rc: Add GetFsNamedFileOK to get an fs which could also be a file

fs/rc/cache.go

@@ -5,27 +5,71 @@ package rc
 import (
 	"context"
 	"errors"
+	"fmt"
 
 	"github.com/rclone/rclone/fs"
 	"github.com/rclone/rclone/fs/cache"
 	"github.com/rclone/rclone/fs/config/configmap"
+	"github.com/rclone/rclone/fs/filter"
+	"github.com/rclone/rclone/fs/fspath"
 )
 
-// GetFsNamed gets an fs.Fs named fsName either from the cache or creates it afresh
-func GetFsNamed(ctx context.Context, in Params, fsName string) (f fs.Fs, err error) {
-	fsString, err := in.GetString(fsName)
+// getFsName gets an fs name from fsName either from the cache or direct
+func getFsName(in Params, fsName string) (fsString string, err error) {
+	fsString, err = in.GetString(fsName)
 	if err != nil {
 		if !IsErrParamInvalid(err) {
-			return nil, err
+			return fsString, err
 		}
 		fsString, err = getConfigMap(in, fsName)
 		if err != nil {
-			return nil, err
+			return fsString, err
 		}
 	}
+	return fsString, err
+}
+
+// GetFsNamed gets an fs.Fs named fsName either from the cache or creates it afresh
+func GetFsNamed(ctx context.Context, in Params, fsName string) (f fs.Fs, err error) {
+	fsString, err := getFsName(in, fsName)
+	if err != nil {
+		return nil, err
+	}
 	return cache.Get(ctx, fsString)
 }
 
+// GetFsNamedFileOK gets an fs.Fs named fsName either from the cache or creates it afresh
+//
+// If the fs.Fs points to a single file then it returns a new ctx with
+// filters applied to make the listings return only that file.
+func GetFsNamedFileOK(ctx context.Context, in Params, fsName string) (newCtx context.Context, f fs.Fs, err error) {
+	fsString, err := getFsName(in, fsName)
+	if err != nil {
+		return ctx, nil, err
+	}
+	f, err = cache.Get(ctx, fsString)
+	if err == nil {
+		return ctx, f, nil
+	} else if !errors.Is(err, fs.ErrorIsFile) {
+		return ctx, nil, err
+	}
+	// f points to the directory above the file so find the remote name
+	_, fileName, err := fspath.Split(fsString)
+	if err != nil {
+		return ctx, f, err
+	}
+	ctx, fi := filter.AddConfig(ctx)
+	if !fi.InActive() {
+		return ctx, f, fmt.Errorf("can't limit to single files when using filters: %q", fileName)
+	}
+	// Limit transfers to this file
+	err = fi.AddFile(fileName)
+	if err != nil {
+		return ctx, f, fmt.Errorf("failed to limit to single file: %w", err)
+	}
+	return ctx, f, nil
+}
+
 // getConfigMap gets the config as a map from in and converts it to a
 // config string
 //

fs/rc/cache_test.go

@@ -5,18 +5,26 @@ import (
 	"fmt"
 	"testing"
 
+	"github.com/rclone/rclone/fs"
 	"github.com/rclone/rclone/fs/cache"
+	"github.com/rclone/rclone/fs/filter"
 	"github.com/rclone/rclone/fstest/mockfs"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
 func mockNewFs(t *testing.T) func() {
-	f, err := mockfs.NewFs(context.Background(), "mock", "mock", nil)
+	ctx := context.Background()
+	f, err := mockfs.NewFs(ctx, "/", "", nil)
 	require.NoError(t, err)
 	cache.Put("/", f)
+	f, err = mockfs.NewFs(ctx, "mock", "/", nil)
+	require.NoError(t, err)
 	cache.Put("mock:/", f)
 	cache.Put(":mock:/", f)
+	f, err = mockfs.NewFs(ctx, "mock", "dir/file.txt", nil)
+	require.NoError(t, err)
+	cache.PutErr("mock:dir/file.txt", f, fs.ErrorIsFile)
 	return func() {
 		cache.Clear()
 	}
@@ -64,6 +72,40 @@ func TestGetFsNamedStruct(t *testing.T) {
 	assert.NotNil(t, f)
 }
 
+func TestGetFsNamedFileOK(t *testing.T) {
+	defer mockNewFs(t)()
+	ctx := context.Background()
+
+	in := Params{
+		"potato": "/",
+	}
+	newCtx, f, err := GetFsNamedFileOK(ctx, in, "potato")
+	require.NoError(t, err)
+	assert.NotNil(t, f)
+	assert.Equal(t, ctx, newCtx)
+
+	in = Params{
+		"sausage": "/",
+	}
+	newCtx, f, err = GetFsNamedFileOK(ctx, in, "potato")
+	require.Error(t, err)
+	assert.Nil(t, f)
+	assert.Equal(t, ctx, newCtx)
+
+	in = Params{
+		"potato": "mock:dir/file.txt",
+	}
+	newCtx, f, err = GetFsNamedFileOK(ctx, in, "potato")
+	assert.Nil(t, err)
+	assert.NotNil(t, f)
+	assert.NotEqual(t, ctx, newCtx)
+
+	fi := filter.GetConfig(newCtx)
+	assert.False(t, fi.InActive())
+	assert.True(t, fi.IncludeRemote("file.txt"))
+	assert.False(t, fi.IncludeRemote("other.txt"))
+}
+
 func TestGetConfigMap(t *testing.T) {
 	for _, test := range []struct {
 		in           Params