fix: Better loading of SvelteKit routes directory

.changeset/sveltekit-public-config-loader.md

@@ -0,0 +1,5 @@
+---
+'@workflow/sveltekit': patch
+---
+
+Load SvelteKit route configuration through `@sveltejs/load-config`, including projects that configure SvelteKit exclusively in `vite.config`.

packages/sveltekit/package.json

@@ -22,9 +22,11 @@
   "scripts": {
     "build": "tsc",
     "dev": "tsc --watch",
+    "test": "vitest run src",
     "clean": "tsc --build --clean && rm -rf dist"
   },
   "dependencies": {
+    "@sveltejs/load-config": "^0.2.3",
     "@swc/core": "catalog:",
     "@workflow/builders": "workspace:*",
     "@workflow/rollup": "workspace:*",
@@ -39,6 +41,7 @@
     "@types/node": "catalog:",
     "@workflow/tsconfig": "workspace:*",
     "typescript": "catalog:",
-    "vite": "7.3.6"
+    "vite": "7.3.6",
+    "vitest": "catalog:"
   }
 }

packages/sveltekit/src/builder.ts

@@ -8,9 +8,7 @@ import {
   stat,
   writeFile,
 } from 'node:fs/promises';
-import { createRequire } from 'node:module';
-import { dirname, join, resolve } from 'node:path';
-import { pathToFileURL } from 'node:url';
+import { join, resolve } from 'node:path';
 import {
   BaseBuilder,
   createBaseBuilderConfig,
@@ -27,7 +25,7 @@ const SVELTEKIT_VIRTUAL_MODULES = [
 ];
 
 export class SvelteKitBuilder extends BaseBuilder {
-  #routesDir: string | undefined;
+  #routesDir: string;
 
   constructor(config: Partial<SvelteKitConfig> & { routesDir?: string } = {}) {
     const workingDir = resolve(config.workingDir || process.cwd());
@@ -38,9 +36,7 @@ export class SvelteKitBuilder extends BaseBuilder {
       'src/routes',
     ];
     const projectRoot = config.projectRoot ?? resolveProjectRoot(workingDir);
-    const routesDir = config.routesDir
-      ? resolve(workingDir, config.routesDir)
-      : undefined;
+    const routesDir = resolve(workingDir, config.routesDir ?? 'src/routes');
     super({
       ...createBaseBuilderConfig({
         workingDir,
@@ -197,37 +193,11 @@ export const OPTIONS = createSvelteKitHandler('OPTIONS');`
   }
 
   private async loadRoutesDirectory(): Promise<string> {
-    const routesDir =
-      this.#routesDir ?? (await loadSvelteKitRoutesDir(this.config.workingDir));
-    await assertDirectory(routesDir);
-    return routesDir;
+    await assertDirectory(this.#routesDir);
+    return this.#routesDir;
   }
 }
 
-export async function loadSvelteKitRoutesDir(
-  workingDir: string
-): Promise<string> {
-  const require = createRequire(join(workingDir, 'package.json'));
-  const packageJsonPath = require.resolve('@sveltejs/kit/package.json');
-  const loaderPath = join(dirname(packageJsonPath), 'src/core/config/index.js');
-
-  const configModule = await import(pathToFileURL(loaderPath).href);
-  // SvelteKit 2.62+ `load_config()` resolves Vite config first. Calling it
-  // while `workflow/sveltekit` is imported from vite.config.ts recursively
-  // reloads vite.config.ts and leaves this top-level build unresolved.
-  const config =
-    configModule.load_svelte_config != null
-      ? await configModule.load_svelte_config(workingDir)
-      : await configModule.load_config({ cwd: workingDir });
-  const routesDir = config.kit?.files?.routes;
-  if (routesDir == null || typeof routesDir !== 'string') {
-    throw new Error(
-      'Expected SvelteKit config loader to return kit.files.routes as a string.'
-    );
-  }
-  return routesDir;
-}
-
 async function assertDirectory(path: string): Promise<void> {
   await access(path, constants.F_OK);
   const stats = await stat(path);

packages/sveltekit/src/index.ts

@@ -2,16 +2,8 @@ import path from 'node:path';
 import { getWorkflowQueueTrigger } from '@workflow/builders';
 import fs from 'fs-extra';
 
-import { SvelteKitBuilder } from './builder.js';
 import { stripWorkflowQueueTriggers } from './vc-config.js';
 
