Make BaseComponent Sealed. (#2359)

packages/yew/Cargo.toml

@@ -65,6 +65,8 @@ features = [
 easybench-wasm = "0.2"
 wasm-bindgen-test = "0.3"
 gloo = { version = "0.6", features = ["futures"] }
+rustversion = "1"
+trybuild = "1"
 
 [features]
 doc_test = []

packages/yew/Makefile.toml

@@ -1,4 +1,10 @@
+[tasks.native-test]
+command = "cargo"
+toolchain = "1.56"
+args = ["test", "native_"]
+
 [tasks.test]
+dependencies = ["native-test"]
 extend = "core::wasm-pack-base"
 command = "wasm-pack"
 args = [

packages/yew/src/functional/mod.rs

@@ -24,6 +24,9 @@ mod hooks;
 pub use hooks::*;
 
 use crate::html::Context;
+
+use crate::html::SealedBaseComponent;
+
 /// This attribute creates a function component from a normal Rust function.
 ///
 /// Functions with this attribute **must** return `Html` and can optionally take an argument for props.
@@ -100,9 +103,9 @@ where
     }
 }
 
-impl<T: 'static> BaseComponent for FunctionComponent<T>
+impl<T> BaseComponent for FunctionComponent<T>
 where
-    T: FunctionProvider,
+    T: FunctionProvider + 'static,
 {
     type Message = Box<dyn FnOnce() -> bool>;
     type Properties = T::TProps;
@@ -167,6 +170,8 @@ pub(crate) fn get_current_scope() -> Option<AnyScope> {
     }
 }
 
+impl<T> SealedBaseComponent for FunctionComponent<T> where T: FunctionProvider + 'static {}
+
 #[derive(Clone, Default)]
 struct MsgQueue(Rc<RefCell<Vec<Msg>>>);
 

packages/yew/src/html/component/mod.rs

@@ -34,13 +34,17 @@ impl<COMP: BaseComponent> Context<COMP> {
     }
 }
 
+/// A Sealed trait that prevents direct implementation of
+/// [BaseComponent].
+pub trait SealedBaseComponent {}
+
 /// The common base of both function components and struct components.
 ///
 /// If you are taken here by doc links, you might be looking for [`Component`] or
 /// [`#[function_component]`](crate::functional::function_component).
 ///
 /// We provide a blanket implementation of this trait for every member that implements [`Component`].
-pub trait BaseComponent: Sized + 'static {
+pub trait BaseComponent: SealedBaseComponent + Sized + 'static {
     /// The Component's Message.
     type Message: 'static;
 
@@ -160,3 +164,5 @@ where
         Component::destroy(self, ctx)
     }
 }
+
+impl<T> SealedBaseComponent for T where T: Sized + Component + 'static {}

packages/yew/tests/failed_tests/base_component_impl-fail.rs

@@ -0,0 +1,26 @@
+use yew::html::BaseComponent;
+use yew::prelude::*;
+
+pub struct Comp;
+
+impl BaseComponent for Comp {
+    type Message = ();
+    type Properties = ();
+
+    fn create(_ctx: &Context<Self>) -> Self {
+        Self
+    }
+    fn update(&mut self, _ctx: &Context<Self>, _msg: Self::Message) -> bool {
+        false
+    }
+    fn changed(&mut self, _ctx: &Context<Self>) -> bool {
+        false
+    }
+    fn view(&self, _ctx: &Context<Self>) -> HtmlResult {
+        todo!()
+    }
+    fn rendered(&mut self, _ctx: &Context<Self>, _first_render: bool) {}
+    fn destroy(&mut self, _ctx: &Context<Self>) {}
+}
+
+fn main() {}

packages/yew/tests/failed_tests/base_component_impl-fail.stderr

@@ -0,0 +1,12 @@
+error[E0277]: the trait bound `Comp: yew::Component` is not satisfied
+  --> tests/failed_tests/base_component_impl-fail.rs:6:6
+   |
+6  | impl BaseComponent for Comp {
+   |      ^^^^^^^^^^^^^ the trait `yew::Component` is not implemented for `Comp`
+   |
+   = note: required because of the requirements on the impl of `SealedBaseComponent` for `Comp`
+note: required by a bound in `BaseComponent`
+  --> src/html/component/mod.rs
+   |
+   | pub trait BaseComponent: SealedBaseComponent + Sized + 'static {
+   |                          ^^^^^^^^^^^^^^^^^^^ required by this bound in `BaseComponent`

packages/yew/tests/failed_tests/sealed_base_component_impl-fail.rs

@@ -0,0 +1,28 @@
+use yew::html::BaseComponent;
+use yew::prelude::*;
+
+pub struct Comp;
+
+impl BaseComponent for Comp {
+    type Message = ();
+    type Properties = ();
+
+    fn create(_ctx: &Context<Self>) -> Self {
+        Self
+    }
+    fn update(&mut self, _ctx: &Context<Self>, _msg: Self::Message) -> bool {
+        false
+    }
+    fn changed(&mut self, _ctx: &Context<Self>) -> bool {
+        false
+    }
+    fn view(&self, _ctx: &Context<Self>) -> HtmlResult {
+        todo!()
+    }
+    fn rendered(&mut self, _ctx: &Context<Self>, _first_render: bool) {}
+    fn destroy(&mut self, _ctx: &Context<Self>) {}
+}
+
+impl yew::html::component::SealedBaseComponent for Comp {}
+
+fn main() {}

packages/yew/tests/failed_tests/sealed_base_component_impl-fail.stderr

@@ -0,0 +1,11 @@
+error[E0603]: module `component` is private
+  --> tests/failed_tests/sealed_base_component_impl-fail.rs:26:17
+   |
+26 | impl yew::html::component::SealedBaseComponent for Comp {}
+   |                 ^^^^^^^^^ private module
+   |
+note: the module `component` is defined here
+  --> src/html/mod.rs
+   |
+   | mod component;
+   | ^^^^^^^^^^^^^^

packages/yew/tests/native_failed_test.rs

@@ -0,0 +1,7 @@
+#[allow(dead_code)]
+#[cfg(not(target_arch = "wasm32"))]
+#[rustversion::attr(stable(1.56), test)]
+fn native_failed_tests() {
+    let t = trybuild::TestCases::new();
+    t.compile_fail("tests/failed_tests/*-fail.rs");
+}