fix: use / for path separation on all platforms and speed up listing with delimiter

Uses / for path separation for all platforms including ones that have other native os path separators. This ensures client compatibility across server platforms.

Fixes performance issue with ListObjects recursing into all subdirectories, even when using a delimiter. With delimiter, only contents at the top level prefix are returned with all other objects represented below common prefixes. Since the common prefixes don't list all objects separately, there is no need to traverse into the directories below the top level list-objects contents.

Fixes #903

backend/walk.go

@@ -19,7 +19,6 @@ import (
 	"errors"
 	"fmt"
 	"io/fs"
-	"os"
 	"sort"
 	"strings"
 
@@ -76,6 +75,9 @@ func Walk(ctx context.Context, fileSystem fs.FS, prefix, delimiter, marker strin
 			return fs.SkipAll
 		}
 
+		// After this point, return skipflag instead of nil
+		// so we can skip a directory without an early return
+		var skipflag error
 		if d.IsDir() {
 			// If prefix is defined and the directory does not match prefix,
 			// do not descend into the directory because nothing will
@@ -85,51 +87,57 @@ func Walk(ctx context.Context, fileSystem fs.FS, prefix, delimiter, marker strin
 			// building to match. So only skip if path isn't a prefix of prefix
 			// and prefix isn't a prefix of path.
 			if prefix != "" &&
-				!strings.HasPrefix(path+string(os.PathSeparator), prefix) &&
-				!strings.HasPrefix(prefix, path+string(os.PathSeparator)) {
+				!strings.HasPrefix(path+"/", prefix) &&
+				!strings.HasPrefix(prefix, path+"/") {
 				return fs.SkipDir
 			}
 
-			// TODO: can we do better here rather than a second readdir
-			// per directory?
-			ents, err := fs.ReadDir(fileSystem, path)
-			if err != nil {
-				return fmt.Errorf("readdir %q: %w", path, err)
-			}
-
-			path += string(os.PathSeparator)
-
-			if len(ents) == 0 && delimiter == "" {
-				dirobj, err := getObj(path, d)
-				if err == ErrSkipObj {
-					return nil
-				}
+			// Don't recurse into subdirectories which contain the delimiter
+			// after reaching the prefix
+			if delimiter != "" &&
+				strings.HasPrefix(path+"/", prefix) &&
+				strings.Contains(strings.TrimPrefix(path+"/", prefix), delimiter) {
+				skipflag = fs.SkipDir
+			} else {
+				// TODO: can we do better here rather than a second readdir
+				// per directory?
+				ents, err := fs.ReadDir(fileSystem, path)
 				if err != nil {
-					return fmt.Errorf("directory to object %q: %w", path, err)
+					return fmt.Errorf("readdir %q: %w", path, err)
 				}
-				objects = append(objects, dirobj)
+				if len(ents) == 0 && delimiter == "" {
+					dirobj, err := getObj(path+"/", d)
+					if err == ErrSkipObj {
+						return skipflag
+					}
+					if err != nil {
+						return fmt.Errorf("directory to object %q: %w", path, err)
+					}
+					objects = append(objects, dirobj)
 
-				return nil
-			}
+					return skipflag
+				}
 
-			if len(ents) != 0 {
-				return nil
+				if len(ents) != 0 {
+					return skipflag
+				}
 			}
+			path += "/"
 		}
 
 		if !pastMarker {
 			if path == marker {
 				pastMarker = true
-				return nil
+				return skipflag
 			}
 			if path < marker {
-				return nil
+				return skipflag
 			}
 		}
 
 		// If object doesn't have prefix, don't include in results.
 		if prefix != "" && !strings.HasPrefix(path, prefix) {
-			return nil
+			return skipflag
 		}
 
 		if delimiter == "" {
@@ -137,7 +145,7 @@ func Walk(ctx context.Context, fileSystem fs.FS, prefix, delimiter, marker strin
 			// prefix are included in results
 			obj, err := getObj(path, d)
 			if err == ErrSkipObj {
-				return nil
+				return skipflag
 			}
 			if err != nil {
 				return fmt.Errorf("file to object %q: %w", path, err)
@@ -148,7 +156,7 @@ func Walk(ctx context.Context, fileSystem fs.FS, prefix, delimiter, marker strin
 				pastMax = true
 			}
 
-			return nil
+			return skipflag
 		}
 
 		// Since delimiter is specified, we only want results that
@@ -177,7 +185,7 @@ func Walk(ctx context.Context, fileSystem fs.FS, prefix, delimiter, marker strin
 		if !found {
 			obj, err := getObj(path, d)
 			if err == ErrSkipObj {
-				return nil
+				return skipflag
 			}
 			if err != nil {
 				return fmt.Errorf("file to object %q: %w", path, err)
@@ -186,7 +194,7 @@ func Walk(ctx context.Context, fileSystem fs.FS, prefix, delimiter, marker strin
 			if (len(objects) + len(cpmap)) == int(max) {
 				pastMax = true
 			}
-			return nil
+			return skipflag
 		}
 
 		// Common prefixes are a set, so should not have duplicates.
@@ -196,12 +204,12 @@ func Walk(ctx context.Context, fileSystem fs.FS, prefix, delimiter, marker strin
 		cpref := prefix + before + delimiter
 		if cpref == marker {
 			pastMarker = true
-			return nil
+			return skipflag
 		}
 
 		if marker != "" && strings.HasPrefix(marker, cprefNoDelim) {
 			// skip common prefixes that are before the marker
-			return nil
+			return skipflag
 		}
 
 		cpmap[cpref] = struct{}{}
@@ -211,7 +219,7 @@ func Walk(ctx context.Context, fileSystem fs.FS, prefix, delimiter, marker strin
 			return fs.SkipAll
 		}
 
-		return nil
+		return skipflag
 	})
 	if err != nil {
 		return WalkResults{}, err
@@ -315,8 +323,16 @@ func WalkVersions(ctx context.Context, fileSystem fs.FS, prefix, delimiter, keyM
 			// building to match. So only skip if path isn't a prefix of prefix
 			// and prefix isn't a prefix of path.
 			if prefix != "" &&
-				!strings.HasPrefix(path+string(os.PathSeparator), prefix) &&
-				!strings.HasPrefix(prefix, path+string(os.PathSeparator)) {
+				!strings.HasPrefix(path+"/", prefix) &&
+				!strings.HasPrefix(prefix, path+"/") {
+				return fs.SkipDir
+			}
+
+			// Don't recurse into subdirectories when listing with delimiter.
+			if delimiter == "/" &&
+				prefix != path+"/" &&
+				strings.HasPrefix(path+"/", prefix) {
+				cpmap[path+"/"] = struct{}{}
 				return fs.SkipDir
 			}