Hello everyone, I created a new thread for version 2 of the FilePath APIs. I received so much valuable insight in the other thread that I've incorporated into this design, so I thought it would be cleaner to make a new thread.
You can find the full version with extended rationale and future directions in the gist. Below is an excerpt, trimmed due to forum character limits.
FilePath Syntactic Operations
- Authors: Michael Ilseman, Saleem Abdulrasool
- Implementation: PR-14
- Previous version: version 1, changes
Introduction
FilePath appeared in System 0.0.1 with a minimal API. This proposal adds API for syntactic operations, which are performed on the structure of the path and thus do not consult with the file system or make any system calls. These include inspecting the structure of paths, modifying paths, and accessing individual components.
Additionally, this proposal greatly expands Windows support and enables writing platform-agnostic path manipulation code.
Design
Windows support
Furthering Swift's push for Windows and System's initial Windows support, this proposal updates FilePath to work well on Windows in addition to Unix platforms.
The proposed API is designed to work naturally and intuitively with both Unix-style and Windows paths. Most of the concepts and even terminology are shared across platforms, though there are some minor differences (e.g. this proposal uses the word "absolute" to refer to what is formally called "fully-qualified" on Windows).
Introducing FilePath.Root and FilePath.Component
FilePath.Root represents the root of a path. On Unix, this is simply /, but on Windows it can include volume and server/share information.
extension FilePath {
/// Represents a root of a file path.
///
/// On Unix, a root is simply the directory separator `/`.
///
/// On Windows, a root contains the entire path prefix up to and including
/// the final separator.
///
/// Examples:
/// * Unix:
/// * `/`
/// * Windows:
/// * `C:\`
/// * `C:`
/// * `\`
/// * `\\server\share\`
/// * `\\?\UNC\server\share\`
/// * `\\?\Volume{12345678-abcd-1111-2222-123445789abc}\`
public struct Root { }
}
FilePath.Component represents a single non-root component of a path. A component can be a file or directory name or one of the special directories . or ... Components are always non-empty and do not contain a directory separator.
extension FilePath {
/// Represents an individual, non-root component of a file path.
///
/// Components can be one of the special directory components (`.` or `..`)
/// or a file or directory name. Components are never empty and never
/// contain the directory separator.
///
/// Example:
///
/// var path: FilePath = "/tmp"
/// let file: FilePath.Component = "foo.txt"
/// file.kind == .regular // true
/// file.extension // "txt"
/// path.append(file) // path is "/tmp/foo.txt"
///
public struct Component {
/// Whether a component is a regular file or directory name, or a special
/// directory `.` or `..`
public enum Kind {
/// The special directory `.`, representing the current directory.
case currentDirectory
/// The special directory `..`, representing the parent directory.
case parentDirectory
/// A file or directory name
case regular
}
/// The kind of this component
public var kind: Kind { get }
/// Whether this component is either special directory `.` or `..`.
public var isSpecialDirectory: Bool { get }
}
}
These can conveniently be created from a string literal and can be printed, just like FilePath.
(See the gist for CustomStringConvertible, CustomDebugStringConvertible, ExpressibleByStringLiteral conformances for Root and Component.)
FilePath.ComponentView
FilePath.ComponentView is a BidirectionalCollection and RangeReplaceableCollection of the non-root components that comprise a path. The Index type is an opaque wrapper around FilePath's underlying storage index.
extension FilePath {
/// A bidirectional, range replaceable collection of the non-root components
/// that make up a file path.
///
/// ComponentView provides access to standard `BidirectionalCollection`
/// algorithms for accessing components from the front or back, as well as
/// standard `RangeReplaceableCollection` algorithms for modifying the
/// file path using component or range of components granularity.
///
/// Example:
///
/// var path: FilePath = "/./home/./username/scripts/./tree"
/// let scriptIdx = path.components.lastIndex(of: "scripts")!
