feat: add custom Datastar.js configuration support

Allow users to provide their own Datastar.js script (e.g., Datastar Pro
or custom builds) via Via's Options configuration. Adds DatastarConfig
struct with Content ([]byte) and Path (string) fields.

configuration.go

@@ -2,6 +2,17 @@ package via
 
 import "github.com/alexedwards/scs/v2"
 
+// DatastarConfig configures a custom Datastar.js script.
+type DatastarConfig struct {
+	// Content is the Datastar.js script content.
+	// If nil, the embedded default is used.
+	Content []byte
+
+	// Path is the URL path where the script is served.
+	// Defaults to "/_datastar.js" if empty.
+	Path string
+}
+
 type LogLevel int
 
 const (
@@ -37,4 +48,8 @@ type Options struct {
 	// with scs LoadAndSave middleware. Configure the session manager before
 	// passing it (lifetime, cookie settings, store, etc).
 	SessionManager *scs.SessionManager
+
+	// Datastar configures a custom Datastar.js script.
+	// If nil, Via uses its embedded default.
+	Datastar *DatastarConfig
 }

h/h.go

@@ -79,7 +79,6 @@ func HTML5(p HTML5Props) H {
 		Body:        retype(p.Body),
 		HTMLAttrs:   retype(p.HTMLAttrs),
 	}
-	gp.Head = append(gp.Head, Script(Type("module"), Src("/_datastar.js")))
 	return gc.HTML5(gp)
 }
 

via.go

@@ -40,6 +40,9 @@ type V struct {
 	documentFootIncludes      []h.H
 	devModePageInitFnMap      map[string]func(*Context)
 	sessionManager            *scs.SessionManager
+	datastarPath              string
+	datastarContent           []byte
+	datastarHandlerRegistered bool
 }
 
 func (v *V) logFatal(format string, a ...any) {
@@ -108,6 +111,14 @@ func (v *V) Config(cfg Options) {
 	if cfg.SessionManager != nil {
 		v.sessionManager = cfg.SessionManager
 	}
+	if cfg.Datastar != nil {
+		if cfg.Datastar.Content != nil {
+			v.datastarContent = cfg.Datastar.Content
+		}
+		if cfg.Datastar.Path != "" {
+			v.datastarPath = cfg.Datastar.Path
+		}
+	}
 }
 
 // AppendToHead appends the given h.H nodes to the head of the base HTML document.
@@ -141,6 +152,7 @@ func (v *V) AppendToFoot(elements ...h.H) {
 //		})
 //	})
 func (v *V) Page(route string, initContextFn func(c *Context)) {
+	v.ensureDatastarHandler()
 	// check for panics
 	func() {
 		defer func() {
@@ -176,7 +188,7 @@ func (v *V) Page(route string, initContextFn func(c *Context)) {
 		if v.cfg.DevMode {
 			v.devModePersist(c)
 		}
-		headElements := []h.H{}
+		headElements := []h.H{h.Script(h.Type("module"), h.Src(v.datastarPath))}
 		headElements = append(headElements, v.documentHeadIncludes...)
 		headElements = append(headElements,
 			h.Meta(h.Data("signals", fmt.Sprintf("{'via-ctx':'%s'}", id))),
@@ -258,6 +270,17 @@ func (v *V) HTTPServeMux() *http.ServeMux {
 	return v.mux
 }
 
+func (v *V) ensureDatastarHandler() {
+	if v.datastarHandlerRegistered {
+		return
+	}
+	v.datastarHandlerRegistered = true
+	v.mux.HandleFunc("GET "+v.datastarPath, func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/javascript")
+		_, _ = w.Write(v.datastarContent)
+	})
+}
+
 func (v *V) devModePersist(c *Context) {
 	p := filepath.Join(".via", "devmode", "ctx.json")
 	if err := os.MkdirAll(filepath.Dir(p), 0755); err != nil {
@@ -378,6 +401,8 @@ func New() *V {
 		contextRegistry:      make(map[string]*Context),
 		devModePageInitFnMap: make(map[string]func(*Context)),
 		sessionManager:       scs.New(),
+		datastarPath:         "/_datastar.js",
+		datastarContent:      datastarJS,
 		cfg: Options{
 			DevMode:       false,
 			ServerAddress: ":3000",
@@ -386,11 +411,6 @@ func New() *V {
 		},
 	}
 
-	v.mux.HandleFunc("GET /_datastar.js", func(w http.ResponseWriter, r *http.Request) {
-		w.Header().Set("Content-Type", "application/javascript")
-		_, _ = w.Write(datastarJS)
-	})
-
 	v.mux.HandleFunc("GET /_sse", func(w http.ResponseWriter, r *http.Request) {
 		isReconnect := false
 		if r.Header.Get("last-event-id") == "via" {

via_test.go

@@ -28,6 +28,10 @@ func TestPageRoute(t *testing.T) {
 
 func TestDatastarJS(t *testing.T) {
 	v := New()
+	v.Page("/", func(c *Context) {
+		c.View(func() h.H { return h.Div() })
+	})
+
 	req := httptest.NewRequest("GET", "/_datastar.js", nil)
 	w := httptest.NewRecorder()
 	v.mux.ServeHTTP(w, req)
@@ -37,6 +41,54 @@ func TestDatastarJS(t *testing.T) {
 	assert.Contains(t, w.Body.String(), "🖕JS_DS🚀")
 }
 
+func TestCustomDatastarContent(t *testing.T) {
+	customScript := []byte("// Custom Datastar Script")
+	v := New()
+	v.Config(Options{
+		Datastar: &DatastarConfig{
+			Content: customScript,
+		},
+	})
+	v.Page("/", func(c *Context) {
+		c.View(func() h.H { return h.Div() })
+	})
+
+	req := httptest.NewRequest("GET", "/_datastar.js", nil)
+	w := httptest.NewRecorder()
+	v.mux.ServeHTTP(w, req)
+
+	assert.Equal(t, http.StatusOK, w.Code)
+	assert.Equal(t, "application/javascript", w.Header().Get("Content-Type"))
+	assert.Contains(t, w.Body.String(), "Custom Datastar Script")
+}
+
+func TestCustomDatastarPath(t *testing.T) {
+	v := New()
+	v.Config(Options{
+		Datastar: &DatastarConfig{
+			Path: "/assets/datastar.js",
+		},
+	})
+	v.Page("/test", func(c *Context) {
+		c.View(func() h.H { return h.Div() })
+	})
+
+	// Custom path should serve the script
+	req := httptest.NewRequest("GET", "/assets/datastar.js", nil)
+	w := httptest.NewRecorder()
+	v.mux.ServeHTTP(w, req)
+
+	assert.Equal(t, http.StatusOK, w.Code)
+	assert.Equal(t, "application/javascript", w.Header().Get("Content-Type"))
+	assert.Contains(t, w.Body.String(), "🖕JS_DS🚀")
+
+	// Page should reference the custom path in script tag
+	req2 := httptest.NewRequest("GET", "/test", nil)
+	w2 := httptest.NewRecorder()
+	v.mux.ServeHTTP(w2, req2)
+	assert.Contains(t, w2.Body.String(), `src="/assets/datastar.js"`)
+}
+
 func TestSignal(t *testing.T) {
 	var sig *signal
 	v := New()