Merge pull request #1001 from stffabi/feature/fsfs-assets

proposal: [v2] Support fs.FS for assets

v2/cmd/wails/internal/commands/dev/dev.go

@@ -63,6 +63,7 @@ type devFlags struct {
 	compilerCommand string
 	assetDir        string
 	extensions      string
+	reloadDirs      string
 	openBrowser     bool
 	noReload        bool
 	wailsjsdir      string
@@ -83,8 +84,9 @@ func AddSubcommand(app *clir.Cli, w io.Writer) error {
 	flags := defaultDevFlags()
 	command.StringFlag("ldflags", "optional ldflags", &flags.ldflags)
 	command.StringFlag("compiler", "Use a different go compiler to build, eg go1.15beta1", &flags.compilerCommand)
-	command.StringFlag("assetdir", "Serve assets from the given directory", &flags.assetDir)
+	command.StringFlag("assetdir", "Serve assets from the given directory instead of using the provided asset FS", &flags.assetDir)
 	command.StringFlag("e", "Extensions to trigger rebuilds (comma separated) eg go", &flags.extensions)
+	command.StringFlag("reloaddirs", "Additional directories to trigger reloads (comma separated)", &flags.reloadDirs)
 	command.BoolFlag("browser", "Open application in browser", &flags.openBrowser)
 	command.BoolFlag("noreload", "Disable reload on asset change", &flags.noReload)
 	command.StringFlag("wailsjsdir", "Directory to generate the Wails JS modules", &flags.wailsjsdir)
@@ -301,10 +303,6 @@ func loadAndMergeProjectConfig(cwd string, flags *devFlags) (*project.Project, e
 
 	var shouldSaveConfig bool
 
-	if projectConfig.AssetDirectory == "" && flags.assetDir == "" {
-		return nil, fmt.Errorf("No asset directory provided. Please use -assetdir to indicate which directory contains your built assets.")
-	}
-
 	if flags.assetDir == "" && projectConfig.AssetDirectory != "" {
 		flags.assetDir = projectConfig.AssetDirectory
 	}
@@ -313,9 +311,19 @@ func loadAndMergeProjectConfig(cwd string, flags *devFlags) (*project.Project, e
 		projectConfig.AssetDirectory = filepath.ToSlash(flags.assetDir)
 	}
 
-	flags.assetDir, err = filepath.Abs(flags.assetDir)
-	if err != nil {
-		return nil, err
+	if flags.assetDir != "" {
+		flags.assetDir, err = filepath.Abs(flags.assetDir)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	if flags.reloadDirs == "" && projectConfig.ReloadDirectories != "" {
+		flags.reloadDirs = projectConfig.ReloadDirectories
+	}
+
+	if flags.reloadDirs != projectConfig.ReloadDirectories {
+		projectConfig.ReloadDirectories = filepath.ToSlash(flags.reloadDirs)
 	}
 
 	if flags.devServerURL == defaultDevServerURL && projectConfig.DevServerURL != defaultDevServerURL && projectConfig.DevServerURL != "" {
@@ -503,11 +511,26 @@ func doWatcherLoop(buildOptions *build.Options, debugBinaryProcess *process.Proc
 		newBinaryProcess *process.Process
 	)
 	var extensionsThatTriggerARebuild = sliceToMap(strings.Split(flags.extensions, ","))
+	var dirsThatTriggerAReload []string
+	for _, dir := range strings.Split(flags.reloadDirs, ",") {
+		if dir == "" {
+			continue
+		}
+		path, err := filepath.Abs(dir)
+		if err != nil {
+			LogRed("Unable to expand reloadDir '%s': %s", dir, err)
+			continue
+		}
+		dirsThatTriggerAReload = append(dirsThatTriggerAReload, path)
+	}
+
 	quit := false
 	interval := time.Duration(flags.debounceMS) * time.Millisecond
 	timer := time.NewTimer(interval)
 	rebuild := false
 	reload := false
+	assetDir := ""
+	changedPaths := map[string]struct{}{}
 	for quit == false {
 		//reload := false
 		select {
@@ -519,12 +542,13 @@ func doWatcherLoop(buildOptions *build.Options, debugBinaryProcess *process.Proc
 			// Check for file writes
 			if item.Op&fsnotify.Write == fsnotify.Write {
 				// Ignore directories
-				if fs.DirExists(item.Name) {
+				itemName := item.Name
+				if fs.DirExists(itemName) {
 					continue
 				}
 
