vfs: re-implement CacheMode with fs.Enum

This almost 100% backwards compatible. The only difference being that
in the rc options/get output CacheMode will be output as strings
instead of integers. This is a lot more convenient for the user. They
still accept integer inputs though so the fallout from this should be
minimal.

vfs/vfscommon/cachemode.go

@@ -2,13 +2,22 @@
 package vfscommon
 
 import (
-	"fmt"
-
 	"github.com/rclone/rclone/fs"
 )
 
+type cacheModeChoices struct{}
+
+func (cacheModeChoices) Choices() []string {
+	return []string{
+		CacheModeOff:     "off",
+		CacheModeMinimal: "minimal",
+		CacheModeWrites:  "writes",
+		CacheModeFull:    "full",
+	}
+}
+
 // CacheMode controls the functionality of the cache
-type CacheMode byte
+type CacheMode = fs.Enum[cacheModeChoices]
 
 // CacheMode options
 const (
@@ -18,44 +27,7 @@ const (
 	CacheModeFull                     // cache all files opened in any mode
 )
 
-var cacheModeToString = []string{
-	CacheModeOff:     "off",
-	CacheModeMinimal: "minimal",
-	CacheModeWrites:  "writes",
-	CacheModeFull:    "full",
-}
-
-// String turns a CacheMode into a string
-func (l CacheMode) String() string {
-	if l >= CacheMode(len(cacheModeToString)) {
-		return fmt.Sprintf("CacheMode(%d)", l)
-	}
-	return cacheModeToString[l]
-}
-
-// Set a CacheMode
-func (l *CacheMode) Set(s string) error {
-	for n, name := range cacheModeToString {
-		if s != "" && name == s {
-			*l = CacheMode(n)
-			return nil
-		}
-	}
-	return fmt.Errorf("unknown cache mode level %q", s)
-}
-
 // Type of the value
-func (l *CacheMode) Type() string {
+func (cacheModeChoices) Type() string {
 	return "CacheMode"
 }
-
-// UnmarshalJSON makes sure the value can be parsed as a string or integer in JSON
-func (l *CacheMode) UnmarshalJSON(in []byte) error {
-	return fs.UnmarshalJSONFlag(in, l, func(i int64) error {
-		if i < 0 || i >= int64(len(cacheModeToString)) {
-			return fmt.Errorf("unknown cache mode level %d", i)
-		}
-		*l = CacheMode(i)
-		return nil
-	})
-}

vfs/vfscommon/cachemode_test.go

@@ -18,7 +18,7 @@ var _ json.Unmarshaler = (*CacheMode)(nil)
 func TestCacheModeString(t *testing.T) {
 	assert.Equal(t, "off", CacheModeOff.String())
 	assert.Equal(t, "full", CacheModeFull.String())
-	assert.Equal(t, "CacheMode(17)", CacheMode(17).String())
+	assert.Equal(t, "Unknown(17)", CacheMode(17).String())
 }
 
 func TestCacheModeSet(t *testing.T) {