build: modernize Go usage

This commit modernizes Go usage. This was done with:

go run golang.org/x/tools/gopls/internal/analysis/modernize/cmd/modernize@latest -fix -test ./...

Then files needed to be `go fmt`ed and a few comments needed to be
restored.

The modernizations include replacing

- if/else conditional assignment by a call to the built-in min or max functions added in go1.21
- sort.Slice(x, func(i, j int) bool) { return s[i] < s[j] } by a call to slices.Sort(s), added in go1.21
- interface{} by the 'any' type added in go1.18
- append([]T(nil), s...) by slices.Clone(s) or slices.Concat(s), added in go1.21
- loop around an m[k]=v map update by a call to one of the Collect, Copy, Clone, or Insert functions from the maps package, added in go1.21
- []byte(fmt.Sprintf...) by fmt.Appendf(nil, ...), added in go1.19
- append(s[:i], s[i+1]...) by slices.Delete(s, i, i+1), added in go1.21
- a 3-clause for i := 0; i < n; i++ {} loop by for i := range n {}, added in go1.22

backend/cache/cache.go

@@ -1092,7 +1092,7 @@ func (f *Fs) recurse(ctx context.Context, dir string, list *walk.ListRHelper) er
 		return err
 	}
 
-	for i := 0; i < len(entries); i++ {
+	for i := range entries {
 		innerDir, ok := entries[i].(fs.Directory)
 		if ok {
 			err := f.recurse(ctx, innerDir.Remote(), list)
@@ -1428,7 +1428,7 @@ func (f *Fs) cacheReader(u io.Reader, src fs.ObjectInfo, originalRead func(inn i
 	}()
 
 	// wait until both are done
-	for c := 0; c < 2; c++ {
+	for range 2 {
 		<-done
 	}
 }
@@ -1753,7 +1753,7 @@ func (f *Fs) About(ctx context.Context) (*fs.Usage, error) {
 }
 
 // Stats returns stats about the cache storage
-func (f *Fs) Stats() (map[string]map[string]interface{}, error) {
+func (f *Fs) Stats() (map[string]map[string]any, error) {
 	return f.cache.Stats()
 }
 
@@ -1933,7 +1933,7 @@ var commandHelp = []fs.CommandHelp{
 // The result should be capable of being JSON encoded
 // If it is a string or a []string it will be shown to the user
 // otherwise it will be JSON encoded and shown to the user like that
-func (f *Fs) Command(ctx context.Context, name string, arg []string, opt map[string]string) (interface{}, error) {
+func (f *Fs) Command(ctx context.Context, name string, arg []string, opt map[string]string) (any, error) {
 	switch name {
 	case "stats":
 		return f.Stats()

backend/cache/cache_internal_test.go

@@ -360,7 +360,7 @@ func TestInternalWrappedWrittenContentMatches(t *testing.T) {
 	require.NoError(t, err)
 	require.Equal(t, int64(len(checkSample)), o.Size())
 
-	for i := 0; i < len(checkSample); i++ {
+	for i := range checkSample {
 		require.Equal(t, testData[i], checkSample[i])
 	}
 }
@@ -387,7 +387,7 @@ func TestInternalLargeWrittenContentMatches(t *testing.T) {
 
 	readData, err := runInstance.readDataFromRemote(t, rootFs, "data.bin", 0, testSize, false)
 	require.NoError(t, err)
-	for i := 0; i < len(readData); i++ {
+	for i := range readData {
 		require.Equalf(t, testData[i], readData[i], "at byte %v", i)
 	}
 }
@@ -688,7 +688,7 @@ func TestInternalMaxChunkSizeRespected(t *testing.T) {
 	co, ok := o.(*cache.Object)
 	require.True(t, ok)
 
-	for i := 0; i < 4; i++ { // read first 4
+	for i := range 4 { // read first 4
 		_ = runInstance.readDataFromObj(t, co, chunkSize*int64(i), chunkSize*int64(i+1), false)
 	}
 	cfs.CleanUpCache(true)
@@ -971,7 +971,7 @@ func (r *run) randomReader(t *testing.T, size int64) io.ReadCloser {
 	f, err := os.CreateTemp("", "rclonecache-tempfile")
 	require.NoError(t, err)
 
-	for i := 0; i < int(cnt); i++ {
+	for range int(cnt) {
 		data := randStringBytes(int(chunk))
 		_, _ = f.Write(data)
 	}
@@ -1085,9 +1085,9 @@ func (r *run) rm(t *testing.T, f fs.Fs, remote string) error {
 	return err
 }
 