-const builder = new SvelteKitBuilder();
-
-// This needs to be in the top-level as we need to create these
-// entries before svelte plugin is started or the entries are
-// a race to be created before svelte discovers entries
-await builder.build();
-
 process.on('beforeExit', () => {
   // Don't patch functions output if not in Vercel adapter
   if (!process.env.VERCEL_DEPLOYMENT_ID) {

packages/sveltekit/src/plugin.test.ts

@@ -0,0 +1,147 @@
+import { mkdir, mkdtemp, rm, writeFile } from 'node:fs/promises';
+import { tmpdir } from 'node:os';
+import { join } from 'node:path';
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+
+const mocks = vi.hoisted(() => ({
+  build: vi.fn<() => Promise<void>>(),
+  builderConfigs: [] as Array<Record<string, unknown>>,
+  loadConfig: vi.fn(),
+}));
+
+vi.mock('@sveltejs/load-config', () => ({
+  loadConfig: mocks.loadConfig,
+}));
+
+vi.mock('@workflow/builders', () => ({
+  createBuildQueue: () => (fn: () => Promise<void>) => fn(),
+}));
+
+vi.mock('@workflow/rollup', () => ({
+  workflowTransformPlugin: () => ({ name: 'workflow:transform' }),
+}));
+
+vi.mock('@workflow/vite', () => ({
+  workflowHotUpdatePlugin: () => ({ name: 'workflow:hot-update' }),
+}));
+
+vi.mock('./builder.js', () => ({
+  SvelteKitBuilder: class {
+    constructor(config: Record<string, unknown>) {
+      mocks.builderConfigs.push(config);
+    }
+
+    build = mocks.build;
+  },
+}));
+
+import { workflowPlugin } from './plugin.js';
+
+const originalWorkingDir = process.cwd();
+let workingDir: string;
+
+beforeEach(async () => {
+  workingDir = await mkdtemp(join(tmpdir(), 'workflow-sveltekit-'));
+  process.chdir(workingDir);
+  workingDir = process.cwd(); // MacOS: resolves symlink of generated /var/folders/... through to /private/var/folders/...
+  mocks.build.mockResolvedValue(undefined);
+});
+
+afterEach(async () => {
+  process.chdir(originalWorkingDir);
+  await rm(workingDir, { force: true, recursive: true });
+  vi.clearAllMocks();
+  mocks.builderConfigs.length = 0;
+});
+
+describe('workflowPlugin', () => {
+  it('loads svelte.config.js directly and uses the default routes directory', async () => {
+    const configPath = join(workingDir, 'svelte.config.js');
+    await writeFile(configPath, 'export default {};');
+    mocks.loadConfig.mockResolvedValue({
+      config: {},
+      configFilePath: configPath,
+      configSource: 'svelte',
+    });
+
+    const [plugins] = workflowPlugin();
+    await plugins;
+
+    expect(mocks.loadConfig).toHaveBeenCalledWith(configPath, {
+      traverse: false,
+    });
+    expect(mocks.builderConfigs).toEqual([
+      { routesDir: join(workingDir, 'src/routes'), workingDir },
+    ]);
+    expect(mocks.build).toHaveBeenCalledOnce();
+  });
+
+  it('loads routes from the SvelteKit Vite plugin without recursing', async () => {
+    const routesDir = join(workingDir, 'app/routes');
+    let nestedPlugins: ReturnType<typeof workflowPlugin> | undefined;
+    mocks.loadConfig.mockImplementation(async () => {
+      nestedPlugins = workflowPlugin();
+      return {
+        config: { kit: { files: { routes: routesDir } } },
+        configFilePath: join(workingDir, 'vite.config.ts'),
+        configSource: 'vite',
+      };
+    });
+
+    const [plugins] = workflowPlugin();
+    await plugins;
+
+    expect(nestedPlugins).toEqual([]);
+    expect(mocks.loadConfig).toHaveBeenCalledWith(workingDir, {
+      traverse: false,
+    });
+    expect(mocks.builderConfigs).toEqual([{ routesDir, workingDir }]);
+    expect(mocks.build).toHaveBeenCalledOnce();
+  });
+
+  it('reuses routes generated by another Vite config context', async () => {
+    const routesDir = join(workingDir, 'app/routes');
+    await mkdir(join(workingDir, 'node_modules/.cache/workflow'), {
+      recursive: true,
+    });
+    await mkdir(join(routesDir, '.well-known/workflow/v1/flow'), {
+      recursive: true,
+    });
+    await writeFile(
+      join(workingDir, 'node_modules/.cache/workflow/sveltekit-build.json'),
+      JSON.stringify({ pid: process.pid, routesDir })
+    );
+    await writeFile(
+      join(routesDir, '.well-known/workflow/v1/flow/+server.js'),
+      ''
+    );
+
+    const [plugins] = workflowPlugin();
+    await plugins;
+
+    expect(mocks.loadConfig).not.toHaveBeenCalled();
+    expect(mocks.builderConfigs).toEqual([{ routesDir, workingDir }]);
+    expect(mocks.build).not.toHaveBeenCalled();
+  });
+
+  it('passes source map options to the builder', async () => {
+    const configPath = join(workingDir, 'svelte.config.js');
+    await writeFile(configPath, 'export default {};');
+    mocks.loadConfig.mockResolvedValue({
+      config: {},
+      configFilePath: configPath,
+      configSource: 'svelte',
+    });
+
+    const [plugins] = workflowPlugin({ sourcemap: 'external' });
+    await plugins;
+
+    expect(mocks.builderConfigs).toEqual([
+      {
+        routesDir: join(workingDir, 'src/routes'),
+        workingDir,
+        sourcemap: 'external',
+      },
+    ]);
+  });
+});