From 17adf7cc1467aa1ddd41ffa16fcd3c438068bb98 Mon Sep 17 00:00:00 2001
From: Greg Johnston <greg.johnston@gmail.com>
Date: Mon, 5 Jun 2023 20:48:22 -0400
Subject: [PATCH] feat: pass components with no props directly into the view as
 a function that takes only `Scope` (#1144)

---
 examples/README.md                  |  7 +++
 examples/hackernews/src/lib.rs      |  6 +--
 examples/hackernews_axum/src/lib.rs |  6 +--
 examples/router/src/lib.rs          | 12 ++---
 examples/ssr_modes/src/app.rs       |  4 +-
 examples/ssr_modes_axum/src/app.rs  |  6 +--
 leptos/Cargo.toml                   |  2 +-
 leptos/src/lib.rs                   | 83 +++++++++++++++++++++++++++--
 leptos_macro/example/src/lib.rs     |  1 -
 leptos_macro/src/component.rs       | 50 +++++++++++++----
 leptos_macro/src/lib.rs             | 18 ++-----
 leptos_macro/src/view.rs            | 29 +++++-----
 leptos_reactive/src/context.rs      |  3 --
 13 files changed, 160 insertions(+), 67 deletions(-)
 create mode 100644 examples/README.md

diff --git a/examples/README.md b/examples/README.md
new file mode 100644
index 000000000..d641b1310
--- /dev/null
+++ b/examples/README.md
@@ -0,0 +1,7 @@
+# Examples
+
+The examples in this directory are all built and tested against the current `main` branch.
+
+To the extent that new features have been released or breaking changes have been made since the previous release, the examples are compatible with the `main` branch and not the current release.
+
+To see the examples as they were at the time of the `0.3.0` release, [click here](https://github.com/leptos-rs/leptos/tree/v0.3.0/examples).
\ No newline at end of file
diff --git a/examples/hackernews/src/lib.rs b/examples/hackernews/src/lib.rs
index 748533e69..3dd6a214d 100644
--- a/examples/hackernews/src/lib.rs
+++ b/examples/hackernews/src/lib.rs
@@ -22,9 +22,9 @@ pub fn App(cx: Scope) -> impl IntoView {
             <Nav />
             <main>
                 <Routes>
-                    <Route path="users/:id" view=|cx| view! { cx,  <User/> }/>
-                    <Route path="stories/:id" view=|cx| view! { cx,  <Story/> }/>
-                    <Route path=":stories?" view=|cx| view! { cx,  <Stories/> }/>
+                    <Route path="users/:id" view=User/>
+                    <Route path="stories/:id" view=Story/>
+                    <Route path=":stories?" view=Stories/>
                 </Routes>
             </main>
         </Router>
diff --git a/examples/hackernews_axum/src/lib.rs b/examples/hackernews_axum/src/lib.rs
index 23eb4e1db..d8c1d1578 100644
--- a/examples/hackernews_axum/src/lib.rs
+++ b/examples/hackernews_axum/src/lib.rs
@@ -22,9 +22,9 @@ pub fn App(cx: Scope) -> impl IntoView {
                 <Nav />
                 <main>
                     <Routes>
-                        <Route path="users/:id" view=|cx| view! { cx,  <User/> }/>
-                        <Route path="stories/:id" view=|cx| view! { cx,  <Story/> }/>
-                        <Route path=":stories?" view=|cx| view! { cx,  <Stories/> }/>
+                        <Route path="users/:id" view=User/>
+                        <Route path="stories/:id" view=Story/>
+                        <Route path=":stories?" view=Stories/>
                     </Routes>
                 </main>
             </Router>
diff --git a/examples/router/src/lib.rs b/examples/router/src/lib.rs
index a4d85be25..041718e81 100644
--- a/examples/router/src/lib.rs
+++ b/examples/router/src/lib.rs
@@ -36,15 +36,15 @@ pub fn RouterExample(cx: Scope) -> impl IntoView {
                     <ContactRoutes/>
                     <Route
                         path="about"
-                        view=move |cx| view! { cx,  <About/> }
+                        view=About
                     />
                     <Route
                         path="settings"
-                        view=move |cx| view! { cx,  <Settings/> }
+                        view=Settings
                     />
                     <Route
                         path="redirect-home"
-                        view=move |cx| view! { cx, <Redirect path="/"/> }
+                        view=|cx| view! { cx, <Redirect path="/"/> }
                     />
                 </AnimatedRoutes>
             </main>
@@ -59,15 +59,15 @@ pub fn ContactRoutes(cx: Scope) -> impl IntoView {
     view! { cx,
         <Route
             path=""
-            view=move |cx| view! { cx,  <ContactList/> }
+            view=ContactList
         >
             <Route
                 path=":id"
-                view=move |cx| view! { cx,  <Contact/> }
+                view=Contact
             />
             <Route
                 path="/"
-                view=move |_| view! { cx,  <p>"Select a contact."</p> }
+                view=|cx| view! { cx,  <p>"Select a contact."</p> }
             />
         </Route>
     }
diff --git a/examples/ssr_modes/src/app.rs b/examples/ssr_modes/src/app.rs
index 3fbb461a5..f85d431e8 100644
--- a/examples/ssr_modes/src/app.rs
+++ b/examples/ssr_modes/src/app.rs
@@ -18,13 +18,13 @@ pub fn App(cx: Scope) -> impl IntoView {
             <main>
                 <Routes>
                     // We’ll load the home page with out-of-order streaming and <Suspense/>
-                    <Route path="" view=|cx| view! { cx, <HomePage/> }/>
+                    <Route path="" view=HomePage/>
 
