[feat] allow users to override IllegalModuleGuard default behaviour

.changeset/fair-pumas-admire.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+[feat] allow users to override IllegalModuleGuard default behaviour

packages/kit/src/exports/vite/dev/index.js

@@ -97,7 +97,8 @@ export async function dev(vite, vite_config, svelte_config) {
 								prevent_illegal_vite_imports(
 									module_node,
 									normalizePath(svelte_config.kit.files.lib),
-									extensions
+									extensions,
+									{ allow_server_import_from_client: svelte_config.kit.allowServerImportFromClient }
 								);
 
 								return module.default;
@@ -114,7 +115,8 @@ export async function dev(vite, vite_config, svelte_config) {
 							prevent_illegal_vite_imports(
 								module_node,
 								normalizePath(svelte_config.kit.files.lib),
-								extensions
+								extensions,
+								{ allow_server_import_from_client: svelte_config.kit.allowServerImportFromClient }
 							);
 						}
 

packages/kit/src/exports/vite/graph_analysis/index.js

@@ -3,6 +3,7 @@ import { normalizePath } from 'vite';
 import { remove_query_from_id, get_module_types } from './utils.js';
 
 /** @typedef {import('./types').ImportGraph} ImportGraph */
+/** @typedef {import('./types').IllegalModuleGuardOptions} IllegalModuleGuardOptions */
 
 const CWD_ID = normalizePath(process.cwd());
 const NODE_MODULES_ID = normalizePath(path.resolve(process.cwd(), 'node_modules'));
@@ -24,12 +25,18 @@ export class IllegalModuleGuard {
 	/** @type {Array<ImportGraph>} */
 	#chain = [];
 
+	/** @type {(filepath: string) => boolean} */
+	#allow_server_import_from_client;
+
 	/**
 	 * @param {string} lib_dir
+	 * @param {IllegalModuleGuardOptions} [options]
 	 */
-	constructor(lib_dir) {
+	constructor(lib_dir, options) {
 		this.#lib_dir = normalizePath(lib_dir);
 		this.#server_dir = normalizePath(path.resolve(lib_dir, 'server'));
+		this.#allow_server_import_from_client =
+			options?.allow_server_import_from_client ?? (() => false);
 	}
 
 	/**
@@ -40,13 +47,18 @@ export class IllegalModuleGuard {
 	assert_legal(node) {
 		this.#chain.push(node);
 		for (const child of node.children) {
-			if (this.#is_illegal(child.id)) {
-				this.#chain.push(child);
-				const error = this.#format_illegal_import_chain(this.#chain);
-				this.#chain = []; // Reset the chain in case we want to reuse this guard
-				throw new Error(error);
+			if (this.#allow_server_import_from_client(child.id)) {
+				// Do not assert child nodes if module is allowed by user config
+				continue;
+			} else {
+				if (this.#is_illegal(child.id)) {
+					this.#chain.push(child);
+					const error = this.#format_illegal_import_chain(this.#chain);
+					this.#chain = []; // Reset the chain in case we want to reuse this guard
+					throw new Error(error);
+				}
+				this.assert_legal(child);
 			}
-			this.assert_legal(child);
 		}
 		this.#chain.pop();
 	}
@@ -255,11 +267,12 @@ export class ViteImportGraph {
  * @param {(id: string) => import('rollup').ModuleInfo | null} node_getter
  * @param {import('rollup').ModuleInfo} node
  * @param {string} lib_dir
+ * @param {IllegalModuleGuardOptions} [options]
  * @returns {void}
  */
-export function prevent_illegal_rollup_imports(node_getter, node, lib_dir) {
+export function prevent_illegal_rollup_imports(node_getter, node, lib_dir, options) {
 	const graph = new RollupImportGraph(node_getter, node);
-	const guard = new IllegalModuleGuard(lib_dir);
+	const guard = new IllegalModuleGuard(lib_dir, options);
 	guard.assert_legal(graph);
 }
 
@@ -268,10 +281,11 @@ export function prevent_illegal_rollup_imports(node_getter, node, lib_dir) {
  * @param {import('vite').ModuleNode} node
  * @param {string} lib_dir
  * @param {Iterable<string>} module_types File extensions to analyze in addition to the defaults: `.ts`, `.js`, etc.
+ * @param {IllegalModuleGuardOptions} [options]
  * @returns {void}
  */
-export function prevent_illegal_vite_imports(node, lib_dir, module_types) {
+export function prevent_illegal_vite_imports(node, lib_dir, module_types, options) {
 	const graph = new ViteImportGraph(get_module_types(module_types), node);
-	const guard = new IllegalModuleGuard(lib_dir);
+	const guard = new IllegalModuleGuard(lib_dir, options);
 	guard.assert_legal(graph);
 }

packages/kit/src/exports/vite/graph_analysis/index.spec.js

@@ -181,6 +181,37 @@ describe('IllegalImportGuard', (test) => {
 
 		assert.not.throws(() => guard.assert_legal(module_graph));
 	});
+
+	test('assert ignores illegal server-only modules when allowed by user config', () => {
+		const guard = new IllegalModuleGuard(FAKE_LIB_DIR, {
+			allow_server_import_from_client: (moduleId) => moduleId.includes('.allowed.')
+		});
+
+		const module_graph = get_module_graph({
+			id: 'entry.svelte',
+			dynamic: false,
+			children: generator_from_array([
+				{
+					id: 'something.allowed.js',
+					dynamic: false,
+					children: generator_from_array([
+						{
+							id: PROD_VIRTUAL_STATIC_ID,
+							dynamic: false,
+							children: generator_from_array([])
+						},
+						{
+							id: USER_SERVER_FOLDER_ID,
+							dynamic: false,
+							children: generator_from_array([])
+						}
+					])
+				}
+			])
+		});
+
+		assert.not.throws(() => guard.assert_legal(module_graph));
+	});
 });
 
 /*

packages/kit/src/exports/vite/graph_analysis/types.d.ts

@@ -3,3 +3,7 @@ export interface ImportGraph {
 	readonly dynamic: boolean;
 	readonly children: Generator<ImportGraph>;
 }
+
+export interface IllegalModuleGuardOptions {
+	readonly allow_server_import_from_client?: (filepath: string) => boolean;
+}

packages/kit/src/exports/vite/index.js

@@ -359,7 +359,8 @@ function kit() {
 						prevent_illegal_rollup_imports(
 							this.getModuleInfo.bind(this),
 							module_node,
-							vite.normalizePath(svelte_config.kit.files.lib)
+							vite.normalizePath(svelte_config.kit.files.lib),
+							{ allow_server_import_from_client: svelte_config.kit.allowServerImportFromClient }
 						);
 					}
 				});

packages/kit/types/index.d.ts

@@ -236,6 +236,7 @@ export interface KitConfig {
 		name?: string;
 		pollInterval?: number;
 	};
+	allowServerImportFromClient?: (filepath: string) => boolean;
 }
 
 export interface Handle {