-func (r *run) list(t *testing.T, f fs.Fs, remote string) ([]interface{}, error) {
+func (r *run) list(t *testing.T, f fs.Fs, remote string) ([]any, error) {
 	var err error
-	var l []interface{}
+	var l []any
 	var list fs.DirEntries
 	list, err = f.List(context.Background(), remote)
 	for _, ll := range list {
@@ -1215,7 +1215,7 @@ func (r *run) listenForBackgroundUpload(t *testing.T, f fs.Fs, remote string) ch
 		var err error
 		var state cache.BackgroundUploadState
 
-		for i := 0; i < 2; i++ {
+		for range 2 {
 			select {
 			case state = <-buCh:
 				// continue
@@ -1293,7 +1293,7 @@ func (r *run) completeAllBackgroundUploads(t *testing.T, f fs.Fs, lastRemote str
 
 func (r *run) retryBlock(block func() error, maxRetries int, rate time.Duration) error {
 	var err error
-	for i := 0; i < maxRetries; i++ {
+	for range maxRetries {
 		err = block()
 		if err == nil {
 			return nil

backend/cache/cache_upload_test.go

@@ -162,7 +162,7 @@ func TestInternalUploadQueueMoreFiles(t *testing.T) {
 	randInstance := rand.New(rand.NewSource(time.Now().Unix()))
 
 	lastFile := ""
-	for i := 0; i < totalFiles; i++ {
+	for i := range totalFiles {
 		size := int64(randInstance.Intn(maxSize-minSize) + minSize)
 		testReader := runInstance.randomReader(t, size)
 		remote := "test/" + strconv.Itoa(i) + ".bin"

backend/cache/handle.go

@@ -182,7 +182,7 @@ func (r *Handle) queueOffset(offset int64) {
 			}
 		}
 
-		for i := 0; i < r.workers; i++ {
+		for i := range r.workers {
 			o := r.preloadOffset + int64(r.cacheFs().opt.ChunkSize)*int64(i)
 			if o < 0 || o >= r.cachedObject.Size() {
 				continue
@@ -222,7 +222,7 @@ func (r *Handle) getChunk(chunkStart int64) ([]byte, error) {
 	if !found {
 		// we're gonna give the workers a chance to pickup the chunk
 		// and retry a couple of times
-		for i := 0; i < r.cacheFs().opt.ReadRetries*8; i++ {
+		for i := range r.cacheFs().opt.ReadRetries * 8 {
 			data, err = r.storage().GetChunk(r.cachedObject, chunkStart)
 			if err == nil {
 				found = true

backend/cache/plex.go

@@ -209,7 +209,7 @@ func (p *plexConnector) authenticate() error {
 	if err != nil {
 		return err
 	}
-	var data map[string]interface{}
+	var data map[string]any
 	err = json.NewDecoder(resp.Body).Decode(&data)
 	if err != nil {
 		return fmt.Errorf("failed to obtain token: %w", err)
@@ -273,11 +273,11 @@ func (p *plexConnector) isPlaying(co *Object) bool {
 }
 
 // adapted from: https://stackoverflow.com/a/28878037 (credit)
-func get(m interface{}, path ...interface{}) (interface{}, bool) {
+func get(m any, path ...any) (any, bool) {
 	for _, p := range path {
 		switch idx := p.(type) {
 		case string:
-			if mm, ok := m.(map[string]interface{}); ok {
+			if mm, ok := m.(map[string]any); ok {
 				if val, found := mm[idx]; found {
 					m = val
 					continue
@@ -285,7 +285,7 @@ func get(m interface{}, path ...interface{}) (interface{}, bool) {
 			}
 			return nil, false
 		case int:
-			if mm, ok := m.([]interface{}); ok {
+			if mm, ok := m.([]any); ok {
 				if len(mm) > idx {
 					m = mm[idx]
 					continue

backend/cache/storage_persistent.go

@@ -607,16 +607,16 @@ func (b *Persistent) CleanChunksBySize(maxSize int64) {
 }
 
 // Stats returns a go map with the stats key values
-func (b *Persistent) Stats() (map[string]map[string]interface{}, error) {
-	r := make(map[string]map[string]interface{})
-	r["data"] = make(map[string]interface{})
+func (b *Persistent) Stats() (map[string]map[string]any, error) {
+	r := make(map[string]map[string]any)
+	r["data"] = make(map[string]any)
 	r["data"]["oldest-ts"] = time.Now()
 	r["data"]["oldest-file"] = ""
 	r["data"]["newest-ts"] = time.Now()
 	r["data"]["newest-file"] = ""
 	r["data"]["total-chunks"] = 0
 	r["data"]["total-size"] = int64(0)
-	r["files"] = make(map[string]interface{})
+	r["files"] = make(map[string]any)
 	r["files"]["oldest-ts"] = time.Now()
 	r["files"]["oldest-name"] = ""
 	r["files"]["newest-ts"] = time.Now()