From 5e325d5a8718d3b00fc5682863ebd5e7e77ffa5f Mon Sep 17 00:00:00 2001
From: Rich Harris <richard.a.harris@gmail.com>
Date: Sun, 3 Sep 2017 12:45:45 -0400
Subject: [PATCH] remove redundant input blowback guard - closes #645

---
 .../dom/visitors/Element/Binding.ts           |  34 ++-
 .../expected-bundle.js                        | 237 ++++++++++++++++++
 .../input-without-blowback-guard/expected.js  |  66 +++++
 .../input-without-blowback-guard/input.html   |   1 +
 4 files changed, 325 insertions(+), 13 deletions(-)
 create mode 100644 test/js/samples/input-without-blowback-guard/expected-bundle.js
 create mode 100644 test/js/samples/input-without-blowback-guard/expected.js
 create mode 100644 test/js/samples/input-without-blowback-guard/input.html

diff --git a/src/generators/dom/visitors/Element/Binding.ts b/src/generators/dom/visitors/Element/Binding.ts
index 7f28184e802b..8878af17d09c 100644
--- a/src/generators/dom/visitors/Element/Binding.ts
+++ b/src/generators/dom/visitors/Element/Binding.ts
@@ -51,10 +51,13 @@ export default function visitBinding(
 
 	let setter = getSetter(block, name, snippet, state.parentNode, attribute, dependencies, value);
 	let updateElement = `${state.parentNode}.${attribute.name} = ${snippet};`;
+
+	const needsLock = node.name !== 'input' || !/radio|checkbox|range|color/.test(type); // TODO others?
 	const lock = `#${state.parentNode}_updating`;
-	let updateCondition = `!${lock}`;
+	let updateConditions = needsLock ? [`!${lock}`] : [];
+	let readOnly = false;
 
-	block.addVariable(lock, 'false');
+	if (needsLock) block.addVariable(lock, 'false');
 
 	// <select> special case
 	if (node.name === 'select') {
@@ -125,24 +128,24 @@ export default function visitBinding(
 				${setter}
 			`;
 
-			updateCondition += ` && !isNaN(${snippet})`;
+			updateConditions.push(`!isNaN(${snippet})`);
 		} else if (attribute.name === 'duration') {
-			updateCondition = null;
+			readOnly = true;
 		} else if (attribute.name === 'paused') {
 			// this is necessary to prevent the audio restarting by itself
 			const last = block.getUniqueName(`${state.parentNode}_paused_value`);
 			block.addVariable(last, 'true');
 
-			updateCondition = `${last} !== (${last} = ${snippet})`;
+			updateConditions = [`${last} !== (${last} = ${snippet})`];
 			updateElement = `${state.parentNode}[${last} ? "pause" : "play"]();`;
 		}
 	}
 
 	block.builders.init.addBlock(deindent`
 		function ${handler}() {
-			${lock} = true;
+			${needsLock && `${lock} = true;`}
 			${setter}
-			${lock} = false;
+			${needsLock && `${lock} = false;`}
 		}
 	`);
 
@@ -172,13 +175,18 @@ export default function visitBinding(
 		node.initialUpdateNeedsStateObject = !block.contexts.has(name);
 	}
 
-	if (updateCondition !== null) {
-		// audio/video duration is read-only, it never updates
-		block.builders.update.addBlock(deindent`
-			if (${updateCondition}) {
+	if (!readOnly) { // audio/video duration is read-only, it never updates
+		if (updateConditions.length) {
+			block.builders.update.addBlock(deindent`
+				if (${updateConditions.join(' && ')}) {
+					${updateElement}
+				}
+			`);
+		} else {
+			block.builders.update.addBlock(deindent`
 				${updateElement}
-			}
-		`);
+			`);
+		}
 	}
 
