Enable Link tests without Router (#9951)

[rendoh]

Link.handleRef sometimes raises a TypeError because singleton router may not exist in unit tests. I think it should deal with the case without router. Would you be able to review this, please?

Fixes #9951

[ijjk]

Stats from current PR

Default Server Mode

General Overall increase ⚠️

	zeit/next.js canary	rendoh/next.js hotfix/link-prefetching	Change
buildDuration	13.2s	13.3s	⚠️ +64ms
nodeModulesSize	48.9 MB	48.9 MB	⚠️ +26 B

Client Bundles (main, webpack, commons)

	zeit/next.js canary	rendoh/next.js hotfix/link-prefetching	Change
main-HASH.js gzip	5.13 kB	5.13 kB	✓
webpack-HASH.js gzip	746 B	746 B	✓
4952ddcd88e7..54d3.js gzip	4.68 kB	4.68 kB	✓
commons.HASH.js gzip	4.06 kB	4.06 kB	✓
de003c3a9d30..4cf7.js gzip	13.7 kB	13.7 kB	✓
framework.HASH.js gzip	39.1 kB	39.1 kB	✓
Overall change	67.5 kB	67.5 kB	✓

Client Bundles (main, webpack, commons) Modern

	zeit/next.js canary	rendoh/next.js hotfix/link-prefetching	Change
main-HASH.module.js gzip	4.19 kB	4.19 kB	✓
webpack-HASH..dule.js gzip	746 B	746 B	✓
4952ddcd88e7..dule.js gzip	5.56 kB	5.56 kB	✓
de003c3a9d30..dule.js gzip	12.5 kB	12.5 kB	✓
framework.HA..dule.js gzip	39.1 kB	39.1 kB	✓
Overall change	62.1 kB	62.1 kB	✓

Legacy Client Bundles (polyfills)

	zeit/next.js canary	rendoh/next.js hotfix/link-prefetching	Change
polyfills-HASH.js gzip	4.76 kB	4.76 kB	✓
Overall change	4.76 kB	4.76 kB	✓

Client Pages Overall increase ⚠️

	zeit/next.js canary	rendoh/next.js hotfix/link-prefetching	Change
_app.js gzip	1.33 kB	1.33 kB	✓
_error.js gzip	4.07 kB	4.07 kB	✓
hooks.js gzip	779 B	779 B	✓
index.js gzip	222 B	222 B	✓
link.js gzip	2.9 kB	2.9 kB	⚠️ +3 B
routerDirect.js gzip	283 B	283 B	✓
withRouter.js gzip	282 B	282 B	✓
Overall change	9.87 kB	9.87 kB	⚠️ +3 B

Client Pages Modern Overall increase ⚠️

	zeit/next.js canary	rendoh/next.js hotfix/link-prefetching	Change
_app.module.js gzip	757 B	757 B	✓
_error.module.js gzip	3.06 kB	3.06 kB	✓
hooks.module.js gzip	371 B	371 B	✓
index.module.js gzip	212 B	212 B	✓
link.module.js gzip	2.47 kB	2.48 kB	⚠️ +4 B
routerDirect..dule.js gzip	273 B	273 B	✓
withRouter.m..dule.js gzip	272 B	272 B	✓
Overall change	7.41 kB	7.42 kB	⚠️ +4 B

Client Build Manifests

	zeit/next.js canary	rendoh/next.js hotfix/link-prefetching	Change
_buildManifest.js gzip	61 B	61 B	✓
_buildManife..dule.js gzip	61 B	61 B	✓
Overall change	122 B	122 B	✓

Rendered Page Sizes

	zeit/next.js canary	rendoh/next.js hotfix/link-prefetching	Change
index.html gzip	1.02 kB	1.02 kB	✓
link.html gzip	1.03 kB	1.03 kB	✓
withRouter.html gzip	1.02 kB	1.02 kB	✓
Overall change	3.07 kB	3.07 kB	✓

Diffs

Diff for link.js

@@ -655,6 +655,7 @@
                 var _this2 = this
 
                 var isPrefetched =
+                  _router['default'].router &&
                   _router['default'].router.pageLoader.prefetched[
                     this.getHref()
                   ]

