test(router-core): regression test for streaming teardown

packages/router-core/tests/tsr-script-teardown.test.ts

@@ -0,0 +1,78 @@
+import { afterEach, beforeEach, describe, expect, test } from 'vitest'
+import minifiedTsrBootStrapScript from '../src/ssr/tsrScript?script-string'
+
+type TsrBootstrap = {
+  h: () => void
+  e: () => void
+  c: () => void
+}
+
+// Assign `self.$_TSR`.
+function installBootstrap(): TsrBootstrap {
+  new Function(minifiedTsrBootStrapScript)()
+  return (window as any).$_TSR
+}
+
+function setReadyState(value: DocumentReadyState) {
+  Object.defineProperty(document, 'readyState', {
+    configurable: true,
+    get: () => value,
+  })
+}
+
+describe('$_TSR client teardown', () => {
+  beforeEach(() => {
+    ;(window as any).$R = { tsr: [] }
+    delete (window as any).$_TSR
+  })
+
+  afterEach(() => {
+    delete (window as any).$_TSR
+    delete (window as any).$R
+    setReadyState('complete')
+  })
+
+  test('does not tear down until both hydrated and streamEnded', () => {
+    setReadyState('complete')
+    const tsr = installBootstrap()
+
+    tsr.h()
+    expect((window as any).$_TSR).toBeDefined()
+
+    tsr.e()
+    expect((window as any).$_TSR).toBeUndefined()
+  })
+
+  test('tears down immediately when the document is already parsed', () => {
+    setReadyState('complete')
+    const tsr = installBootstrap()
+
+    tsr.h()
+    tsr.e()
+
+    expect((window as any).$_TSR).toBeUndefined()
+    expect((window as any).$R.tsr).toBeUndefined()
+  })
+
+  // Regression: deferred/streamed deserializations can still arrive after the
+  // `$_TSR.e()` stream-end marker (e.g. Solid 2 streams resource hydration past
+  // it). Tearing `$_TSR` down immediately would make those late references
+  // throw `$_TSR is not defined`, so teardown waits for the document to finish
+  // parsing.
+  test('keeps $_TSR alive until DOMContentLoaded while the document is still loading', () => {
+    setReadyState('loading')
+    const tsr = installBootstrap()
+
+    tsr.h()
+    tsr.e()
+
+    // Still available for late streamed scripts.
+    expect((window as any).$_TSR).toBeDefined()
+    expect((window as any).$R.tsr).toBeDefined()
+
+    document.dispatchEvent(new Event('DOMContentLoaded'))
+
+    expect((window as any).$_TSR).toBeUndefined()
+    expect((window as any).$R.tsr).toBeUndefined()
+  })
+})