test: add tests for folder route pattern (route.tsx) migration

- isColocatedFile: route entries inside + folders are not colocated
- import-rewriter: +types/route specifier rewriting, /index.ts stripping
- normalizers: route segment collapsed to parent in snapshot comparison
- CLI: folder route migration, +types/route rewriting, snapshot equivalence

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: coji

test/migrate-cli.test.ts

@@ -279,6 +279,93 @@ describe('migrate CLI', () => {
     )
   })
 
+  it('migrates folder route pattern (route.tsx) correctly', () => {
+    const fixture = createRoutesFixture({
+      'app/routes/demo+/_layout/route.tsx':
+        'import { Outlet } from "react-router"\nexport default function DemoLayout() { return <Outlet /> }\n',
+      'app/routes/demo+/_index/route.tsx':
+        'export default function DemoIndex() { return null }\n',
+      'app/routes/demo+/about/route.tsx':
+        "import type { Route } from './+types/route'\nexport default function About() { return null }\n",
+      'app/routes/demo+/conform.nested-array/route.tsx':
+        "import { schema } from './schema'\nexport default function ConformNestedArray() { return null }\n",
+      'app/routes/demo+/conform.nested-array/schema.ts':
+        'export const schema = {}\n',
+      'app/routes/demo+/conform.nested-array/components/field.tsx':
+        'export function Field() { return null }\n',
+    })
+
+    const sourceAbsolute = fixture.sourceDir
+    const sourceArg = fixture.toCwdRelativePath(sourceAbsolute)
+
+    const targetAbsolute = fixture.resolve('app', 'new-routes')
+    const targetArg = fixture.toCwdRelativePath(targetAbsolute)
+
+    migrate(sourceArg, targetArg, {
+      force: true,
+    })
+
+    const files = fixture.listRelativeFiles(targetAbsolute)
+
+    // route.tsx files should become flat files or index.tsx, not +prefixed folders
+    expect(files).toContain('demo/_layout.tsx')
+    expect(files).toContain('demo/_index.tsx')
+    expect(files).toContain('demo/about.tsx')
+    expect(files).toContain('demo/conform.nested-array.tsx')
+
+    // Colocated files should get + prefix
+    expect(files).toContain('demo/+conform.nested-array/schema.ts')
+    expect(files).toContain('demo/+conform.nested-array/components/field.tsx')
+
+    // No route.tsx files should remain at the top level
+    expect(files).not.toContain('demo/+_layout/route.tsx')
+    expect(files).not.toContain('demo/+_index/route.tsx')
+    expect(files).not.toContain('demo/+about/route.tsx')
+  })
+
+  it('rewrites +types/route imports when migrating folder routes', () => {
+    const fixture = createRoutesFixture({
+      'app/routes/demo+/about/route.tsx':
+        "import type { Route } from './+types/route'\nexport default function About({ loaderData }: Route.ComponentProps) { return null }\n",
+    })
+
+    const sourceAbsolute = fixture.sourceDir
+    const sourceArg = fixture.toCwdRelativePath(sourceAbsolute)
+    const targetAbsolute = fixture.resolve('app', 'new-routes')
+    const targetArg = fixture.toCwdRelativePath(targetAbsolute)
+
+    migrate(sourceArg, targetArg, { force: true })
+
+    const aboutPath = path.join(targetAbsolute, 'demo', 'about.tsx')
+    const contents = fs.readFileSync(aboutPath, 'utf8')
+    expect(contents).toContain("from './+types/about'")
+    expect(contents).not.toContain("from './+types/route'")
+  })
+
+  it('treats folder route (route.tsx) as equivalent to flat file in snapshots', () => {
+    const before = normalizeSnapshot(
+      `<Routes>
+  <Route file="root.tsx">
+    <Route file="routes/demo+/about/route.tsx" />
+    <Route file="routes/demo+/_index/route.tsx" index />
+  </Route>
+</Routes>
+`,
+    )
+
+    const after = normalizeSnapshot(
+      `<Routes>
+  <Route file="root.tsx">
+    <Route file="routes/demo/about.tsx" />
+    <Route file="routes/demo/_index.tsx" index />
+  </Route>
+</Routes>
+`,
+    )
+
+    expect(before).toBe(after)
+  })
+
   it('treats dot notation index files as index routes', () => {
     const fixture = createRoutesFixture({
       'app/routes/settings+/profile.two-factor.tsx':

test/migration-convert-to-route.test.ts

@@ -75,9 +75,21 @@ describe('normalizeSnapshotRouteFilePath', () => {
     ).toBe('routes/settings/profile.index.tsx')
   })
 
-  it('merges pathless underscore segments', () => {
+  it('collapses folder route files (route.tsx) to their parent route', () => {
+    expect(normalizeSnapshotRouteFilePath('routes/demo/about/route.tsx')).toBe(
+      'routes/demo/about.tsx',
+    )
+    expect(normalizeSnapshotRouteFilePath('routes/demo/_index/route.tsx')).toBe(
+      'routes/demo/_index.tsx',
+    )
     expect(
-      normalizeSnapshotRouteFilePath('routes/root_/__public.tsx'),
-    ).toBe('routes/root_.public.tsx')
+      normalizeSnapshotRouteFilePath('routes/_public/($lang)._index/route.tsx'),
+    ).toBe('routes/_public/($lang)._index.tsx')
+  })
+
+  it('merges pathless underscore segments', () => {
+    expect(normalizeSnapshotRouteFilePath('routes/root_/__public.tsx')).toBe(
+      'routes/root_.public.tsx',
+    )
   })
 })

