backend, options: Prefer strings.Cut to SplitN

Also realigned the various "split into host🪣prefix"
implementations.

internal/backend/azure/config.go

@@ -43,14 +43,13 @@ func ParseConfig(s string) (interface{}, error) {
 
 	// use the first entry of the path as the bucket name and the
 	// remainder as prefix
-	data := strings.SplitN(s, ":", 2)
-	if len(data) < 2 {
+	container, prefix, colon := strings.Cut(s, ":")
+	if !colon {
 		return nil, errors.New("azure: invalid format: bucket name or path not found")
 	}
-	container, path := data[0], path.Clean(data[1])
-	path = strings.TrimPrefix(path, "/")
+	prefix = strings.TrimPrefix(path.Clean(prefix), "/")
 	cfg := NewConfig()
 	cfg.Container = container
-	cfg.Prefix = path
+	cfg.Prefix = prefix
 	return cfg, nil
 }

internal/backend/b2/config.go

@@ -37,7 +37,7 @@ var bucketName = regexp.MustCompile("^[a-zA-Z0-9-]+$")
 // https://help.backblaze.com/hc/en-us/articles/217666908-What-you-need-to-know-about-B2-Bucket-names
 func checkBucketName(name string) error {
 	if name == "" {
-		return errors.New("bucket name is empty")
+		return errors.New("bucket name not found")
 	}
 
 	if len(name) < 6 {
@@ -64,30 +64,18 @@ func ParseConfig(s string) (interface{}, error) {
 	}
 
 	s = s[3:]
-	data := strings.SplitN(s, ":", 2)
-	if len(data) == 0 || len(data[0]) == 0 {
-		return nil, errors.New("bucket name not found")
-	}
-
-	cfg := NewConfig()
-	cfg.Bucket = data[0]
-
-	if err := checkBucketName(cfg.Bucket); err != nil {
+	bucket, prefix, _ := strings.Cut(s, ":")
+	if err := checkBucketName(bucket); err != nil {
 		return nil, err
 	}
 
-	if len(data) == 2 {
-		p := data[1]
-		if len(p) > 0 {
-			p = path.Clean(p)
-		}
-
-		if len(p) > 0 && path.IsAbs(p) {
-			p = p[1:]
-		}
-
-		cfg.Prefix = p
+	if len(prefix) > 0 {
+		prefix = strings.TrimPrefix(path.Clean(prefix), "/")
 	}
 
+	cfg := NewConfig()
+	cfg.Bucket = bucket
+	cfg.Prefix = prefix
+
 	return cfg, nil
 }

internal/backend/gs/config.go

@@ -42,17 +42,15 @@ func ParseConfig(s string) (interface{}, error) {
 
 	// use the first entry of the path as the bucket name and the
 	// remainder as prefix
-	data := strings.SplitN(s, ":", 2)
-	if len(data) < 2 {
+	bucket, prefix, colon := strings.Cut(s, ":")
+	if !colon {
 		return nil, errors.New("gs: invalid format: bucket name or path not found")
 	}
 
-	bucket, path := data[0], path.Clean(data[1])
-
-	path = strings.TrimPrefix(path, "/")
+	prefix = strings.TrimPrefix(path.Clean(prefix), "/")
 
 	cfg := NewConfig()
 	cfg.Bucket = bucket
-	cfg.Prefix = path
+	cfg.Prefix = prefix
 	return cfg, nil
 }

internal/backend/location/location.go

@@ -127,6 +127,6 @@ func StripPassword(s string) string {
 }
 
 func extractScheme(s string) string {
-	data := strings.SplitN(s, ":", 2)
-	return data[0]
+	scheme, _, _ := strings.Cut(s, ":")
+	return scheme
 }

internal/backend/s3/config.go

@@ -59,8 +59,8 @@ func ParseConfig(s string) (interface{}, error) {
 			return nil, errors.New("s3: bucket name not found")
 		}
 
-		path := strings.SplitN(url.Path[1:], "/", 2)
-		return createConfig(url.Host, path, url.Scheme == "http")
+		bucket, path, _ := strings.Cut(url.Path[1:], "/")
+		return createConfig(url.Host, bucket, path, url.Scheme == "http")
 	case strings.HasPrefix(s, "s3://"):
 		s = s[5:]
 	case strings.HasPrefix(s, "s3:"):
@@ -70,24 +70,24 @@ func ParseConfig(s string) (interface{}, error) {
 	}
 	// use the first entry of the path as the endpoint and the
 	// remainder as bucket name and prefix
-	path := strings.SplitN(s, "/", 3)
-	return createConfig(path[0], path[1:], false)
+	endpoint, rest, _ := strings.Cut(s, "/")
+	bucket, prefix, _ := strings.Cut(rest, "/")
+	return createConfig(endpoint, bucket, prefix, false)
 }
 
