refactor: modules and defaults.

playwright/app.spec.ts

@@ -11,6 +11,14 @@ const waitForInitialRender = async (page: Page) => {
   await expect(page.locator('#cdn-loading')).toHaveAttribute('hidden', '')
 }
 
+const expectPreviewHasRenderedContent = async (page: Page) => {
+  const previewHost = page.locator('#preview-host')
+  await expect(previewHost.locator('pre')).toHaveCount(0)
+  await expect
+    .poll(() => previewHost.evaluate(node => node.childElementCount))
+    .toBeGreaterThan(0)
+}
+
 const setComponentEditorSource = async (page: Page, source: string) => {
   const editorContent = page.locator('.component-panel .cm-content').first()
   await editorContent.fill(source)
@@ -26,10 +34,7 @@ test('renders default playground preview', async ({ page }) => {
 
   await page.getByLabel('ShadowRoot (open)').uncheck()
   await expect(page.locator('#status')).toHaveText('Rendered')
-
-  const previewItems = page.locator('#preview-host li')
-  await expect(previewItems).toHaveCount(3)
-  await expect(previewItems.first()).toContainText('apple')
+  await expectPreviewHasRenderedContent(page)
 })
 
 test('supports layout and theme toggles', async ({ page }) => {
@@ -56,10 +61,7 @@ test('renders in react mode with css modules', async ({ page }) => {
   await page.locator('#render-mode').selectOption('react')
   await page.locator('#style-mode').selectOption('module')
   await expect(page.locator('#status')).toHaveText('Rendered')
-
-  const previewItems = page.locator('#preview-host li')
-  await expect(previewItems).toHaveCount(3)
-  await expect(previewItems.first()).toContainText('apple')
+  await expectPreviewHasRenderedContent(page)
 })
 
 test('transpiles TypeScript annotations in component source', async ({ page }) => {
@@ -156,10 +158,7 @@ test('renders with less style mode', async ({ page }) => {
   await expect(page.locator('#style-warning')).toContainText(
     'Less is compiled in-browser via @knighted/css/browser.',
   )
-
-  const previewItems = page.locator('#preview-host li')
-  await expect(previewItems).toHaveCount(3)
-  await expect(previewItems.first()).toContainText('apple')
+  await expectPreviewHasRenderedContent(page)
 })
 
 test('renders with sass style mode', async ({ page }) => {
@@ -171,10 +170,7 @@ test('renders with sass style mode', async ({ page }) => {
   await expect(page.locator('#style-warning')).toContainText(
     'Sass is compiled in-browser via @knighted/css/browser.',
   )
-
-  const previewItems = page.locator('#preview-host li')
-  await expect(previewItems).toHaveCount(3)
-  await expect(previewItems.first()).toContainText('apple')
+  await expectPreviewHasRenderedContent(page)
 })
 
 test('style compilation errors populate styles diagnostics scope', async ({ page }) => {

scripts/build-prepare.js

@@ -1,7 +1,7 @@
 import { cp, mkdir, readFile, rm, writeFile } from 'node:fs/promises'
 import { dirname, resolve } from 'node:path'
 import { fileURLToPath } from 'node:url'
-import { cdnImportSpecs } from '../src/cdn.js'
+import { cdnImportSpecs } from '../src/modules/cdn.js'
 
 const validPrimaryCdns = new Set(['importMap', 'esm', 'jspmGa'])
 
@@ -49,12 +49,14 @@ const createProdImportsModule = async () => {
   ]
 
   if (specifiers.length === 0) {
-    throw new Error('No importMap specifiers found in src/cdn.js (cdnImportSpecs).')
+    throw new Error(
+      'No importMap specifiers found in src/modules/cdn.js (cdnImportSpecs).',
+    )
   }
 
   const lines = [
     '/*',
-    ' * Generated by scripts/build-prepare.js from src/cdn.js (cdnImportSpecs).',
+    ' * Generated by scripts/build-prepare.js from src/modules/cdn.js (cdnImportSpecs).',
     ' * JSPM links this module to trace top-level production imports.',
     ' */',
     ...specifiers.map(specifier => `import '${specifier}'`),

src/app.js

@@ -1,11 +1,15 @@
-import { cdnImports, getTypeScriptLibUrls, importFromCdnWithFallback } from './cdn.js'
-import { createCodeMirrorEditor } from './editor-codemirror.js'
-import { defaultCss, defaultJsx } from './defaults.js'
-import { createDiagnosticsUiController } from './diagnostics-ui.js'
-import { createLayoutThemeController } from './layout-theme.js'
-import { createPreviewBackgroundController } from './preview-background.js'
-import { createRenderRuntimeController } from './render-runtime.js'
-import { createTypeDiagnosticsController } from './type-diagnostics.js'
+import {
+  cdnImports,
+  getTypeScriptLibUrls,
+  importFromCdnWithFallback,
+} from './modules/cdn.js'
+import { createCodeMirrorEditor } from './modules/editor-codemirror.js'
+import { defaultCss, defaultJsx, defaultReactJsx } from './modules/defaults.js'
+import { createDiagnosticsUiController } from './modules/diagnostics-ui.js'
+import { createLayoutThemeController } from './modules/layout-theme.js'
+import { createPreviewBackgroundController } from './modules/preview-background.js'
+import { createRenderRuntimeController } from './modules/render-runtime.js'
+import { createTypeDiagnosticsController } from './modules/type-diagnostics.js'
 
 const statusNode = document.getElementById('status')
 const appGrid = document.querySelector('.app-grid')
@@ -48,6 +52,7 @@ let getCssSource = () => cssEditor.value
 let renderRuntime = null
 let pendingClearAction = null
 let suppressEditorChangeSideEffects = false
+let hasAppliedReactModeDefault = false
 const clipboardSupported = Boolean(navigator.clipboard?.writeText)
 
 const previewBackground = createPreviewBackgroundController({
@@ -346,7 +351,15 @@ const updateRenderButtonVisibility = () => {
   renderButton.hidden = autoRenderToggle.checked
 }
 
