fix: Add quirks mode for FTP compatibility, where read permission is required even if O_WRONLY is set

cmd/stfs/cmd/serve_ftp.go

@@ -193,6 +193,7 @@ var serveFTPCmd = &cobra.Command{
 				)
 			},
 			viper.GetBool(readOnlyFlag),
+			true, // FTP requires read permission even if `O_WRONLY` is set if cache is enabled
 
 			func(hdr *config.Header) {
 				jsonLogger.Trace("Header transform", hdr)

cmd/stfs/cmd/serve_http.go

@@ -128,9 +128,10 @@ var serveHTTPCmd = &cobra.Command{
 				Metadata: metadataPersister,
 			},
 
-			"",   // We never write
-			nil,  // We never write
-			true, // We never write
+			"",    // We never write
+			nil,   // We never write
+			true,  // We never write
+			false, // We never write
 
 			func(hdr *config.Header) {
 				jsonLogger.Trace("Header transform", hdr)

examples/full/main.go

@@ -172,6 +172,7 @@ func createFs(
 			)
 		},
 		readOnly,
+		false,
 
 		func(hdr *config.Header) {
 			jsonLogger.Trace("Header transform", hdr)

examples/simple/main.go

@@ -99,6 +99,7 @@ func main() {
 			)
 		},
 		false,
+		false,
 
 		func(hdr *config.Header) {
 			l.Trace("Header transform", hdr)

pkg/fs/filesystem.go

@@ -34,6 +34,7 @@ type STFS struct {
 	compressionLevel string
 	getFileBuffer    func() (cache.WriteCache, func() error, error)
 	readOnly         bool
+	writeImpliesRead bool
 
 	ioLock sync.Mutex
 
@@ -50,6 +51,7 @@ func NewSTFS(
 	compressionLevel string,
 	getFileBuffer func() (cache.WriteCache, func() error, error),
 	readOnly bool,
+	writeImpliesRead bool,
 
 	onHeader func(hdr *config.Header),
 	log logging.StructuredLogger,
@@ -63,6 +65,7 @@ func NewSTFS(
 		compressionLevel: compressionLevel,
 		getFileBuffer:    getFileBuffer,
 		readOnly:         readOnly,
+		writeImpliesRead: writeImpliesRead,
 
 		onHeader: onHeader,
 		log:      log,
@@ -373,6 +376,10 @@ func (f *STFS) OpenFile(name string, flag int, perm os.FileMode) (afero.File, er
 		if (flag & O_ACCMODE) == os.O_RDONLY {
 			flags.Read = true
 		} else if (flag & O_ACCMODE) == os.O_WRONLY {
+			if f.writeImpliesRead {
+				flags.Read = true
+			}
+
 			flags.Write = true
 		} else if (flag & O_ACCMODE) == os.O_RDWR {
 			flags.Read = true

pkg/fs/filesystem_test.go

@@ -407,6 +407,7 @@ func createSTFS(
 			)
 		},
 		readOnly,
+		false,
 
 		func(hdr *config.Header) {
 			jsonLogger.Trace("Header transform", hdr)