/// path.components.insert("bin", at: scriptIdx)
/// // path is "/./home/./username/bin/scripts/./tree"
///
/// path.components.removeAll { $0.kind == .currentDirectory }
/// // path is "/home/username/bin/scripts/tree"
///
public struct ComponentView: BidirectionalCollection, RangeReplaceableCollection { }
/// View the non-root components that make up this path.
public var components: ComponentView { get set }
}
FilePath can be created by a given root and components. FilePath.init(root:_:ComponentView.SubSequence) is a more efficient overload that can directly access the underlying storage, which already has normalized separators between components.
extension FilePath {
/// Create a file path from a root and a collection of components.
public init<C: Collection>(root: Root?, _ components: C)
where C.Element == Component
/// Create a file path from a root and any number of components.
public init(root: Root?, components: Component...)
/// Create a file path from an optional root and a slice of another path's
/// components.
public init(root: Root?, _ components: ComponentView.SubSequence)
}
Basic queries
/// Returns whether `other` is a prefix of `self`, only considering
/// whole path components.
///
/// Example:
///
/// let path: FilePath = "/usr/bin/ls"
/// path.starts(with: "/") // true
/// path.starts(with: "/usr/bin") // true
/// path.starts(with: "/usr/bin/ls") // true
/// path.starts(with: "/usr/bin/ls///") // true
/// path.starts(with: "/us") // false
///
public func starts(with other: FilePath) -> Bool
/// Returns whether `other` is a suffix of `self`, only considering
/// whole path components.
///
/// Example:
///
/// let path: FilePath = "/usr/bin/ls"
/// path.ends(with: "ls") // true
/// path.ends(with: "bin/ls") // true
/// path.ends(with: "usr/bin/ls") // true
/// path.ends(with: "/usr/bin/ls///") // true
/// path.ends(with: "/ls") // false
///
public func ends(with other: FilePath) -> Bool
/// Whether this path is empty
public var isEmpty: Bool { get }
}
Windows roots are more complex and can take several different syntactic forms, carry additional information within them such as a drive letter or server/share information, and the presence of a root does not mean that the path is absolute (i.e. "fully-qualified" in Windows-speak).
For example, C:foo refers to foo relative to the current directory on the C drive, and \foo refers to foo at the root of the current drive. Neither of those are absolute, i.e. fully-qualified, even though they have roots.
extension FilePath {
/// Returns true if this path uniquely identifies the location of
/// a file without reference to an additional starting location.
///
/// On Unix platforms, absolute paths begin with a `/`. `isAbsolute` is
/// equivalent to `root != nil`.
///
/// On Windows, absolute paths are fully qualified paths. `isAbsolute` is
/// _not_ equivalent to `root != nil` for traditional DOS paths
/// (e.g. `C:foo` and `\bar` have roots but are not absolute). UNC paths
/// and device paths are always absolute. Traditional DOS paths are
/// absolute only if they begin with a volume or drive followed by
/// a `:` and a separator.
///
/// NOTE: This does not perform shell expansion or substitute
/// environment variables; paths beginning with `~` are considered relative.
///
/// Examples:
/// * Unix:
/// * `/usr/local/bin`
/// * `/tmp/foo.txt`
/// * `/`
/// * Windows:
/// * `C:\Users\`
/// * `\\?\UNC\server\share\bar.exe`
/// * `\\server\share\bar.exe`
public var isAbsolute: Bool { get }
/// Returns true if this path is not absolute (see `isAbsolute`).
///
/// Examples:
/// * Unix:
/// * `~/bar`
/// * `tmp/foo.txt`
/// * Windows:
/// * `bar\baz`
/// * `C:Users\`
/// * `\Users`
public var isRelative: Bool { get }
}
Path decomposition and analysis
Paths can be decomposed into their (optional) root and their (potentially empty) components.
extension FilePath {
/// Returns the root of a path if there is one, otherwise `nil`.
///
/// On Unix, this will return the leading `/` if the path is absolute
/// and `nil` if the path is relative.
