syscall: disable O_DIRECTORY on Windows for js/wasm

O_DIRECTORY is not available on all platforms, as described at

https://nodejs.org/docs/latest/api/fs.html#file-open-constants .

On Windows, only O_APPEND, O_CREAT, O_EXCL, O_RDONLY, O_RDWR,
O_TRUNC, O_WRONLY, and UV_FS_O_FILEMAP are available.

Fixes #71758

Change-Id: Iacc890ba9a30dcd75eb746ec324fa0c3e368048e
GitHub-Last-Rev: a0160e8
GitHub-Pull-Request: #71770
Reviewed-on: https://go-review.googlesource.com/c/go/+/650015
Reviewed-by: Dmitri Shuralyov <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>
Reviewed-by: Michael Knyszek <[email protected]>
Auto-Submit: Dmitri Shuralyov <[email protected]>
TryBot-Bypass: Dmitri Shuralyov <[email protected]>

Author: Zxilly

src/syscall/fs_js.go

@@ -23,15 +23,26 @@ var constants = jsFS.Get("constants")
 var uint8Array = js.Global().Get("Uint8Array")
 
 var (
-	nodeWRONLY    = constants.Get("O_WRONLY").Int()
-	nodeRDWR      = constants.Get("O_RDWR").Int()
-	nodeCREATE    = constants.Get("O_CREAT").Int()
-	nodeTRUNC     = constants.Get("O_TRUNC").Int()
-	nodeAPPEND    = constants.Get("O_APPEND").Int()
-	nodeEXCL      = constants.Get("O_EXCL").Int()
-	nodeDIRECTORY = constants.Get("O_DIRECTORY").Int()
+	nodeWRONLY = constants.Get("O_WRONLY").Int()
+	nodeRDWR   = constants.Get("O_RDWR").Int()
+	nodeCREATE = constants.Get("O_CREAT").Int()
+	nodeTRUNC  = constants.Get("O_TRUNC").Int()
+	nodeAPPEND = constants.Get("O_APPEND").Int()
+	nodeEXCL   = constants.Get("O_EXCL").Int()
+
+	// NodeJS on Windows does not support O_DIRECTORY, so we default
+	// to -1 and assign it in init if available.
+	// See https://nodejs.org/docs/latest/api/fs.html#file-open-constants.
+	nodeDIRECTORY = -1
 )
 
+func init() {
+	oDir := constants.Get("O_DIRECTORY")
+	if !oDir.IsUndefined() {
+		nodeDIRECTORY = oDir.Int()
+	}
+}
+
 type jsFile struct {
 	path    string
 	entries []string
@@ -85,7 +96,11 @@ func Open(path string, openmode int, perm uint32) (int, error) {
 		return 0, errors.New("syscall.Open: O_SYNC is not supported by js/wasm")
 	}
 	if openmode&O_DIRECTORY != 0 {
-		flags |= nodeDIRECTORY
+		if nodeDIRECTORY != -1 {
+			flags |= nodeDIRECTORY
+		} else {
+			return 0, errors.New("syscall.Open: O_DIRECTORY is not supported on Windows")
+		}
 	}
 
 	jsFD, err := fsCall("open", path, flags, perm)