-renderMode.addEventListener('change', maybeRender)
+renderMode.addEventListener('change', () => {
+  if (renderMode.value === 'react' && !hasAppliedReactModeDefault) {
+    hasAppliedReactModeDefault = true
+    setJsxSource(defaultReactJsx)
+    markTypeDiagnosticsStale()
+  }
+
+  maybeRender()
+})
 styleMode.addEventListener('change', () => {
   if (cssCodeEditor) {
     cssCodeEditor.setLanguage(getStyleEditorLanguage(styleMode.value))

src/bootstrap.js

@@ -1,10 +1,10 @@
-import { getPrimaryCdnImportUrls } from './cdn.js'
+import { getPrimaryCdnImportUrls } from './modules/cdn.js'
 
 /*
  * Preload only the modules needed for the initial render path.
  * - Included: core runtime + React runtime modules used immediately.
  * - Excluded: optional style compilers (sass/less/lightningCssWasm), which stay lazy.
- * Keep this list aligned with cdnImports keys in cdn.js.
+ * Keep this list aligned with cdnImports keys in modules/cdn.js.
  */
 const preloadImportKeys = [
   'cssBrowser',

src/modules/defaults.js

@@ -0,0 +1,94 @@
+export const defaultJsx = [
+  'type CounterButtonProps = {',
+  '  label: string',
+  '  onClick: (event: MouseEvent) => void',
+  '}',
+  '',
+  'const CounterButton = ({ label, onClick }: CounterButtonProps) => (',
+  '  <button id="counter-button" type="button" onClick={onClick}>',
+  '    {label}',
+  '  </button>',
+  ')',
+  '',
+  'const App = () => {',
+  '  let count = 0',
+  '  const handleClick = (event: MouseEvent) => {',
+  '    count += 1',
+  '    const button = event.currentTarget as HTMLButtonElement',
+  '    button.textContent = `Clicks: ${count}`',
+  "    button.dataset.active = count % 2 === 0 ? 'false' : 'true'",
+  "    button.classList.toggle('is-even', count % 2 === 0)",
+  '  }',
+  '',
+  "  return <CounterButton label='Clicks: 0' onClick={handleClick} />",
+  '}',
+  '',
+].join('\n')
+
+export const defaultReactJsx = [
+  'type CounterButtonProps = {',
+  '  label: string',
+  '  active: boolean',
+  '  onClick: (event: MouseEvent) => void',
+  '}',
+  '',
+  'const CounterButton = ({ label, active, onClick }: CounterButtonProps) => (',
+  '  <button',
+  '    id="counter-button"',
+  '    type="button"',
+  '    data-active={active ? "true" : "false"}',
+  '    className={active ? "is-even" : ""}',
+  '    onClick={onClick}',
+  '  >',
+  '    {label}',
+  '  </button>',
+  ')',
+  '',
+  'const App = () => {',
+  '  const { useState } = React',
+  '  const [count, setCount] = useState(0)',
+  '  const handleClick = (_event: MouseEvent) => {',
+  '    setCount(current => current + 1)',
+  '  }',
+  '',
+  '  return (',
+  '    <CounterButton',
+  '      label={`React clicks: ${count}`}',
+  '      active={count % 2 === 0}',
+  '      onClick={handleClick}',
+  '    />',
+  '  )',
+  '}',
+  '',
+].join('\n')
+
+export const defaultCss = `#counter-button {
+  margin: 0;
+  padding: 0.75rem 1rem;
+  border: 1px solid #3558b8;
+  border-radius: 0.5rem;
+  background: #e9efff;
+  color: #1a2a52;
+  font-weight: 600;
+  cursor: pointer;
+  transition: background-color 120ms ease;
+}
+
+#counter-button:hover {
+  background: #dce6ff;
+}
+
+#counter-button[data-active='true'] {
+  background: #3558b8;
+  color: #fff;
+}
+
+#counter-button.is-even {
+  border-style: dashed;
+}
+
+#counter-button:focus-visible {
+  outline: 2px solid #6a84d8;
+  outline-offset: 2px;
+}
+`

src/diagnostics-ui.js → src/modules/diagnostics-ui.js

@@ -55,6 +55,10 @@ export const createDiagnosticsUiController = ({
       return 'pending'
     }
 
+    if (diagnosticsByScope.component.level === 'ok') {
+      return 'ok'
+    }
+
     return 'neutral'
   }
 
@@ -67,6 +71,7 @@ export const createDiagnosticsUiController = ({
     if (diagnosticsToggle) {
       diagnosticsToggle.classList.remove(
         'diagnostics-toggle--neutral',
+        'diagnostics-toggle--ok',
         'diagnostics-toggle--pending',
         'diagnostics-toggle--error',
       )
@@ -108,7 +113,10 @@ export const createDiagnosticsUiController = ({
 
     if (hasHeadline) {
       const headingNode = document.createElement('div')
-      headingNode.className = 'type-diagnostics-heading'
+      headingNode.className =
+        state.level === 'ok'
+          ? 'type-diagnostics-heading type-diagnostics-heading--ok'
+          : 'type-diagnostics-heading'
       headingNode.textContent = state.headline
       root.append(headingNode)
     }