                     // We'll load the posts with async rendering, so they can set
                     // the title and metadata *after* loading the data
                     <Route
                         path="/post/:id"
-                        view=|cx| view! { cx, <Post/> }
+                        view=Post
                         ssr=SsrMode::Async
                     />
                 </Routes>
diff --git a/examples/ssr_modes_axum/src/app.rs b/examples/ssr_modes_axum/src/app.rs
index 0989045bc..4276bca50 100644
--- a/examples/ssr_modes_axum/src/app.rs
+++ b/examples/ssr_modes_axum/src/app.rs
@@ -18,18 +18,18 @@ pub fn App(cx: Scope) -> impl IntoView {
             <main>
                 <Routes>
                     // We’ll load the home page with out-of-order streaming and <Suspense/>
-                    <Route path="" view=|cx| view! { cx, <HomePage/> }/>
+                    <Route path="" view=HomePage/>
 
                     // We'll load the posts with async rendering, so they can set
                     // the title and metadata *after* loading the data
                     <Route
                         path="/post/:id"
-                        view=|cx| view! { cx, <Post/> }
+                        view=Post
                         ssr=SsrMode::Async
                     />
                     <Route
                         path="/post_in_order/:id"
-                        view=|cx| view! { cx, <Post/> }
+                        view=Post
                         ssr=SsrMode::InOrder
                     />
                 </Routes>
diff --git a/leptos/Cargo.toml b/leptos/Cargo.toml
index 0a3787967..875980892 100644
--- a/leptos/Cargo.toml
+++ b/leptos/Cargo.toml
@@ -60,7 +60,7 @@ rkyv = ["leptos_reactive/rkyv"]
 tracing = ["leptos_macro/tracing"]
 
 [package.metadata.cargo-all-features]
-denylist = ["stable", "tracing", "template_macro"]
+denylist = ["stable", "tracing", "template_macro", "rustls", "default-tls", "web-sys", "wasm-bindgen"]
 skip_feature_sets = [
   [
     "csr",
diff --git a/leptos/src/lib.rs b/leptos/src/lib.rs
index 33a421e80..7337f7b84 100644
--- a/leptos/src/lib.rs
+++ b/leptos/src/lib.rs
@@ -240,11 +240,84 @@ pub trait Props {
     fn builder() -> Self::Builder;
 }
 