 	if (attribute.name === 'paused') {
diff --git a/test/js/samples/input-without-blowback-guard/expected-bundle.js b/test/js/samples/input-without-blowback-guard/expected-bundle.js
new file mode 100644
index 000000000000..58f498a9bbc9
--- /dev/null
+++ b/test/js/samples/input-without-blowback-guard/expected-bundle.js
@@ -0,0 +1,237 @@
+function noop() {}
+
+function assign(target) {
+	var k,
+		source,
+		i = 1,
+		len = arguments.length;
+	for (; i < len; i++) {
+		source = arguments[i];
+		for (k in source) target[k] = source[k];
+	}
+
+	return target;
+}
+
+function insertNode(node, target, anchor) {
+	target.insertBefore(node, anchor);
+}
+
+function detachNode(node) {
+	node.parentNode.removeChild(node);
+}
+
+function createElement(name) {
+	return document.createElement(name);
+}
+
+function addListener(node, event, handler) {
+	node.addEventListener(event, handler, false);
+}
+
+function removeListener(node, event, handler) {
+	node.removeEventListener(event, handler, false);
+}
+
+function destroy(detach) {
+	this.destroy = noop;
+	this.fire('destroy');
+	this.set = this.get = noop;
+
+	if (detach !== false) this._fragment.unmount();
+	this._fragment.destroy();
+	this._fragment = this._state = null;
+}
+
+function differs(a, b) {
+	return a !== b || ((a && typeof a === 'object') || typeof a === 'function');
+}
+
+function dispatchObservers(component, group, changed, newState, oldState) {
+	for (var key in group) {
+		if (!changed[key]) continue;
+
+		var newValue = newState[key];
+		var oldValue = oldState[key];
+
+		var callbacks = group[key];
+		if (!callbacks) continue;
+
+		for (var i = 0; i < callbacks.length; i += 1) {
+			var callback = callbacks[i];
+			if (callback.__calling) continue;
+
+			callback.__calling = true;
+			callback.call(component, newValue, oldValue);
+			callback.__calling = false;
+		}
+	}
+}
+
+function get(key) {
+	return key ? this._state[key] : this._state;
+}
+
+function fire(eventName, data) {
+	var handlers =
+		eventName in this._handlers && this._handlers[eventName].slice();
+	if (!handlers) return;
+
+	for (var i = 0; i < handlers.length; i += 1) {
+		handlers[i].call(this, data);
+	}
+}
+
+function observe(key, callback, options) {
+	var group = options && options.defer
+		? this._observers.post
+		: this._observers.pre;
+
+	(group[key] || (group[key] = [])).push(callback);
+
+	if (!options || options.init !== false) {
+		callback.__calling = true;
+		callback.call(this, this._state[key]);
+		callback.__calling = false;
+	}
+
+	return {
+		cancel: function() {
+			var index = group[key].indexOf(callback);
+			if (~index) group[key].splice(index, 1);
+		}
+	};
+}
+
+function on(eventName, handler) {
+	if (eventName === 'teardown') return this.on('destroy', handler);
+
+	var handlers = this._handlers[eventName] || (this._handlers[eventName] = []);
+	handlers.push(handler);
+
+	return {
+		cancel: function() {
+			var index = handlers.indexOf(handler);
+			if (~index) handlers.splice(index, 1);
+		}
+	};
+}
+
+function set(newState) {
+	this._set(assign({}, newState));
+	if (this._root._lock) return;
+	this._root._lock = true;
+	callAll(this._root._beforecreate);
+	callAll(this._root._oncreate);
+	callAll(this._root._aftercreate);
+	this._root._lock = false;
+}
+
+function _set(newState) {
+	var oldState = this._state,
+		changed = {},
+		dirty = false;
+
+	for (var key in newState) {
+		if (differs(newState[key], oldState[key])) changed[key] = dirty = true;
+	}
+	if (!dirty) return;
+
+	this._state = assign({}, oldState, newState);
+	this._recompute(changed, this._state, oldState, false);
+	if (this._bind) this._bind(changed, this._state);
+	dispatchObservers(this, this._observers.pre, changed, this._state, oldState);
+	this._fragment.update(changed, this._state);
+	dispatchObservers(this, this._observers.post, changed, this._state, oldState);
