Add html_nested! macro to support nested iterable children access (y…

…ewstack#843)

* Revert "Revert "Improve nested html! expansion by unwrapping VNodes (yewstack#820)" (yewstack#842)"

This reverts commit 70862a4

* Add minor fix to VList to conform with yewstack#820

* Add unittest for the regression bug yewstack#839

* Resolve yewstack#839 regression issue introduced by yewstack#820

* wip

* Revert "Resolve yewstack#839 regression issue introduced by yewstack#820"

This reverts commit 34dc935.

* Use explicit html_nested

* Remove NodeSeq from prelude

* Clean up tests

* Add list and tag tests

* Revert vtag children change

Co-authored-by: Justin Starry <justin.m.starry@gmail.com>

crates/macro/src/html_tree/html_component.rs

@@ -127,9 +127,11 @@ impl ToTokens for HtmlComponent {
 
         let set_children = if !children.is_empty() {
             quote! {
-                .children(::yew::html::ChildrenRenderer::new(
-                    vec![#(#children.into(),)*]
-                ))
+                .children(::yew::html::ChildrenRenderer::new({
+                    let mut v = ::std::vec::Vec::new();
+                    #(v.extend(::yew::utils::NodeSeq::from(#children));)*
+                    v
+                }))
             }
         } else {
             quote! {}

crates/macro/src/html_tree/html_list.rs

@@ -49,10 +49,14 @@ impl Parse for HtmlList {
 
 impl ToTokens for HtmlList {
     fn to_tokens(&self, tokens: &mut proc_macro2::TokenStream) {
-        let html_trees = &self.0;
+        let children = &self.0;
         tokens.extend(quote! {
             ::yew::virtual_dom::VNode::VList(
-                ::yew::virtual_dom::vlist::VList::new_with_children(vec![#(#html_trees,)*])
+                ::yew::virtual_dom::vlist::VList::new_with_children({
+                    let mut v = ::std::vec::Vec::new();
+                    #(v.extend(::yew::utils::NodeSeq::from(#children));)*
+                    v
+                })
             )
         });
     }

crates/macro/src/html_tree/html_node.rs

@@ -4,6 +4,7 @@ use quote::{quote, quote_spanned, ToTokens};
 use syn::buffer::Cursor;
 use syn::parse::{Parse, ParseStream, Result};
 use syn::spanned::Spanned;
+use syn::Expr;
 use syn::Lit;
 
 pub struct HtmlNode(Node);
@@ -18,7 +19,7 @@ impl Parse for HtmlNode {
             }
             Node::Literal(lit)
         } else {
-            Node::Raw(input.parse()?)
+            Node::Expression(input.parse()?)
         };
 
         Ok(HtmlNode(node))
@@ -46,12 +47,8 @@ impl ToTokens for HtmlNode {
 impl ToTokens for Node {
     fn to_tokens(&self, tokens: &mut TokenStream) {
         let node_token = match &self {
-            Node::Literal(lit) => quote! {
-                ::yew::virtual_dom::VNode::from(#lit)
-            },
-            Node::Raw(stream) => quote_spanned! {stream.span()=>
-                ::yew::virtual_dom::VNode::from({#stream})
-            },
+            Node::Literal(lit) => quote! {#lit},
+            Node::Expression(expr) => quote_spanned! {expr.span()=> {#expr} },
         };
 
         tokens.extend(node_token);
@@ -60,5 +57,5 @@ impl ToTokens for Node {
 
 enum Node {
     Literal(Lit),
-    Raw(TokenStream),
+    Expression(Expr),
 }

crates/macro/src/html_tree/mod.rs

@@ -126,6 +126,19 @@ impl HtmlTree {
     }
 }
 
+pub struct HtmlRootNested(HtmlTreeNested);
+impl Parse for HtmlRootNested {
+    fn parse(input: ParseStream) -> Result<Self> {
+        Ok(HtmlRootNested(HtmlTreeNested::parse(input)?))
+    }
+}
+
+impl ToTokens for HtmlRootNested {
+    fn to_tokens(&self, tokens: &mut proc_macro2::TokenStream) {
+        self.0.to_tokens(tokens);
+    }
+}
+
 pub struct HtmlTreeNested(HtmlTree);
 impl Parse for HtmlTreeNested {
     fn parse(input: ParseStream) -> Result<Self> {

crates/macro/src/lib.rs

@@ -63,7 +63,7 @@ mod derive_props;
 mod html_tree;
 
 use derive_props::DerivePropsInput;
-use html_tree::HtmlRoot;
+use html_tree::{HtmlRoot, HtmlRootNested};
 use proc_macro::TokenStream;
 use proc_macro_hack::proc_macro_hack;
 use quote::{quote, ToTokens};
@@ -94,6 +94,12 @@ pub fn derive_props(input: TokenStream) -> TokenStream {
     TokenStream::from(input.into_token_stream())
 }
 
