fix: soften html style recommendations from errors on stable to warnings by injecting deprecated functions

Cargo.toml

@@ -30,7 +30,6 @@ unexpected_cfgs = { level = "warn", check-cfg = [
     "cfg(verbose_tests)",
     "cfg(yew_lints)",
     "cfg(nightly_yew)",
-    "cfg(yew_macro_nightly)",
     "cfg(wasm_bindgen_unstable_test_coverage)"
 ]}
 [workspace.dependencies]

packages/yew-macro/Cargo.toml

@@ -15,9 +15,6 @@ rust-version.workspace = true
 [lib]
 proc-macro = true
 
-[build-dependencies]
-version_check = "0.9"
-
 [dependencies]
 proc-macro-error = "1"
 proc-macro2.workspace = true

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

@@ -1,4 +1,4 @@
-use proc_macro2::Delimiter;
+use proc_macro2::{Delimiter, TokenStream};
 use quote::{ToTokens, quote, quote_spanned};
 use syn::buffer::Cursor;
 use syn::parse::{Parse, ParseStream};
@@ -11,6 +11,7 @@ use crate::PeekValue;
 pub struct HtmlBlock {
     pub content: BlockContent,
     brace: token::Brace,
+    pub(super) deprecations: TokenStream,
 }
 
 pub enum BlockContent {
@@ -28,32 +29,36 @@ impl Parse for HtmlBlock {
     fn parse(input: ParseStream) -> syn::Result<Self> {
         let content;
         let brace = braced!(content in input);
+        let mut deprecations = TokenStream::new();
         let content = if HtmlIterable::peek(content.cursor()).is_some() {
             BlockContent::Iterable(Box::new(content.parse()?))
         } else {
             let node: HtmlNode = content.parse()?;
             if let HtmlNode::Expression(ref expr) = node {
-                check_deprecated_html_call(expr);
+                deprecations = check_deprecated_html_call(expr);
             }
             BlockContent::Node(Box::new(node))
         };
 
-        Ok(HtmlBlock { content, brace })
+        Ok(HtmlBlock {
+            content,
+            brace,
+            deprecations,
+        })
     }
 }
 
 /// Check for deprecated `html!` usage patterns inside expression blocks.
-fn check_deprecated_html_call(expr: &Expr) {
+fn check_deprecated_html_call(expr: &Expr) -> TokenStream {
     // Pattern 1: { match expr { arm => html! { ... }, ... } }
     if let Expr::Match(match_expr) = expr {
         for arm in &match_expr.arms {
             if let Some(span) = html_macro_call_span(&arm.body) {
-                super::emit_deprecated!(
+                return super::deprecated_call(
                     span,
                     "Use bare elements in arms directly \n\nmatch value {\n    pattern => \
-                     <Element />,\n}"
+                     <Element />,\n}",
                 );
-                return;
             }
         }
     }
@@ -66,13 +71,46 @@ fn check_deprecated_html_call(expr: &Expr) {
             .last()
             .and_then(stmt_tail_html_macro_span)
         {
-            super::emit_deprecated!(
+            return super::deprecated_call(
                 span,
                 "`html!` is not needed inside expression blocks. Use `let` bindings and bare \
-                 elements directly"
+                 elements directly",
             );
         }
     }
+
+    // Pattern 3: { if cond { html! { ... } } else { html! { ... } } }
+    if let Expr::If(if_expr) = expr {
+        if let Some(span) = if_branch_html_macro_span(if_expr) {
+            return super::deprecated_call(
+                span,
+                "`html!` is not needed inside `if`/`else` branches. Use bare elements directly",
+            );
+        }
+    }
+
+    TokenStream::new()
+}
+
+/// Walk through an `if`/`else if`/`else` chain and return the span of the first tail `html!` call.
+fn if_branch_html_macro_span(if_expr: &syn::ExprIf) -> Option<proc_macro2::Span> {
+    if let Some(span) = if_expr
+        .then_branch
+        .stmts
+        .last()
+        .and_then(stmt_tail_html_macro_span)
+    {
+        return Some(span);
+    }
+    match if_expr.else_branch.as_ref().map(|(_, expr)| expr.as_ref()) {
+        Some(Expr::Block(block_expr)) => block_expr
+            .block
+            .stmts
+            .last()
+            .and_then(stmt_tail_html_macro_span),
+        Some(Expr::If(nested)) => if_branch_html_macro_span(nested),
+        _ => None,
+    }
 }
 
