[v2] Add reloaddirs flag to add additional reload directories

This is interesting if someone uses an asset FS which is not an embed.FS,
but still has some special handling to include loading data from disk in
dev mode. E.g. one might conditionally use an embed.FS or os.DirFS
depending on the build mode.

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
@@ -85,6 +86,7 @@ func AddSubcommand(app *clir.Cli, w io.Writer) error {
 	command.StringFlag("compiler", "Use a different go compiler to build, eg go1.15beta1", &flags.compilerCommand)
 	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)
@@ -316,6 +318,14 @@ func loadAndMergeProjectConfig(cwd string, flags *devFlags) (*project.Project, e
 		}
 	}
 
+	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 != "" {
 		flags.devServerURL = projectConfig.DevServerURL
 	}
@@ -501,10 +511,24 @@ 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 {
@@ -534,7 +558,16 @@ func doWatcherLoop(buildOptions *build.Options, debugBinaryProcess *process.Proc
 					}
 				}
 
-				changedPaths[filepath.Dir(itemName)] = struct{}{}
+				for _, reloadDir := range dirsThatTriggerAReload {
+					if strings.HasPrefix(itemName, reloadDir) {
+						reload = true
+						break
+					}
+				}
+
+				if !reload {
+					changedPaths[filepath.Dir(itemName)] = struct{}{}
+				}
 
 				timer.Reset(interval)
 			}
@@ -567,7 +600,6 @@ func doWatcherLoop(buildOptions *build.Options, debugBinaryProcess *process.Proc
 					debugBinaryProcess = newBinaryProcess
 				}
 			}
-			reload := false
 			if len(changedPaths) != 0 {
 				if assetDir == "" {
 					resp, err := http.Get("http://localhost:34115/wails/assetdir")
@@ -591,6 +623,8 @@ func doWatcherLoop(buildOptions *build.Options, debugBinaryProcess *process.Proc
 							break
 						}
 					}
+				} else if len(dirsThatTriggerAReload) == 0 {
+					LogRed("Reloading couldn't be triggered: Please specify -assetdir or -reloaddirs")
 				}
 
 				changedPaths = map[string]struct{}{}

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"`