 				// Iterate all file patterns
-				ext := filepath.Ext(item.Name)
+				ext := filepath.Ext(itemName)
 				if ext != "" {
 					ext = ext[1:]
 					if _, exists := extensionsThatTriggerARebuild[ext]; exists {
@@ -534,9 +558,17 @@ func doWatcherLoop(buildOptions *build.Options, debugBinaryProcess *process.Proc
 					}
 				}
 
-				if strings.HasPrefix(item.Name, flags.assetDir) {
-					reload = true
+				for _, reloadDir := range dirsThatTriggerAReload {
+					if strings.HasPrefix(itemName, reloadDir) {
+						reload = true
+						break
+					}
 				}
+
+				if !reload {
+					changedPaths[filepath.Dir(itemName)] = struct{}{}
+				}
+
 				timer.Reset(interval)
 			}
 			// Check for new directories
@@ -568,6 +600,35 @@ func doWatcherLoop(buildOptions *build.Options, debugBinaryProcess *process.Proc
 					debugBinaryProcess = newBinaryProcess
 				}
 			}
+			if len(changedPaths) != 0 {
+				if assetDir == "" {
+					resp, err := http.Get("http://localhost:34115/wails/assetdir")
+					if err != nil {
+						LogRed("Error during retrieving assetdir: %s", err.Error())
+					} else {
+						content, err := io.ReadAll(resp.Body)
+						if err != nil {
+							LogRed("Error reading assetdir from devserver: %s", err.Error())
+						} else {
+							assetDir = string(content)
+						}
+						resp.Body.Close()
+					}
+				}
+
+				if assetDir != "" {
+					for path := range changedPaths {
+						if strings.HasPrefix(path, assetDir) {
+							reload = true
+							break
+						}
+					}
+				} else if len(dirsThatTriggerAReload) == 0 {
+					LogRed("Reloading couldn't be triggered: Please specify -assetdir or -reloaddirs")
+				}
+
+				changedPaths = map[string]struct{}{}
+			}
 			if reload {
 				reload = false
 				_, err = http.Get("http://localhost:34115/wails/reload")

v2/cmd/wails/internal/commands/generate/template/base/NEXTSTEPS.md.template

@@ -10,7 +10,6 @@ The next steps to complete the template are:
      - It is really important to ensure `helpurl` is valid as this is where users of the template will be directed for help.
   2. Update `README.md`.
   3. Edit `wails.json` and ensure all fields are correct, especially:
-     - `assetdir` - path to your assets
      - `wailsjsdir` - path to generate wailsjs modules
      - `frontend:install` - The command to install your frontend dependencies
      - `frontend:build` - The command to build your frontend

v2/cmd/wails/internal/commands/generate/template/base/wails.tmpl.json

@@ -1,7 +1,6 @@
 {
   "name": "{{.ProjectName}}",
   "outputfilename": "{{.BinaryName}}",
-  "assetdir": "frontend/dist",
   "frontend:install": "npm install",
   "frontend:build": "npm run build",
   "author": {

v2/cmd/wails/internal/commands/initialise/templates/ides/goland/workspace.tmpl.xml

