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Andrew Clark
94327e8ade
The test suite has accumulated a bunch of patterns for disabling tests
that are known to fail under some configuration: `it.skip`, `if
(isNextDev) { test('skipped in dev mode', () => {}); return }`, whole
describes toggled off by checking `process.env.__NEXT_CACHE_COMPONENTS`.
These all have the same flaw: nothing tells you when the thing you
skipped starts working. The test stays disabled forever, and the
workaround it was guarding rots along with it.
React solves this with the `@gate` pragma, and this PR ports it to the
Next.js e2e harness:
```ts
// Blocked on the optimization that marks a route as fully static when
// no dynamic params are referenced in Server Components.
// @gate !cacheComponents
it('navigates to a page with a lazily-generated static param', async () => {
// body unchanged
})
```
The test still runs. If the condition is false and the test fails, the
failure is absorbed and the suite stays green. If it _passes_, the suite
fails: the gate is stale, delete it. So instead of a skip that hides a
fixed bug indefinitely, you get a CI failure the day the fix lands.
When the condition is static, the inversion is Jest's own `test.failing`
under the hood. A lazy condition isn't known until the fixture's
resolved config is read inside the body, so those tests invert at
runtime instead.
`// @force-gate <condition>` skips for real — for tests that can't even
be attempted (prefetching is disabled in dev, deploy has no local build
output, the fixture won't build under the condition), and for tests of a
new API, where the disabled state can only throw and running it proves
nothing:
```ts
// Prefetching is disabled in dev, so this suite has nothing to test.
// @force-gate prefetching
describe('segment cache prefetch scheduling', () => {
// ...
})
```
There's no staleness check in that case, so this is a judgment call:
prefer `@gate` when the off state fails for a meaningful reason — the
flag changes behavior that already exists — and `@force-gate` when the
body can only throw because the API doesn't exist. A static condition
(mode, bundler) resolves at collection time into a normal Jest skip. A
lazy condition resolves at runtime, and when a lazy force-gate on a
describe is false, we skip the fixture build entirely — that's what
makes it usable for suites whose fixtures are build-incompatible with
the condition. (One caveat: Jest has no way to skip a test that's
already running, so these report as passing with a warning in the log,
not as skipped.)
Conditions live in a hand-written registry. I considered deriving the
lazy ones from the config schema automatically, but a gate is a claim
about which dimension of the test matrix explains a failure, and I'd
rather each of those claims be spelled out with a description.
Referencing an undeclared name fails the suite at collection time, so a
typo can't silently disable a gate.
The important design decision for lazy conditions is that they read the
fixture's _resolved_ config, never `process.env`. The env var isn't the
truth: `__NEXT_CACHE_COMPONENTS=true` only applies when the fixture
doesn't set `cacheComponents` itself, and config resolution implies
flags the fixture never mentions (`cacheComponents: true` alone turns on
`experimental.ppr`). Resolution happens in a child process, because
in-process `loadConfig` would leak the fixture's `.env` files into the
Jest worker. Suites with no lazy gate never pay for any of this.
The condition expression is parsed using a small grammar (also ported
from the React repo). An expression that doesn't parse fails the suite:
```ts
// @gate mode === 'start' && !cacheComponents
// @gate !(turbopack || rspack)
```
There's also a runtime version, mirroring React's `gate(flags =>
flags.enableFoo)`, for tests that run under both states but assert
differently (and for `it.each`, where the pragma can't attach):
```ts
import { gate } from 'next-test-utils'
it('renders the fallback', async () => {
if (await gate((conditions) => conditions.cacheComponents)) {
// PPR: the fallback is part of the static shell
} else {
// fully dynamic: the fallback streams in
}
})
```
It also accepts the pragma expression language as a string: `await
gate('cacheComponents && !dev')`.
Docs are in `test/lib/gate/README.md`; `test/unit/gate/` covers the
transform, the expression language, and the runtime.
79 lines
3.6 KiB
TypeScript
79 lines
3.6 KiB
TypeScript
import { nextTestSetup } from 'e2e-utils'
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import { retry } from 'next-test-utils'
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const NOT_IMPLEMENTED_ERROR =
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'Not implemented: this behavior is not yet supported when ' +
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'`experimental.concurrentRouterQueue` is enabled.'
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// `experimental.concurrentRouterQueue` swaps the router's entry-point modules
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// (the navigator and the callServer action door) for the concurrent
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// implementations at the bundler level. The concurrent implementations are
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// currently stubs that throw a single distinctive error from every operation,
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// so this suite verifies the fork wiring: the app boots on the concurrent
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// modules without touching them, and every old-world entry point fails
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// loudly instead of silently running the sequential implementation.
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describe('concurrent-router-queue', () => {
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const { next } = nextTestSetup({
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files: __dirname,
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})
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// Not gated: a clean hydration is expected in both states of the flag.
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it('hydrates cleanly without invoking the forked entry points', async () => {
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// `pushErrorAsConsoleLog` records uncaught page errors into the console
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// log capture, which works in both dev and start modes.
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const browser = await next.browser('/', { pushErrorAsConsoleLog: true })
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expect(await browser.elementByCss('#home').text()).toBe('home')
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// Hydration is complete once the client components are interactive.
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await browser.waitForElementByCss('#invoke-action')
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// Nothing at boot may call into the stubs (or fail in any other way).
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const errors = (await browser.log()).filter((log) => log.source === 'error')
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expect(errors).toEqual([])
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})
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// The stubs only throw when the fork is active; with the flag off, the
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// sequential router handles the navigation and the test fails its
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// expectations — which is what the gate asserts on the axis-A run.
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// @gate concurrentRouterQueue
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it('fails loudly on link navigation', async () => {
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const browser = await next.browser('/', { pushErrorAsConsoleLog: true })
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await browser.waitForElementByCss('#invoke-action')
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await browser.elementByCss('#to-target-page').click()
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// The stub throws synchronously inside the click handler, which surfaces
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// as an uncaught page error. Wait for it to confirm the click was
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// processed.
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await retry(async () => {
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const errors = (await browser.log()).filter(
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(log) =>
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log.source === 'error' && log.message.includes(NOT_IMPLEMENTED_ERROR)
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)
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expect(errors.length).toBeGreaterThan(0)
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})
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// No navigation happened, soft or hard: Link calls preventDefault()
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// before dispatching, and the stub throws before any router state or
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// pending-URL bookkeeping, so there is no fallback hard navigation.
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expect(new URL(await browser.url()).pathname).toBe('/')
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// The home page is still rendered; the target page never appears.
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expect(await browser.elementByCss('#home').text()).toBe('home')
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expect(await browser.hasElementByCssSelector('#target-page')).toBe(false)
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})
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// @gate concurrentRouterQueue
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it('fails loudly on server action invocation', async () => {
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const browser = await next.browser('/')
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await browser.waitForElementByCss('#invoke-action')
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await browser.elementByCss('#invoke-action').click()
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// callServer is async, so the stub surfaces as a rejection of the promise
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// returned to the action caller, which the fixture renders. The result
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// element is empty (and hidden) until the rejection renders, so
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// elementByCss waits for it to appear.
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expect(await browser.elementByCss('#action-result').text()).toBe(
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`rejected: ${NOT_IMPLEMENTED_ERROR}`
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)
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})
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})
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