Guard out user/group related code on WASI (#783)

* Guard out user/group related code on WASI

This change guards out the user/group related code on WASI, as WASI does
not have the concept of users or groups.

* Throw explicit unsupported error if trying to set user or group on WASI

Instead of implicitly ignoring user-given values, we should throw
exception to make it clear that those values cannot be set on WASI.

Author: kateinoigakukun

Sources/FoundationEssentials/Data/Data+Writing.swift

@@ -519,6 +519,7 @@ private func writeToFileAux(path inPath: PathOrURL, buffer: UnsafeRawBufferPoint
 
                 cleanupTemporaryDirectory(at: temporaryDirectoryPath)
 
+#if !os(WASI) // WASI does not support fchmod for now
                 if let mode {
                     // Try to change the mode if the path has not changed. Do our best, but don't report an error.
 #if FOUNDATION_FRAMEWORK
@@ -542,6 +543,7 @@ private func writeToFileAux(path inPath: PathOrURL, buffer: UnsafeRawBufferPoint
                     fchmod(fd, mode)
 #endif
                 }
+#endif // os(WASI)
             }
         }
     }

Sources/FoundationEssentials/FileManager/FileManager+Files.swift

@@ -922,13 +922,18 @@ extension _FileManagerImpl {
             let groupID = _readFileAttributePrimitive(attributes[.groupOwnerAccountID], as: UInt.self)
 
             if user != nil || userID != nil || group != nil || groupID != nil {
+                #if os(WASI)
+                // WASI does not have the concept of users or groups
+                throw CocoaError.errorWithFilePath(.featureUnsupported, path)
+                #else
                 // Bias toward userID & groupID - try to prevent round trips to getpwnam if possible.
                 var leaveUnchanged: UInt32 { UInt32(bitPattern: -1) }
                 let rawUserID = userID.flatMap(uid_t.init) ?? user.flatMap(Self._userAccountNameToNumber) ?? leaveUnchanged
                 let rawGroupID = groupID.flatMap(gid_t.init) ?? group.flatMap(Self._groupAccountNameToNumber) ?? leaveUnchanged
                 if chown(fileSystemRepresentation, rawUserID, rawGroupID) != 0 {
                     throw CocoaError.errorWithFilePath(path, errno: errno, reading: false)
                 }
+                #endif
             }
 
             try Self._setCatInfoAttributes(attributes, path: path)

Sources/FoundationEssentials/FileManager/FileManager+Utilities.swift

@@ -271,7 +271,7 @@ extension _FileManagerImpl {
     }
     #endif
 
-#if !os(Windows)
+#if !os(Windows) && !os(WASI)
     static func _userAccountNameToNumber(_ name: String) -> uid_t? {
         name.withCString { ptr in
             getpwnam(ptr)?.pointee.pw_uid

Sources/FoundationEssentials/FileManager/FileOperations.swift

@@ -855,12 +855,14 @@ enum _FileOperations {
         }
         defer { close(dstfd) }
 
+        #if !os(WASI) // WASI doesn't have fchmod for now
         // Set the file permissions using fchmod() instead of when open()ing to avoid umask() issues
         let permissions = fileInfo.st_mode & ~S_IFMT
         guard fchmod(dstfd, permissions) == 0 else {
             try delegate.throwIfNecessary(errno, String(cString: srcPtr), String(cString: dstPtr))
             return
         }
+        #endif
 
         if fileInfo.st_size == 0 {
             // no copying required

Sources/FoundationEssentials/Platform.swift

@@ -113,7 +113,7 @@ private let _cachedUGIDs: (uid_t, gid_t) = {
 }()
 #endif
 
-#if !os(Windows)
+#if !os(Windows) && !os(WASI)
 extension Platform {
     private static var ROOT_USER: UInt32 { 0 }
     static func getUGIDs(allowEffectiveRootUID: Bool = true) -> (uid: UInt32, gid: UInt32) {
@@ -174,7 +174,7 @@ extension Platform {
         // FIXME: bionic implements this as `return 0;` and does not expose the
         // function via headers. We should be able to shim this and use the call
         // if it is available.
-#if !os(Android)
+#if !os(Android) && !os(WASI)
         guard issetugid() == 0 else { return nil }
 #endif
         if let value = getenv(name) {

Sources/FoundationEssentials/String/String+Path.swift

@@ -450,6 +450,7 @@ extension String {
             return envVar.standardizingPath
         }
 
+        #if !os(WASI) // WASI does not have user concept
         // Next, attempt to find the home directory via getpwnam/getpwuid
         var pass: UnsafeMutablePointer<passwd>?
         if let user {
@@ -463,6 +464,7 @@ extension String {
         if let dir = pass?.pointee.pw_dir {
             return String(cString: dir).standardizingPath
         }
+        #endif
 
         // Fallback to HOME for the current user if possible
         if user == nil, let home = getenv("HOME") {