Incremental performance improvements to element creation (#3169)

* enable interning

* intern tag names

* intern attribute keys and event listener types

* intern attribute values

* cache and clone elements

* clean up the node cloning version a bit

* use HashMap instead of Vec for element cache

* Revert "intern attribute values"

This reverts commit 28653c4660dcf1942fab3b0ad7d4c840b96e0f2a.

* add `enable-interning` feature to Yew that activates the same in wasm-bindgen

* remove interning feature

packages/yew/Cargo.toml

@@ -75,7 +75,7 @@ features = [
   "WheelEvent",
   "Window",
   "HtmlScriptElement",
-  "SubmitEvent"
+  "SubmitEvent",
 ]
 
 [target.'cfg(not(target_arch = "wasm32"))'.dev-dependencies]
@@ -89,11 +89,7 @@ trybuild = "1"
 
 [dev-dependencies.web-sys]
 version = "0.3"
-features = [
+features = ["ShadowRootInit", "ShadowRootMode", "HtmlButtonElement"]
-  "ShadowRootInit",
-  "ShadowRootMode",
-  "HtmlButtonElement"
-]
 
 [features]
 ssr = ["dep:html-escape", "dep:base64ct", "dep:bincode"]

packages/yew/src/dom_bundle/btag/attributes.rs

@@ -2,7 +2,7 @@ use std::collections::HashMap;
 use std::ops::Deref;
 
 use indexmap::IndexMap;
-use wasm_bindgen::JsValue;
+use wasm_bindgen::{intern, JsValue};
 use web_sys::{Element, HtmlInputElement as InputElement, HtmlTextAreaElement as TextAreaElement};
 use yew::AttrValue;
 
@@ -163,9 +163,9 @@ impl Attributes {
 
     fn set(el: &Element, key: &str, value: &str, apply_as: ApplyAttributeAs) {
         match apply_as {
-            ApplyAttributeAs::Attribute => {
+            ApplyAttributeAs::Attribute => el
-                el.set_attribute(key, value).expect("invalid attribute key")
+                .set_attribute(intern(key), value)
-            }
+                .expect("invalid attribute key"),
             ApplyAttributeAs::Property => {
                 let key = JsValue::from_str(key);
                 let value = JsValue::from_str(value);
@@ -177,7 +177,7 @@ impl Attributes {
     fn remove(el: &Element, key: &str, apply_as: ApplyAttributeAs) {
         match apply_as {
             ApplyAttributeAs::Attribute => el
-                .remove_attribute(key)
+                .remove_attribute(intern(key))
                 .expect("could not remove attribute"),
             ApplyAttributeAs::Property => {
                 let key = JsValue::from_str(key);

packages/yew/src/dom_bundle/btag/mod.rs

@@ -4,6 +4,8 @@ mod attributes;
 mod listeners;
 
 use std::borrow::Cow;
+use std::cell::RefCell;
+use std::collections::HashMap;
 use std::hint::unreachable_unchecked;
 use std::ops::DerefMut;
 
@@ -252,9 +254,31 @@ impl VTag {
                 .create_element_ns(namespace, tag)
                 .expect("can't create namespaced element for vtag")
         } else {
-            document()
+            thread_local! {
-                .create_element(tag)
+                static CACHED_ELEMENTS: RefCell<HashMap<String, Element>> = RefCell::new(HashMap::with_capacity(32));
-                .expect("can't create element for vtag")
+            }
+
+            CACHED_ELEMENTS.with(|cache| {
+                let mut cache = cache.borrow_mut();
+                let cached = cache.get(tag).map(|el| {
+                    el.clone_node()
+                        .expect("couldn't clone cached element")
+                        .unchecked_into::<Element>()
+                });
+                cached.unwrap_or_else(|| {
+                    let to_be_cached = document()
+                        .create_element(tag)
+                        .expect("can't create element for vtag");
+                    cache.insert(
+                        tag.to_string(),
+                        to_be_cached
+                            .clone_node()
+                            .expect("couldn't clone node to be cached")
+                            .unchecked_into(),
+                    );
+                    to_be_cached
+                })
+            })
         }
     }
 }

packages/yew/src/dom_bundle/subtree_root.rs

@@ -8,7 +8,7 @@ use std::rc::{Rc, Weak};
 use std::sync::atomic::{AtomicBool, AtomicU32, Ordering};
 
 use wasm_bindgen::prelude::{wasm_bindgen, Closure};
-use wasm_bindgen::{JsCast, UnwrapThrowExt};
+use wasm_bindgen::{intern, JsCast, UnwrapThrowExt};
 use web_sys::{
     AddEventListenerOptions, Element, Event, EventTarget as HtmlEventTarget, ShadowRoot,
 };
@@ -157,7 +157,7 @@ impl EventListener {
 
         target
             .add_event_listener_with_callback_and_add_event_listener_options(
-                &event_type,
+                intern(&event_type),
                 callback.as_ref().unchecked_ref(),
                 &options,
             )