+#[proc_macro_hack]
+pub fn html_nested(input: TokenStream) -> TokenStream {
+    let root = parse_macro_input!(input as HtmlRootNested);
+    TokenStream::from(quote! {#root})
+}
+
 #[proc_macro_hack]
 pub fn html(input: TokenStream) -> TokenStream {
     let root = parse_macro_input!(input as HtmlRoot);

src/lib.rs

@@ -72,9 +72,14 @@ use proc_macro_hack::proc_macro_hack;
 #[proc_macro_hack(support_nested)]
 pub use yew_macro::html;
 
+#[doc(hidden)]
+#[proc_macro_hack(support_nested)]
+pub use yew_macro::html_nested;
+
 /// This module contains macros which implements html! macro and JSX-like templates
 pub mod macros {
     pub use crate::html;
+    pub use crate::html_nested;
     pub use yew_macro::Properties;
 }
 

src/utils.rs

@@ -1,6 +1,7 @@
 //! This module contains useful utils to get information about the current document.
 
 use failure::{err_msg, Error};
+use std::marker::PhantomData;
 use stdweb::web::document;
 
 /// Returns `host` for the current document. Useful to connect to a server that server the app.
@@ -10,3 +11,31 @@ pub fn host() -> Result<String, Error> {
         .ok_or_else(|| err_msg("can't get location"))
         .and_then(|l| l.host().map_err(Error::from))
 }
+
+/// Specialty type necessary for helping flattening components returned from nested html macros.
+#[derive(Debug)]
+pub struct NodeSeq<IN, OUT>(Vec<OUT>, PhantomData<IN>);
+
+impl<IN: Into<OUT>, OUT> From<IN> for NodeSeq<IN, OUT> {
+    fn from(val: IN) -> Self {
+        Self(vec![val.into()], PhantomData::default())
+    }
+}
+
+impl<IN: Into<OUT>, OUT> From<Vec<IN>> for NodeSeq<IN, OUT> {
+    fn from(val: Vec<IN>) -> Self {
+        Self(
+            val.into_iter().map(|x| x.into()).collect(),
+            PhantomData::default(),
+        )
+    }
+}
+
+impl<IN: Into<OUT>, OUT> IntoIterator for NodeSeq<IN, OUT> {
+    type Item = OUT;
+    type IntoIter = std::vec::IntoIter<Self::Item>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.0.into_iter()
+    }
+}

tests/macro/html-component-fail.rs

@@ -2,7 +2,6 @@
 
 use std::marker::PhantomData;
 use yew::prelude::*;
-use yew::virtual_dom::{VChild, VComp, VNode};
 
 #[derive(Clone, Properties, PartialEq)]
 pub struct ChildProperties {
@@ -21,18 +20,6 @@ impl Component for Child {
     fn view(&self) -> Html { unimplemented!() }
 }
 
-impl From<VChild<Child>> for ChildProperties {
-    fn from(comp: VChild<Child>) -> Self {
-        comp.props
-    }
-}
-
-impl Into<VNode> for ChildProperties {
-    fn into(self) -> VNode {
-        VComp::new::<Child>(self, NodeRef::default()).into()
-    }
-}
-
 #[derive(Clone, Properties)]
 pub struct ChildContainerProperties {
     #[props(required)]
@@ -92,7 +79,7 @@ fn compile_fail() {
     html! { <ChildContainer></ChildContainer> };
     html! { <ChildContainer>{ "Not allowed" }</ChildContainer> };
     html! { <ChildContainer><></></ChildContainer> };
-    html! { <ChildContainer><Child int=1 /><other /></ChildContainer> };
+    html! { <ChildContainer><other /></ChildContainer> };
 
     html! { <Generic<String>></Generic> };
     html! { <Generic<String>></Generic<Vec<String>>> };