Merge pull request #3062 from leptos-rs/into-render

feat: add `IntoRender` for rendering custom data

leptos_macro/src/view/mod.rs

@@ -548,7 +548,9 @@ fn node_to_tokens(
             view_marker,
             disable_inert_html,
         ),
-        Node::Block(block) => Some(quote! { #block }),
+        Node::Block(block) => {
+            Some(quote! { ::leptos::prelude::IntoRender::into_render(#block) })
+        }
         Node::Text(text) => Some(text_to_tokens(&text.value)),
         Node::RawText(raw) => {
             let text = raw.to_string_best();
@@ -878,7 +880,7 @@ fn attribute_to_tokens(
                     NodeName::Path(path) => path.path.get_ident(),
                     _ => unreachable!(),
                 };
-                let value = attribute_value(node);
+                let value = attribute_value(node, false);
                 quote! {
                     .#node_ref(#value)
                 }
@@ -928,13 +930,13 @@ fn attribute_to_tokens(
                 // we don't provide statically-checked methods for SVG attributes
                 || (tag_type == TagType::Svg && name != "inner_html")
             {
-                let value = attribute_value(node);
+                let value = attribute_value(node, true);
                 quote! {
                     .attr(#name, #value)
                 }
             } else {
                 let key = attribute_name(&node.key);
-                let value = attribute_value(node);
+                let value = attribute_value(node, true);
 
                 // special case of global_class and class attribute
                 if &node.key.to_string() == "class"
@@ -971,18 +973,19 @@ pub(crate) fn attribute_absolute(
                 let id = &parts[0];
                 match id {
                     NodeNameFragment::Ident(id) => {
-                        let value = attribute_value(node);
                         // ignore `let:` and `clone:`
                         if id == "let" || id == "clone" {
                             None
                         } else if id == "attr" {
+                        let value = attribute_value(node, true);
                             let key = &parts[1];
                             let key_name = key.to_string();
                             if key_name == "class" || key_name == "style" {
                                 Some(
                                     quote! { ::leptos::tachys::html::#key::#key(#value) },
                                 )
                             } else if key_name == "aria" {
+                                let value = attribute_value(node, true);
                                 let mut parts_iter = parts.iter();
                                 parts_iter.next();
                                 let fn_name = parts_iter.map(|p| p.to_string()).collect::<Vec<String>>().join("_");
@@ -1011,6 +1014,7 @@ pub(crate) fn attribute_absolute(
                                 },
                             )
                         } else if id == "style" || id == "class" {
+                            let value = attribute_value(node, false);
                             let key = &node.key.to_string();
                             let key = key
                                 .replacen("style:", "", 1)
@@ -1019,6 +1023,7 @@ pub(crate) fn attribute_absolute(
                                 quote! { ::leptos::tachys::html::#id::#id((#key, #value)) },
                             )
                         } else if id == "prop" {
+                            let value = attribute_value(node, false);
                             let key = &node.key.to_string();
                             let key = key.replacen("prop:", "", 1);
                             Some(
@@ -1075,7 +1080,7 @@ pub(crate) fn two_way_binding_to_tokens(
     name: &str,
     node: &KeyedAttribute,
 ) -> TokenStream {
-    let value = attribute_value(node);
+    let value = attribute_value(node, false);
 
     let ident =
         format_ident!("{}", name.to_case(UpperCamel), span = node.key.span());
@@ -1100,7 +1105,7 @@ pub(crate) fn event_type_and_handler(
     name: &str,
     node: &KeyedAttribute,
 ) -> (TokenStream, TokenStream, TokenStream) {
-    let handler = attribute_value(node);
+    let handler = attribute_value(node, false);
 
     let (event_type, is_custom, is_force_undelegated, is_targeted) =
         parse_event_name(name);
@@ -1157,7 +1162,7 @@ fn class_to_tokens(
     class: TokenStream,
     class_name: Option<&str>,
 ) -> TokenStream {
-    let value = attribute_value(node);
+    let value = attribute_value(node, false);
     if let Some(class_name) = class_name {
         quote! {
             .#class((#class_name, #value))
@@ -1174,7 +1179,7 @@ fn style_to_tokens(
     style: TokenStream,
     style_name: Option<&str>,
 ) -> TokenStream {
-    let value = attribute_value(node);
+    let value = attribute_value(node, false);
     if let Some(style_name) = style_name {
         quote! {
             .#style((#style_name, #value))
@@ -1191,7 +1196,7 @@ fn prop_to_tokens(
     prop: TokenStream,
     key: &str,
 ) -> TokenStream {
-    let value = attribute_value(node);
+    let value = attribute_value(node, false);
     quote! {
         .#prop(#key, #value)
     }
@@ -1348,7 +1353,10 @@ fn attribute_name(name: &NodeName) -> TokenStream {
     }
 }
 