-func createConfig(endpoint string, p []string, useHTTP bool) (interface{}, error) {
-	if len(p) < 1 {
+func createConfig(endpoint, bucket, prefix string, useHTTP bool) (interface{}, error) {
+	if endpoint == "" {
 		return nil, errors.New("s3: invalid format, host/region or bucket name not found")
 	}
 
-	var prefix string
-	if len(p) > 1 && p[1] != "" {
-		prefix = path.Clean(p[1])
+	if prefix != "" {
+		prefix = path.Clean(prefix)
 	}
 
 	cfg := NewConfig()
 	cfg.Endpoint = endpoint
 	cfg.UseHTTP = useHTTP
-	cfg.Bucket = p[0]
+	cfg.Bucket = bucket
 	cfg.Prefix = prefix
 	return cfg, nil
 }

internal/backend/s3/config_test.go

@@ -1,6 +1,9 @@
 package s3
 
-import "testing"
+import (
+	"strings"
+	"testing"
+)
 
 var configTests = []struct {
 	s   string
@@ -111,3 +114,14 @@ func TestParseConfig(t *testing.T) {
 		}
 	}
 }
+
+func TestParseError(t *testing.T) {
+	const prefix = "s3: invalid format,"
+
+	for _, s := range []string{"", "/", "//", "/bucket/prefix"} {
+		_, err := ParseConfig("s3://" + s)
+		if err == nil || !strings.HasPrefix(err.Error(), prefix) {
+			t.Errorf("expected %q, got %q", prefix, err)
+		}
+	}
+}

internal/backend/sftp/config.go

@@ -60,14 +60,13 @@ func ParseConfig(s string) (interface{}, error) {
 		// "user@host:path" in s
 		s = s[5:]
 		// split user@host and path at the colon
-		data := strings.SplitN(s, ":", 2)
-		if len(data) < 2 {
+		var colon bool
+		host, dir, colon = strings.Cut(s, ":")
+		if !colon {
 			return nil, errors.New("sftp: invalid format, hostname or path not found")
 		}
-		host = data[0]
-		dir = data[1]
 		// split user and host at the "@"
-		data = strings.SplitN(host, "@", 3)
+		data := strings.SplitN(host, "@", 3)
 		if len(data) == 3 {
 			user = data[0] + "@" + data[1]
 			host = data[2]

internal/backend/swift/config.go

@@ -51,17 +51,13 @@ func NewConfig() Config {
 
 // ParseConfig parses the string s and extract swift's container name and prefix.
 func ParseConfig(s string) (interface{}, error) {
-	data := strings.SplitN(s, ":", 3)
-	if len(data) != 3 {
+	if !strings.HasPrefix(s, "swift:") {
 		return nil, errors.New("invalid URL, expected: swift:container-name:/[prefix]")
 	}
+	s = strings.TrimPrefix(s, "swift:")
 
-	scheme, container, prefix := data[0], data[1], data[2]
-	if scheme != "swift" {
-		return nil, errors.Errorf("unexpected prefix: %s", data[0])
-	}
-
-	if len(prefix) == 0 {
+	container, prefix, _ := strings.Cut(s, ":")
+	if prefix == "" {
 		return nil, errors.Errorf("prefix is empty")
 	}
 

internal/options/options.go

@@ -92,14 +92,10 @@ func (h helpList) Swap(i, j int) {
 
 // splitKeyValue splits at the first equals (=) sign.
 func splitKeyValue(s string) (key string, value string) {
-	data := strings.SplitN(s, "=", 2)
-	key = strings.ToLower(strings.TrimSpace(data[0]))
-	if len(data) == 1 {
-		// no equals sign is treated as the empty value
-		return key, ""
-	}
-
-	return key, strings.TrimSpace(data[1])
+	key, value, _ = strings.Cut(s, "=")
+	key = strings.ToLower(strings.TrimSpace(key))
+	value = strings.TrimSpace(value)
+	return key, value
 }
 
 // Parse takes a slice of key=value pairs and returns an Options type.