///
/// On Windows, for traditional DOS paths, this will return
/// the path prefix up to and including a root directory or
/// a supplied drive or volume. Otherwise, if the path is relative to
/// both the current directory and current drive, returns `nil`.
///
/// On Windows, for UNC or device paths, this will return the path prefix
/// up to and including the host and share for UNC paths or the volume for
/// device paths followed by any subsequent separator.
///
/// Examples:
/// * Unix:
/// * `/foo/bar => /`
/// * `foo/bar => nil`
/// * Windows:
/// * `C:\foo\bar => C:\`
/// * `C:foo\bar => C:`
/// * `\foo\bar => \`
/// * `foo\bar => nil`
/// * `\\server\share\file => \\server\share\`
/// * `\\?\UNC\server\share\file => \\?\UNC\server\share\`
/// * `\\.\device\folder => \\.\device\`
///
/// Setting the root to `nil` will remove the root and setting a new
/// root will replace the root.
///
/// Example:
///
/// var path: FilePath = "/foo/bar"
/// path.root = nil // path is "foo/bar"
/// path.root = "/" // path is "/foo/bar"
///
/// Example (Windows):
///
/// var path: FilePath = #"\foo\bar"#
/// path.root = nil // path is #"foo\bar"#
/// path.root = "C:" // path is #"C:foo\bar"#
/// path.root = #"C:\"# // path is #"C:\foo\bar"#
///
public var root: FilePath.Root? { get set }
/// Creates a new path containing just the components, i.e. everything
/// after `root`.
///
/// Returns self if `root == nil`.
///
/// Examples:
/// * Unix:
/// * `/foo/bar => foo/bar`
/// * `foo/bar => foo/bar`
/// * `/ => ""`
/// * Windows:
/// * `C:\foo\bar => foo\bar`
/// * `foo\bar => foo\bar`
/// * `\\?\UNC\server\share\file => file`
/// * `\\?\device\folder\file.exe => folder\file.exe`
/// * `\\server\share\file => file`
/// * `\ => ""`
///
public func removingRoot() -> FilePath
}
Setters allow for in-place mutation. FilePath.root's setter allows making a path relative or absolute, and even allows switching root representations on Windows.
A common decomposition of a path is between it's last non-root component and everything prior to this (e.g. basename and dirname in C).
extension FilePath {
/// Returns the final component of the path.
/// Returns `nil` if the path is empty or only contains a root.
///
/// Note: Even if the final component is a special directory
/// (`.` or `..`), it will still be returned. See `lexicallyNormalize()`.
///
/// Examples:
/// * Unix:
/// * `/usr/local/bin/ => bin`
/// * `/tmp/foo.txt => foo.txt`
/// * `/tmp/foo.txt/.. => ..`
/// * `/tmp/foo.txt/. => .`
/// * `/ => nil`
/// * Windows:
/// * `C:\Users\ => Users`
/// * `C:Users\ => Users`
/// * `C:\ => nil`
/// * `\Users\ => Users`
/// * `\\?\UNC\server\share\bar.exe => bar.exe`
/// * `\\server\share => nil`
/// * `\\?\UNC\server\share\ => nil`
///
public var lastComponent: Component? { get }
/// Creates a new path with everything up to but not including
/// `lastComponent`.
///
/// If the path only contains a root, returns `self`.
/// If the path has no root and only includes a single component,
/// returns an empty FilePath.
///
/// Examples:
/// * Unix:
/// * `/usr/bin/ls => /usr/bin`
/// * `/foo => /`
/// * `/ => /`
/// * `foo => ""`
/// * Windows:
/// * `C:\foo\bar.exe => C:\foo`
/// * `C:\ => C:\`
/// * `\\server\share\folder\file.txt => \\server\share\folder`
/// * `\\server\share\ => \\server\share\`
public func removingLastComponent() -> FilePath
(See the gist for dirname and basename unavailable-renamed declarations to aid discoverability.)
