Repository: sveltejs/svelte (JavaScript) — Bug Fix

Issue:
Can not bind to 'files' attribute of input element
I recently tried:
```
<input type="file" multiple bind:files="files">
```

And received the compile time error:
```
[!] (svelte plugin) ValidationError: 'files' is not a valid binding
```

Am currently working on a PR.



Discussion:

Resolving patch:
diff --git a/src/validate/html/validateElement.ts b/src/validate/html/validateElement.ts
--- a/src/validate/html/validateElement.ts
+++ b/src/validate/html/validateElement.ts
@@ -145,6 +145,22 @@ export default function validateElement(
 						message: `'checked' binding can only be used with <input type="checkbox"> or <input type="radio">`
 					});
 				}
+			} else if (name == 'files') {
+				if (node.name !== 'input') {
+					validator.error(attribute, {
+						code: `invalid-binding`,
+						message: `'files' binding acn only be used with <input type="file">`
+					});
+				}
+
+				const type = checkTypeAttribute(validator, node);
+
+				if (type !== 'file') {
+					validator.error(attribute, {
+						code: `invalid-binding`,
+						message: `'files' binding can only be used with <input type="file">`
+					});
+				}
 			} else if (
 				name === 'currentTime' ||
 				name === 'duration' ||


Test patch:
diff --git a/test/js/samples/input-files/expected-bundle.js b/test/js/samples/input-files/expected-bundle.js
new file mode 100644
--- /dev/null
+++ b/test/js/samples/input-files/expected-bundle.js
@@ -0,0 +1,199 @@
+function noop() {}
+
+function assign(tar, src) {
+	for (var k in src) tar[k] = src[k];
+	return tar;
+}
+
+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 setAttribute(node, attribute, value) {
+	node.setAttribute(attribute, value);
+}
+
+function blankObject() {
+	return Object.create(null);
+}
+
+function destroy(detach) {
+	this.destroy = noop;
+	this.fire('destroy');
+	this.set = noop;
+
+	this._fragment.d(detach !== false);
+	this._fragment = null;
+	this._state = {};
+}
+
+function _differs(a, b) {
+	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || typeof a === 'function');
+}
+
+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) {
+		var handler = handlers[i];
+
+		if (!handler.__calling) {
+			try {
+				handler.__calling = true;
+				handler.call(this, data);
+			} finally {
+				handler.__calling = false;
+			}
+		}
+	}
+}
+
+function get() {
+	return this._state;
+}
+
+function init(component, options) {
+	component._handlers = blankObject();
+	component._bind = options._bind;
+
+	component.options = options;
+	component.root = options.root || component;
+	component.store = options.store || component.root.store;
+}
+
+function on(eventName, 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 (this._differs(newState[key], oldState[key])) changed[key] = dirty = true;
+	}
+	if (!dirty) return;
+
+	this._state = assign(assign({}, oldState), newState);
+	this._recompute(changed, this._state);
+	if (this._bind) this._bind(changed, this._state);
+
+	if (this._fragment) {
+		this.fire("state", { changed: changed, current: this._state, previous: oldState });
+		this._fragment.p(changed, this._state);
+		this.fire("update", { changed: changed, current: this._state, previous: oldState });
+	}
+}
+
+function callAll(fns) {
+	while (fns && fns.length) fns.shift()();
+}
+
+function _mount(target, anchor) {
+	this._fragment[this._fragment.i ? 'i' : 'm'](target, anchor || null);
+}
+
+var proto = {
+	destroy,
+	get,
+	fire,
+	on,
+	set,
+	_recompute: noop,
+	_set,
+	_mount,
+	_differs
+};
+
+/* generated by Svelte vX.Y.Z */
+
+function create_main_fragment(component, ctx) {
+	var input, input_updating = false;
+
+	function input_input_handler() {
+		input_updating = true;
+		component.set({ files: input.files });
+		input_updating = false;
+	}
+
+	return {
+		c() {
+			input = createElement("input");
+			addListener(input, "input", input_input_handler);
+			setAttribute(input, "type", "file");
+			input.multiple = true;
+		},
+
+		m(target, anchor) {
+			insertNode(input, target, anchor);
+
+			input.files = ctx.files;
+		},
+
+		p(changed, ctx) {
+			if (!input_updating) input.files = ctx.files;
+		},
+
+		d(detach) {
+			if (detach) {
+				detachNode(input);
+			}
+
+			removeListener(input, "input", input_input_handler);
+		}
+	};
+}
+
+function SvelteComponent(options) {
+	init(this, options);
+	this._state = assign({}, options.data);
+	this._intro = true;
+
+	this._fragment = create_main_fragment(this, this._state);
+
+	if (options.target) {
+		this._fragment.c();
+		this._mount(options.target, options.anchor);
+	}
+}
+
+assign(SvelteComponent.prototype, proto);
+
+export default SvelteComponent;
diff --git a/test/js/samples/input-files/expected.js b/test/js/samples/input-files/expected.js
new file mode 100644
--- /dev/null
+++ b/test/js/samples/input-files/expected.js
@@ -0,0 +1,55 @@
+/* generated by Svelte vX.Y.Z */
+import { addListener, assign, createElement, detachNode, init, insertNode, proto, removeListener, setAttribute } from "svelte/shared.js";
+
+function create_main_fragment(component, ctx) {
+	var input, input_updating = false;
+
+	function input_input_handler() {
+		input_updating = true;
+		component.set({ files: input.files });
+		input_updating = false;
+	}
+
+	return {
+		c() {
+			input = createElement("input");
+			addListener(input, "input", input_input_handler);
+			setAttribute(input, "type", "file");
+			input.multiple = true;
+		},
+
+		m(target, anchor) {
+			insertNode(input, target, anchor);
+
+			input.files = ctx.files;
+		},
+
+		p(changed, ctx) {
+			if (!input_updating) input.files = ctx.files;
+		},
+
+		d(detach) {
+			if (detach) {
+				detachNode(input);
+			}
+
+			removeListener(input, "input", input_input_handler);
+		}
+	};
+}
+
+function SvelteComponent(options) {
+	init(this, options);
+	this._state = assign({}, options.data);
+	this._intro = true;
+
+	this._fragment = create_main_fragment(this, this._state);
+
+	if (options.target) {
+		this._fragment.c();
+		this._mount(options.target, options.anchor);
+	}
+}
+
+assign(SvelteComponent.prototype, proto);
+export default SvelteComponent;
diff --git a/test/js/samples/input-files/input.html b/test/js/samples/input-files/input.html
new file mode 100644
--- /dev/null
+++ b/test/js/samples/input-files/input.html
@@ -0,0 +1 @@
+<input type="file" multiple bind:files>
\ No newline at end of file