@@ -36,7 +36,6 @@
             <working_directory value="$PROJECT_DIR$"/>
             <go_parameters value="-gcflags &quot;all=-N -l&quot; -tags dev -o {{.PathToDesktopBinary}}"/>
             <useCustomBuildTags value="true"/>
-            <parameters value="-assetdir {{.AssetDir}}"/>
             <envs>
                 <env name="CGO_ENABLED" value="&quot;{{.CGOEnabled}}&quot;"/>
             </envs>

v2/cmd/wails/internal/commands/initialise/templates/ides/vscode/launch.tmpl.json

@@ -9,11 +9,7 @@
       "program": "${workspaceFolder}/{{.PathToDesktopBinary}}",
       "preLaunchTask": "build",
       "cwd": "${workspaceFolder}",
-      "env": {},
-      "args": [
-        "-assetdir",
-        "{{.AssetDir}}"
-      ]
+      "env": {}
     }
   ]
 }

v2/cmd/wails/internal/commands/initialise/templates/templates.go

@@ -42,7 +42,6 @@ type Data struct {
 	AuthorNameAndEmail string
 	WailsDirectory     string
 	GoSDKPath          string
-	AssetDir           string
 	WindowsFlags       string
 	CGOEnabled         string
 	OutputFile         string
@@ -60,7 +59,6 @@ type Options struct {
 	InitGit             bool
 	AuthorName          string
 	AuthorEmail         string
-	AssetDir            string
 	IDE                 string
 	ProjectNameFilename string // The project name but as a valid filename
 	WailsVersion        string
@@ -261,7 +259,6 @@ func Install(options *Options) (bool, *Template, error) {
 		AuthorName:     options.AuthorName,
 		WailsVersion:   options.WailsVersion,
 		GoSDKPath:      options.GoSDKPath,
-		AssetDir:       options.AssetDir,
 	}
 
 	// Create a formatted name and email combo.
@@ -408,22 +405,6 @@ func installIDEFiles(o ideOptions) error {
 		binaryName += ".exe"
 	}
 
-	// Parse wails.json for assetdir
-	wailsJSONBytes, err := os.ReadFile(filepath.Join(o.options.TargetDir, "wails.json"))
-	if err != nil {
-		return err
-	}
-	var wailsJSON map[string]interface{}
-	err = json.Unmarshal(wailsJSONBytes, &wailsJSON)
-	if err != nil {
-		return err
-	}
-	assetDir := wailsJSON["assetdir"]
-	if assetDir == "" {
-		return fmt.Errorf("Unable to find 'assetdir' in 'wails.json' ")
-	}
-
-	o.options.AssetDir = assetDir.(string)
 	o.options.PathToDesktopBinary = filepath.ToSlash(filepath.Join("build", "bin", binaryName))
 
 	o.options.WindowsFlags = ""

v2/cmd/wails/internal/commands/initialise/templates/templates/svelte/wails.tmpl.json

@@ -1,7 +1,6 @@
 {
   "name": "{{.ProjectName}}",
   "outputfilename": "{{.BinaryName}}",
-  "assetdir": "frontend/dist",
   "frontend:install": "npm install",
   "frontend:build": "npm run build",
   "wailsjsdir": "./frontend",

v2/cmd/wails/internal/commands/initialise/templates/templates/vanilla/wails.tmpl.json

@@ -1,7 +1,6 @@
 {
   "name": "{{.ProjectName}}",
   "outputfilename": "{{.BinaryName}}",
-  "assetdir": "frontend/src",
   "wailsjsdir": "./frontend",
   "author": {
     "name": "{{.AuthorName}}",

v2/internal/appng/app_dev.go

@@ -5,7 +5,10 @@ package appng
 
 import (
 	"context"
+	"embed"
 	"flag"
+	"fmt"
+	iofs "io/fs"
 	"os"
 	"path/filepath"
 
@@ -91,12 +94,30 @@ func CreateApp(appoptions *options.App) (*App, error) {
 		}
 	}
 
