said > previously, just a poor man’s package access level. Yes, private was scoped > to a file before Swift 3, but at least there wasn’t two kinds of private > for a single file. Also scoping private to a file makes sense in Swift > because it plays well with the ability to organize the implementation of a > type inside of a file into the base type and a number of extensions. I now > have to use fileprivate in Swift 3 to pull this off while there isn’t a > requirement for a separate private access level. The fileprivate / private > distinction also needlessly gets in the way when you want to refactor an > existing type implementation into base type + extensions, all living in the > same file. > > Anyway, I don’t see a good reason why we should end up with this, once > sub-modules exist: > > open, public, module, fileprivate, private > > when we can live with this: > > open, public, module, private > > and we’re not losing anything that would be significant compared to the > alternative scenario. > Well, there's also internal: open, public, internal, (submodule, however it is named), private. The question being discussed here is whether private should have the old or new meaning. I tend to agree with others that the new `private` doesn't add much. Modules are a different conversation. > Regards, > > Dietmar Planitzer > > > On Feb 12, 2017, at 18:16, Xiaodi Wu <xiaodi...@gmail.com> wrote: > > > > What was added in Swift 3 was `private`; the old `private` was renamed > `fileprivate` with no change in behavior. Certainly, submodules are a big > topic that deserves careful consideration. But the question being discussed > here is about rolling back the change that was implemented in Swift 3 by > removing `private` and restoring `fileprivate` to its old name. > > > > > > On Sun, Feb 12, 2017 at 8:08 PM, Dietmar Planitzer via swift-evolution < > swift-evolution@swift.org> wrote: > > Fileprivate is a feature that should not have been added to Swift 3 > because it is in the end just a needlessly limited version of the Java > package access level. Fileprivate forces me to put all types which are > related on an implementation level into the same file while Java packages > allow me to put each type implementation into a separate file. The only > thing that Java requires is that all files which are part of the same > package are tagged with the same package id. Java’s package access level is > more powerful than fileprivate because it gives me more freedom in how I > want to organize my code while still making sure that code in sibling and > parent packages can not access symbols inside my package which form part of > the implementation details of my package. > > > > The first thing that needs to happen before any more access levels are > added is that a concept of sub-modules is added to Swift along the lines of: > > > > 1) modules can be organized into a tree with one module as the root. > > > > 2) all modules which are nodes in the same module tree form a single > resilience domain. > > > > IMO, the sub-module stuff should be designed similar if not the same way > as Java packages because there are already lots and lots of SDEs who know > how Java packages work, and Java packages are well understood, simple and > straight-forward in their mechanics. > > > > Once sub-modules are in place, it makes sense to revisit the access > level topic. Eg in order to add a “module” access level that represents the > scope of a module. So “module” could then do what file private can do today > plus more. But we should stop trying to add more access level to the > language until then. We also need to look much more at the bigger picture > of things instead of getting too much hung up on a single component of a > larger mechanism, when it is that larger mechanism that is primarily > interesting and relevant. > > > > > > > > Regards, > > > > Dietmar Planitzer > > > > > On Feb 12, 2017, at 16:16, Zach Waldowski via swift-evolution < > swift-evolution@swift.org> wrote: > > > > > > I vehemently agree on these points. New-private and fileprivate "[add] > more information" to a file the same way requiring `self.` and other sorts > of visual noise that Swift normally eschews. > > > > > > I wish for the Swift community to be introspective enough to count > both its successes and failures. SE-0025 was a botched addition to the > language. That the migrator did such a bad job is evidence of its poor > overall consideration. Adding a fix-it strikes me as the compiler waggling > its finger at me for code that would've been perfectly fine in the past, > something that it is not at all true with the "let" fix it; accidental > mutation has been discussed a ton by the larger programming community, > not-so-much for obscure access control mechanics. > > > > > > It's perplexing that fileprivate advocates continue to stand on mostly > theoretical benefits about new-private. I feel nothing for the mathematical > purity about the types in a file. In practice, I can with much experience > now