disallow calling getContext inside element

src/compiler/compile/render_ssr/index.ts

@@ -198,7 +198,7 @@ export default function ssr(
 		instance_javascript,
 		...parent_bindings,
 		css.code && b`$$result.css.add(#css);`,
-		main
+		b`return @no_current_component(() => { ${main} });`
 	].filter(Boolean);
 
 	const css_sourcemap_enabled = check_enable_sourcemap(options.enableSourcemap, 'css');

src/runtime/internal/Component.ts

@@ -1,5 +1,5 @@
 import { add_render_callback, flush, schedule_update, dirty_components } from './scheduler';
-import { current_component, set_current_component } from './lifecycle';
+import { current_component, no_current_component, set_current_component } from './lifecycle';
 import { blank_object, is_empty, is_function, run, run_all, noop } from './utils';
 import { children, detach, start_hydrating, end_hydrating } from './dom';
 import { transition_in } from './transitions';
@@ -152,9 +152,11 @@ export function init(component, options, instance, create_fragment, not_equal, p
 	ready = true;
 	run_all($$.before_update);
 
+	no_current_component(() => {
 		// `false` as a special case of no DOM component
 		$$.fragment = create_fragment ? create_fragment($$.ctx) : false;
 		
+
 		if (options.target) {
 			if (options.hydrate) {
 				start_hydrating();
@@ -172,6 +174,7 @@ export function init(component, options, instance, create_fragment, not_equal, p
 			end_hydrating();
 			flush();
 		}
+	});
 
 	set_current_component(parent_component);
 }

src/runtime/internal/lifecycle.ts

@@ -11,6 +11,14 @@ export function get_current_component() {
 	return current_component;
 }
 
+export function no_current_component(callback: () => void) {
+	const old_current_component = current_component;
+	current_component = undefined;
+	const value = callback();
+	current_component = old_current_component;
+	return value;
+}
+
 export function beforeUpdate(fn: () => any) {
 	get_current_component().$$.before_update.push(fn);
 }

test/runtime/samples/context-api-in-element-1/_config.js

@@ -0,0 +1,3 @@
+export default {
+	error: 'Function called outside component initialization'
+};

test/runtime/samples/context-api-in-element-1/main.svelte

@@ -0,0 +1,5 @@
+<script>
+	import { getContext } from 'svelte';
+</script>
+
+<a href={getContext('test')}>{getContext('test')}</a>

test/runtime/samples/context-api-in-element-2/_config.js

@@ -0,0 +1,3 @@
+export default {
+	error: 'Function called outside component initialization'
+};

test/runtime/samples/context-api-in-element-2/main.svelte

@@ -0,0 +1,5 @@
+<script>
+	import { getContext } from 'svelte';
+</script>
+
+<a href={getContext('test')}>xxx</a>

test/runtime/samples/context-api-in-element-3/_config.js

@@ -0,0 +1,3 @@
+export default {
+	error: 'Function called outside component initialization'
+};

test/runtime/samples/context-api-in-element-3/main.svelte

@@ -0,0 +1,5 @@
+<script>
+	import { getContext } from 'svelte';
+</script>
+
+<span>{getContext('test')}</span>