fix: add missing files binding (#9415)

no two-way binding because setting it involves a `DataTransfer` workaround, so it's not really officially supported that way - if you need that, you shouldn't use that binding probably. This matches the behavior in Svelte 4.

Co-authored-by: Rich Harris <rich.harris@vercel.com>

Author: dummdidumm

.changeset/poor-eggs-enjoy.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: add missing files binding

packages/svelte/src/compiler/phases/2-analyze/validation.js

@@ -325,6 +325,10 @@ export const validation = {
 					if (node.name === 'checked' && type?.value[0].data !== 'checkbox') {
 						error(node, 'invalid-binding', node.name, '<input type="checkbox">');
 					}
+
+					if (node.name === 'files' && type?.value[0].data !== 'file') {
+						error(node, 'invalid-binding', node.name, '<input type="file">');
+					}
 				}
 
 				if (parent.name === 'select') {

packages/svelte/src/compiler/phases/bindings.js

@@ -179,5 +179,10 @@ export const binding_properties = {
 	},
 	value: {
 		valid_elements: ['input', 'textarea', 'select']
+	},
+	files: {
+		event: 'change',
+		valid_elements: ['input'],
+		omit_in_ssr: true
 	}
 };