Components may be decomposed into their stem and (optional) extension (.txt, .o, .app, etc.) FilePath gains convenience APIs for dealing with the stem and extension of the last component, if it exists. FilePath also gains a setter for extension for easy and efficient in-place mutation.
extension FilePath.Component {
/// The extension of this file or directory component.
///
/// If `self` does not contain a `.` anywhere, or only
/// at the start, returns `nil`. Otherwise, returns everything after the dot.
///
/// Examples:
/// * `foo.txt => txt`
/// * `foo.tar.gz => gz`
/// * `Foo.app => app`
/// * `.hidden => nil`
/// * `.. => nil`
///
public var `extension`: String? { get }
/// The non-extension portion of this file or directory component.
///
/// Examples:
/// * `foo.txt => foo`
/// * `foo.tar.gz => foo.tar`
/// * `Foo.app => Foo`
/// * `.hidden => .hidden`
/// * `.. => ..`
///
public var stem: String { get }
}
extension FilePath {
/// The extension of the file or directory last component.
///
/// If `lastComponent` is `nil` or one of the special path components
/// `.` or `..`, `get` returns `nil` and `set` does nothing.
///
/// If `lastComponent` does not contain a `.` anywhere, or only
/// at the start, `get` returns `nil` and `set` will append a
/// `.` and `newValue` to `lastComponent`.
///
/// Otherwise `get` returns everything after the last `.` and `set` will
/// replace the extension.
///
/// Examples:
/// * `/tmp/foo.txt => txt`
/// * `/Appliations/Foo.app/ => app`
/// * `/Appliations/Foo.app/bar.txt => txt`
/// * `/tmp/foo.tar.gz => gz`
/// * `/tmp/.hidden => nil`
/// * `/tmp/.hidden. => ""`
/// * `/tmp/.. => nil`
///
/// Example:
///
/// var path = "/tmp/file"
/// path.extension = ".txt" // path is "/tmp/file.txt"
/// path.extension = ".o" // path is "/tmp/file.o"
/// path.extension = nil // path is "/tmp/file"
/// path.extension = "" // path is "/tmp/file."
///
public var `extension`: String? { get set }
/// The non-extension portion of the file or directory last component.
///
/// Returns `nil` if `lastComponent` is `nil`
///
/// * `/tmp/foo.txt => foo`
/// * `/Appliations/Foo.app/ => Foo`
/// * `/Appliations/Foo.app/bar.txt => bar`
/// * `/tmp/.hidden => .hidden`
/// * `/tmp/.. => ..`
/// * `/ => nil`
public var stem: String? { get }
}
FilePath.extension's setter allows for convenient in-place reassigning or adding/removing of an extension.
Lexical operations
FilePath supports lexical (i.e. does not call into the file system to e.g. follow symlinks) operations such as normalization of special directory components (. and ..).
extension FilePath {
/// Whether the path is in lexical-normal form, that is `.` and `..`
/// components have been collapsed lexically (i.e. without following
/// symlinks).
///
/// Examples:
/// * `"/usr/local/bin".isLexicallyNormal == true`
/// * `"../local/bin".isLexicallyNormal == true`
/// * `"local/bin/..".isLexicallyNormal == false`
public var isLexicallyNormal: Bool { get }
/// Collapse `.` and `..` components lexically (i.e. without following
/// symlinks).
///
/// Examples:
/// * `/usr/./local/bin/.. => /usr/local`
/// * `/../usr/local/bin => /usr/local/bin`
/// * `../usr/local/../bin => ../usr/bin`
public mutating func lexicallyNormalize()
/// Returns a copy of `self` in lexical-normal form, that is `.` and `..`
/// components have been collapsed lexically (i.e. without following
/// symlinks). See `lexicallyNormalize`
public var lexicallyNormal: FilePath { get }
}
FilePath provides API to help protect against arbitrary path traversal from untrusted sub-paths:
extension FilePath {
/// Create a new `FilePath` by resolving `subpath` relative to `self`,
/// ensuring that the result is lexically contained within `self`.
