> On Mar 5, 2017, at 2:06 PM, Xiaodi Wu <[email protected]> wrote: > > Punycode would readily cover your first issue about legal identifier > characters.
Well, it would cover… I’m not sure if “readily” would be the right word. If I have a sub-module I want to call `Bücher`, and I have to name the directory `Bcher-kva`, what do I use to refer to the sub-module in my code? It’s not at all readable, nor is it discoverable to a 3rd party who if they don’t “know” about Punycode, have no reason to associate the `Bücher` sub-module with the `Bcher-kva` directory. Not that’s a show-stopper, mind. I wouldn’t mind further exploring the directory-name + “extension" approach. —Karim > As to the second, having enumerated the essential properties of a Foo, what > "growth" are you envisioning? > On Sun, Mar 5, 2017 at 12:51 Karim Nassar via swift-evolution > <[email protected] <mailto:[email protected]>> wrote: > >> On Mar 5, 2017, at 10:10 AM, Rien <[email protected] >> <mailto:[email protected]>> wrote: >> >>> >>> On 05 Mar 2017, at 15:52, Karim Nassar via swift-evolution >>> <[email protected] <mailto:[email protected]>> wrote: >>> >>> >>>> On Mar 4, 2017, at 2:54 PM, Matthew Johnson <[email protected] >>>> <mailto:[email protected]>> wrote: >>>> >>>>> >>>>> On Mar 4, 2017, at 9:56 AM, Karim Nassar <[email protected] >>>>> <mailto:[email protected]>> wrote: >>>>> >>>>> >>>>>> On Mar 3, 2017, at 5:21 PM, Matthew Johnson <[email protected] >>>>>> <mailto:[email protected]>> wrote: >>>>>> >>>>>>> >>>>>>> On Mar 3, 2017, at 9:24 AM, Karim Nassar via swift-evolution >>>>>>> <[email protected] <mailto:[email protected]>> wrote: >>>>>>> >>>>>>> Changes that *are* necessary are: >>>>>>> >>>>>>> * Change the spelling of `internal` to `module` (making `module` the >>>>>>> new default) >>>>>>> * Introduce a new modifier `internal` to mean "Internal to the current >>>>>>> sub-module and its child-sub-modules” >>>>>> >>>>>> Can you give concrete examples of use cases where a descendent submodule >>>>>> needs access to symbols declared by an ancestor? I gave some thought to >>>>>> this when drafting my proposal and came to the conclusion that this runs >>>>>> against the grain of layering and is likely to be a bad idea in >>>>>> practice. If there are use cases I didn’t consider I am very interested >>>>>> in learning about them. >>>>> >>>>> On further reflection and examination of my notes, I think you’re right, >>>>> and that the `internal` encapsulation should be purely horizontal. Will >>>>> adjust to reflect that. >>>>> >>>>>>> ### Making a Sub-module >>>>>>> >>>>>>> To create a sub-module within a Module (or sub-module) is simple: The >>>>>>> author creates a directory, and places a "sub-module declaration file" >>>>>>> within the directory: >>>>>>> >>>>>>> ``` >>>>>>> // __submodule.swift >>>>>> >>>>>> Why the double underscore prefix? To make it sort to the top in a file >>>>>> browser? >>>>>> >>>>>> Is this file allowed to have any Swift code? Or is it limited to >>>>>> submodule-related declarations only? If the latter, why not use an >>>>>> extension such as `.submodule` or `.swiftmodule` to differentiate it >>>>>> from ordinary Swift files and allow the submodule to be named by the >>>>>> name of this file? >>>>> >>>>> So, my reasoning was that by requiring a specific standard name for the >>>>> declaration file, we guarantee that any directory can only describe one >>>>> submodule. Prefixing the proposed name with underscores was simply a way >>>>> of preventing naming collision with potential “real code” files (and yes, >>>>> as a side-effect alpha-floating it to the top). Since the `submodule` >>>>> declaration might expand to include statements & configuration about the >>>>> sub-module, I see no reason to prohibit Swift code from existing in that >>>>> sub-module declaration file… Disallowing/controlling that seems to be a >>>>> style/linter concern. >>>>> >>>>> However, as I mentioned above, all the specific spellings (except >>>>> `internal`) for the different concepts in this proposal are straw-men >>>>> awaiting input. I’d say the addition of a new type of file extension >>>>> raises some concerns for me, but there’s already been a lot of push back >>>>> on the general idea of using filesystem structures to organize >>>>> sub-modules, so the whole idea may be moot. >>>> >>>> I’ve actually been starting to come around to the idea of using the file >>>> system. Not so much because I really like it, but because I have been >>>> considering further some of the drawbacks of other approaches. >>>> >>>> One big reason is that a submodule should form a scope and scopes should >>>> consist of code that is physically adjacent. In practice this means it >>>> should reside in close proximity in the file system. Allowing any file in >>>> a project to be a part of any submodule partly defeats the purpose of >>>> using them to structure a project internally. If we’re going to