how awful it is. There has been no end to the confusion its > introduction has inflicted upon my team(s), people new to the language, and > people revisiting the language: > > > > > > - My teams and coworkers are less effective at code review from > constant litigation about access control. "'Did this need to change?' / > 'No, it was just the migrator.'" has become a disturbingly common refrain. > > > > > > - New users are just struggling to figure out where to put the curly > braces in the first place. Having to make them check and re-check where > things go in a file, or just tell them to use this clunky > get-out-of-jail-free keyword, feels like visiting a special kind of > Pythonic hell on a language I otherwise love and love to teach. > > > > > > - People returning to the language feel (and often say - just look at > Twitter) Swift has a lot of syntax, and are frustrated that the addition of > a new keyword was burned on adding something that amounts to mostly a > stylistic opinion. > > > > > > All the best, > > > Zachary Waldowski > > > z...@waldowski.me > > > > > > On Sun, Feb 12, 2017, at 04:45 PM, Xiaodi Wu via swift-evolution wrote: > > >> On Sun, Feb 12, 2017 at 3:24 PM, Matthew Johnson < > matt...@anandabits.com> wrote: > > >> > > >> > > >>> On Feb 12, 2017, at 2:35 PM, Xiaodi Wu via swift-evolution < > swift-evolution@swift.org> wrote: > > >>> > > >>> _Potentially_ meaningful, certainly. But what I'm hearing is that it > isn't actually meaningful. Here's why: > > >>> > > >>> If I see `fileprivate` and can understand that to mean "gee, the > author _designed_ this member to be visible elsewhere inside the file," > then it's actually meaningful. OTOH, if I see `fileprivate` and can only > deduce "gee, the author mashed some button in his or her IDE," then it's > not really telling me anything. > > >> > > >> > > >> You’re looking at it backward. It’s when you see `private` and can > deduce “this member is only visible inside it’s declaring scope” that can > be really helpful. *This* is what matters. > > >> > > >> In what ways can that information help you? > > >> > > >> > > >>> What you've said above, as I understand it, is that it's not > currently meaningful to see `fileprivate` because the migrator is writing > it and not the author. The improved approach you proposed is the additional > warning. In that case, the compiler will help to ensure that when I see > `fileprivate`, at least I know it's necessary. But that's only telling me a > fact (this member is accessed at least once outside the private scope), but > it's still machine-based bookkeeping, not authorial intent. > > >> > > >> > > >> The important thing is that this machine-based bookkeeping results in > a proof about the code. This facilitates reasoning about the code. You > can make an argument that this proof is not important enough to matter, but > you must admit that this is a real concrete gain in information that is > immediately available to a reader of the code (after they know that it > compiles). Personally, I find this proof to be valuable. > > >> > > >> Comparison has been made to `let` and `var`. In that case, whether a > variable is mutated can be non-trivial to deduce (as Swift has no uniform > scheme for distinguishing mutating from non-mutating functions; the ed/ing > rule has many exceptions). By contrast, here, I don't see any gain in > information. You can literally *see* where the (file)private member is > accessed, and when a file gets too long, even a simple text editor can do a > decent enough find. > > >> > > >> If you're right that the real value is that seeing `private` helps > you reason about the code, then that value must be commensurate to how > often we see Swift users amending the migrator to take advantage of it. For > me, the compelling evidence that Swift users don't find this proof to be > valuable is that, by examination of Swift 3 code, Swift users haven't > bothered. If we add a new fix-it to force them to, then of course they'll > mash the buttons, but it's pretty much declaring that they are wrong not to > care about what it seems they do not care at present. > > >> > > >>> On Sun, Feb 12, 2017 at 2:14 PM, Chris Lattner <sa...@nondot.org> > wrote: > > >>> I don't fully agree: you are right that that is the case when > writing code. However, when reading/maintaining code, the distinction is > meaningful and potentially important. > > >>> > > >>> -Chris > > >>> > > >>> > > >>> On Feb 12, 2017, at 12:02 PM, Xiaodi Wu <xiaodi...