Add os(WASI) platform condition to FileHandle methods

Most of the file handle methods should be the same on WASI as on Linux.
The only exception is file locking, which is not yet supported on WASI.

Author: kateinoigakukun

Sources/Testing/Support/FileHandle.swift

@@ -141,7 +141,7 @@ struct FileHandle: ~Copyable, Sendable {
   /// descriptor, `nil` is passed to `body`.
   borrowing func withUnsafePOSIXFileDescriptor<R>(_ body: (CInt?) throws -> R) rethrows -> R {
     try withUnsafeCFILEHandle { handle in
-#if SWT_TARGET_OS_APPLE || os(Linux)
+#if SWT_TARGET_OS_APPLE || os(Linux) || os(WASI)
       let fd = fileno(handle)
 #elseif os(Windows)
       let fd = _fileno(handle)
@@ -210,6 +210,8 @@ struct FileHandle: ~Copyable, Sendable {
       defer {
         _unlock_file(handle)
       }
+#elseif os(WASI)
+      // No file locking on WASI yet.
 #else
 #warning("Platform-specific implementation missing: cannot lock a file handle")
 #endif
@@ -233,7 +235,7 @@ extension FileHandle {
     // If possible, reserve enough space in the resulting buffer to contain
     // the contents of the file being read.
     var size: Int?
-#if SWT_TARGET_OS_APPLE || os(Linux)
+#if SWT_TARGET_OS_APPLE || os(Linux) || os(WASI)
     withUnsafePOSIXFileDescriptor { fd in
       var s = stat()
       if let fd, 0 == fstat(fd, &s) {
@@ -371,7 +373,7 @@ extension FileHandle {
 extension FileHandle {
   /// Is this file handle a TTY or PTY?
   var isTTY: Bool {
-#if SWT_TARGET_OS_APPLE || os(Linux)
+#if SWT_TARGET_OS_APPLE || os(Linux) || os(WASI)
     // If stderr is a TTY and TERM is set, that's good enough for us.
     withUnsafePOSIXFileDescriptor { fd in
       if let fd, 0 != isatty(fd), let term = Environment.variable(named: "TERM"), !term.isEmpty {
@@ -397,7 +399,7 @@ extension FileHandle {
 
   /// Is this file handle a pipe or FIFO?
   var isPipe: Bool {
-#if SWT_TARGET_OS_APPLE || os(Linux)
+#if SWT_TARGET_OS_APPLE || os(Linux) || os(WASI)
     withUnsafePOSIXFileDescriptor { fd in
       guard let fd else {
         return false