Add experimental onlyGenereated flag for unstable_revalidate

[ijjk]

This adds experimental support for only manually revalidating if a page has been generated and is in the cache e.g. skipping revalidating pages that have yet to be generated with fallback: true.

[ijjk]

Stats from current PR

Default Build (Decrease detected ✓)

General Overall increase ⚠️

	vercel/next.js canary	ijjk/next.js feat/revalidate-if-generated	Change
buildDuration	19.5s	19.4s	-142ms
buildDurationCached	7.5s	7.4s	-73ms
nodeModulesSize	484 MB	484 MB	⚠️ +2.24 kB

Page Load Tests Overall decrease ⚠️

	vercel/next.js canary	ijjk/next.js feat/revalidate-if-generated	Change
/ failed reqs	0	0	✓
/ total time (seconds)	3.944	4.048	⚠️ +0.1
/ avg req/sec	633.83	617.57	⚠️ -16.26
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.707	1.703	0
/error-in-render avg req/sec	1464.88	1468.08	+3.2

Client Bundles (main, webpack)

	vercel/next.js canary	ijjk/next.js feat/revalidate-if-generated	Change
925.HASH.js gzip	179 B	179 B	✓
framework-HASH.js gzip	42 kB	42 kB	✓
main-HASH.js gzip	28.3 kB	28.3 kB	✓
webpack-HASH.js gzip	1.44 kB	1.44 kB	✓
Overall change	72 kB	72 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	ijjk/next.js feat/revalidate-if-generated	Change
polyfills-HASH.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	ijjk/next.js feat/revalidate-if-generated	Change
_app-HASH.js gzip	1.36 kB	1.36 kB	✓
_error-HASH.js gzip	192 B	192 B	✓
amp-HASH.js gzip	309 B	309 B	✓
css-HASH.js gzip	327 B	327 B	✓
dynamic-HASH.js gzip	3.05 kB	3.05 kB	✓
head-HASH.js gzip	351 B	351 B	✓
hooks-HASH.js gzip	920 B	920 B	✓
image-HASH.js gzip	5.73 kB	5.73 kB	✓
index-HASH.js gzip	263 B	263 B	✓
link-HASH.js gzip	2.36 kB	2.36 kB	✓
routerDirect..HASH.js gzip	320 B	320 B	✓
script-HASH.js gzip	392 B	392 B	✓
withRouter-HASH.js gzip	319 B	319 B	✓
85e02e95b279..7e3.css gzip	107 B	107 B	✓
Overall change	16 kB	16 kB	✓

Client Build Manifests

	vercel/next.js canary	ijjk/next.js feat/revalidate-if-generated	Change
_buildManifest.js gzip	460 B	460 B	✓
Overall change	460 B	460 B	✓

Rendered Page Sizes

	vercel/next.js canary	ijjk/next.js feat/revalidate-if-generated	Change
index.html gzip	532 B	532 B	✓
link.html gzip	546 B	546 B	✓
withRouter.html gzip	527 B	527 B	✓
Overall change	1.6 kB	1.6 kB	✓

---

Default Build with SWC (Decrease detected ✓)

General Overall increase ⚠️

	vercel/next.js canary	ijjk/next.js feat/revalidate-if-generated	Change
buildDuration	22.5s	22.2s	-359ms
buildDurationCached	7.3s	7.4s	⚠️ +101ms
nodeModulesSize	484 MB	484 MB	⚠️ +2.24 kB

Page Load Tests Overall decrease ⚠️

	vercel/next.js canary	ijjk/next.js feat/revalidate-if-generated	Change
/ failed reqs	0	0	✓
/ total time (seconds)	3.984	3.881	-0.1
/ avg req/sec	627.55	644.24	+16.69
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.692	1.726	⚠️ +0.03
/error-in-render avg req/sec	1477.29	1448.32	⚠️ -28.97

Client Bundles (main, webpack)

	vercel/next.js canary	ijjk/next.js feat/revalidate-if-generated	Change
925.HASH.js gzip	178 B	178 B	✓
framework-HASH.js gzip	42.3 kB	42.3 kB	✓
main-HASH.js gzip	28.7 kB	28.7 kB	✓
webpack-HASH.js gzip	1.45 kB	1.45 kB	✓
Overall change	72.6 kB	72.6 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	ijjk/next.js feat/revalidate-if-generated	Change
polyfills-HASH.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	ijjk/next.js feat/revalidate-if-generated	Change
_app-HASH.js gzip	1.35 kB	1.35 kB	✓
_error-HASH.js gzip	179 B	179 B	✓
amp-HASH.js gzip	313 B	313 B	✓
css-HASH.js gzip	325 B	325 B	✓
dynamic-HASH.js gzip	3.03 kB	3.03 kB	✓
head-HASH.js gzip	351 B	351 B	✓
hooks-HASH.js gzip	921 B	921 B	✓
image-HASH.js gzip	5.77 kB	5.77 kB	✓
index-HASH.js gzip	261 B	261 B	✓
link-HASH.js gzip	2.44 kB	2.44 kB	✓
routerDirect..HASH.js gzip	322 B	322 B	✓
script-HASH.js gzip	393 B	393 B	✓
withRouter-HASH.js gzip	317 B	317 B	✓
85e02e95b279..7e3.css gzip	107 B	107 B	✓
Overall change	16.1 kB	16.1 kB	✓

Client Build Manifests

	vercel/next.js canary	ijjk/next.js feat/revalidate-if-generated	Change
_buildManifest.js gzip	458 B	458 B	✓
Overall change	458 B	458 B	✓

Rendered Page Sizes

	vercel/next.js canary	ijjk/next.js feat/revalidate-if-generated	Change
index.html gzip	532 B	532 B	✓
link.html gzip	547 B	547 B	✓
withRouter.html gzip	527 B	527 B	✓
Overall change	1.61 kB	1.61 kB	✓

Commit: d62d9e6

[styfle]

How about changing ifGenerated to onlyGenerated?