Support Linux

[chrispomeroyhale]

In the past support for Linux has been unavailable because this library uses Scanner from the Foundation framework to parse CSV text. Unfortunately the implementation of Scanner has been incomplete in swift-corelibs-foundation.

This may have changed recently. Foundation support is listed here and it appears the Scanner APIs have also been updated to better reflect the changes on Apple platforms for better API compatibility which had also been a blocker.

• https://github.com/apple/swift-corelibs-foundation/blob/main/Docs/Status.md
• Update to newer Scanner methods. swiftlang/swift-corelibs-foundation#2184

[chrispomeroyhale]

There continue to be two type issues. Apple's version of Scanner (formerly NSScanner) continues to use NSString while the corelibs uses String:

Sources/ImportParser.swift:66:70: error: cannot convert value of type 'UnsafeMutablePointer<NSString?>' to expected argument type 'UnsafeMutablePointer<String?>'
            if !scanner.scanUpToCharacters(from: characterSet, into: &fieldPartition), scanner.isAtEnd {
                                                                     ^
Sources/ImportParser.swift:66:70: note: arguments to generic parameter 'Pointee' ('NSString?' and 'String?') are expected to be equal
            if !scanner.scanUpToCharacters(from: characterSet, into: &fieldPartition), scanner.isAtEnd {
                                                                     ^

And

Sources/ImportParser.swift:79:68: error: cannot convert value of type 'UnsafeMutablePointer<NSString?>' to expected argument type 'UnsafeMutablePointer<String?>'
            guard scanner.scanCharacters(from: characterSet, into: &characters), let specials = characters as String? else {
                                                                   ^
Sources/ImportParser.swift:79:68: note: arguments to generic parameter 'Pointee' ('NSString?' and 'String?') are expected to be equal
            guard scanner.scanCharacters(from: characterSet, into: &characters), let specials = characters as String? else {
                                                                   ^

This error is protected by an if #available(iOS 13, macOS 10.15, *) so this error is unexpected:

Sources/InputHandler.swift:143:37: error: 'seek(toOffset:)' is unavailable
                try self.fileHandle.seek(toOffset: startOffset)
                                    ^~~~
Foundation.FileHandle:21:17: note: 'seek(toOffset:)' was introduced in Swift 5.0
    public func seek(toOffset offset: UInt64) throws
                ^