 /// Check if a statement is a tail `html!`/`html_nested!` macro call (no trailing semicolon).
@@ -101,25 +139,41 @@ fn macro_path_html_span(path: &syn::Path) -> Option<proc_macro2::Span> {
 
 impl ToTokens for HtmlBlock {
     fn to_tokens(&self, tokens: &mut proc_macro2::TokenStream) {
-        let HtmlBlock { content, .. } = self;
+        let HtmlBlock {
+            content,
+            deprecations,
+            ..
+        } = self;
         let new_tokens = match content {
             BlockContent::Iterable(html_iterable) => quote! {#html_iterable},
             BlockContent::Node(html_node) => quote! {#html_node},
         };
 
-        tokens.extend(quote! {#new_tokens});
+        if deprecations.is_empty() {
+            tokens.extend(new_tokens);
+        } else {
+            tokens.extend(quote! { { #deprecations #new_tokens } });
+        }
     }
 }
 
 impl ToNodeIterator for HtmlBlock {
     fn to_node_iterator_stream(&self) -> Option<proc_macro2::TokenStream> {
-        let HtmlBlock { content, brace } = self;
+        let HtmlBlock {
+            content,
+            brace,
+            deprecations,
+        } = self;
         let new_tokens = match content {
             BlockContent::Iterable(iterable) => iterable.to_node_iterator_stream(),
             BlockContent::Node(node) => node.to_node_iterator_stream(),
         }?;
 
-        Some(quote_spanned! {brace.span=> #new_tokens})
+        if deprecations.is_empty() {
+            Some(quote_spanned! {brace.span=> #new_tokens})
+        } else {
+            Some(quote_spanned! {brace.span=> { #deprecations #new_tokens }})
+        }
     }
 
     fn is_singular(&self) -> bool {

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

@@ -24,6 +24,7 @@ pub struct HtmlFor {
     iter: Expr,
     let_stmts: Vec<Local>,
     body: HtmlChildrenTree,
+    deprecations: TokenStream,
 }
 
 impl PeekValue<()> for HtmlFor {
@@ -53,7 +54,7 @@ impl Parse for HtmlFor {
         }
 
         let body = HtmlChildrenTree::parse_delimited_with_nodes(&body_stream)?;
-        super::check_unnecessary_fragment(&body);
+        let deprecations = super::check_unnecessary_fragment(&body);
         // TODO: more concise code by using if-let guards (MSRV 1.95)
         for child in body.0.iter() {
             let HtmlTree::Element(element) = child else {
@@ -77,6 +78,7 @@ impl Parse for HtmlFor {
             iter,
             let_stmts,
             body,
+            deprecations,
         })
     }
 }
@@ -88,6 +90,7 @@ impl ToTokens for HtmlFor {
             iter,
             let_stmts,
             body,
+            deprecations,
         } = self;
         let acc = Ident::new("__yew_v", iter.span());
 
@@ -129,6 +132,7 @@ impl ToTokens for HtmlFor {
             });
 
         tokens.extend(quote!({
+            #deprecations
             let mut #acc = ::std::vec::Vec::<::yew::virtual_dom::VNode>::new();
             ::std::iter::Iterator::for_each(
                 ::std::iter::IntoIterator::into_iter(#iter),

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

@@ -30,8 +30,12 @@ enum HtmlMatchArmBody {
         brace: token::Brace,
         let_stmts: Vec<Local>,
         children: HtmlChildrenTree,
+        deprecations: TokenStream,
+    },
+    Unbraced {
+        tree: Box<super::HtmlTree>,
+        deprecations: TokenStream,
     },
-    Unbraced(Box<super::HtmlTree>),
 }
 
 impl PeekValue<()> for HtmlMatch {
@@ -100,7 +104,7 @@ impl Parse for HtmlMatchArm {
 
         let fat_arrow_token: Token![=>] = input.parse()?;
 