-fn attribute_value(attr: &KeyedAttribute) -> TokenStream {
+fn attribute_value(
+    attr: &KeyedAttribute,
+    is_attribute_proper: bool,
+) -> TokenStream {
     match attr.possible_value.to_value() {
         None => quote! { true },
         Some(value) => match &value.value {
@@ -1363,14 +1371,26 @@ fn attribute_value(attr: &KeyedAttribute) -> TokenStream {
                     }
                 }
 
-                quote! {
-                    {#expr}
+                if matches!(expr, Expr::Lit(_)) || !is_attribute_proper {
+                    quote! {
+                        #expr
+                    }
+                } else {
+                    quote! {
+                        ::leptos::prelude::IntoAttributeValue::into_attribute_value(#expr)
+                    }
                 }
             }
             // any value in braces: expand as-is to give proper r-a support
             KVAttributeValue::InvalidBraced(block) => {
-                quote! {
-                    #block
+                if is_attribute_proper {
+                    quote! {
+                        ::leptos::prelude::IntoAttributeValue::into_attribute_value(#block)
+                    }
+                } else {
+                    quote! {
+                        #block
+                    }
                 }
             }
         },

tachys/src/html/attribute/value.rs

@@ -11,6 +11,26 @@ use std::{
     sync::Arc,
 };
 
+/// Declares that this type can be converted into some other type, which is a valid attribute value.
+pub trait IntoAttributeValue {
+    /// The attribute value into which this type can be converted.
+    type Output;
+
+    /// Consumes this value, transforming it into an attribute value.
+    fn into_attribute_value(self) -> Self::Output;
+}
+
+impl<T> IntoAttributeValue for T
+where
+    T: AttributeValue,
+{
+    type Output = Self;
+
+    fn into_attribute_value(self) -> Self::Output {
+        self
+    }
+}
+
 /// A possible value for an HTML attribute.
 pub trait AttributeValue: Send {
     /// The state that should be retained between building and rebuilding.

tachys/src/html/element/mod.rs

@@ -4,8 +4,8 @@ use crate::{
     renderer::{CastFrom, Rndr},
     ssr::StreamBuilder,
     view::{
-        add_attr::AddAnyAttr, Mountable, Position, PositionState, Render,
-        RenderHtml, ToTemplate,
+        add_attr::AddAnyAttr, IntoRender, Mountable, Position, PositionState,
+        Render, RenderHtml, ToTemplate,
     },
 };
 use const_str_slice_concat::{
@@ -65,11 +65,13 @@ impl<E, At, Ch, NewChild> ElementChild<NewChild> for HtmlElement<E, At, Ch>
 where
     E: ElementWithChildren,
     Ch: Render + NextTuple,
-    <Ch as NextTuple>::Output<NewChild>: Render,
+    <Ch as NextTuple>::Output<NewChild::Output>: Render,
 
-    NewChild: Render,
+    NewChild: IntoRender,
+    NewChild::Output: Render,
 {
-    type Output = HtmlElement<E, At, <Ch as NextTuple>::Output<NewChild>>;
+    type Output =
+        HtmlElement<E, At, <Ch as NextTuple>::Output<NewChild::Output>>;
 
     fn child(self, child: NewChild) -> Self::Output {
         let HtmlElement {
@@ -82,7 +84,7 @@ where
             tag,
 
             attributes,
-            children: children.next_tuple(child),
+            children: children.next_tuple(child.into_render()),
         }
     }
 }
@@ -116,7 +118,7 @@ where
 /// Adds a child to the element.
 pub trait ElementChild<NewChild>
 where
-    NewChild: Render,
+    NewChild: IntoRender,
 {
     /// The type of the element, with the child added.
     type Output;

tachys/src/lib.rs

@@ -19,15 +19,16 @@ pub mod prelude {
                     OnAttribute, OnTargetAttribute, PropAttribute,
                     StyleAttribute,
                 },
+                IntoAttributeValue,
             },
             directive::DirectiveAttribute,
             element::{ElementChild, ElementExt, InnerHtmlAttribute},
             node_ref::NodeRefAttribute,
         },
         renderer::{dom::Dom, Renderer},
         view::{
-            add_attr::AddAnyAttr, any_view::IntoAny, Mountable, Render,
-            RenderHtml,
+            add_attr::AddAnyAttr, any_view::IntoAny, IntoRender, Mountable,
+            Render, RenderHtml,
         },
     };
 }

tachys/src/view/mod.rs

@@ -432,3 +432,23 @@ pub enum Position {
     /// This is the last child of its parent.
     LastChild,
 }
+
+/// Declares that this type can be converted into some other type, which can be renderered.
+pub trait IntoRender {
+    /// The renderable type into which this type can be converted.
+    type Output;
+
+    /// Consumes this value, transforming it into the renderable type.
+    fn into_render(self) -> Self::Output;
+}
+
+impl<T> IntoRender for T
+where
+    T: Render,
+{
+    type Output = Self;
+
+    fn into_render(self) -> Self::Output {
+        self
+    }
+}