Merge #271

271: Support passing a struct instance as properties r=DenisKolodin a=limira

If we have
```rust
#[derive(Debug, Default, Eq, PartialEq)]
pub struct MyProps {
    val: i32,
}

impl Component<Context> for MyComp {
    type Message = Msg;
    type Properties = MyProps;
}
```
then if we have an instance of `MyProps`, we can pass it directly to its Component:
```rust
let my_props = MyProps {val: 64 };
html! {
    <MyComp: props=my_props, />
}
```
Is there a better syntax for this?
If this is merged as is, any `struct` that is used for a Component's properties will not allowed to contain a field named `props`!

Edit: I you merge this, please squash all commits. While working on this, I got stuck by an error I don't know how to solve, just commit to get back to the original working code (from master).

Co-authored-by: Limira <20672976+limira@users.noreply.github.com>

src/macros.rs

@@ -21,6 +21,13 @@ macro_rules! html_impl {
         let mut pair = $crate::virtual_dom::VComp::lazy::<$comp>();
         html_impl! { @vcomp $stack pair ($($tail)*) }
     };
+    // Set a whole struct as a properties
+    (@vcomp $stack:ident $pair:ident (with $props:ident, $($tail:tt)*)) => {
+        $pair.0 = $props;
+        html_impl! { @vcomp $stack $pair ($($tail)*) }
+    };
+    // Set a specific field as a property.
+    // It uses `Transformer` trait to convert a type used in template to a type of the field.
     (@vcomp $stack:ident $pair:ident ($attr:ident = $val:expr, $($tail:tt)*)) => {
         // It cloned for ergonomics in templates. Attribute with
         // `self.param` value could be reused and sholdn't be cloned

tests/vcomp_test.rs

@@ -0,0 +1,71 @@
+#[macro_use]
+extern crate yew;
+
+use yew::html::{Component, Env, Html, Renderable, ShouldRender};
+use yew::virtual_dom::VNode;
+
+type Ctx = ();
+
+struct Comp;
+
+#[derive(PartialEq, Clone)]
+struct Props {
+    field_1: u32,
+    field_2: u32,
+}
+
+impl Default for Props {
+    fn default() -> Self {
+        Props {
+            field_1: 0,
+            field_2: 0,
+        }
+    }
+}
+
+impl Component<Ctx> for Comp {
+    type Message = ();
+    type Properties = Props;
+
+    fn create(_: Self::Properties, _: &mut Env<Ctx, Self>) -> Self {
+        Comp
+    }
+
+    fn update(&mut self, _: Self::Message, _: &mut Env<Ctx, Self>) -> ShouldRender {
+        unimplemented!();
+    }
+}
+
+impl Renderable<Ctx, Comp> for Comp {
+    fn view(&self) -> Html<Ctx, Self> {
+        unimplemented!();
+    }
+}
+
+#[test]
+fn set_properties_to_component() {
+    let _: VNode<Ctx, Comp> = html! {
+        <Comp: />
+    };
+
+    let _: VNode<Ctx, Comp> = html! {
+        <Comp: field_1=1, />
+    };
+
+    let _: VNode<Ctx, Comp> = html! {
+        <Comp: field_2=2, />
+    };
+
+    let _: VNode<Ctx, Comp> = html! {
+        <Comp: field_1=1, field_2=2, />
+    };
+
+    let props = Props {
+        field_1: 1,
+        field_2: 1,
+    };
+
+    let _: VNode<Ctx, Comp> = html! {
+        <Comp: with props, field_2=2, />
+    };
+}