Add test for Server Components HMR after navigating to page with Edge runtime (#67782)

Author: eps1lon

test/development/app-hmr/hmr.test.ts

@@ -3,6 +3,8 @@ import { retry, waitFor } from 'next-test-utils'
 
 const envFile = '.env.development.local'
 
+const isPPREnabledByDefault = process.env.__NEXT_EXPERIMENTAL_PPR === 'true'
+
 describe(`app-dir-hmr`, () => {
   const { next } = nextTestSetup({
     files: __dirname,
@@ -54,7 +56,86 @@ describe(`app-dir-hmr`, () => {
       }
     })
 
+    it('should update server components after navigating to a page with a different runtime', async () => {
+      const envContent = await next.readFile(envFile)
+
+      const browser = await next.browser('/env/node')
+      await browser.loadPage(`${next.url}/env/edge`)
+      await browser.eval('window.__TEST_NO_RELOAD = true')
+
+      await next.patchFile(envFile, 'MY_DEVICE="ipad"')
+
+      try {
+        const logs = await browser.log()
+
+        if (process.env.TURBOPACK) {
+          await retry(async () => {
+            const fastRefreshLogs = logs.filter((log) => {
+              return log.message.startsWith('[Fast Refresh]')
+            })
+            // FIXME:  3+ "rebuilding" but single "done" is confusing.
+            // There may actually be more "rebuilding" but not reliably.
+            // To ignore this flakiness, we just assert on subset matches.
+            // Once the  bug is fixed, each "rebuilding" should be paired with a "done in" exactly.
+            expect(fastRefreshLogs).toEqual(
+              expect.arrayContaining([
+                { source: 'log', message: '[Fast Refresh] rebuilding' },
+                { source: 'log', message: '[Fast Refresh] rebuilding' },
+                {
+                  source: 'log',
+                  message: expect.stringContaining('[Fast Refresh] done in '),
+                },
+                { source: 'log', message: '[Fast Refresh] rebuilding' },
+              ])
+            )
+          })
+        } else {
+          await retry(
+            async () => {
+              const fastRefreshLogs = logs.filter((log) => {
+                return log.message.startsWith('[Fast Refresh]')
+              })
+              // FIXME: Should be either a single "rebuilding"+"done" or the last "rebuilding" should be followed by "done"
+              expect(fastRefreshLogs).toEqual([
+                { source: 'log', message: '[Fast Refresh] rebuilding' },
+                { source: 'log', message: '[Fast Refresh] rebuilding' },
+                {
+                  source: 'log',
+                  message: expect.stringContaining('[Fast Refresh] done in '),
+                },
+                { source: 'log', message: '[Fast Refresh] rebuilding' },
+              ])
+            },
+            // Very slow Hot Update for some reason.
+            // May be related to receiving 3 rebuild events but only one finish event
+            5000
+          )
+        }
+        const envValue = await browser.elementByCss('p').text()
+        const mpa = await browser.eval('window.__TEST_NO_RELOAD === undefined')
+        // Flaky sometimes in Webpack:
+        // A. misses update and just receives `{ envValue: 'mac', mpa: false }`
+        // B. triggers error on server resulting in MPA: `{ envValue: 'ipad', mpa: true }` and server logs: ⨯ [TypeError: Cannot read properties of undefined (reading 'polyfillFiles')] ⨯ [TypeError: Cannot read properties of null (reading 'default')]
+        // A is more common than B.
+        expect({ envValue, mpa }).toEqual({
+          envValue:
+            isPPREnabledByDefault && !process.env.TURBOPACK
+              ? // FIXME: Should be 'ipad' but PPR+Webpack swallows the update reliably
+                'mac'
+              : 'ipad',
+          mpa: false,
+        })
+      } finally {
+        await next.patchFile(envFile, envContent)
+      }
+    })
+
     it('should update server components pages when env files is changed (nodejs)', async () => {
+      // If "should update server components after navigating to a page with a different runtime" failed, the dev server is in a corrupted state.
+      // Restart fixes this.
+      await next.stop()
+      await next.start()
+
       const envContent = await next.readFile(envFile)
       const browser = await next.browser('/env/node')
       expect(await browser.elementByCss('p').text()).toBe('mac')
@@ -91,6 +172,10 @@ describe(`app-dir-hmr`, () => {
     })
 
     it('should update server components pages when env files is changed (edge)', async () => {
+      // Restart to work around a bug highlighted in the flakiness of "should update server components after navigating to a page with a different runtime"
+      await next.stop()
+      await next.start()
+
       const envContent = await next.readFile(envFile)
       const browser = await next.browser('/env/edge')
       expect(await browser.elementByCss('p').text()).toBe('mac')