Fix duplicate with props error messages.

packages/yew-macro/src/props/component.rs

@@ -38,6 +38,16 @@ impl Parse for WithProps {
         while !input.is_empty() {
             // no need to check if it's followed by `=` because `with` isn't a special prop
             if input.peek(kw::with) {
+                if let Some((with, expr)) = with_expr {
+                    return Err(syn::Error::new_spanned(
+                        {
+                            let mut res = with.into_token_stream();
+                            expr.to_tokens(&mut res);
+                            res
+                        },
+                        "there are two `with <props>` definitions for this component (note: you can only define `with <props>` once)"
+                    ));
+                }
                 let with = input.parse::<kw::with>()?;
                 if input.is_empty() {
                     return Err(syn::Error::new_spanned(

packages/yew-macro/tests/html_macro/html-component-fail.rs

@@ -80,6 +80,8 @@ fn compile_fail() {
     html! { <Child with /> };
     html! { <Child props /> };
     html! { <Child with props > };
+    let (p1, p2);
+    html! { <Child with p1 with p2 /> };
     html! { <Child with props ref=() ref=() /> };
     html! { <Child with props ref=() ref=() value=1 /> };
     html! { <Child with props ref=() value=1 ref=() /> };

packages/yew-macro/tests/html_macro/html-component-fail.stderr

@@ -28,6 +28,12 @@ error: this opening tag has no corresponding closing tag
 82 |     html! { <Child with props > };
    |             ^^^^^^^^^^^^^^^^^^^
 
+error: there are two `with <props>` definitions for this component (note: you can only define `with <props>` once)
+  --> $DIR/html-component-fail.rs:84:20
+   |
+84 |     html! { <Child with p1 with p2 /> };
+   |                    ^^^^^^^
+
 error: `ref` can only be set once
   --> $DIR/html-component-fail.rs:83:38
    |