@gmail.com> wrote: > > >>>> If the overwhelming use case is that developers should pick one > over the other primarily because it looks nicer, then blindly click the > fix-it when things stop working, then the distinction between private and > fileprivate is pretty clearly a mere nuisance that doesn't carry its own > weight. > > >>>> On Sun, Feb 12, 2017 at 13:33 Jean-Daniel via swift-evolution < > swift-evolution@swift.org> wrote: > > >>>>> Le 12 févr. 2017 à 18:24, Chris Lattner via swift-evolution < > swift-evolution@swift.org> a écrit : > > >>>>> > > >>>>> On Feb 12, 2017, at 8:19 AM, David Hart via swift-evolution < > swift-evolution@swift.org> wrote: > > >>>>>> Final > > >>>>>> Can someone tell me what is the use of 'final' now that we have > 'public' default to disallowing subclassing in importing modules? I know > that 'final' has the added constraint of disallowing subclassing in the > same module, but how useful is that? Does it hold its weight? Would we add > it now if it did not exist? > > >>>>> > > >>>>> As Matthew says, this is still important. > > >>>>> > > >>>>>> Lazy > > >>>>>> This one is clearer: if Joe Groff's property behaviors proposal > from last year is brought forward again, lazy can be demoted from a > language keyword to a Standard Library property behavior. If Joe or anybody > from the core team sees this: do we have any luck of having this awesome > feature we discussed/designed/implemented in the Swift 4 timeframe? > > >>>>> > > >>>>> Sadly, there is no chance to get property behaviors into Swift 4. > Hopefully Swift 5, but it’s impossible to say right now. > > >>>>> > > >>>>>> Fileprivate > > >>>>>> > > >>>>>> I started the discussion early during the Swift 4 timeframe that > I regret the change in Swift 3 which introduced a scoped private keyword. > For me, it's not worth the increase in complexity in access modifiers. I > was very happy with the file-scope of Swift pre-3. When discussing that, > Chris Latner mentioned we'd have to wait for Phase 2 to re-discuss it and > also show proof that people mostly used 'fileprivate' and not the new > 'private' modifier as proof if we want the proposal to have any weight. > Does anybody have a good idea for compiling stats from GitHub on this > subject? First of all, I've always found the GitHub Search quite bad and > don't know how much it can be trusted. Secondly, because 'private' in Swift > 2 and 3 have different meanings, a simple textual search might get us wrong > results if we don't find a way to filter on Swift 3 code. > > >>>>> > > >>>>> I would still like to re-evaluate fileprivate based on information > in the field. The theory of the SE-0025 (https://github.com/apple/ > swift-evolution/blob/master/proposals/0025-scoped-access-level.md) was > that the fileprivate keyword would be used infrequently: this means that it > would uglify very little code and when it occurred, it would carry meaning > and significance. > > >>>> > > >>>> Infrequent use and significance are orthogonal. > > >>>> I still think developers would declare all ivars private (this is > less ugly and shorter), and then will happily convert them to fileprivate > each time the compiler will tell them they are not accessible somewhere > else in the file. > > >>>> As the code that try to access that ivar is in the same file > anyway, it has full knowledge of the implementation details and there is no > good reason it shouldn’t be able to access the ivar when needed. > > >>>> > > >>>>> We have a problem with evaluating that theory though: the Swift > 2->3 migrator mechanically changed all instances of private into > fileprivate. This uglified a ton of code unnecessarily and (even worse) > lead programmers to think they should use fileprivate everywhere. Because > of this, it is hard to look at a random Swift 3 codebase and determine > whether SE-0025 is working out as intended. > > >>>>> > > >>>>> The best way out of this that I can think of is to add a *warning* > to the Swift 3.1 or 4 compiler which detects uses of fileprivate that can > be tightened to “private” and provide a fixit to do the change. This would > be similar to how we suggest changing ‘var’ into ‘let’ where possible. > Over time, this would have the effect of getting us back to the world we > intended in SE-0025. > > >>>>> > > >>>>> -Chris > > >>>>> > > >>>>> _______________________________________________ > > >>>>> swift-evolution mailing list > > >>>>> swift-evolution@swift.org > > >>>>> https://lists.swift.org/mailman/listinfo/swift-evolution > > >>>> _______________________________________________ > > >>>> swift-evolution mailing list > > >>>> swift-evolution@swift.org > > >>>> https://lists.swift.org/mailman/listinfo/swift-evolution > > >>> > > >>> _______________________________________________ > > >>> swift-evolution mailing list > > >>> swift-evolution@swift.org > > >>> https://lists.swift.org/mailman/listinfo/swift-evolution > > >> _______________________________________________ > > >> swift-evolution mailing list > > >> swift-evolution@swift.org > > >> https://lists.swift.org/mailman/listinfo/swift-evolution > > > > > > _______________________________________________ > > > swift-evolution mailing list > > > swift-evolution@swift.org > > > https://lists.swift.org/mailman/listinfo/swift-evolution > > > > _______________________________________________ > > swift-evolution mailing list > > swift-evolution@swift.org > > https://lists.swift.org/mailman/listinfo/swift-evolution > > > >
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