error on undefined export

Author: Rich-Harris

documentation/docs/98-reference/.generated/compile-errors.md

@@ -400,6 +400,12 @@ Expected token %token%
 Expected whitespace
 ```
 
+### export_undefined
+
+```
+`%name%` is not defined
+```
+
 ### global_reference_invalid
 
 ```

packages/svelte/messages/compile-errors/script.md

@@ -38,6 +38,10 @@
 
 > `$effect()` can only be used as an expression statement
 
+## export_undefined
+
+> `%name%` is not defined
+
 ## global_reference_invalid
 
 > `%name%` is an illegal variable name. To reference a global variable called `%name%`, use `globalThis.%name%`

packages/svelte/src/compiler/errors.js

@@ -168,6 +168,16 @@ export function effect_invalid_placement(node) {
 	e(node, "effect_invalid_placement", "`$effect()` can only be used as an expression statement");
 }
 
+/**
+ * `%name%` is not defined
+ * @param {null | number | NodeLike} node
+ * @param {string} name
+ * @returns {never}
+ */
+export function export_undefined(node, name) {
+	e(node, "export_undefined", `\`${name}\` is not defined`);
+}
+
 /**
  * `%name%` is an illegal variable name. To reference a global variable called `%name%`, use `globalThis.%name%`
  * @param {null | number | NodeLike} node

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

@@ -692,6 +692,17 @@ export function analyze_component(root, source, options) {
 		analysis.reactive_statements = order_reactive_statements(analysis.reactive_statements);
 	}
 
+	for (const node of analysis.module.ast.body) {
+		if (node.type === 'ExportNamedDeclaration' && node.specifiers !== null) {
+			for (const specifier of node.specifiers) {
+				if (specifier.local.type !== 'Identifier') continue;
+
+				const binding = analysis.module.scope.get(specifier.local.name);
+				if (!binding) e.export_undefined(specifier, specifier.local.name);
+			}
+		}
+	}
+
 	if (analysis.event_directive_node && analysis.uses_event_attributes) {
 		e.mixed_event_handler_syntaxes(
 			analysis.event_directive_node,

packages/svelte/src/compiler/phases/2-analyze/visitors/SnippetBlock.js

@@ -1,4 +1,4 @@
-/** @import { AST } from '#compiler' */
+/** @import { AST, Binding } from '#compiler' */
 /** @import { Context } from '../types' */
 import { validate_block_not_empty, validate_opening_tag } from './shared/utils.js';
 import * as e from '../../../errors.js';
@@ -31,6 +31,11 @@ export function SnippetBlock(node, context) {
 	const undefined_exports = context.state.analysis.undefined_exports;
 	const name = node.expression.name;
 
+	if (can_hoist) {
+		const binding = /** @type {Binding} */ (context.state.scope.get(name));
+		context.state.analysis.module.scope.declarations.set(name, binding);
+	}
+
 	if (!can_hoist && undefined_exports.has(name)) {
 		e.snippet_invalid_export(/** @type {any} */ (undefined_exports.get(name)));
 	}

packages/svelte/tests/compiler-errors/samples/export-not-defined-module/_config.js

@@ -0,0 +1,9 @@
+import { test } from '../../test';
+
+export default test({
+	error: {
+		code: 'export_undefined',
+		message: '`blah` is not defined',
+		position: [26, 30]
+	}
+});

packages/svelte/tests/compiler-errors/samples/export-not-defined-module/main.svelte

@@ -0,0 +1,3 @@
+<script module>
+	export { blah };
+</script>