PropertyListSerialization on Linux doesn't compile with mutableContainersAndLeaves

Using Swift
1

I couldn't find any particular reason for this, but a function call on Linux of

let serialized = try PropertyListSerialization.propertyList(
    from: plistXML,
    options: .mutableContainersAndLeaves,
    format: &propertyListFormat
)

doesn't compile when running on the Swift docker image, giving an error of extra argument 'format' in call format: &propertyListFormat. But:

let serialized = try PropertyListSerialization.propertyList(
    from: plistXML,
    options: [],
    format: &propertyListFormat
)

compiles fine. Anything I'm missing?

2

I experimented on macOS, not Linux, but it kept hitting the error you describe until I got the argument for format declared correctly:

let plistXML = Data()
var propertyListFormat: PropertyListSerialization.PropertyListFormat = .xml // Some nonā€nil placeholder.

let serialized = try PropertyListSerialization.propertyList(
    from: plistXML,
    options: .mutableContainersAndLeaves,
    format: &propertyListFormat
)

So the compiler may be diagnosing your problem incorrectly; it may instead have something to do with a mismatched type being passed to one of the arguments.

3

Yeah, code looks the same and that compiles fine on MacOS but still not on Linux.

Although you bring up a good point if it was giving you the same error, might be something with how UnsafeMutablePointer<PropertyListFormat>? is treated.

4

How do you have propertyListFormat declared? My mistake had been to declare it as optional. But UnsafeMutablePointer<PropertyListFormat>? is an optional pointer, not a pointer to an optional format. (See the comment in the earlier code sample. You may have to scroll to the right.)

5

If you extract the mutableContainersAndLeaves reference you end up with this error:

xcodeproj/Sources/xcodeproj/Project/XcodeProj.swift:85:48: error: 'mutableContainersAndLeaves' is inaccessible due to 'internal' protection level
        let a = PropertyListSerialization.ReadOptions.mutableContainersAndLeaves
                                                      ^

Which makes sense because it turns out these are declared internally swift-corelibs-foundation/PropertyListSerialization.swift at 753e621b5f6c483bd8ef25d7b511a437b6f90f0c Ā· apple/swift-corelibs-foundation Ā· GitHub

It makes sense that this works on macOS because it's not using swift-corelibs-foundation. I'm not sure if this was intentional or not, but I've submitted Make PropertyListSerialization.MutabilityOptions constants public by keith Ā· Pull Request #1944 Ā· apple/swift-corelibs-foundation Ā· GitHub for discussion

In the meantime you could work around this on Linux by using what that constant refers to MutabilityOptions(rawValue: 2) directly.

2 Likes
6

Yup, thatā€™d be it.