docs: improve bundling documentation (#498)

Co-authored-by: Claude <noreply@anthropic.com>

Author: harlan-zw

docs/content/docs/1.guides/2.bundling.md

@@ -72,9 +72,12 @@ useScript('https://example.com/script.js', {
 ```
 
 ```ts [Registry Script]
-// Registry script must support bundling
-useScriptGoogleAnalytics('https://example.com/script.js', {
-  bundle: true,
+// Registry script bundling using scriptOptions
+useScriptGoogleAnalytics({
+  id: 'GA_MEASUREMENT_ID',
+  scriptOptions: {
+    bundle: true
+  }
 })
 ```
 ::
@@ -93,15 +96,130 @@ export default defineNuxtConfig({
 })
 ```
 
-### Limitations of Bundling
+### Build-time vs Runtime Behavior
+
+Understanding when bundling happens and how it affects runtime behavior is crucial for effective usage.
+
+#### Build-time Processing
+
+Bundling occurs during the build phase through static code analysis:
+
+```ts
+// ✅ Bundled at build-time (static values)
+useScript('https://example.com/script.js', { bundle: true })
+
+// ❌ Cannot be bundled (dynamic values)
+const scriptUrl = computed(() => getScriptUrl())
+useScript(scriptUrl, { bundle: dynamic.value })
+```
+
+#### Runtime Behavior
 
-While many scripts can be bundled, there are exceptions you need to be aware of.
+At runtime, bundled scripts behave differently:
 
-For instance, certain scripts:
-- Require tracking all user interactions for security reasons, like fraud detection (e.g., Stripe).
-- Must be served directly from their original source to function properly (e.g., Fathom Analytics).
+```ts
+// Original code
+useScript('https://example.com/script.js', { bundle: true })
 
-Scripts from known registries are pre-configured to either allow or disallow bundling. For your own scripts, you'll need to decide whether bundling is appropriate on a case-by-case basis.
+// After build transformation
+useScript('/_scripts/abc123.js', {})
+```
+
+**Important**: Once bundled, you lose access to the original URL at runtime. If you need the original URL for tracking or analytics, store it separately.
+
+#### Static URL Requirements
+
+For bundling to work, the transformer requires **completely static values**:
+
+::code-group
+
+```ts [✅ Valid for Bundling]
+// Static string literals
+useScript('https://cdn.example.com/lib.js', { bundle: true })
+
+// Static template literals (no variables)
+useScript(`https://cdn.example.com/lib.js`, { bundle: true })
+
+// Constants defined at module level
+const SCRIPT_URL = 'https://cdn.example.com/lib.js'
+useScript(SCRIPT_URL, { bundle: true })
+```
+
+```ts [❌ Cannot be Bundled]
+// Runtime variables
+const url = getScriptUrl()
+useScript(url, { bundle: true })
+
+// Computed values
+const scriptUrl = computed(() => `https://cdn.example.com/${version.value}.js`)
+useScript(scriptUrl, { bundle: true })
+
+// Environment variables at runtime
+useScript(process.env.SCRIPT_URL, { bundle: true })
+
+// Props or reactive values
+useScript(props.scriptUrl, { bundle: true })
+```
+
+::
+
+#### Manual Injection Patterns
+
+When automatic bundling isn't possible, you can manually inject bundled scripts:
+
+```ts [Manual Bundling Workaround]
+// 1. Bundle during build with static URL
+const staticScript = useScript('https://cdn.example.com/static.js', {
+  bundle: true,
+  trigger: 'manual' // Don't auto-load
+})
+
+// 2. Conditionally load based on runtime logic
+function loadScript() {
+  if (shouldLoadScript.value) {
+    staticScript.load()
+  }
+}
+
+// 3. Alternative: Use multiple static configurations
+const scriptVariants = {
+  dev: useScript('https://cdn.example.com/dev.js', { bundle: true, trigger: 'manual' }),
+  prod: useScript('https://cdn.example.com/prod.js', { bundle: true, trigger: 'manual' })
+}
+
+// Load appropriate variant
+const currentScript = computed(() =>
+  isDev ? scriptVariants.dev : scriptVariants.prod
+)
+```
+
+#### Working with Dynamic URLs
+
+For truly dynamic scenarios, consider these patterns:
+
+```ts [Dynamic URL Strategies]
+// Option 1: Pre-bundle known variants
+const analytics = {
+  google: useScript('https://www.googletagmanager.com/gtag/js', { bundle: true }),
+  plausible: useScript('https://plausible.io/js/script.js', { bundle: true })
+}
+
+// Option 2: Fallback to runtime loading
+function loadDynamicScript(url: string) {
+  // This won't be bundled, but will work at runtime
+  return useScript(url, {
+    bundle: false, // Explicitly disable
+    trigger: 'manual'
+  })
+}
+
+// Option 3: Use server-side bundling
+// Store script content in your bundle and inject manually
+const { $script } = useNuxtApp()
+$script.add({
+  innerHTML: await $fetch('/api/dynamic-script-content'),
+})
+```
 
 ### Change Asset Behavior
 

test/unit/transform.test.ts

@@ -147,6 +147,70 @@ describe('nuxtScriptTransformer', () => {
     expect(code).toMatchInlineSnapshot(`"const instance = useScriptFathomAnalytics({ src: '/_scripts/custom.js.js' }, )"`)
   })
 
+  it('registry script with scriptOptions.bundle - correct usage', async () => {
+    vi.mocked(hash).mockImplementationOnce(() => 'analytics')
+    const code = await transform(
+      `const instance = useScriptGoogleAnalytics({
+        id: 'GA_MEASUREMENT_ID',
+        scriptOptions: {
+          bundle: true
+        }
+      })`,
+      {
+        defaultBundle: false,
+        scripts: [
+          {
+            scriptBundling() {
+              return 'https://www.googletagmanager.com/gtag/js'
+            },
+            import: {
+              name: 'useScriptGoogleAnalytics',
+              from: '',
+            },
+          },
+        ],
+      },
+    )
+    expect(code).toMatchInlineSnapshot(`
+      "const instance = useScriptGoogleAnalytics({ scriptInput: { src: '/_scripts/analytics.js' }, 
+              id: 'GA_MEASUREMENT_ID',
+              scriptOptions: {
+                bundle: true
+              }
+            })"
+    `)
+  })
+
+  it('registry script with top-level bundle also transforms', async () => {
+    vi.mocked(hash).mockImplementationOnce(() => 'gtag/js')
+    const code = await transform(
+      `const instance = useScriptGoogleAnalytics({
+        id: 'GA_MEASUREMENT_ID'
+      }, {
+        bundle: true
+      })`,
+      {
+        defaultBundle: false,
+        scripts: [
+          {
+            scriptBundling() {
+              return 'https://www.googletagmanager.com/gtag/js'
+            },
+            import: {
+              name: 'useScriptGoogleAnalytics',
+              from: '',
+            },
+          },
+        ],
+      },
+    )
+    expect(code).toMatchInlineSnapshot(`
+      "const instance = useScriptGoogleAnalytics({ scriptInput: { src: '/_scripts/gtag/js.js' }, 
+              id: 'GA_MEASUREMENT_ID'
+            }, )"
+    `)
+  })
+
   it('static src integration is transformed - opt-in', async () => {
     const code = await transform(
       `const instance = useScriptFathomAnalytics({ site: '123' }, { bundle: true, })`,