-impl<P, F, R> Component<P> for F where F: FnOnce(::leptos::Scope, P) -> R {}
+#[doc(hidden)]
+pub trait PropsOrNoPropsBuilder {
+    type Builder;
+    fn builder_or_not() -> Self::Builder;
+}
 
 #[doc(hidden)]
-pub fn component_props_builder<P: Props>(
-    _f: &impl Component<P>,
-) -> <P as Props>::Builder {
-    <P as Props>::builder()
+#[derive(Copy, Clone, Debug, Default)]
+pub struct EmptyPropsBuilder {}
+
+impl EmptyPropsBuilder {
+    pub fn build(self) {}
+}
+
+impl<P: Props> PropsOrNoPropsBuilder for P {
+    type Builder = <P as Props>::Builder;
+    fn builder_or_not() -> Self::Builder {
+        Self::builder()
+    }
+}
+
+impl PropsOrNoPropsBuilder for EmptyPropsBuilder {
+    type Builder = EmptyPropsBuilder;
+    fn builder_or_not() -> Self::Builder {
+        EmptyPropsBuilder {}
+    }
+}
+
+impl<F, R> Component<EmptyPropsBuilder> for F where
+    F: FnOnce(::leptos::Scope) -> R
+{
+}
+
+impl<P, F, R> Component<P> for F
+where
+    F: FnOnce(::leptos::Scope, P) -> R,
+    P: Props,
+{
+}
+
+#[doc(hidden)]
+pub fn component_props_builder<P: PropsOrNoPropsBuilder>(
+    _f: &impl Component<P>,
+) -> <P as PropsOrNoPropsBuilder>::Builder {
+    <P as PropsOrNoPropsBuilder>::builder_or_not()
+}
+
+#[doc(hidden)]
+pub fn component_view<P>(
+    f: impl ComponentConstructor<P>,
+    cx: Scope,
+    props: P,
+) -> View {
+    f.construct(cx, props)
+}
+
+#[doc(hidden)]
+pub trait ComponentConstructor<P> {
+    fn construct(self, cx: Scope, props: P) -> View;
+}
+
+impl<Func, V> ComponentConstructor<()> for Func
+where
+    Func: FnOnce(Scope) -> V,
+    V: IntoView,
+{
+    fn construct(self, cx: Scope, (): ()) -> View {
+        (self)(cx).into_view(cx)
+    }
+}
+
+impl<Func, V, P> ComponentConstructor<P> for Func
+where
+    Func: FnOnce(Scope, P) -> V,
+    V: IntoView,
+    P: PropsOrNoPropsBuilder,
+{
+    fn construct(self, cx: Scope, props: P) -> View {
+        (self)(cx, props).into_view(cx)
+    }
 }
diff --git a/leptos_macro/example/src/lib.rs b/leptos_macro/example/src/lib.rs
index b7b4b37fe..27e11334e 100644
--- a/leptos_macro/example/src/lib.rs
+++ b/leptos_macro/example/src/lib.rs
@@ -36,6 +36,5 @@ pub fn TestComponent(
     and_another: usize,
 ) -> impl IntoView {
     _ = (key, another, and_another);
-    todo!()
 }
 
diff --git a/leptos_macro/src/component.rs b/leptos_macro/src/component.rs
index 1e37f48fe..2584e92c9 100644
--- a/leptos_macro/src/component.rs
+++ b/leptos_macro/src/component.rs
@@ -131,6 +131,8 @@ impl ToTokens for Model {
             ret,
         } = self;
 
+        let no_props = props.len() == 1;
+
         let mut body = body.to_owned();
 
         // check for components that end ;
@@ -213,6 +215,42 @@ impl ToTokens for Model {
             }
         };
 