Diff for link.module.js

@@ -497,6 +497,7 @@
 
         handleRef(ref) {
           var isPrefetched =
+            _router.default.router &&
             _router.default.router.pageLoader.prefetched[this.getHref()]
 
           if (this.p && IntersectionObserver && ref && ref.tagName) {

---

Serverless Mode

General Overall increase ⚠️

	zeit/next.js canary	rendoh/next.js hotfix/link-prefetching	Change
buildDuration	13.7s	13.7s	⚠️ +75ms
nodeModulesSize	48.9 MB	48.9 MB	⚠️ +26 B

Client Bundles (main, webpack, commons)

	zeit/next.js canary	rendoh/next.js hotfix/link-prefetching	Change
main-HASH.js gzip	5.13 kB	5.13 kB	✓
webpack-HASH.js gzip	746 B	746 B	✓
4952ddcd88e7..54d3.js gzip	4.68 kB	4.68 kB	✓
commons.HASH.js gzip	4.06 kB	4.06 kB	✓
de003c3a9d30..4cf7.js gzip	13.7 kB	13.7 kB	✓
framework.HASH.js gzip	39.1 kB	39.1 kB	✓
Overall change	67.5 kB	67.5 kB	✓

Client Bundles (main, webpack, commons) Modern

	zeit/next.js canary	rendoh/next.js hotfix/link-prefetching	Change
main-HASH.module.js gzip	4.19 kB	4.19 kB	✓
webpack-HASH..dule.js gzip	746 B	746 B	✓
4952ddcd88e7..dule.js gzip	5.56 kB	5.56 kB	✓
de003c3a9d30..dule.js gzip	12.5 kB	12.5 kB	✓
framework.HA..dule.js gzip	39.1 kB	39.1 kB	✓
Overall change	62.1 kB	62.1 kB	✓

Legacy Client Bundles (polyfills)

	zeit/next.js canary	rendoh/next.js hotfix/link-prefetching	Change
polyfills-HASH.js gzip	4.76 kB	4.76 kB	✓
Overall change	4.76 kB	4.76 kB	✓

Client Pages Overall increase ⚠️

	zeit/next.js canary	rendoh/next.js hotfix/link-prefetching	Change
_app.js gzip	1.33 kB	1.33 kB	✓
_error.js gzip	4.07 kB	4.07 kB	✓
hooks.js gzip	779 B	779 B	✓
index.js gzip	222 B	222 B	✓
link.js gzip	2.9 kB	2.9 kB	⚠️ +3 B
routerDirect.js gzip	283 B	283 B	✓
withRouter.js gzip	282 B	282 B	✓
Overall change	9.87 kB	9.87 kB	⚠️ +3 B

Client Pages Modern Overall increase ⚠️

	zeit/next.js canary	rendoh/next.js hotfix/link-prefetching	Change
_app.module.js gzip	757 B	757 B	✓
_error.module.js gzip	3.06 kB	3.06 kB	✓
hooks.module.js gzip	371 B	371 B	✓
index.module.js gzip	212 B	212 B	✓
link.module.js gzip	2.47 kB	2.48 kB	⚠️ +4 B
routerDirect..dule.js gzip	273 B	273 B	✓
withRouter.m..dule.js gzip	272 B	272 B	✓
Overall change	7.41 kB	7.42 kB	⚠️ +4 B

Client Build Manifests

	zeit/next.js canary	rendoh/next.js hotfix/link-prefetching	Change
_buildManifest.js gzip	61 B	61 B	✓
_buildManife..dule.js gzip	61 B	61 B	✓
Overall change	122 B	122 B	✓

Serverless bundles Overall increase ⚠️

	zeit/next.js canary	rendoh/next.js hotfix/link-prefetching	Change
_error.js gzip	77.8 kB	77.8 kB	✓
hooks.html gzip	1.06 kB	1.06 kB	✓
index.js gzip	78 kB	78 kB	✓
link.js gzip	80.4 kB	80.4 kB	⚠️ +5 B
routerDirect.js gzip	78.1 kB	78.1 kB	✓
withRouter.js gzip	78.1 kB	78.1 kB	✓
Overall change	393 kB	393 kB	⚠️ +5 B

Commit: 23cf67b