Parse blocks in html! as Rust block expressions

.gitignore

@@ -7,3 +7,8 @@ target/
 *.iml
 /.idea/
 /.vscode/
+
+# artifacts from tools like prettier
+node_modules/
+package.json
+package-lock.json

packages/yew-macro/src/html_tree/html_node.rs

@@ -3,15 +3,15 @@ use quote::{quote, quote_spanned, ToTokens};
 use syn::buffer::Cursor;
 use syn::parse::{Parse, ParseStream, Result};
 use syn::spanned::Spanned;
-use syn::{Expr, Lit};
+use syn::{Block, Lit, Stmt};
 
 use super::ToNodeIterator;
 use crate::stringify::Stringify;
 use crate::PeekValue;
 
 pub enum HtmlNode {
  Literal(Box<Lit>),
- Expression(Box<Expr>),
+ Expression(Vec<Stmt>),
 }
 
 impl Parse for HtmlNode {
@@ -23,7 +23,7 @@ impl Parse for HtmlNode {
  }
  HtmlNode::Literal(Box::new(lit))
  } else {
- HtmlNode::Expression(Box::new(input.parse()?))
+ HtmlNode::Expression(Block::parse_within(input)?)
  };
 
  Ok(node)
@@ -49,7 +49,17 @@ impl ToTokens for HtmlNode {
  let sr = lit.stringify();
  quote_spanned! {lit.span()=> ::yew::virtual_dom::VText::new(#sr) }
  }
- HtmlNode::Expression(expr) => quote! {#expr},
+ HtmlNode::Expression(stmts) => {
+ if let [expr] = &stmts[..] {
+ quote! {#expr}
+ } else {
+ let mut block = TokenStream::new();
+ for stmt in stmts.iter() {
+ stmt.to_tokens(&mut block)
+ }
+ quote_spanned! {block.span()=> {#block}}
+ }
+ }
  });
  }
 }
@@ -58,11 +68,23 @@ impl ToNodeIterator for HtmlNode {
  fn to_node_iterator_stream(&self) -> Option<TokenStream> {
  match self {
  HtmlNode::Literal(_) => None,
- HtmlNode::Expression(expr) => {
- // NodeSeq turns both Into<T> and Vec<Into<T>> into IntoIterator<Item = T>
- Some(quote_spanned! {expr.span().resolved_at(Span::call_site())=>
- ::std::convert::Into::<::yew::utils::NodeSeq<_, _>>::into(#expr)
- })
+ HtmlNode::Expression(stmts) => {
+ if let [expr] = &stmts[..] {
+ Some(quote_spanned! {expr.span().resolved_at(Span::call_site())=>
+ ::std::convert::Into::<::yew::utils::NodeSeq<_, _>>::into(#expr)
+ })
+ } else {
+ let mut block = TokenStream::new();
+ for stmt in stmts.iter() {
+ stmt.to_tokens(&mut block)
+ }
+ // NodeSeq turns both Into<T> and Vec<Into<T>> into IntoIterator<Item = T>
+ Some(
+ quote_spanned! {block.span().resolved_at(Span::call_site())=>
+ ::std::convert::Into::<::yew::utils::NodeSeq<_, _>>::into({#block})
+ },
+ )
+ }
  }
  }
  }

packages/yew-macro/tests/html_macro/block-pass.rs

@@ -62,4 +62,11 @@ fn main() {
  { for ::std::iter::Iterator::map(0..3, item) }
  </ul>
  };
+
+ ::yew::html! {
+ <span>{
+ let version = 0.21;
+ ::std::format!("Yew {version}")
+ }</span>
+ };
 }

website/docs/concepts/function-components/pure-components.mdx

@@ -30,7 +30,7 @@ fn HelloWorld(props: &Props) -> Html {
 :::note
 If you have an internal pure component that makes no use of hooks and other component machinery, you can often write it instead
 as a normal function returning `Html` and avoid a bit of overhead for Yew, related to running the component lifecycle. Use
-[expression syntax](concepts/html/literals-and-expressions.mdx#expressions) to render them in `html!`.
+[code block syntax](concepts/html/literals-and-expressions.mdx#code-blocks) to render them in `html!`.
 :::
 
 ## Impure components

website/docs/concepts/html/literals-and-expressions.mdx

@@ -1,5 +1,5 @@
 ---
-title: 'Literals and Expressions'
+title: 'Literals and Code Blocks'
 ---
 
 ## Literals
@@ -27,16 +27,19 @@ html!{
 
 ## Expressions
 
-You can insert expressions in your HTML using `{}` blocks, as long as they resolve to `Html`
+You can insert blocks of Rust code in your HTML, as long as they resolve to `Html`
 
 ```rust
 use yew::prelude::*;
 
-let show_link = true;
+fn some_computation() -> bool {
+ true
+}
 
 html! {
  <div>
  {
+ let show_link = some_computation();
  if show_link {
  html! {
  <a href="https://example.com">{"Link"}</a>