+        let props_arg = if no_props {
+            quote! {}
+        } else {
+            quote! {
+                props: #props_name #generics
+            }
+        };
+
+        let destructure_props = if no_props {
+            quote! {}
+        } else {
+            quote! {
+                let #props_name {
+                    #prop_names
+                } = props;
+            }
+        };
+
+        let into_view = if no_props {
+            quote! {
+                impl #generics ::leptos::IntoView for #props_name #generics #where_clause {
+                    fn into_view(self, cx: ::leptos::Scope) -> ::leptos::View {
+                        #name(cx).into_view(cx)
+                    }
+                }
+            }
+        } else {
+            quote! {
+                impl #generics ::leptos::IntoView for #props_name #generics #where_clause {
+                    fn into_view(self, cx: ::leptos::Scope) -> ::leptos::View {
+                        #name(cx, self).into_view(cx)
+                    }
+                }
+            }
+        };
+
         let output = quote! {
             #[doc = #builder_name_doc]
             #[doc = ""]
@@ -231,11 +269,7 @@ impl ToTokens for Model {
                 }
             }
 
-            impl #generics ::leptos::IntoView for #props_name #generics #where_clause {
-                fn into_view(self, cx: ::leptos::Scope) -> ::leptos::View {
-                    #name(cx, self).into_view(cx)
-                }
-            }
+            #into_view
 
             #docs
             #component_fn_prop_docs
@@ -244,15 +278,13 @@ impl ToTokens for Model {
             #vis fn #name #generics (
                 #[allow(unused_variables)]
                 #scope_name: ::leptos::Scope,
-                props: #props_name #generics
+                #props_arg
             ) #ret #(+ #lifetimes)*
             #where_clause
             {
                 #body
 
-                let #props_name {
-                    #prop_names
-                } = props;
+                #destructure_props
 
                 #tracing_span_expr
 
diff --git a/leptos_macro/src/lib.rs b/leptos_macro/src/lib.rs
index fdf5dbd1a..6768c9b55 100644
--- a/leptos_macro/src/lib.rs
+++ b/leptos_macro/src/lib.rs
@@ -502,15 +502,11 @@ pub fn template(tokens: TokenStream) -> TokenStream {
 ///
 /// // PascalCase: Generated component will be called MyComponent
 /// #[component]
-/// fn MyComponent(cx: Scope) -> impl IntoView {
-///     todo!()
-/// }
+/// fn MyComponent(cx: Scope) -> impl IntoView {}
 ///
 /// // snake_case: Generated component will be called MySnakeCaseComponent
 /// #[component]
-/// fn my_snake_case_component(cx: Scope) -> impl IntoView {
-///     todo!()
-/// }
+/// fn my_snake_case_component(cx: Scope) -> impl IntoView {}
 /// ```
 ///
 /// 3. The macro generates a type `ComponentProps` for every `Component` (so, `HomePage` generates `HomePageProps`,
@@ -526,9 +522,7 @@ pub fn template(tokens: TokenStream) -> TokenStream {
 ///     use leptos::*;
 ///
 ///     #[component]
-///     pub fn MyComponent(cx: Scope) -> impl IntoView {
-///         todo!()
-///     }
+///     pub fn MyComponent(cx: Scope) -> impl IntoView {}
 /// }
 /// ```
 /// ```
@@ -542,9 +536,7 @@ pub fn template(tokens: TokenStream) -> TokenStream {
 ///     use leptos::*;
 ///
 ///     #[component]
-///     pub fn my_snake_case_component(cx: Scope) -> impl IntoView {
-///         todo!()
-///     }
+///     pub fn my_snake_case_component(cx: Scope) -> impl IntoView {}
 /// }
 /// ```
 ///
@@ -557,7 +549,6 @@ pub fn template(tokens: TokenStream) -> TokenStream {
 ///
 /// #[component]
 /// fn MyComponent<T: Fn() -> HtmlElement<Div>>(cx: Scope, render_prop: T) -> impl IntoView {
-///   todo!()
 /// }
 /// ```
 ///
@@ -571,7 +562,6 @@ pub fn template(tokens: TokenStream) -> TokenStream {
 /// where
 ///     T: Fn() -> HtmlElement<Div>,
 /// {
-///     todo!()
 /// }
 /// ```
 ///
diff --git a/leptos_macro/src/view.rs b/leptos_macro/src/view.rs
index cf27585d5..03ea28210 100644
--- a/leptos_macro/src/view.rs
+++ b/leptos_macro/src/view.rs
@@ -436,6 +436,7 @@ fn element_to_tokens_ssr(
         template.push('<');
         template.push_str(&tag_name);
 