///
/// `subpath` will be lexically normalized (see `lexicallyNormalize`) as
/// part of resolution, meaning any contained `.` and `..` components will
/// be collapsed without resolving symlinks. Any root in `subpath` will be
/// ignored.
///
/// Returns `nil` if the result would "escape" from `self` through use of
/// the special directory component `..`.
///
/// This is useful for protecting against arbitrary path traversal from an
/// untrusted subpath: the result is guaranteed to be lexically contained
/// within `self`. Since this operation does not consult the file system to
/// resolve symlinks, any escaping symlinks nested inside of `self` can still
/// be targeted by the result.
///
/// Example:
///
/// let staticContent: FilePath = "/var/www/my-website/static"
/// let links: [FilePath] =
/// ["index.html", "/assets/main.css", "../../../../etc/passwd"]
/// links.map { staticContent.lexicallyResolving($0) }
/// // ["/var/www/my-website/static/index.html",
/// // "/var/www/my-website/static/assets/main.css",
/// // nil]
public func lexicallyResolving(_ subpath: FilePath) -> FilePath?
}
Modifying paths
FilePath supports common mutation operations.
extension FilePath {
/// If `prefix` is a prefix of `self`, removes it and returns `true`.
/// Otherwise returns `false`.
///
/// Example:
///
/// var path: FilePath = "/usr/local/bin"
/// path.removePrefix("/usr/bin") // false
/// path.removePrefix("/us") // false
/// path.removePrefix("/usr/local") // true, path is "bin"
///
public mutating func removePrefix(_ prefix: FilePath) -> Bool
/// Append a `component` on to the end of this path.
///
/// Example:
///
/// var path: FilePath = "/tmp"
/// let sub: FilePath = "foo/./bar/../baz/."
/// for comp in sub.components.filter({ $0.kind != .currentDirectory }) {
/// path.append(comp)
/// }
/// // path is "/tmp/foo/bar/../baz"
///
public mutating func append(_ component: FilePath.Component)
/// Append `components` on to the end of this path.
///
/// Example:
///
/// var path: FilePath = "/"
/// path.append(["usr", "local"]) // path is "/usr/local"
/// let otherPath: FilePath = "/bin/ls"
/// path.append(otherPath.components) // path is "/usr/local/bin/ls"
///
public mutating func append<C: Collection>(_ components: C)
where C.Element == FilePath.Component
/// Append the contents of `other`, ignoring any spurious leading separators.
///
/// A leading separator is spurious if `self` is non-empty.
///
/// Example:
/// var path: FilePath = ""
/// path.append("/var/www/website") // "/var/www/website"
/// path.append("static/assets") // "/var/www/website/static/assets"
/// path.append("/main.css") // "/var/www/website/static/assets/main.css"
///
public mutating func append(_ other: String)
/// Non-mutating version of `append(_:Component)`.
public func appending(_ other: Component) -> FilePath
/// Non-mutating version of `append(_:C)`.
public func appending<C: Collection>(
_ components: C
) -> FilePath where C.Element == FilePath.Component
/// Non-mutating version of `append(_:String)`.
public func appending(_ other: String) -> FilePath
/// If `other` does not have a root, append each component of `other`. If
/// `other` has a root, replaces `self` with other.
///
/// This operation mimics traversing a directory structure (similar to the
/// `cd` command), where pushing a relative path will append its components
/// and pushing an absolute path will first clear `self`'s existing
/// components.
///
/// Example:
///
/// var path: FilePath = "/tmp"
/// path.push("dir/file.txt") // path is "/tmp/dir/file.txt"
/// path.push("/bin") // path is "/bin"
///
public mutating func push(_ other: FilePath)
/// Non-mutating version of `push()`
public func pushing(_ other: FilePath) -> FilePath
/// In-place mutating variant of `removingLastComponent`.
///
/// If `self` only contains a root, does nothing and returns `false`.
/// Otherwise removes `lastComponent` and returns `true`.
