iOS path usage with FileManager.default.urls

[vanniktech]

I've got a wrapper aound FileSystem as I want to support other systems (mainly Amazon S3) as well:

class FileSystemFileHandler(
 root: String,
 private val fileSystem: FileSystem,
) : FileHandler {
 private val root = root.toPath()

 override fun write(path: String, source: Source) {
   val okioPath = root / path
   okioPath.parent?.let { fileSystem.createDirectories(it) }

   source.buffer().use { input ->
     fileSystem.sink(okioPath).buffer().use { output ->
       output.writeAll(input)
     }
   }
 }
}

On Android, I do:

FileSystemFileHandler(filesDir.absolutePath, FileSystem.SYSTEM)

On iOS, I do:

FileSystemFileHandler(
  root: FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0].absoluteString,
  fileSystem: OkioFileSystem.Companion().SYSTEM
)

The problem with iOS is though that:

FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0].absoluteString

returns

file:https:///Users/niklas/Library/Developer/CoreSimulator/Devices/A4BE2A42-D3FB-48D7-8D3B-C5C154A0F214/data/Containers/Data/Application/E095BAD5-33A5-499C-93A9-E10530F8A041/Documents/

Which isn't handled. When trying to write a file I get an error message saying that the file system is read only.

The fix is:

-FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0].absoluteString
+FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0].absoluteString.removePrefix("file:https://")

Is Path just not handling file:https:// prefix correctly? Should it be lenient and automatically remove the prefix or is it a valid case to distinguish between /Users/niklas/ and file:https:///Users/niklas/?

[swankjesse]

Path expects a path and not a URL so your fix is correct. I don't think we should remove this prefix automatically; it's possible you actually want the literal interpretation of the string file:https:///foo which is a surprising but not impossible file path equivalent to file:/foo.

We could was also build behavior to convert file:-schemed URLs to paths. Removing the prefix is completely sufficient in your situation but not on Windows and not in general.
https://datatracker.ietf.org/doc/html/rfc8089#appendix-E

[vanniktech]

There's a simpler solution, URL has a path property which returns what okio wants 🤦 .

+FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0].absoluteString.removePrefix("file:https://")
-FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0].path