be >>>> organizing the files in a submodule physically anyway maybe we should just >>>> take advantage of that fact and prevent a stray file in a distant part of >>>> the file system from being part of the submodule. >>>> >>>> The second reason is that there is a big problem with placing a simple >>>> `submodule Foo` declaration at the top of each file in a submodule. We >>>> all make typos from time to time. This method makes it too easy to >>>> accidentally type `submodule Fooo` and end up in a submodule you didn’t >>>> intend. This mistake would likely be caught relatively quickly but it >>>> seems silly to have a system subject to this kind of mistake. This means >>>> we would end arbitrarily placing the declaration in one file and saying >>>> `extends submodule Foo` in the rest of the files. Your design avoids the >>>> need to arbitrarily choose where to place the declaration and avoids the >>>> need for a declaration in the rest of the files. >>> >>> I’m not dead-set on this approach, but as you say, it solves a *lot* of >>> problems that other approaches introduce. I do recognize the reasonableness >>> of the main argument against, that file location shouldn’t have such a >>> dramatic affect on behavior… *but* the fact is (whether by convention or >>> expediency) we already *do* have filesystem location dependencies on our >>> code projects… >>> >>> * One can’t willy-nilly move files around the disk and expect a project to >>> build… if you move it somewhere the compiler doesn’t know to look for it, >>> you’re going to break things >>> * One can’t just move a file out of your SCM repo root, or you’ll “lose” >>> the file >> >> True, but if other files do not refer to the lost file, you don’t even know >> for which file to look. >> (imo this is already a weak point in swift, but this approach to submodules >> would make it -much?- worse) >> >> If you were to include filenames in the “submodule declaration file” at >> least this omission in swift would be partly covered, and you would not need >> to move the other files into special places. (You could though) >> > > But isn’t this exactly the same case if you’re using Swift without an IDE? > It’s true that Xcode keeps track of files in your project, and there’s no > reason it couldn’t also keep track of files in a submodule (in fact it would… > it just might not know they belong in the sub-module without some work from > the Xcode dev team). > > But as a thought-experiment, here’s how I’m thinking of this problem: > > Swift (as a language) has established that a file *is* a unit of code. Not > the only one of course, but it is one, as evidenced by access controls > (fileprivate, Swift2 private) which bound on the file. > > I (and many others) want to be able to describe another unit of code larger > than a file and smaller than a Module to help organize the file-units we have > which go together within a Module, but which shouldn’t (for various reasons) > describe a complete Module in and of themselves. > > For the moment—though we actually propose to call this unit a > sub-module—we'll call this new unit a Foo. Let's describe properties of a Foo: > > * A Foo should serve to organize one or more File code units by: > - ensuring a File (the code-unit) may belong to one and only one Foo > - making clear (with or without an IDE) to which Foo a given file might > belong > * A Foo should have a unique name > * A Foo should be able to nest under another Foo, and the name of that > nesting should be clear & unique > * A Foo should be able to be easily created, split, and merged as the > codebase evolves > * A Foo should be able to be moved, copied, and SCMed as a unit, without > reference to anything outside the Foo > > Having now described the critical properties of this new unit called “Foo” > have we not also described a filesystem directory? > > Naturally, we don’t want *all* directories to become Foos (that would be > overly restrictive to authors, and backwards-incompatible), so we need a way > to distinguish a normal directory from one that is acting as a Foo. I > originally proposed a special “sub-module declaration file”, but there may be > other ways. For example, we might establish that a directory whose name > matches `[SubModuleName].swift-sub-module` becomes a sub-module of designated > name, however this can cause problems due to the disjoint sets of “Legal > Filesystem Directory Characters” and “Legal Swift Identifier Characters”. It > also doesn’t give us a place to “grow” the declaration in the future if we > choose to add additional properties to the sub-module declaration. > > > —Karim > > > > > > _______________________________________________ > swift-evolution mailing list > [email protected] <mailto:[email protected]> > https://lists.swift.org/mailman/listinfo/swift-evolution > <https://lists.swift.org/mailman/listinfo/swift-evolution>
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