remove unneeded error (#16636)

This is not needed anymore since absolute urls are supported.
Also added an extra test for `mailto:` urls

packages/next/next-server/lib/router/router.ts

@@ -115,23 +115,6 @@ function prepareUrlAs(router: NextRouter, url: Url, as: Url) {
   }
 }
 
-function tryParseRelativeUrl(
-  url: string
-): null | ReturnType<typeof parseRelativeUrl> {
-  try {
-    return parseRelativeUrl(url)
-  } catch (err) {
-    if (process.env.NODE_ENV !== 'production') {
-      setTimeout(() => {
-        throw new Error(
-          `Invalid href passed to router: ${url} https://err.sh/vercel/next.js/invalid-href-passed`
-        )
-      }, 0)
-    }
-    return null
-  }
-}
-
 export type BaseRouter = {
   route: string
   pathname: string
@@ -503,9 +486,7 @@ export default class Router implements BaseRouter {
     const pages = await this.pageLoader.getPageList()
     const { __rewrites: rewrites } = await this.pageLoader.promisedBuildManifest
 
-    let parsed = tryParseRelativeUrl(url)
-
-    if (!parsed) return false
+    let parsed = parseRelativeUrl(url)
 
     let { pathname, searchParams } = parsed
 
@@ -899,9 +880,7 @@ export default class Router implements BaseRouter {
     asPath: string = url,
     options: PrefetchOptions = {}
   ): Promise<void> {
-    let parsed = tryParseRelativeUrl(url)
-
-    if (!parsed) return
+    let parsed = parseRelativeUrl(url)
 
     let { pathname } = parsed
 

test/integration/invalid-href/test/index.test.js

@@ -135,6 +135,12 @@ describe('Invalid hrefs', () => {
       const $ = cheerio.load(await res.text())
       expect($('#click-me').attr('href')).toBe('https://')
     })
+
+    it('renders a link with mailto: href', async () => {
+      const res = await fetchViaHTTP(appPort, '/first')
+      const $ = cheerio.load(await res.text())
+      expect($('#click-me').attr('href')).toBe('mailto:idk@idk.com')
+    })
   })
 
   describe('dev mode', () => {