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> On Feb 21, 2017, at 1:47 AM, Rien via swift-evolution > <swift-evolution@swift.org> wrote: > > I don’t know if you want to add this to the ‘criticism’ or not. > > 1) The information content added by “fileprivate” is questionable because of > the ‘soft default’: > > - People will switch from private to fileprivate without much thought if that > is desirable or not. > - Other people will default to ‘fileprivate’, necessary or not. > > > 2) Since the difference between ‘fileprivate’ and ‘private’ only works > within a file, anybody who is affected by it also has the possibility to > change it from one to the other. Making the distinction between them rather > arbitrary. Teams relying on the distinction may find themselves in a place > where a developer changed private to fileprivate for a quick > investigation/solution, and forgetting to revert the change before committing > his solution. This error might remain undiscovered until several revisions > later (or never). > > > 3) Mixing scope and file based access levels makes the entire access level > concept hard to understand. But a file is a scope, so in that sense it's not mixing too separate concepts. Now that the submodule discussion has heated up I'm going to share some thoughts on how I want to see `scoped` be enhanced to support encapsulation by allowing it to accept the name of a containing scope, which could be broader than a file (a submodule). I'm very busy today so this probably won't happen until tomorrow. > > > Regards, > Rien > > Site: http://balancingrock.nl > Blog: http://swiftrien.blogspot.com > Github: http://github.com/Balancingrock > Project: http://swiftfire.nl > > > > > >> On 21 Feb 2017, at 07:58, David Hart via swift-evolution >> <swift-evolution@swift.org> wrote: >> >> Hello list, >> >> Matthew Johnson and I have been putting our proposals together towards a >> joint “let’s fix private access levels” proposal. As the community seems >> quite divided on the issue, we offer two solutions in our proposal to let >> the community debate and to let the core team make the final decision. >> >> I’d like to concentrate this round of feedback on the quality of the >> proposal, and not on the merits of Solution 1 or 2. thoughts? >> >> https://github.com/hartbit/swift-evolution/blob/fix-private-access-levels/proposals/XXXX-fix-private-access-levels.md >> >> David. >> >> Fix Private Access Levels >> >> • Proposal: SE-XXXX >> • Authors: David Hart, Matthew Johnson >> • Review Manager: TBD >> • Status: TBD >> Introduction >> >> This proposal presents the problems the came with the the access level >> modifications in SE-0025 and presents two community driven solutions to fix >> them. As a consensus will not easily emerge, this proposal will allow a last >> round of voting and let the core team decide. Once that is done, this >> proposal will be ammended to describe the chosen solution. >> >> Motivation >> >> Since the release of Swift 3, the access level change of SE-0025 was met >> with dissatisfaction by a substantial proportion of the general Swift >> community. Before offering solutions, lets discuss how and why it can be >> viewed as actiely harmful, the new requirement for syntax/API changes. >> >> Criticisms of SE-0025 >> >> There are two primary criticism that have been offered. >> >> The first is that private is a "soft default" access modifier for >> restricting access within a file. Scoped access is not a good behavior for a >> "soft default" because it is extremely common to use several extensions >> within a file. A "soft default" (and therefore private) should work well >> with this idiom. It is fair to say that changing the behavior of private >> such that it does not work well with extensions meets the criteria of >> actively harmful in the sense that it subtly encourages overuse of scoped >> access control and discourages the more reasonable default by giving it the >> awkward name fileprivate. >> >> The second is that Swift's system of access control is too complex. Many >> people feel like restricting access control to scopes less than a file is of >> dubious value and therefore wish to simplify Swift's access control story by >> removing scoped access. However, there are many others who like the ability >> to have the compiler verify tighter access levels and believe it helps make >> it easier to reason about code which is protecting invariants. >> >> Detailed design >> >> Both authors agree that the private keyword should be reverted back to its >> Swift 2 file-based meaning, resolving the first criticism. But the authors >> disagree on what should be done about the scoped access level and the >> following solutions represent the two main opinions in the community: >> >> Solution 1: Remove the scoped access level >> >> Compared to a file-based access level, the scoped-based access level adds >> meaningful information by hiding implementation details which do not concern >> other types or extensions in the same file. But is that distinction between >> private and fileprivate actively used by the larger community of Swift >> developers? And if it were used pervasively, would it be worth the cognitive >> load and complexity of keeping two very similar access levels in the >> language? This solution argues that answer to both questions is no and that >> the scoped access level should be removed to resolve the complexity >> criticism. >> >> This solution has the added advantage of leaving the most design >> breathing-room for future discussions about access levels in regards to >> submodules. >> >> Solution 2: Rename the scoped access level to scoped >> >> It is difficult to make the case that a feature which a nontrivial number of >> Swift users find valuable and which is easy for teams to avoid is actively >> harmful. It seems like something that falls more into the category of a >> debate over style (which could be addressed by a linter). Should we remove a >> feature whose utility is a question of style, but is not actively harmful in >> the sense of causing programmer error? The second solution argues against it >> and proposes renaming it to scoped. >> >> The scoped keyword is a good choice not only because the community has been >> calling this feature “scoped access control” all along, but also because the >> principle underlying all of Swift’s access levels is the idea of a scope. >> >> Source compatibility >> >> In Swift 3 compatibility mode, the compiler will continue to treat private >> and fileprivate as was previously the case. >> >> In Swift 4 mode, the compiler will deprecate the fileprivate keyword and >> revert the semantics of the private access level to be file based. The >> migrator will rename all uses of fileprivate to private. In solution 2, the >> migrator will also rename all uses of private to scoped. >> >> With solution 1 (and with solution 2 if the migrator is not run), cases >> where a type had private declarations with the same signature in different >> scopes will produce a compiler error. For example, the following piece of >> code compiles in Swift 3 compatibilty mode but generates a Invalid >> redeclaration of 'foo()' error in Swift 4 mode. >> >> struct Foo >> { >> >> private func bar >> () {} >> } >> >> >> extension Foo >> { >> >> private func bar >> () {} >> } >> >> Alternatives Considered >> >> • Deprecate fileprivate and modify the semantics of private to include >> same-type extension scopes in the same file. >> • Deprecate fileprivate and modify the semantics of private to include >> same-type extension scopes in the same module. >> The alternatives are potentially interesting but completely remove the file >> access level while making the new privateaccess level more complicated to >> explain and understand. >> _______________________________________________ >> 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