///
/// Example:
///
/// var path = "/usr/bin"
/// path.removeLastComponent() == true // path is "/usr"
/// path.removeLastComponent() == true // path is "/"
/// path.removeLastComponent() == false // path is "/"
///
@discardableResult
public mutating func removeLastComponent() -> Bool
/// Remove the contents of the path, keeping the null terminator.
public mutating func removeAll(keepingCapacity: Bool = false)
/// Reserve enough storage space to store `minimumCapacity` platform
/// characters.
public mutating func reserveCapacity(_ minimumCapacity: Int)
}
Paths and strings
Just like FilePath, FilePath.Component and FilePath.Root can be decoded/validated into a Swift String.
extension String {
/// Creates a string by interpreting the path component's content as UTF-8 on
/// Unix and UTF-16 on Windows.
///
/// - Parameter path: The path component to be interpreted as
/// `CTypes.PlatformUnicodeEncoding`.
///
/// If the content of the path component isn't a well-formed Unicode string,
/// this initializer replaces invalid bytes with U+FFFD.
/// This means that, depending on the semantics of the specific file system,
/// conversion to a string and back to a path component
/// might result in a value that's different from the original path component.
public init(decoding component: FilePath.Component)
/// Creates a string from a path component, validating its contents as UTF-8
/// on Unix and UTF-16 on Windows.
///
/// - Parameter path: The path component to be interpreted as
/// `CTypes.PlatformUnicodeEncoding`.
///
/// If the contents of the path component isn't a well-formed Unicode string,
/// this initializer returns `nil`.
public init?(validating component: FilePath.Component)
/// On Unix, creates the string `"/"`
///
/// On Windows, creates a string by interpreting the path root's content as
/// UTF-16.
///
/// - Parameter path: The path root to be interpreted as
/// `CTypes.PlatformUnicodeEncoding`.
///
/// If the content of the path root isn't a well-formed Unicode string,
/// this initializer replaces invalid bytes with U+FFFD.
/// This means that on Windows,
/// conversion to a string and back to a path root
/// might result in a value that's different from the original path root.
public init(decoding root: FilePath.Root) {
self.init(_decoding: root)
}
/// On Unix, creates the string `"/"`
///
/// On Windows, creates a string from a path root, validating its contents as
/// UTF-16 on Windows.
///
/// - Parameter path: The path root to be interpreted as
/// `CTypes.PlatformUnicodeEncoding`.
///
/// On Windows, if the contents of the path root isn't a well-formed Unicode
/// string, this initializer returns `nil`.
public init?(validating root: FilePath.Root) {
self.init(_validating: root)
}
}
FilePath, FilePath.Component, and FilePath.Root gain convenience properties for viewing their content as Strings.
extension FilePath {
/// Creates a string by interpreting the path’s content as UTF-8 on Unix
/// and UTF-16 on Windows.
///
/// This property is equivalent to calling `String(decoding: path)`
public var string: String
}
extension FilePath.Component {
/// Creates a string by interpreting the component’s content as UTF-8 on Unix
/// and UTF-16 on Windows.
///
/// This property is equivalent to calling `String(decoding: component)`.
public var string: String
}
extension FilePath.Root {
/// On Unix, this returns `"/"`.
///
/// On Windows, interprets the root's content as UTF-16.
///
/// This property is equivalent to calling `String(decoding: root)`.
public var string: String
}
Separators are always normalized
FilePath now normalizes directory separators on construction and maintains this invariant across mutations. In the relative portion of the path, FilePath will strip trailing separators and coalesce repeated separators.
FilePath("/a/b/") == "/a/b"
FilePath("a///b") == "a/b"
Windows accepts either forwards slashes (/) or backslashes (\) as directory separators, though the platform's preferred separator is backslash. On Windows, FilePath normalizes forwards slashes to backslashes on construction. Backslashes after a UNC server/share or DOS device path's volume are treated as part of the root.
