⚗️ Add internal api for getting the root element of a running app.

src/lustre.ffi.mjs

@@ -229,8 +229,9 @@ export class LustreClientApplication {
           }),
         );
       const select = () => {};
+      const root = this.root;
 
-      effect({ dispatch, emit, select });
+      effect({ dispatch, emit, select, root });
     }
 
     // If any effects immediately dispatched a message we can process it
@@ -494,8 +495,9 @@ export const make_lustre_client_component = (
             }),
           );
         const select = () => {};
+        const root = this.shadowRoot;
 
-        effect({ dispatch, emit, select });
+        effect({ dispatch, emit, select, root });
       }
 
       // If any effects immediately dispatched a message we can process it
@@ -693,8 +695,9 @@ export class LustreServerApplication {
           }),
         );
       const select = () => {};
+      const root = null;
 
-      effect({ dispatch, emit, select });
+      effect({ dispatch, emit, select, root });
     }
 
     // If any effects immediately dispatched a message we can process it

src/lustre/effect.gleam

@@ -41,6 +41,7 @@
 
 // IMPORTS ---------------------------------------------------------------------
 
+import gleam/dynamic.{type Dynamic}
 import gleam/erlang/process.{type Selector}
 import gleam/json.{type Json}
 import gleam/list
@@ -65,6 +66,7 @@ type Actions(msg) {
     dispatch: fn(msg) -> Nil,
     emit: fn(String, Json) -> Nil,
     select: fn(Selector(msg)) -> Nil,
+    root: Dynamic,
   )
 }
 
@@ -101,7 +103,7 @@ type Actions(msg) {
 /// }
 /// ```
 pub fn from(effect: fn(fn(msg) -> Nil) -> Nil) -> Effect(msg) {
-  use dispatch, _, _ <- custom
+  use dispatch, _, _, _ <- custom
 
   effect(dispatch)
 }
@@ -113,7 +115,7 @@ pub fn from(effect: fn(fn(msg) -> Nil) -> Nil) -> Effect(msg) {
 ///
 @internal
 pub fn event(name: String, data: Json) -> Effect(msg) {
-  use _, emit, _ <- custom
+  use _, emit, _, _ <- custom
 
   emit(name, data)
 }
@@ -122,12 +124,17 @@ pub fn event(name: String, data: Json) -> Effect(msg) {
 ///
 @internal
 pub fn custom(
-  run: fn(fn(msg) -> Nil, fn(String, Json) -> Nil, fn(Selector(msg)) -> Nil) ->
+  run: fn(
+    fn(msg) -> Nil,
+    fn(String, Json) -> Nil,
+    fn(Selector(msg)) -> Nil,
+    Dynamic,
+  ) ->
     Nil,
 ) -> Effect(msg) {
   Effect([
     fn(actions: Actions(msg)) {
-      run(actions.dispatch, actions.emit, actions.select)
+      run(actions.dispatch, actions.emit, actions.select, actions.root)
     },
   ])
 }
@@ -172,15 +179,14 @@ pub fn map(effect: Effect(a), f: fn(a) -> b) -> Effect(b) {
   Effect({
     use eff <- list.map(effect.all)
     fn(actions: Actions(b)) {
-      eff(
-        Actions(
-          dispatch: fn(msg) { actions.dispatch(f(msg)) },
-          emit: actions.emit,
-          select: fn(selector) {
-            actions.select(process.map_selector(selector, f))
-          },
-        ),
-      )
+      eff(Actions(
+        dispatch: fn(msg) { actions.dispatch(f(msg)) },
+        emit: actions.emit,
+        select: fn(selector) {
+          actions.select(process.map_selector(selector, f))
+        },
+        root: actions.root,
+      ))
     }
   })
 }
@@ -204,6 +210,7 @@ pub fn map(effect: Effect(a), f: fn(a) -> b) -> Effect(b) {
         // we have to use `@target` for this and duplicate the function but
         // so be it.
         select: fn(_) { Nil },
+        root: actions.root,
       ))
     }
   })
@@ -225,8 +232,9 @@ pub fn perform(
   dispatch: fn(a) -> Nil,
   emit: fn(String, Json) -> Nil,
   select: fn(Selector(a)) -> Nil,
+  root: Dynamic,
 ) -> Nil {
-  let actions = Actions(dispatch, emit, select)
+  let actions = Actions(dispatch, emit, select, root)
   use eff <- list.each(effect.all)
 
   eff(actions)

src/lustre/element.gleam

@@ -8,10 +8,12 @@
 
 // IMPORTS ---------------------------------------------------------------------
 
+import gleam/dynamic.{type Dynamic}
 import gleam/list
 import gleam/string
 import gleam/string_builder.{type StringBuilder}
 import lustre/attribute.{type Attribute, attribute}
+import lustre/effect.{type Effect}
 import lustre/internals/vdom.{Element, Map, Text}
 
 // TYPES -----------------------------------------------------------------------
@@ -289,6 +291,15 @@ pub fn map(element: Element(a), f: fn(a) -> b) -> Element(b) {
   }
 }
 
+// EFFECTS ---------------------------------------------------------------------
+
+@internal
+pub fn get_root(effect: fn(fn(msg) -> Nil, Dynamic) -> Nil) -> Effect(msg) {
+  use dispatch, _, _, root <- effect.custom
+
+  effect(dispatch, root)
+}
+
 // CONVERSIONS -----------------------------------------------------------------
 
 /// Convert a Lustre `Element` to a string. This is _not_ pretty-printed, so

src/lustre/internals/runtime.gleam

@@ -244,7 +244,7 @@ fn run_effects(effects: Effect(msg), self: Subject(Action(msg, runtime))) -> Nil
   let dispatch = fn(msg) { actor.send(self, Dispatch(msg)) }
   let emit = fn(name, event) { actor.send(self, Emit(name, event)) }
   let select = fn(selector) { actor.send(self, SetSelector(selector)) }
-  let root = fn(_) { Nil }
+  let root = unsafe_coerce(Nil)
 
   effect.perform(effects, dispatch, emit, select, root)
 }

src/lustre/server_component.gleam

@@ -236,7 +236,7 @@ pub fn select(
 fn do_select(
   sel: fn(fn(msg) -> Nil, Subject(a)) -> Selector(msg),
 ) -> Effect(msg) {
-  use dispatch, _, select <- effect.custom
+  use dispatch, _, select, _ <- effect.custom
   let self = process.new_subject()
   let selector = sel(dispatch, self)