+	if assetdir == "" {
+		// If no assetdir has been defined, let's try to infer it from the project root and the asset FS.
+		assetdir, err = tryInferAssetDirFromFS(appoptions.Assets)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	if assetdir != "" {
+		// Let's override the assets to serve from on disk, if needed
+		absdir, err := filepath.Abs(assetdir)
+		if err != nil {
+			return nil, err
+		}
+
+		myLogger.Info("Serving assets from disk: %s", absdir)
+		appoptions.Assets = os.DirFS(absdir)
+
+		ctx = context.WithValue(ctx, "assetdir", assetdir)
+	}
+
 	if devServerURL != "" {
 		ctx = context.WithValue(ctx, "devserverurl", devServerURL)
 	}
-	if assetdir != "" {
-		ctx = context.WithValue(ctx, "assetdir", assetdir)
-	}
 
 	if loglevel != "" {
 		level, err := pkglogger.StringToLogLevel(loglevel)
@@ -203,3 +224,32 @@ func generateBindings(bindings *binding.Bindings) error {
 	return nil
 
 }
+
+func tryInferAssetDirFromFS(assets iofs.FS) (string, error) {
+	if _, isEmbedFs := assets.(embed.FS); !isEmbedFs {
+		// We only infer the assetdir for embed.FS assets
+		return "", nil
+	}
+
+	path, err := fs.FindPathToFile(assets, "index.html")
+	if err != nil {
+		return "", err
+	}
+
+	path, err = filepath.Abs(path)
+	if err != nil {
+		return "", err
+	}
+
+	if _, err := os.Stat(filepath.Join(path, "index.html")); err != nil {
+		if os.IsNotExist(err) {
+			err = fmt.Errorf(
+				"inferred assetdir '%s' does not exist or does not contain an 'index.html' file, "+
+					"please specify it with -assetdir or set it in wails.json",
+				path)
+		}
+		return "", err
+	}
+
+	return path, nil
+}

v2/internal/frontend/assetserver/assetserver_browser_dev.go

@@ -5,10 +5,13 @@ package assetserver
 
 import (
 	"bytes"
+	"context"
+	"io/fs"
+	"strings"
+
 	"github.com/wailsapp/wails/v2/internal/frontend/runtime"
-	"github.com/wailsapp/wails/v2/pkg/options"
+	"github.com/wailsapp/wails/v2/internal/logger"
 	"golang.org/x/net/html"
-	"path/filepath"
 )
 
 /*
@@ -18,35 +21,41 @@ It injects a websocket based IPC script into `index.html`.
 
 */
 
-import (
-	"os"
-)
-
 type BrowserAssetServer struct {
-	runtimeJS  []byte
-	assetdir   string
-	appOptions *options.App
+	assets    fs.FS
+	runtimeJS []byte
+	logger    *logger.Logger
 }
 
-func NewBrowserAssetServer(assetdir string, bindingsJSON string, appOptions *options.App) (*BrowserAssetServer, error) {
-	result := &BrowserAssetServer{
-		assetdir:   assetdir,
-		appOptions: appOptions,
+func NewBrowserAssetServer(ctx context.Context, assets fs.FS, bindingsJSON string) (*BrowserAssetServer, error) {
+	result := &BrowserAssetServer{}
+	_logger := ctx.Value("logger")
+	if _logger != nil {
+		result.logger = _logger.(*logger.Logger)
+	}
+
+	var err error
+	result.assets, err = prepareAssetsForServing(assets)
+	if err != nil {
+		return nil, err
 	}
 
 	var buffer bytes.Buffer
 	buffer.WriteString(`window.wailsbindings='` + bindingsJSON + `';` + "\n")
 	buffer.Write(runtime.RuntimeDesktopJS)
 	result.runtimeJS = buffer.Bytes()
+
 	return result, nil
 }
 