+        #[cfg(debug_assertions)]
         stmts_for_ide.save_element_completion(node);
 
         let mut inner_html = None;
@@ -1671,7 +1672,8 @@ pub(crate) fn component_to_tokens(
     });
 
     let mut component = quote! {
-        #name(
+        ::leptos::component_view(
+            &#name,
             #cx,
             ::leptos::component_props_builder(&#name)
                 #(#props)*
@@ -1681,7 +1683,8 @@ pub(crate) fn component_to_tokens(
         )
     };
 
-    IdeTagHelper::add_component_completion(&mut component, cx, node);
+    #[cfg(debug_assertions)]
+    IdeTagHelper::add_component_completion(&mut component, node);
 
     if events.is_empty() {
         component
@@ -2093,13 +2096,12 @@ impl IdeTagHelper {
         }
     }
 
+    /// Add completion to the closing tag of the component.
     ///
-    /// Add completion to close tag of the component definition.
+    /// In order to ensure that generics are passed through correctly in the
+    /// current builder pattern, this clones the whole component constructor,
+    /// but it will never be used.
     ///
-    /// we can emit full copy of open_tag builder (close_tag.props().slots().children().build()),
-    /// but i choose to replace props with unreachable! call,
-    /// so expansion output will be shorter.
-    /// The output is looking like:
     /// ```no_build
     /// if false {
     ///     close_tag(cx, unreachable!())
@@ -2108,24 +2110,17 @@ impl IdeTagHelper {
     ///     open_tag(open_tag.props().slots().children().build())
     /// }
     /// ```
-    ///
-    /// Because element type can have generics, we cant construct simple statement like
-    /// let _ = #name; or (let _: #name = unreachable!()) both syntax require to know generics params.
     pub fn add_component_completion(
         component: &mut TokenStream,
-        cx: &Ident,
         node: &NodeElement,
     ) {
         // emit ide helper info
-        if let Some(close_tag) = node.close_tag.as_ref().map(|c| &c.name) {
-            let name = close_tag;
+        if node.close_tag.is_some() {
+            let constructor = component.clone();
             *component = quote! {
                 if false {
                     #[allow(unreachable_code)]
-                    #name(
-                        #cx,
-                        unreachable!()
-                    )
+                    #constructor
                 } else {
                     #component
                 }
diff --git a/leptos_reactive/src/context.rs b/leptos_reactive/src/context.rs
index 28fe2b2f3..e4c2c47ed 100644
--- a/leptos_reactive/src/context.rs
+++ b/leptos_reactive/src/context.rs
@@ -43,8 +43,6 @@ use std::any::{Any, TypeId};
 ///     // consume the provided context of type `ValueSetter` using `use_context`
 ///     // this traverses up the tree of `Scope`s and gets the nearest provided `ValueSetter`
 ///     let set_value = use_context::<ValueSetter>(cx).unwrap().0;
-///
-///     todo!()
 /// }
 /// ```
 #[cfg_attr(
@@ -107,7 +105,6 @@ where
 ///     // this traverses up the tree of `Scope`s and gets the nearest provided `ValueSetter`
 ///     let set_value = use_context::<ValueSetter>(cx).unwrap().0;
 ///
-///     todo!()
 /// }
 /// ```
 #[cfg_attr(