global binding group

src/compiler/compile/Component.ts

@@ -445,8 +445,12 @@ export default class Component {
 		});
 	}
 
-	extract_imports(node) {
+	extract_imports(node: ImportDeclaration) {
 		this.imports.push(node);
+		for (const specifier of node.specifiers) {
+			const variable = this.var_lookup.get(specifier.local.name);
+			variable.imported = true;
+		}
 	}
 
 	extract_exports(node) {

src/compiler/compile/render_dom/wrappers/Element/Binding.ts

@@ -121,18 +121,30 @@ export default class BindingWrapper {
 		switch (this.node.name) {
 			case 'group':
 			{
-				const binding_group = get_binding_group(parent.renderer, this.node.expression.node);
-
-				block.renderer.add_to_context(`$$binding_groups`);
-				const reference = block.renderer.reference(`$$binding_groups`);
-
-				block.chunks.hydrate.push(
-					b`${reference}[${binding_group}].push(${parent.var});`
-				);
-
-				block.chunks.destroy.push(
-					b`${reference}[${binding_group}].splice(${reference}[${binding_group}].indexOf(${parent.var}), 1);`
-				);
+				const variable = block.renderer.component.var_lookup.get(this.object);
+				const use_global_binding_group = variable && (variable.imported || variable.export_name);
+				if (use_global_binding_group) {
+					block.chunks.hydrate.push(
+						b`@add_into_binding_group(${this.snippet}, ${parent.var});`
+					);
+
+					block.chunks.destroy.push(
+						b`@remove_from_binding_group(${this.snippet}, ${parent.var});`
+					);
+				} else {
+					const binding_group = get_binding_group(parent.renderer, this.node.expression.node);
+
+					block.renderer.add_to_context(`$$binding_groups`);
+					const reference = block.renderer.reference(`$$binding_groups`);
+
+					block.chunks.hydrate.push(
+						b`${reference}[${binding_group}].push(${parent.var});`
+					);
+
+					block.chunks.destroy.push(
+						b`${reference}[${binding_group}].splice(${reference}[${binding_group}].indexOf(${parent.var}), 1);`		
+					);
+				}
 				break;
 			}
 
@@ -233,7 +245,10 @@ function get_dom_updater(
 			? x`~${binding.snippet}.indexOf(${element.var}.__value)`
 			: x`${element.var}.__value === ${binding.snippet}`;
 
-		return b`${element.var}.checked = ${condition};`;
+		return b`
+			@reattach_binding_group(${binding.snippet}, ${element.var});
+			${element.var}.checked = ${condition};
+		`;
 	}
 
 	if (binding.node.name === 'value') {
@@ -332,6 +347,11 @@ function get_value_from_dom(
 
 	// <input type='checkbox' bind:group='foo'>
 	if (name === 'group') {
+		const variable = renderer.component.var_lookup.get(binding.object);
+		if (variable && (variable.imported || variable.export_name)) {
+			return x`@get_global_binding_group_value(${binding.snippet})`;
+		}
+
 		const binding_group = get_binding_group(renderer, binding.node.expression.node);
 		if (type === 'checkbox') {
 			return x`@get_binding_group_value($$binding_groups[${binding_group}])`;

src/compiler/interfaces.ts

@@ -161,6 +161,7 @@ export interface Var {
 	hoistable?: boolean;
 	subscribable?: boolean;
 	is_reactive_dependency?: boolean;
+	imported?: boolean;
 }
 
 export interface CssResult { 

src/runtime/internal/dom.ts

@@ -126,6 +126,38 @@ export function xlink_attr(node, attribute, value) {
 	node.setAttributeNS('http://www.w3.org/1999/xlink', attribute, value);
 }
 
+const global_binding_group = new WeakMap();
+
+export function add_into_binding_group(array, input) {
+	if (!global_binding_group.has(array)) {
+		global_binding_group.set(array, []);
+	}
+	global_binding_group.get(array).push(input);
+}
+
+export function remove_from_global_binding_group(array, input) {
+	const binding_group = global_binding_group.get(array);
+	if (binding_group) {
+		binding_group.splice(binding_group.indexOf(input), 1);
+	}
+}
+
+export function reattach_global_binding_group(array, input) {
+	// if the array got reassigned, reattach binding group
+	if (!global_binding_group.has(array)) {
+		add_into_binding_group(array, input);
+	}
+}
+
+export function get_global_binding_group_value(array) {
+	const group = global_binding_group.get(array);
+	const value = [];
+	for (let i = 0; i < group.length; i += 1) {
+		if (group[i].checked) value.push(group[i].__value);
+	}
+	return value;
+}
+
 export function get_binding_group_value(group) {
 	const value = [];
 	for (let i = 0; i < group.length; i += 1) {