FilePath("C:/foo/bar/") == #"C:\foo\bar"#
FilePath(#"\\server\share\folder\"#) == #"\\server\share\folder"#
FilePath(#"\\server\share\"#) == #"\\server\share\"#
FilePath(#"\\?\volume\"#) == #"\\?\volume\"#
Wide and narrow characters
Unix paths are represented as contiguous CChars in memory and convert to a String by validating as UTF-8. Windows paths are represented as contiguous UInt16s in memory and are converted to a String by validating as UTF-16. Either platform may have invalid Unicode content, which only affects the conversion to Swift's Unicode-correct String type (i.e. it does not affect the semantics of other FilePath operations).
To avoid polluting the global namespace with more typealiases now and in the future, introduce CTypes to hold typealiases to (often weakly-typed) types imported from C. CModeT was defined as a global typealias in System 0.0.1 and is now nested inside CTypes, alongside CChar.
/// A namespace for C and platform types
public enum CTypes {
#if os(macOS) || os(iOS) || os(watchOS) || os(tvOS)
/// The C `mode_t` type.
public typealias Mode = UInt16
#elseif os(Windows)
/// The C `mode_t` type.
public typealias Mode = Int32
#else
/// The C `mode_t` type.
public typealias Mode = UInt32
#endif
/// The C `char` type
public typealias Char = CChar
}
To aid readability and make it easier to write code agnostic to the platform's character-width, introduce typealiases for the platform's preferred character and Unicode encoding.
extension CTypes {
#if os(Windows)
/// The platform's preferred character type. On Unix, this is an 8-bit C
/// `char` (which may be signed or unsigned, depending on platform). On
/// Windows, this is `UInt16` (a "wide" character).
public typealias PlatformChar = UInt16
#else
/// The platform's preferred character type. On Unix, this is an 8-bit C
/// `char` (which may be signed or unsigned, depending on platform). On
/// Windows, this is `UInt16` (a "wide" character).
public typealias PlatformChar = CTypes.Char
#endif
#if os(Windows)
/// The platform's preferred Unicode encoding. On Unix this is UTF-8 and on
/// Windows it is UTF-16. Native strings may contain invalid Unicode,
/// which will be handled by either error-correction or failing, depending
/// on API.
public typealias PlatformUnicodeEncoding = UTF16
#else
/// The platform's preferred Unicode encoding. On Unix this is UTF-8 and on
/// Windows it is UTF-16. Native strings may contain invalid Unicode,
/// which will be handled by either error-correction or failing, depending
/// on API.
public typealias PlatformUnicodeEncoding = UTF8
#endif
}
String, FilePath, FilePath.Component, and FilePath.Root gain "escape hatch" APIs for C interoperability using these typealiases.
(See the gist for init(platformString:), init?(validatingPlatformString:), and withPlatformString on String, FilePath, Component, and Root.)
Rejected or deferred alternatives
Deferred: Introduce RelativePath and AbsolutePath
See the gist.
Dropped: basename and dirname names and setters
See the gist.
Rejected: "Root" only refers to a separator, does not include Windows volumes
See the gist.
Deferred: Ability to work with paths from another platform
See the gist.
Source and ABI stability impact
API changes are strictly additive.
Separator normalization does not affect the semantics of path operations. It can change how paths are printed, compared, and hashed (this proposal argues these changes are for the better).
Deprecations
A handful of APIs have been deprecated in favor of better-named alternatives.
@available(*, deprecated, renamed: "CTypes.Mode")
public typealias CModeT = CTypes.Mode
extension FilePath {
@available(*, deprecated, renamed: "init(validating:)")
public init?(validatingUTF8 path: FilePath)
@available(*, deprecated, renamed: "init(platformString:)")
public init(cString: UnsafePointer<CChar>)
@available(*, deprecated, renamed: "withPlatformString(_:)")
public func withCString<Result>(
_ body: (UnsafePointer<CChar>) throws -> Result
) rethrows -> Result
}
extension String {
@available(*, deprecated, renamed: "init(validating:)")
public init?(validatingUTF8 path: FilePath)
}
