Do not create rewrites for SSG & HTML pages with static routing

Pages that are statically generated (using getStaticProps)) or
pre-rendered (plain HTML) do not require an entry in the redirects file
thanks to shadowing:
https://docs.netlify.com/routing/redirects/rewrites-proxies/#shadowing

Having too many rewrites or redirects in the _redirects file can
negatively impact performance:
https://community.netlify.com/t/max-number-of-redirects/5095/2

See: #26

Author: FinnWoelm

lib/setupRedirects.js

@@ -15,9 +15,27 @@ const getNetlifyFunctionName      = require('./getNetlifyFunctionName')
 const setupRedirects = () => {
   console.log("\x1b[1m🔀 Setting up redirects\x1b[22m")
 
+  // Step 1: Collect custom redirects defined by the user
+  const customRedirects = []
+  if(existsSync(CUSTOM_REDIRECTS_PATH)) {
+    console.log("  ", "# Prepending custom redirects")
+    customRedirects.push(readFileSync(CUSTOM_REDIRECTS_PATH))
+  }
+
+  // Step 2: Generate redirects for NextJS pages
+
+  // Identify pages that require redirects:
+  // If the page is statically routed and the page is HTML or SSG, we do not
+  // need to add an entry to the redirects file. Netlify automatically routes to
+  // these static pages.
+  // See: https://github.com/netlify/next-on-netlify/issues/26
+  const pagesNeedingRedirect = allNextJsPages.filter(page =>
+    isDynamicRoute(page.route) || page.isSsr() || page.isSsgFallback()
+  )
+
   // Identify static and dynamically routed pages
-  const staticPages   = allNextJsPages.filter(({ route }) => !isDynamicRoute(route))
-  const dynamicPages  = allNextJsPages.filter(({ route }) =>  isDynamicRoute(route))
+  const staticPages   = pagesNeedingRedirect.filter(({ route }) => !isDynamicRoute(route))
+  const dynamicPages  = pagesNeedingRedirect.filter(({ route }) =>  isDynamicRoute(route))
 
   // Sort dynamic pages by route: More-specific routes precede less-specific
   // routes
@@ -30,14 +48,8 @@ const setupRedirects = () => {
   // Assemble sorted pages: static pages first, then sorted dynamic pages
   const sortedPages = [...staticPages, ...sortedDynamicPages]
 
-  // Generate redirects as array
-  const redirects = []
-  if(existsSync(CUSTOM_REDIRECTS_PATH)) {
-    console.log("  ", "# Prepending custom redirects")
-    redirects.push(readFileSync(CUSTOM_REDIRECTS_PATH))
-  }
-  redirects.push("# Next-on-Netlify Redirects")
-
+  // Generate redirects for nextJS pages
+  const nextOnNetlifyRedirects = []
   sortedPages.forEach(page => {
     // Generate redirect for each page route
     page.routesAsArray.forEach(route => {
@@ -65,10 +77,15 @@ const setupRedirects = () => {
       const redirect = `${from}  ${to}  200`
       console.log("  ", redirect)
 
-      redirects.push(redirect)
+      nextOnNetlifyRedirects.push(redirect)
     })
   })
 
+  // Step 3: Combine redirects into one single array
+  const redirects = customRedirects
+  if(nextOnNetlifyRedirects.length)
+    redirects.push("# Next-on-Netlify Redirects", ...nextOnNetlifyRedirects)
+
   // Write redirects to _redirects file
   writeFileSync(
     join(NETLIFY_PUBLISH_PATH, "_redirects"),

tests/__snapshots__/defaults.test.js.snap

@@ -6,15 +6,6 @@ exports[`Routing creates Netlify redirects 1`] = `
 /getServerSideProps/static  /.netlify/functions/next_getServerSideProps_static  200
 /_next/data/%BUILD_ID%/getServerSideProps/static.json  /.netlify/functions/next_getServerSideProps_static  200
 /  /.netlify/functions/next_index  200
-/static  /static.html  200
-/404  /404.html  200
-/getStaticProps/static  /getStaticProps/static.html  200
-/getStaticProps/1  /getStaticProps/1.html  200
-/getStaticProps/2  /getStaticProps/2.html  200
-/getStaticProps/withFallback/my/path/1  /getStaticProps/withFallback/my/path/1.html  200
-/getStaticProps/withFallback/my/path/2  /getStaticProps/withFallback/my/path/2.html  200
-/getStaticProps/withFallback/3  /getStaticProps/withFallback/3.html  200
-/getStaticProps/withFallback/4  /getStaticProps/withFallback/4.html  200
 /api/shows/:id  /.netlify/functions/next_api_shows_id  200
 /api/shows/:params/*  /.netlify/functions/next_api_shows_params  200
 /getServerSideProps/:id  /.netlify/functions/next_getServerSideProps_id  200

tests/__snapshots__/optionalCatchAll.test.js.snap

@@ -2,8 +2,6 @@
 
 exports[`Routing creates Netlify redirects 1`] = `
 "# Next-on-Netlify Redirects
-/  /index.html  200
-/404  /404.html  200
 /catch*  /.netlify/functions/next_catch_all  200
 /_next/data/%BUILD_ID%/catch*  /.netlify/functions/next_catch_all  200"
 `;

tests/customRedirects.test.js

@@ -69,15 +69,15 @@ describe('Next', () => {
 })
 
 describe('Routing',() => {
-  test('includes custom redirect rules', async () => {
+  test('includes only custom redirect rules', async () => {
     // Read _redirects file
     const contents = readFileSync(join(PROJECT_PATH, "out_publish", "_redirects"))
 
-    const redirects = contents.toString().split(/\n/)
+    const redirects = contents.toString().trim().split(/\n/)
     expect(redirects[0]).toEqual("# Custom Redirect Rules")
     expect(redirects[1]).toEqual("https://old.example.com/* https://new.example.com/:splat 301!")
 
-    // Check that other routes are present
-    expect(redirects).toContain("/  /index.html  200")
+    // Check that no other redirects are present
+    expect(redirects).toHaveLength(2)
   })
 })

tests/preRenderedIndexPages.test.js

@@ -89,15 +89,12 @@ describe('404 Page', () => {
 })
 
 describe('Routing',() => {
-  test('creates Netlify redirects', async () => {
+  test('does not create any redirects', async () => {
     // Read _redirects file
     const contents = readFileSync(join(PROJECT_PATH, "out_publish", "_redirects"))
+    const redirects = contents.toString()
 
-    // Convert contents into an array, each line being one element
-    const redirects = contents.toString().split("\n")
-
-    // Check that routes are present
-    expect(redirects).toContain("/  /index.html  200")
-    expect(redirects).toContain("/shows  /shows.html  200")
+    // Check that no redirects are present
+    expect(redirects).toEqual("")
   })
 })

tests/staticIndexPages.test.js

@@ -89,15 +89,12 @@ describe('404 Page', () => {
 })
 
 describe('Routing',() => {
-  test('creates Netlify redirects', async () => {
+  test('does not create any redirects', async () => {
     // Read _redirects file
     const contents = readFileSync(join(PROJECT_PATH, "out_publish", "_redirects"))
+    const redirects = contents.toString()
 
-    // Convert contents into an array, each line being one element
-    const redirects = contents.toString().split("\n")
-
-    // Check that routes are present
-    expect(redirects).toContain("/  /index.html  200")
-    expect(redirects).toContain("/static  /static.html  200")
+    // Check that no redirects are present
+    expect(redirects).toEqual("")
   })
 })