Disable pipes code on WASI.

Package.swift

@@ -133,6 +133,7 @@ extension Array where Element == PackageDescription.SwiftSetting {
       .define("SWT_NO_EXIT_TESTS", .when(platforms: [.iOS, .watchOS, .tvOS, .visionOS, .wasi, .android])),
       .define("SWT_NO_SNAPSHOT_TYPES", .when(platforms: [.linux, .windows, .wasi])),
       .define("SWT_NO_DYNAMIC_LINKING", .when(platforms: [.wasi])),
+      .define("SWT_NO_PIPES", .when(platforms: [.wasi])),
     ]
   }
 

Sources/Testing/ABI/EntryPoints/EntryPoint.swift

@@ -660,12 +660,14 @@ extension Event.ConsoleOutputRecorder.Options {
       return true
     }
 
+#if !SWT_NO_PIPES
     // If the file handle is a pipe, assume the other end is using it to forward
     // output from this process to its own stderr file. This is how `swift test`
     // invokes the testing library, for example.
     if fileHandle.isPipe {
       return true
     }
+#endif
 
     return false
   }

Sources/Testing/ExitTests/ExitTest.swift

@@ -11,6 +11,10 @@
 private import _TestingInternals
 
 #if !SWT_NO_EXIT_TESTS
+#if SWT_NO_PIPES
+#error("Support for exit tests requires support for (anonymous) pipes.")
+#endif
+
 /// A type describing an exit test.
 ///
 /// Instances of this type describe an exit test defined by the test author and

Sources/Testing/Support/FileHandle.swift

@@ -425,6 +425,7 @@ extension FileHandle {
   }
 }
 
+#if !SWT_NO_PIPES
 // MARK: - Pipes
 
 extension FileHandle {
@@ -495,6 +496,7 @@ extension FileHandle {
     }
   }
 }
+#endif
 
 // MARK: - Attributes
 
@@ -525,9 +527,10 @@ extension FileHandle {
 #endif
   }
 
+#if !SWT_NO_PIPES
   /// Is this file handle a pipe or FIFO?
   var isPipe: Bool {
-#if SWT_TARGET_OS_APPLE || os(Linux) || os(FreeBSD) || os(Android) || os(WASI)
+#if SWT_TARGET_OS_APPLE || os(Linux) || os(FreeBSD) || os(Android)
     withUnsafePOSIXFileDescriptor { fd in
       guard let fd else {
         return false
@@ -547,6 +550,7 @@ extension FileHandle {
     return false
 #endif
   }
+#endif
 }
 
 // MARK: - General path utilities

Tests/TestingTests/Support/FileHandleTests.swift

@@ -149,14 +149,16 @@ struct FileHandleTests {
   }
 #endif
 
+#if !SWT_NO_PIPES
   @Test("Can recognize opened pipe")
   func isPipe() throws {
     let pipe = try FileHandle.Pipe()
     #expect(pipe.readEnd.isPipe as Bool)
     #expect(pipe.writeEnd.isPipe as Bool)
   }
+#endif
 
-#if SWT_TARGET_OS_APPLE
+#if SWT_TARGET_OS_APPLE && !SWT_NO_PIPES
   @Test("Can close ends of a pipe")
   func closeEndsOfPipe() async throws {
     try await confirmation("File handle closed", expectedCount: 2) { closed in
@@ -175,7 +177,9 @@ struct FileHandleTests {
   func devNull() throws {
     let fileHandle = try FileHandle.null(mode: "wb")
     #expect(!Bool(fileHandle.isTTY))
+#if !SWT_NO_PIPES
     #expect(!Bool(fileHandle.isPipe))
+#endif
   }
 
 #if !os(Windows)
@@ -186,7 +190,9 @@ struct FileHandleTests {
     let file = try #require(fmemopen(nil, 1, "wb+"))
     let fileHandle = FileHandle(unsafeCFILEHandle: file, closeWhenDone: true)
     #expect(!Bool(fileHandle.isTTY))
+#if !SWT_NO_PIPES
     #expect(!Bool(fileHandle.isPipe))
+#endif
   }
 #endif
 }

cmake/modules/shared/CompilerSettings.cmake

@@ -27,3 +27,7 @@ endif()
 if(NOT APPLE)
   add_compile_definitions("SWT_NO_SNAPSHOT_TYPES")
 endif()
+if(WASI)
+  add_compile_definitions("SWT_NO_DYNAMIC_LINKING")
+  add_compile_definitions("SWT_NO_PIPES")
+endif()