+}
+
+function callAll(fns) {
+	while (fns && fns.length) fns.pop()();
+}
+
+function _mount(target, anchor) {
+	this._fragment.mount(target, anchor);
+}
+
+function _unmount() {
+	this._fragment.unmount();
+}
+
+var proto = {
+	destroy: destroy,
+	get: get,
+	fire: fire,
+	observe: observe,
+	on: on,
+	set: set,
+	teardown: destroy,
+	_recompute: noop,
+	_set: _set,
+	_mount: _mount,
+	_unmount: _unmount
+};
+
+function create_main_fragment(state, component) {
+	var input;
+
+	function input_change_handler() {
+		component.set({ foo: input.checked });
+	}
+
+	return {
+		create: function() {
+			input = createElement( 'input' );
+			this.hydrate();
+		},
+
+		hydrate: function(nodes) {
+			input.type = "checkbox";
+			addListener(input, "change", input_change_handler);
+		},
+
+		mount: function(target, anchor) {
+			insertNode( input, target, anchor );
+
+			input.checked = state.foo;
+		},
+
+		update: function(changed, state) {
+			input.checked = state.foo;
+		},
+
+		unmount: function() {
+			detachNode( input );
+		},
+
+		destroy: function() {
+			removeListener(input, "change", input_change_handler);
+		}
+	};
+}
+
+function SvelteComponent(options) {
+	this.options = options;
+	this._state = options.data || {};
+
+	this._observers = {
+		pre: Object.create(null),
+		post: Object.create(null)
+	};
+
+	this._handlers = Object.create(null);
+
+	this._root = options._root || this;
+	this._yield = options._yield;
+	this._bind = options._bind;
+
+	this._fragment = create_main_fragment(this._state, this);
+
+	if (options.target) {
+		this._fragment.create();
+		this._fragment.mount(options.target, options.anchor || null);
+	}
+}
+
+assign(SvelteComponent.prototype, proto );
+
+export default SvelteComponent;
diff --git a/test/js/samples/input-without-blowback-guard/expected.js b/test/js/samples/input-without-blowback-guard/expected.js
new file mode 100644
index 000000000000..067c9589e582
--- /dev/null
+++ b/test/js/samples/input-without-blowback-guard/expected.js
@@ -0,0 +1,66 @@
+import { addListener, assign, createElement, detachNode, insertNode, proto, removeListener } from "svelte/shared.js";
+
+function create_main_fragment(state, component) {
+	var input;
+
+	function input_change_handler() {
+		component.set({ foo: input.checked });
+	}
+
+	return {
+		create: function() {
+			input = createElement( 'input' );
+			this.hydrate();
+		},
+
+		hydrate: function(nodes) {
+			input.type = "checkbox";
+			addListener(input, "change", input_change_handler);
+		},
+
+		mount: function(target, anchor) {
+			insertNode( input, target, anchor );
+
+			input.checked = state.foo;
+		},
+
+		update: function(changed, state) {
+			input.checked = state.foo;
+		},
+
+		unmount: function() {
+			detachNode( input );
+		},
+
+		destroy: function() {
+			removeListener(input, "change", input_change_handler);
+		}
+	};
+}
+
+function SvelteComponent(options) {
+	this.options = options;
+	this._state = options.data || {};
+
+	this._observers = {
+		pre: Object.create(null),
+		post: Object.create(null)
+	};
+
+	this._handlers = Object.create(null);
+
+	this._root = options._root || this;
+	this._yield = options._yield;
+	this._bind = options._bind;
+
+	this._fragment = create_main_fragment(this._state, this);
+
+	if (options.target) {
+		this._fragment.create();
+		this._fragment.mount(options.target, options.anchor || null);
+	}
+}
+
+assign(SvelteComponent.prototype, proto );
+
+export default SvelteComponent;
\ No newline at end of file
diff --git a/test/js/samples/input-without-blowback-guard/input.html b/test/js/samples/input-without-blowback-guard/input.html
new file mode 100644
index 000000000000..ae28ef4f7dde
--- /dev/null
+++ b/test/js/samples/input-without-blowback-guard/input.html
@@ -0,0 +1 @@
+<input type='checkbox' bind:checked='foo'>
\ No newline at end of file