Hi James, > On May 13, 2016, at 12:25 PM, James Lee via swift-corelibs-dev > <swift-corelibs-dev@swift.org> wrote: > > Following on from a previous discussion with Tests failing on OSX. I have > been looking into the failures. It seems that one of the earliest failures is > due to an error from a try! within NSTask.launch(). This came in with this > commit: > https://github.com/apple/swift-corelibs-foundation/commit/4c6f04cfcad3d4b06688558021595d06751fc66a > > Going by the docs for Foundation - The launch function apparently "Raises an > NSInvalidArgumentException if the launch path has not been set or is invalid > or if it fails to create a process." > > https://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Classes/NSTask_Class/#//apple_ref/occ/instm/NSTask/launch > > My question is, should this be built into the Swift Foundation API? The > documentation for Swift doesn't state that the launch function throws. > > With the test that is failing expecting an error, it feels more Swift-y to > have any errors throw explicitly, rather than looking at what the lower level > fills the data with. > > But before jumping into doing this, I would rather put it out there and see > what the community feels about this? >
Unfortunately the ‘throws’ syntax in Swift often causes a mixup between two different things, because it flipped the terminology from what all of our documentation and header comments use. 1. Cocoa uses exceptions (@throw in ObjC) to indicate programmer errors and they are generally not intended to be recoverable. Example: passing nil where not expected, passing an invalid argument, failing to meet a precondition of an API. 2. Cocoa uses NSError ** to indicate runtime errors that are recoverable or at least presentable to user. Example: out of disk space, name of file already exists. The ‘throws’ syntax in Swift is actually for case #2, not #1. In Swift, #1 is fatalError or preconditionFailure. #2 is ‘throw Error’. In the case of NSTask, when the documentation says “raises an NSInvalidArgumentException” (#1) then in Swift, that should translate to fatalError or preconditionFailure. Hope this helps, - Tony > Cheers > > James > _______________________________________________ > swift-corelibs-dev mailing list > swift-corelibs-dev@swift.org > https://lists.swift.org/mailman/listinfo/swift-corelibs-dev _______________________________________________ swift-corelibs-dev mailing list swift-corelibs-dev@swift.org https://lists.swift.org/mailman/listinfo/swift-corelibs-dev
