fix(db): treat files in db/schema/ beside db/schema.ts as schema files (#504)

Refs #472

Same cause as #472, hit by the default output of `void gen model`. The
#472 layout is not fixed here.

`void gen model` writes `db/schema/<name>.ts`, re-exports it from
`db/schema.ts`, and the generated file imports `sql` from `void/db`.

When `db/schema.ts` exists, the plugin treats only that file as a schema
file. `db/schema/<name>.ts` gets `virtual:void-db`, which imports the
schema, so the import goes around: `db/schema.ts` →
`db/schema/<name>.ts` → `virtual:void-db` → `db/schema.ts`. In dev,
`sql` is not ready yet and every page that imports `void/db` returns 500
(`TypeError: __vite_ssr_import_1__.sql is not a function`). `vp build` →
`vp preview` works.

To reproduce:

```sh
pnpm create void my-app   # React / D1
cd my-app
pnpm add zod
pnpm exec void gen model todos title:string done:boolean
pnpm exec void db generate
pnpm dev                  # / and /api/todos return 500
```

This PR also treats files under `db/schema/` as schema files when
`db/schema.ts` exists. The folder comes from `paths.schemaDir`, the same
path `gen model` writes to.

Out of scope: the #472 layout (a file outside `db/schema/` re-exported
from `db/schema.ts`). Moving the `drizzle-orm` re-export above the
schema import in `virtual:void-db` makes `sql` ready in dev for that
case too (checked locally), but it makes the import order matter, so it
is not in this PR.

Checked:
- `plugin-drizzle.test.ts` (1 new test, fails without the fix)
- typecheck for `void`
- an app after `gen model`: dev (500 → 200) and `vp build` → `vp
preview` (200 before and after)

14 tests in `init.test.ts` and 1 in `nitro.test.ts` fail locally on main
too. This PR adds no new failures.

Author: ashunar0

packages/void/src/plugin-drizzle.ts

@@ -106,7 +106,11 @@ function createVoidDbModule(
           // but schema.path from Node's path.join uses backslashes on Windows.
           const normalizedImporter = normalizePath(importer);
           const normalizedSchemaPath = normalizePath(schema.path);
-          if (schema.type === 'file' && normalizedImporter === normalizedSchemaPath) {
+          if (
+            schema.type === 'file' &&
+            (normalizedImporter === normalizedSchemaPath ||
+              normalizedImporter.startsWith(normalizePath(paths.schemaDir) + '/'))
+          ) {
             return VIRTUAL_SCHEMA_DB_ID;
           }
           if (schema.type === 'directory' && normalizedImporter.startsWith(normalizedSchemaPath)) {

packages/void/test/unit/plugin-drizzle.test.ts

@@ -750,6 +750,24 @@ export const requestPoolOptions = (env) =>
     expect(code).not.toContain('requireRuntimeBinding');
   });
 
+  it('treats files in db/schema/ beside db/schema.ts as schema files', () => {
+    // `void gen model` writes db/schema/<name>.ts and re-exports it from db/schema.ts.
+    const root = createProjectRoot();
+    const plugin = drizzlePlugin(root, false, 'sqlite');
+    const resolveId = getHookHandler(plugin.resolveId) as (
+      this: { environment: { name: string } },
+      source: string,
+      importer: string | undefined,
+      options: { isEntry: boolean },
+    ) => string | undefined;
+    const resolve = (importer: string) =>
+      resolveId.call({ environment: { name: 'ssr' } }, 'void/db', importer, { isEntry: false });
+
+    expect(resolve(join(root, 'db', 'schema', 'todos.ts'))).toBe('\0virtual:void-db-schema');
+    expect(resolve(join(root, 'db', 'schema-helpers.ts'))).toBe('\0virtual:void-db');
+    expect(resolve(join(root, 'routes', 'api', 'todos', 'index.ts'))).toBe('\0virtual:void-db');
+  });
+
   it('can virtualize void/db without a user schema when forced', () => {
     const root = createProjectRoot({ schema: false });
     const plugin = drizzlePlugin(root, false, 'postgresql', { forceVirtualDb: true });