Replace strings.Index usages with strings.Cut (#4930)

caddyconfig/load.go

@@ -189,12 +189,11 @@ func adaptByContentType(contentType string, body []byte) ([]byte, []Warning, err
 	}
 
 	// adapter name should be suffix of MIME type
-	slashIdx := strings.Index(ct, "/")
-	if slashIdx < 0 {
+	_, adapterName, slashFound := strings.Cut(ct, "/")
+	if !slashFound {
 		return nil, nil, fmt.Errorf("malformed Content-Type")
 	}
 
-	adapterName := ct[slashIdx+1:]
 	cfgAdapter := GetAdapter(adapterName)
 	if cfgAdapter == nil {
 		return nil, nil, fmt.Errorf("unrecognized config adapter '%s'", adapterName)

cmd/main.go

@@ -387,11 +387,11 @@ func parseEnvFile(envInput io.Reader) (map[string]string, error) {
 		}
 
 		// split line into key and value
-		fields := strings.SplitN(line, "=", 2)
-		if len(fields) != 2 {
+		before, after, isCut := strings.Cut(line, "=")
+		if !isCut {
 			return nil, fmt.Errorf("can't parse line %d; line should be in KEY=VALUE format", lineNumber)
 		}
-		key, val := fields[0], fields[1]
+		key, val := before, after
 
 		// sometimes keys are prefixed by "export " so file can be sourced in bash; ignore it here
 		key = strings.TrimPrefix(key, "export ")

listeners.go

@@ -468,15 +468,15 @@ func ParseNetworkAddress(addr string) (NetworkAddress, error) {
 	}
 	var start, end uint64
 	if port != "" {
-		ports := strings.SplitN(port, "-", 2)
-		if len(ports) == 1 {
-			ports = append(ports, ports[0])
+		before, after, found := strings.Cut(port, "-")
+		if !found {
+			after = before
 		}
-		start, err = strconv.ParseUint(ports[0], 10, 16)
+		start, err = strconv.ParseUint(before, 10, 16)
 		if err != nil {
 			return NetworkAddress{}, fmt.Errorf("invalid start port: %v", err)
 		}
-		end, err = strconv.ParseUint(ports[1], 10, 16)
+		end, err = strconv.ParseUint(after, 10, 16)
 		if err != nil {
 			return NetworkAddress{}, fmt.Errorf("invalid end port: %v", err)
 		}
@@ -498,9 +498,10 @@ func ParseNetworkAddress(addr string) (NetworkAddress, error) {
 // SplitNetworkAddress splits a into its network, host, and port components.
 // Note that port may be a port range (:X-Y), or omitted for unix sockets.
 func SplitNetworkAddress(a string) (network, host, port string, err error) {
-	if idx := strings.Index(a, "/"); idx >= 0 {
-		network = strings.ToLower(strings.TrimSpace(a[:idx]))
-		a = a[idx+1:]
+	beforeSlash, afterSlash, slashFound := strings.Cut(a, "/")
+	if slashFound {
+		network = strings.ToLower(strings.TrimSpace(beforeSlash))
+		a = afterSlash
 	}
 	if isUnixNetwork(network) {
 		host = a

modules.go

@@ -324,11 +324,11 @@ func ParseStructTag(tag string) (map[string]string, error) {
 		if pair == "" {
 			continue
 		}
-		parts := strings.SplitN(pair, "=", 2)
-		if len(parts) != 2 {
+		before, after, isCut := strings.Cut(pair, "=")
+		if !isCut {
 			return nil, fmt.Errorf("missing key in '%s' (pair %d)", pair, i)
 		}
-		results[parts[0]] = parts[1]
+		results[before] = after
 	}
 	return results, nil
 }

modules/caddyhttp/matchers.go

@@ -610,11 +610,11 @@ func (m *MatchQuery) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
 			if query == "" {
 				continue
 			}
-			parts := strings.SplitN(query, "=", 2)
-			if len(parts) != 2 {
+			before, after, found := strings.Cut(query, "=")
+			if !found {
 				return d.Errf("malformed query matcher token: %s; must be in param=val format", d.Val())
 			}
-			url.Values(*m).Add(parts[0], parts[1])
+			url.Values(*m).Add(before, after)
 		}
 		if d.NextBlock(0) {
 			return d.Err("malformed query matcher: blocks are not supported")

modules/caddyhttp/push/link.go

@@ -52,17 +52,16 @@ func parseLinkHeader(header string) []linkResource {
 		l.uri = strings.TrimSpace(link[li+1 : ri])
 
 		for _, param := range strings.Split(strings.TrimSpace(link[ri+1:]), semicolon) {
-			parts := strings.SplitN(strings.TrimSpace(param), equal, 2)
-			key := strings.TrimSpace(parts[0])
+			before, after, isCut := strings.Cut(strings.TrimSpace(param), equal)
+			key := strings.TrimSpace(before)
 			if key == "" {
 				continue
 			}
-			if len(parts) == 1 {
+			if isCut {
+				l.params[key] = strings.TrimSpace(after)
+			} else {
 				l.params[key] = key
 			}
-			if len(parts) == 2 {
-				l.params[key] = strings.TrimSpace(parts[1])
-			}
 		}
 
 		resources = append(resources, l)

modules/caddyhttp/reverseproxy/addresses.go

@@ -80,9 +80,9 @@ func parseUpstreamDialAddress(upstreamAddr string) (string, string, error) {
 		scheme, host, port = toURL.Scheme, toURL.Hostname(), toURL.Port()
 	} else {
 		// extract network manually, since caddy.ParseNetworkAddress() will always add one
-		if idx := strings.Index(upstreamAddr, "/"); idx >= 0 {
-			network = strings.ToLower(strings.TrimSpace(upstreamAddr[:idx]))
-			upstreamAddr = upstreamAddr[idx+1:]
+		if beforeSlash, afterSlash, slashFound := strings.Cut(upstreamAddr, "/"); slashFound {
+			network = strings.ToLower(strings.TrimSpace(beforeSlash))
+			upstreamAddr = afterSlash
 		}
 		var err error
 		host, port, err = net.SplitHostPort(upstreamAddr)

modules/caddyhttp/reverseproxy/fastcgi/client.go

@@ -424,13 +424,13 @@ func (c *FCGIClient) Request(p map[string]string, req io.Reader) (resp *http.Res
 	resp.Header = http.Header(mimeHeader)
 
 	if resp.Header.Get("Status") != "" {
-		statusParts := strings.SplitN(resp.Header.Get("Status"), " ", 2)
-		resp.StatusCode, err = strconv.Atoi(statusParts[0])
+		statusNumber, statusInfo, statusIsCut := strings.Cut(resp.Header.Get("Status"), " ")
+		resp.StatusCode, err = strconv.Atoi(statusNumber)
 		if err != nil {
 			return
 		}
-		if len(statusParts) > 1 {
-			resp.Status = statusParts[1]
+		if statusIsCut {
+			resp.Status = statusInfo
 		}
 
 	} else {