Please have the html! macro accept html comments

[largenumberhere]

Hi, I'm new to yew, please go easy on me. I notice what I'd personally consider a flaw in the html macro. It is obviously up to the dev time if it's a flaw worth devoting time to. The compiler's feedback is 100% clear, so I wouldn't call it a bug, but I couldn't find a similar discussion or issue, so I felt it was important to open a dialogue on it.

The following causes a hard error in yew 0.21.0, as hosted on crates.io.

use yew::prelude::*;

fn main() {
    // load the framework
    yew::Renderer::<App>::new().render();
}
#[function_component(App)]
fn app() -> Html {
    html! {
        <>
            <!--This is a valid html comment-->
            <h1> { "Hello, world!" } </h1>
        </>
    }
}

Compile error:

error: expected a valid html element
  --> src\main.rs:12:13
   |
12 |             <!--This is a valid html comment-->
   |             ^

Changing the comment to this is rejected the same by the compiler

            <!-- {"This is a valid html comment "} -->

Using a rust-style comment does however work in the way I'd expect a html comment to be treated.

            // <!-- {"This is a valid html comment "} -->

It causes no compile errors, and the line is stripped from the output.

Naive suggestion:

• Ignore html comment elements entirely. If possible, provide a warning that it is ignored and not included in the final html. I believe it is extremely important to be able to comment in one's code where necessary, especially when related to macros, which as a whole are hard to understand. Requiring a rust comment to me looks unintended and wrong in a html context.

What's anyone else's thoughts on this?

[lukajincharadze]

The issue you're encountering with HTML comments in Yew's HTML macro is indeed a valid concern, as HTML comments are commonly used for documentation and code commenting purposes. While the current behavior might be intended for strict HTML compliance, it could be beneficial to consider enhancing Yew's HTML macro to handle HTML comments more gracefully.

One potential solution could be to ignore HTML comment elements entirely within the macro and provide a warning to developers when encountering them, indicating that they are ignored and not included in the final HTML output. This approach would maintain clarity for developers and ensure that their comments are not inadvertently omitted from the rendered output.

Additionally, requiring Rust-style comments (//) within the HTML context might feel unintended and counterintuitive for developers accustomed to working with HTML comments directly.

[ranile]

We could probably give a better error message but a warning is impossible. Not only does warnings from proc-macros are not supported on stable rust yet but also parsing the entire comment would be very hard to do. Just checking if the tag name starts with !-- and giving a nicer error could be done.

Any PRs implementing this would be welcome