-func (a *BrowserAssetServer) loadFileFromDisk(filename string) ([]byte, error) {
-	return os.ReadFile(filepath.Join(a.assetdir, filename))
+func (d *BrowserAssetServer) LogDebug(message string, args ...interface{}) {
+	if d.logger != nil {
+		d.logger.Debug("[BrowserAssetServer] "+message, args...)
+	}
 }
 
 func (a *BrowserAssetServer) processIndexHTML() ([]byte, error) {
-	indexHTML, err := a.loadFileFromDisk("index.html")
+	indexHTML, err := fs.ReadFile(a.assets, "index.html")
 	if err != nil {
 		return nil, err
 	}
@@ -96,7 +105,9 @@ func (a *BrowserAssetServer) Load(filename string) ([]byte, string, error) {
 	case "/wails/ipc.js":
 		content = runtime.WebsocketIPC
 	default:
-		content, err = a.loadFileFromDisk(filename)
+		filename = strings.TrimPrefix(filename, "/")
+		a.LogDebug("Loading file: %s", filename)
+		content, err = fs.ReadFile(a.assets, filename)
 	}
 	if err != nil {
 		return nil, "", err

v2/internal/frontend/assetserver/assetserver_common.go

@@ -0,0 +1,25 @@
+package assetserver
+
+import (
+	iofs "io/fs"
+	"path"
+
+	"github.com/wailsapp/wails/v2/internal/fs"
+)
+
+func prepareAssetsForServing(assets iofs.FS) (iofs.FS, error) {
+	if _, err := assets.Open("."); err != nil {
+		return nil, err
+	}
+
+	subDir, err := fs.FindPathToFile(assets, "index.html")
+	if err != nil {
+		return nil, err
+	}
+
+	assets, err = iofs.Sub(assets, path.Clean(subDir))
+	if err != nil {
+		return nil, err
+	}
+	return assets, nil
+}

v2/internal/frontend/assetserver/assetserver_desktop.go

@@ -3,26 +3,21 @@ package assetserver
 import (
 	"bytes"
 	"context"
-	"embed"
-	"fmt"
-	"github.com/leaanthony/debme"
-	"github.com/leaanthony/slicer"
-	"github.com/wailsapp/wails/v2/internal/frontend/runtime"
-	"github.com/wailsapp/wails/v2/internal/logger"
 	"io/fs"
 	"log"
-	"path/filepath"
 	"strings"
+
+	"github.com/wailsapp/wails/v2/internal/frontend/runtime"
+	"github.com/wailsapp/wails/v2/internal/logger"
 )
 
 type DesktopAssetServer struct {
-	assets    debme.Debme
+	assets    fs.FS
 	runtimeJS []byte
-	assetdir  string
 	logger    *logger.Logger
 }
 
-func NewDesktopAssetServer(ctx context.Context, assets embed.FS, bindingsJSON string) (*DesktopAssetServer, error) {
+func NewDesktopAssetServer(ctx context.Context, assets fs.FS, bindingsJSON string) (*DesktopAssetServer, error) {
 	result := &DesktopAssetServer{}
 
 	_logger := ctx.Value("logger")
@@ -30,22 +25,18 @@ func NewDesktopAssetServer(ctx context.Context, assets embed.FS, bindingsJSON st
 		result.logger = _logger.(*logger.Logger)
 	}
 
-	_assetdir := ctx.Value("assetdir")
-	if _assetdir != nil {
-		result.assetdir = _assetdir.(string)
-		absdir, err := filepath.Abs(result.assetdir)
-		if err != nil {
-			return nil, err
-		}
-		result.LogDebug("Loading assets from: %s", absdir)
+	var err error
+	result.assets, err = prepareAssetsForServing(assets)
+	if err != nil {
+		return nil, err
 	}
 
 	var buffer bytes.Buffer
 	buffer.WriteString(`window.wailsbindings='` + bindingsJSON + `';` + "\n")
 	buffer.Write(runtime.RuntimeDesktopJS)
 	result.runtimeJS = buffer.Bytes()
-	err := result.init(assets)
-	return result, err
+
+	return result, nil
 }
 
 func (d *DesktopAssetServer) LogDebug(message string, args ...interface{}) {
@@ -54,63 +45,8 @@ func (d *DesktopAssetServer) LogDebug(message string, args ...interface{}) {
 	}
 }
 