-        let body = if input.cursor().group(Delimiter::Brace).is_some() {
+        let mut body = if input.cursor().group(Delimiter::Brace).is_some() {
             let content;
             let brace = braced!(content in input);
             let mut let_stmts = Vec::new();
@@ -112,17 +116,31 @@ impl Parse for HtmlMatchArm {
                 }
             }
             let children = HtmlChildrenTree::parse_delimited_with_nodes(&content)?;
-            super::check_unnecessary_fragment(&children);
+            let deprecations = super::check_unnecessary_fragment(&children);
             HtmlMatchArmBody::Braced {
                 brace,
                 let_stmts,
                 children,
+                deprecations,
             }
         } else {
-            HtmlMatchArmBody::Unbraced(Box::new(super::HtmlTree::parse_or_node(input)?))
+            HtmlMatchArmBody::Unbraced {
+                tree: Box::new(super::HtmlTree::parse_or_node(input)?),
+                deprecations: TokenStream::new(),
+            }
         };
 
-        check_arm_html_macro_call(&body);
+        let arm_deprecations = check_arm_html_macro_call(&body);
+        if !arm_deprecations.is_empty() {
+            match &mut body {
+                HtmlMatchArmBody::Braced { deprecations, .. } => {
+                    deprecations.extend(arm_deprecations)
+                }
+                HtmlMatchArmBody::Unbraced { deprecations, .. } => {
+                    deprecations.extend(arm_deprecations);
+                }
+            }
+        }
 
         let comma: Option<Token![,]> = input.parse()?;
 
@@ -143,9 +161,11 @@ impl ToTokens for HtmlMatchArmBody {
                 brace,
                 let_stmts,
                 children,
+                deprecations,
             } => {
                 tokens.extend(quote_spanned! {brace.span.span()=>
                     {
+                        #deprecations
                         #(#let_stmts)*
                         ::yew::virtual_dom::VNode::VList(::std::rc::Rc::new(
                             ::yew::virtual_dom::VList::with_children(
@@ -155,9 +175,12 @@ impl ToTokens for HtmlMatchArmBody {
                     }
                 });
             }
-            Self::Unbraced(tree) => {
+            Self::Unbraced { tree, deprecations } => {
                 tokens.extend(quote_spanned! {tree.span()=>
-                    { ::std::convert::Into::<::yew::virtual_dom::VNode>::into(#tree) }
+                    {
+                        #deprecations
+                        ::std::convert::Into::<::yew::virtual_dom::VNode>::into(#tree)
+                    }
                 });
             }
         }
@@ -197,22 +220,22 @@ impl ToTokens for HtmlMatch {
     }
 }
 
-fn check_arm_html_macro_call(body: &HtmlMatchArmBody) {
+fn check_arm_html_macro_call(body: &HtmlMatchArmBody) -> TokenStream {
     let trees: Box<dyn Iterator<Item = &super::HtmlTree> + '_> = match body {
         HtmlMatchArmBody::Braced { children, .. } => Box::new(children.0.iter()),
-        HtmlMatchArmBody::Unbraced(tree) => Box::new(std::iter::once(tree.as_ref())),
+        HtmlMatchArmBody::Unbraced { tree, .. } => Box::new(std::iter::once(tree.as_ref())),
     };
     for tree in trees {
         if let super::HtmlTree::Node(node) = tree {
             if let HtmlNode::Expression(expr) = node.as_ref() {
                 if let Some(span) = html_macro_call_span(expr) {
-                    super::emit_deprecated!(
+                    return super::deprecated_call(
                         span,
-                        "`html!` is not needed in `match` arms. Use bare elements directly"
+                        "`html!` is not needed in `match` arms. Use bare elements directly",
                     );
-                    return;
                 }
             }
         }
     }
+    TokenStream::new()
 }