test/migration-fs-helpers.test.ts

@@ -19,4 +19,24 @@ describe('isColocatedFile', () => {
     expect(isColocatedFile('marketing/pricing.tsx')).toBe(false)
     expect(isColocatedFile('(_auth)/login.tsx')).toBe(false)
   })
+
+  it('returns false for folder route entries (route.tsx) inside + folders', () => {
+    // remix-flat-routes folder route pattern: demo+/about/route.tsx
+    // The `about/` directory is a route folder, not a colocated directory
+    expect(isColocatedFile('demo+/about/route.tsx')).toBe(false)
+    expect(isColocatedFile('demo+/_index/route.tsx')).toBe(false)
+    expect(isColocatedFile('demo+/_layout/route.tsx')).toBe(false)
+    expect(isColocatedFile('demo+/conform.nested-array/route.tsx')).toBe(false)
+    expect(isColocatedFile('_public+/($lang)._index/route.tsx')).toBe(false)
+    expect(isColocatedFile('app+/reports+/$id+/detail/route.tsx')).toBe(false)
+  })
+
+  it('returns true for non-route files inside folder route directories', () => {
+    // Files that are not route entries should still be colocated
+    expect(isColocatedFile('demo+/about/components/header.tsx')).toBe(true)
+    expect(isColocatedFile('demo+/conform.nested-array/schema.ts')).toBe(true)
+    expect(isColocatedFile('demo+/conform.nested-array/faker.server.ts')).toBe(
+      true,
+    )
+  })
 })

test/migration-import-rewriter.test.ts

@@ -190,6 +190,111 @@ export default function Admin() {
     expect(rewritten).toContain(`from '../utils/auth/index'`)
   })
 
+  it('rewrites +types/route specifier when route.tsx becomes a flat file', () => {
+    workspace = fs.mkdtempSync(path.join(os.tmpdir(), 'rewrite-types-route-'))
+
+    const sourceDir = path.join(workspace, 'app', 'routes')
+    const targetDir = path.join(workspace, 'app', 'new-routes')
+
+    // route.tsx → about.tsx: ./+types/route should become ./+types/about
+    const sourceFile = path.join(sourceDir, 'demo+', 'about', 'route.tsx')
+    const targetFile = path.join(targetDir, 'demo', 'about.tsx')
+
+    fs.mkdirSync(path.dirname(sourceFile), { recursive: true })
+    fs.writeFileSync(
+      sourceFile,
+      `import type { Route } from './+types/route'
+
+export function loader({ params }: Route.LoaderArgs) {
+  return { title: 'About' }
+}
+
+export default function About({ loaderData }: Route.ComponentProps) {
+  return <h1>{loaderData.title}</h1>
+}
+`,
+    )
+
+    const normalizedMapping = new Map<string, string>([
+      [normalizeAbsolutePath(sourceFile), normalizeAbsolutePath(targetFile)],
+    ])
+
+    const specifierReplacements: SpecifierReplacement[] = []
+    rewriteAndCopy(
+      { source: sourceFile, target: targetFile },
+      normalizedMapping,
+      specifierReplacements,
+    )
+
+    const rewritten = fs.readFileSync(targetFile, 'utf8')
+    expect(rewritten).toContain("from './+types/about'")
+    expect(rewritten).not.toContain("from './+types/route'")
+  })
+
+  it('strips /index.ts extension from import specifiers', () => {
+    workspace = fs.mkdtempSync(path.join(os.tmpdir(), 'rewrite-strip-ts-ext-'))
+
+    const sourceDir = path.join(workspace, 'app', 'routes')
+    const targetDir = path.join(workspace, 'app', 'new-routes')
+
+    const sourceFile = path.join(sourceDir, 'demo+', 'example', 'route.tsx')
+    const targetFile = path.join(targetDir, 'demo', 'example.tsx')
+
+    const componentsDir = path.join(sourceDir, 'demo+', 'example', 'components')
+    fs.mkdirSync(componentsDir, { recursive: true })
+    fs.writeFileSync(
+      path.join(componentsDir, 'index.ts'),
+      'export { Header } from "./header"\n',
+    )
+    fs.writeFileSync(
+      path.join(componentsDir, 'header.tsx'),
+      'export function Header() { return null }\n',
+    )
+
+    // Colocated components move to +components/
+    const targetComponentsDir = path.join(
+      targetDir,
+      'demo',
+      '+example',
+      'components',
+    )
+    fs.mkdirSync(targetComponentsDir, { recursive: true })
+    fs.writeFileSync(
+      path.join(targetComponentsDir, 'index.ts'),
+      'export { Header } from "./header"\n',
+    )
+    fs.writeFileSync(
+      path.join(targetComponentsDir, 'header.tsx'),
+      'export function Header() { return null }\n',
+    )
+
+    fs.mkdirSync(path.dirname(sourceFile), { recursive: true })
+    fs.writeFileSync(
+      sourceFile,
+      `import { Header } from './components/index.ts'
+
+export default function Example() {
+  return <Header />
+}
+`,
+    )
+
+    const normalizedMapping = new Map<string, string>([
+      [normalizeAbsolutePath(sourceFile), normalizeAbsolutePath(targetFile)],
+    ])
+
+    const specifierReplacements: SpecifierReplacement[] = []
+    rewriteAndCopy(
+      { source: sourceFile, target: targetFile },
+      normalizedMapping,
+      specifierReplacements,
+    )
+
+    const rewritten = fs.readFileSync(targetFile, 'utf8')
+    // /index.ts should be stripped
+    expect(rewritten).not.toContain('/index.ts')
+  })
+
   it('rewrites aliased imports for parent routes promoted to _layout', () => {
     workspace = fs.mkdtempSync(path.join(os.tmpdir(), 'rewrite-alias-'))