-func (d *DesktopAssetServer) SetAssetDir(assetdir string) {
-	d.assetdir = assetdir
-}
-
-func PathToIndexHTML(assets embed.FS) (string, error) {
-	stat, err := fs.Stat(assets, "index.html")
-	if stat != nil {
-		return ".", nil
-	}
-	var indexFiles slicer.StringSlicer
-	err = fs.WalkDir(assets, ".", func(path string, d fs.DirEntry, err error) error {
-		if err != nil {
-			return err
-		}
-		if strings.HasSuffix(path, "index.html") {
-			indexFiles.Add(path)
-		}
-		return nil
-	})
-	if err != nil {
-		return "", err
-	}
-
-	if indexFiles.Length() > 1 {
-		return "", fmt.Errorf("multiple 'index.html' files found in assets")
-	}
-
-	path, _ := filepath.Split(indexFiles.AsSlice()[0])
-	return path, nil
-}
-
-func processAssets(assets embed.FS) (debme.Debme, error) {
-
-	result, err := debme.FS(assets, ".")
-	if err != nil {
-		return result, err
-	}
-	// Find index.html
-	path, err := PathToIndexHTML(assets)
-	if err != nil {
-		return debme.Debme{}, err
-	}
-	return debme.FS(assets, path)
-}
-
-func (a *DesktopAssetServer) init(assets embed.FS) error {
-
-	var err error
-	a.assets, err = processAssets(assets)
-	if err != nil {
-		return err
-	}
-	return nil
-}
-
 func (a *DesktopAssetServer) processIndexHTML() ([]byte, error) {
-	indexHTML, err := a.ReadFile("index.html")
+	indexHTML, err := fs.ReadFile(a.assets, "index.html")
 	if err != nil {
 		return nil, err
 	}
@@ -146,7 +82,9 @@ func (a *DesktopAssetServer) Load(filename string) ([]byte, string, error) {
 	case "/wails/ipc.js":
 		content = runtime.DesktopIPC
 	default:
-		content, err = a.ReadFile(filename)
+		filename = strings.TrimPrefix(filename, "/")
+		a.LogDebug("Loading file: %s", filename)
+		content, err = fs.ReadFile(a.assets, filename)
 	}
 	if err != nil {
 		return nil, "", err

v2/internal/frontend/assetserver/assetserver_desktop_dev.go

@@ -1,13 +0,0 @@
-//go:build dev
-
-package assetserver
-
-import (
-	"os"
-	"path/filepath"
-)
-
-func (a *DesktopAssetServer) ReadFile(filename string) ([]byte, error) {
-	a.LogDebug("Loading file from disk: %s", filename)
-	return os.ReadFile(filepath.Join(a.assetdir, filename))
-}

v2/internal/frontend/assetserver/assetserver_desktop_production.go

@@ -1,7 +0,0 @@
-//go:build production
-
-package assetserver
-
-func (a *DesktopAssetServer) ReadFile(filename string) ([]byte, error) {
-	return a.assets.ReadFile(filename)
-}

v2/internal/frontend/devserver/devserver.go

@@ -10,7 +10,6 @@ import (
 	"fmt"
 	"io/fs"
 	"log"
-	"path/filepath"
 	"strings"
 	"sync"
 	"time"
@@ -50,6 +49,11 @@ func (d *DevWebServer) WindowReload() {
 func (d *DevWebServer) Run(ctx context.Context) error {
 	d.ctx = ctx
 
