✨ feat: Add support for RebuildTree

docs/api/app.md

@@ -573,3 +573,25 @@ Hooks is a method to return [hooks](./hooks.md) property.
 ```go title="Signature"
 func (app *App) Hooks() *Hooks
 ```
+
+## RebuildTree
+
+RebuildTree is a method destined to rebuild the route tree stack and allow dynamically route registers. It returns an app pointer.
+
+```go title="Signature"
+func (app *App) RebuildTree() *App
+```
+
+**NOTE**: This method should be used in the most careful way possible, since it's not currently possible to make it thread-safe (it would add a big performance overhead to do so) and calling it is very performance-intensive, so it's recommended to be used only in development mode and never concurrently. Here's an example of defining routes dynamically:
+
+```go
+app.Get("/define", func(c Ctx) error {
+  app.Get("/dynamically-defined", func(c Ctx) error {
+  	return c.SendStatus(http.StatusOK)
+  })
+
+  app.RebuildTree()
+
+  return c.SendStatus(http.StatusOK)
+})
+```

router.go

@@ -409,6 +409,21 @@ func (app *App) addRoute(method string, route *Route, isMounted ...bool) {
 	}
 }
 
+// BuildTree rebuilds the prefix tree from the previously registered routes.
+// This method is useful when you want to register routes dynamically after the app has started.
+// It is not recommended to use this method on production environments because rebuilding
+// the tree is performance-intensive and not thread-safe in runtime. Since building the tree
+// is only done in the startupProcess of the app, this method does not makes sure that the
+// routeTree is being safely changed, as it would add a great deal of overhead in the request.
+// Latest benchmark results showed a degradation from 82.79 ns/op to 94.48 ns/op and can be found in:
+// https://github.com/gofiber/fiber/issues/2769#issuecomment-2227385283
+func (app *App) RebuildTree() *App {
+	app.mutex.Lock()
+	defer app.mutex.Unlock()
+
+	return app.buildTree()
+}
+
 // buildTree build the prefix tree from the previously registered routes
 func (app *App) buildTree() *App {
 	if !app.routesRefreshed {

router_test.go

@@ -9,6 +9,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"net/http"
 	"net/http/httptest"
 	"os"
 	"testing"
@@ -368,6 +369,33 @@ func Test_Router_NotFound_HTML_Inject(t *testing.T) {
 	require.Equal(t, "Cannot DELETE /does/not/exist<script>alert('foo');</script>", string(c.Response.Body()))
 }
 
+func Test_App_Rebuild_Tree(t *testing.T) {
+	t.Parallel()
+	app := New()
+
+	app.Get("/test", func(c Ctx) error {
+		app.Get("/dynamically-defined", func(c Ctx) error {
+			return c.SendStatus(http.StatusOK)
+		})
+
+		app.RebuildTree()
+
+		return c.SendStatus(http.StatusOK)
+	})
+
+	resp, err := app.Test(httptest.NewRequest(MethodGet, "/dynamically-defined", nil))
+	require.NoError(t, err, "app.Test(req)")
+	require.Equal(t, http.StatusNotFound, resp.StatusCode, "Status code")
+
+	resp, err = app.Test(httptest.NewRequest(MethodGet, "/test", nil))
+	require.NoError(t, err, "app.Test(req)")
+	require.Equal(t, http.StatusOK, resp.StatusCode, "Status code")
+
+	resp, err = app.Test(httptest.NewRequest(MethodGet, "/dynamically-defined", nil))
+	require.NoError(t, err, "app.Test(req)")
+	require.Equal(t, http.StatusOK, resp.StatusCode, "Status code")
+}
+
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