feat: add TSend generic to Channel (#10139)

* add TSend to Channel

* add changeset

* fix tray Channel

* Update .changes/ipc-channel-generic.md

---------

Co-authored-by: Lucas Fernandes Nogueira <lucas@tauri.app>

.changes/ipc-channel-generic.md

@@ -0,0 +1,5 @@
+---
+"tauri": major:breaking
+---
+
+Add `TSend` generic to `ipc::Channel` for typesafe `send` calls and type inspection in `tauri-specta`

core/tauri/src/ipc/channel.rs

@@ -37,11 +37,19 @@ pub struct ChannelDataIpcQueue(pub(crate) Arc<Mutex<HashMap<u32, InvokeBody>>>);
 
 /// An IPC channel.
 #[derive(Clone)]
-pub struct Channel {
+pub struct Channel<TSend = InvokeBody> {
   id: u32,
   on_message: Arc<dyn Fn(InvokeBody) -> crate::Result<()> + Send + Sync>,
+  phantom: std::marker::PhantomData<TSend>,
 }
 
+#[cfg(feature = "specta")]
+const _: () = {
+  #[derive(specta::Type)]
+  #[specta(remote = Channel, rename = "TAURI_CHANNEL")]
+  struct Channel<TSend>(std::marker::PhantomData<TSend>);
+};
+
 impl Serialize for Channel {
   fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
   where
@@ -88,7 +96,7 @@ impl FromStr for JavaScriptChannelId {
 
 impl JavaScriptChannelId {
   /// Gets a [`Channel`] for this channel ID on the given [`Webview`].
-  pub fn channel_on<R: Runtime>(&self, webview: Webview<R>) -> Channel {
+  pub fn channel_on<R: Runtime, TSend>(&self, webview: Webview<R>) -> Channel<TSend> {
     let callback_id = self.0;
     let counter = AtomicUsize::new(0);
 
@@ -128,7 +136,7 @@ impl<'de> Deserialize<'de> for JavaScriptChannelId {
   }
 }
 
-impl Channel {
+impl<TSend> Channel<TSend> {
   /// Creates a new channel with the given message handler.
   pub fn new<F: Fn(InvokeBody) -> crate::Result<()> + Send + Sync + 'static>(
     on_message: F,
@@ -144,10 +152,15 @@ impl Channel {
     let channel = Self {
       id,
       on_message: Arc::new(on_message),
+      phantom: Default::default(),
     };
 
     #[cfg(mobile)]
-    crate::plugin::mobile::register_channel(channel.clone());
+    crate::plugin::mobile::register_channel(Channel {
+      id,
+      on_message: channel.on_message.clone(),
+      phantom: Default::default(),
+    });
 
     channel
   }
@@ -178,13 +191,16 @@ impl Channel {
   }
 
   /// Sends the given data through the channel.
-  pub fn send<T: IpcResponse>(&self, data: T) -> crate::Result<()> {
+  pub fn send(&self, data: TSend) -> crate::Result<()>
+  where
+    TSend: IpcResponse,
+  {
     let body = data.body()?;
     (self.on_message)(body)
   }
 }
 
-impl<'de, R: Runtime> CommandArg<'de, R> for Channel {
+impl<'de, R: Runtime, TSend: Clone> CommandArg<'de, R> for Channel<TSend> {
   /// Grabs the [`Webview`] from the [`CommandItem`] and returns the associated [`Channel`].
   fn from_command(command: CommandItem<'de, R>) -> Result<Self, InvokeError> {
     let name = command.name;
@@ -196,8 +212,8 @@ impl<'de, R: Runtime> CommandArg<'de, R> for Channel {
       .map(|id| id.channel_on(webview))
       .map_err(|_| {
         InvokeError::from_anyhow(anyhow::anyhow!(
-        "invalid channel value `{value}`, expected a string in the `{IPC_PAYLOAD_PREFIX}ID` format"
-      ))
+	        "invalid channel value `{value}`, expected a string in the `{IPC_PAYLOAD_PREFIX}ID` format"
+	      ))
       })
   }
 }

core/tauri/src/menu/plugin.rs

@@ -350,7 +350,7 @@ fn new<R: Runtime>(
   kind: ItemKind,
   options: Option<NewOptions>,
   channels: State<'_, MenuChannels>,
-  handler: Channel,
+  handler: Channel<MenuId>,
 ) -> crate::Result<(ResourceId, MenuId)> {
   let options = options.unwrap_or_default();
   let mut resources_table = app.resources_table();
@@ -866,7 +866,7 @@ fn set_icon<R: Runtime>(
   }
 }
 
-struct MenuChannels(Mutex<HashMap<MenuId, Channel>>);
+struct MenuChannels(Mutex<HashMap<MenuId, Channel<MenuId>>>);
 
 pub(crate) fn init<R: Runtime>() -> TauriPlugin<R> {
   Builder::new("menu")
@@ -877,7 +877,7 @@ pub(crate) fn init<R: Runtime>() -> TauriPlugin<R> {
     .on_event(|app, e| {
       if let RunEvent::MenuEvent(e) = e {
         if let Some(channel) = app.state::<MenuChannels>().0.lock().unwrap().get(&e.id) {
-          let _ = channel.send(&e.id);
+          let _ = channel.send(e.id.clone());
         }
       }
     })

core/tauri/src/plugin/mobile.rs

@@ -30,7 +30,7 @@ type PendingPluginCallHandler = Box<dyn FnOnce(PluginResponse) + Send + 'static>
 static PENDING_PLUGIN_CALLS_ID: AtomicI32 = AtomicI32::new(0);
 static PENDING_PLUGIN_CALLS: OnceLock<Mutex<HashMap<i32, PendingPluginCallHandler>>> =
   OnceLock::new();
-static CHANNELS: OnceLock<Mutex<HashMap<u32, Channel>>> = OnceLock::new();
+static CHANNELS: OnceLock<Mutex<HashMap<u32, Channel<serde_json::Value>>>> = OnceLock::new();
 
 /// Possible errors when invoking a plugin.
 #[derive(Debug, thiserror::Error)]
@@ -53,7 +53,7 @@ pub enum PluginInvokeError {
   CannotSerializePayload(serde_json::Error),
 }
 
-pub(crate) fn register_channel(channel: Channel) {
+pub(crate) fn register_channel(channel: Channel<serde_json::Value>) {
   CHANNELS
     .get_or_init(Default::default)
     .lock()

core/tauri/src/tray/plugin.rs

@@ -17,7 +17,7 @@ use crate::{
   AppHandle, Manager, Runtime, Webview,
 };
 
-use super::TrayIcon;
+use super::{TrayIcon, TrayIconEvent};
 
 #[derive(Deserialize)]
 #[serde(rename_all = "camelCase")]
@@ -36,7 +36,7 @@ struct TrayIconOptions {
 fn new<R: Runtime>(
   webview: Webview<R>,
   options: TrayIconOptions,
-  handler: Channel,
+  handler: Channel<TrayIconEvent>,
 ) -> crate::Result<(ResourceId, String)> {
   let mut builder = if let Some(id) = options.id {
     TrayIconBuilder::<R>::with_id(id)

core/tauri/src/webview/mod.rs

@@ -1268,7 +1268,7 @@ fn main() {
               for v in map.values() {
                 if let serde_json::Value::String(s) = v {
                   let _ = crate::ipc::JavaScriptChannelId::from_str(s)
-                    .map(|id| id.channel_on(webview.clone()));
+                    .map(|id| id.channel_on::<R, ()>(webview.clone()));
                 }
               }
             }