+	assetdir, _ := ctx.Value("assetdir").(string)
+	d.server.Get("/wails/assetdir", func(fctx *fiber.Ctx) error {
+		return fctx.SendString(assetdir)
+	})
+
 	d.server.Get("/wails/reload", func(fctx *fiber.Ctx) error {
 		d.WindowReload()
 		d.desktopFrontend.WindowReload()
@@ -100,25 +104,14 @@ func (d *DevWebServer) Run(ctx context.Context) error {
 	_devServerURL := ctx.Value("devserverurl")
 	if _devServerURL == "http://localhost:34115" {
 		// Setup internal dev server
-		_assetdir := ctx.Value("assetdir")
-		if _assetdir == nil {
-			return fmt.Errorf("no assetdir provided")
+		bindingsJSON, err := d.appBindings.ToJSON()
+		if err != nil {
+			log.Fatal(err)
 		}
-		if _assetdir != nil {
-			assetdir := _assetdir.(string)
-			bindingsJSON, err := d.appBindings.ToJSON()
-			if err != nil {
-				log.Fatal(err)
-			}
-			d.assetServer, err = assetserver.NewBrowserAssetServer(assetdir, bindingsJSON, d.appoptions)
-			if err != nil {
-				log.Fatal(err)
-			}
-			absdir, err := filepath.Abs(assetdir)
-			if err != nil {
-				return err
-			}
-			d.LogDebug("Serving assets from: %s", absdir)
+
+		d.assetServer, err = assetserver.NewBrowserAssetServer(ctx, d.appoptions.Assets, bindingsJSON)
+		if err != nil {
+			log.Fatal(err)
 		}
 
 		d.server.Get("*", d.loadAsset)

v2/internal/fs/fs.go

@@ -4,9 +4,11 @@ import (
 	"crypto/md5"
 	"fmt"
 	"io"
+	"io/fs"
 	"os"
 	"path/filepath"
 	"runtime"
+	"strings"
 	"unsafe"
 
 	"github.com/leaanthony/slicer"
@@ -394,3 +396,30 @@ func MoveDirExtended(src string, dst string, ignore []string) (err error) {
 
 	return
 }
+
+func FindPathToFile(fsys fs.FS, file string) (string, error) {
+	stat, _ := fs.Stat(fsys, file)
+	if stat != nil {
+		return ".", nil
+	}
+	var indexFiles slicer.StringSlicer
+	err := fs.WalkDir(fsys, ".", func(path string, d fs.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+		if strings.HasSuffix(path, file) {
+			indexFiles.Add(path)
+		}
+		return nil
+	})
+	if err != nil {
+		return "", err
+	}
+
+	if indexFiles.Length() > 1 {
+		return "", fmt.Errorf("multiple '%s' files found in assets", file)
+	}
+
+	path, _ := filepath.Split(indexFiles.AsSlice()[0])
+	return path, nil
+}

v2/internal/project/project.go

@@ -15,6 +15,8 @@ type Project struct {
 	Name           string `json:"name"`
 	AssetDirectory string `json:"assetdir"`
 
+	ReloadDirectories string `json:"reloaddirs"`
+
 	BuildCommand   string `json:"frontend:build"`
 	InstallCommand string `json:"frontend:install"`
 	DevCommand     string `json:"frontend:dev"`

v2/pkg/options/options.go

@@ -2,11 +2,11 @@ package options
 
 import (
 	"context"
-	"embed"
-	"github.com/wailsapp/wails/v2/pkg/options/linux"
+	"io/fs"
 	"log"
 	"runtime"
 
+	"github.com/wailsapp/wails/v2/pkg/options/linux"
 	"github.com/wailsapp/wails/v2/pkg/options/mac"
 	"github.com/wailsapp/wails/v2/pkg/options/windows"
 
@@ -41,7 +41,7 @@ type App struct {
 	HideWindowOnClose bool
 	AlwaysOnTop       bool
 	RGBA              *RGBA
-	Assets            embed.FS
+	Assets            fs.FS
 	Menu              *menu.Menu
 	Logger            logger.Logger `json:"-"`
 	LogLevel          logger.LogLevel