fileserver: New --precompressed flag (#5880)

exposes the file_server precompressed functionality to be used with the
file-server command

Co-authored-by: Matt Holt <mholt@users.noreply.github.com>

modules/caddyhttp/fileserver/command.go

@@ -16,6 +16,7 @@ package fileserver
 
 import (
 	"encoding/json"
+	"fmt"
 	"io"
 	"log"
 	"os"
@@ -31,13 +32,14 @@ import (
 	"github.com/caddyserver/caddy/v2"
 	"github.com/caddyserver/caddy/v2/caddyconfig"
 	"github.com/caddyserver/caddy/v2/modules/caddyhttp"
+	"github.com/caddyserver/caddy/v2/modules/caddyhttp/encode"
 	caddytpl "github.com/caddyserver/caddy/v2/modules/caddyhttp/templates"
 )
 
 func init() {
 	caddycmd.RegisterCommand(caddycmd.Command{
 		Name:  "file-server",
-		Usage: "[--domain <example.com>] [--root <path>] [--listen <addr>] [--browse] [--access-log]",
+		Usage: "[--domain <example.com>] [--root <path>] [--listen <addr>] [--browse] [--access-log] [--precompressed]",
 		Short: "Spins up a production-ready file server",
 		Long: `
 A simple but production-ready file server. Useful for quick deployments,
@@ -60,6 +62,7 @@ respond with a file listing.`,
 			cmd.Flags().BoolP("templates", "t", false, "Enable template rendering")
 			cmd.Flags().BoolP("access-log", "a", false, "Enable the access log")
 			cmd.Flags().BoolP("debug", "v", false, "Enable verbose debug logs")
+			cmd.Flags().StringSliceP("precompressed", "p", []string{}, "Specify precompression file extensions. Compression preference implied from flag order.")
 			cmd.RunE = caddycmd.WrapCommandFuncForCobra(cmdFileServer)
 			cmd.AddCommand(&cobra.Command{
 				Use:     "export-template",
@@ -84,6 +87,10 @@ func cmdFileServer(fs caddycmd.Flags) (int, error) {
 	templates := fs.Bool("templates")
 	accessLog := fs.Bool("access-log")
 	debug := fs.Bool("debug")
+	precompressed, err := fs.GetStringSlice("precompressed")
+	if err != nil {
+		return caddy.ExitCodeFailedStartup, fmt.Errorf("invalid precompressed flag: %v", err)
+	}
 
 	var handlers []json.RawMessage
 
@@ -93,6 +100,30 @@ func cmdFileServer(fs caddycmd.Flags) (int, error) {
 	}
 
 	handler := FileServer{Root: root}
+
+	if len(precompressed) != 0 {
+		// logic mirrors modules/caddyhttp/fileserver/caddyfile.go case "precompressed"
+		var order []string
+		for _, compression := range precompressed {
+			modID := "http.precompressed." + compression
+			mod, err := caddy.GetModule(modID)
+			if err != nil {
+				return caddy.ExitCodeFailedStartup, fmt.Errorf("getting module named '%s': %v", modID, err)
+			}
+			inst := mod.New()
+			precompress, ok := inst.(encode.Precompressed)
+			if !ok {
+				return caddy.ExitCodeFailedStartup, fmt.Errorf("module %s is not a precompressor; is %T", modID, inst)
+			}
+			if handler.PrecompressedRaw == nil {
+				handler.PrecompressedRaw = make(caddy.ModuleMap)
+			}
+			handler.PrecompressedRaw[compression] = caddyconfig.JSON(precompress, nil)
+			order = append(order, compression)
+		}
+		handler.PrecompressedOrder = order
+	}
+
 	if browse {
 		handler.Browse = new(Browse)
 	}
@@ -154,7 +185,7 @@ func cmdFileServer(fs caddycmd.Flags) (int, error) {
 		}
 	}
 
-	err := caddy.Run(cfg)
+	err = caddy.Run(cfg)
 	if err != nil {
 		return caddy.ExitCodeFailedStartup, err
 	}