subscribe to global stores (#2139)

src/compile/Component.ts

@@ -168,7 +168,7 @@ export default class Component {
 			this.add_reference(subscribable_name);
 
 			const variable = this.var_lookup.get(subscribable_name);
-			variable.subscribable = true;
+			if (variable) variable.subscribable = true;
 		} else {
 			this.usedNames.add(name);
 		}

src/compile/nodes/shared/Expression.ts

@@ -149,13 +149,6 @@ export default class Expression {
 							dependencies.add(name);
 						}
 
-						if (name[0] === '$' && !component.var_lookup.get(name.slice(1)) && name !== '$$props') {
-							component.error(node, {
-								code: `missing-store`,
-								message: `Stores must be declared`
-							});
-						}
-
 						component.add_reference(name);
 						component.warn_if_undefined(nodes[0], template_scope);
 					}

src/compile/render-dom/index.ts

@@ -326,7 +326,7 @@ export default function dom(
 	const reactive_store_subscriptions = reactive_stores
 		.filter(store => {
 			const variable = component.var_lookup.get(store.name.slice(1));
-			return variable.hoistable;
+			return !variable || variable.hoistable;
 		})
 		.map(({ name }) => deindent`
 			${component.compileOptions.dev && `@validate_store(${name.slice(1)}, '${name.slice(1)}');`}
@@ -336,7 +336,7 @@ export default function dom(
 	const resubscribable_reactive_store_unsubscribers = reactive_stores
 		.filter(store => {
 			const variable = component.var_lookup.get(store.name.slice(1));
-			return variable.reassigned;
+			return variable && variable.reassigned;
 		})
 		.map(({ name }) => `$$self.$$.on_destroy.push(() => $$unsubscribe_${name.slice(1)}());`);
 
@@ -370,7 +370,7 @@ export default function dom(
 			const name = $name.slice(1);
 
 			const store = component.var_lookup.get(name);
-			if (store.reassigned) {
+			if (store && store.reassigned) {
 				return `${$name}, $$unsubscribe_${name} = @noop, $$subscribe_${name} = () => { $$unsubscribe_${name}(); $$unsubscribe_${name} = ${name}.subscribe($$value => { ${$name} = $$value; $$invalidate('${$name}', ${$name}); }) }`
 			}
 

test/runtime/samples/store-auto-subscribe-missing-global/_config.js

@@ -0,0 +1,3 @@
+export default {
+	error: 'missingGlobal is not defined'
+};

test/runtime/samples/store-auto-subscribe-missing-global/main.svelte

@@ -0,0 +1 @@
+<p>{$missingGlobal}</p>