[gatsby-plugin-vercel-builder] Fix nested SSR routes (#10751)

Fixes SSR / DSG pages that are nested deeper than the root path for Gatsby projects.

Also introduces unit tests for the logic related to determining which page name to use.

.changeset/happy-wolves-exist.md

@@ -0,0 +1,5 @@
+---
+'@vercel/gatsby-plugin-vercel-builder': patch
+---
+
+Fix nested SSR routes

packages/gatsby-plugin-vercel-builder/jest.config.js

@@ -0,0 +1,5 @@
+/** @type {import('@ts-jest/dist/types').InitialOptionsTsJest} */
+module.exports = {
+  preset: 'ts-jest',
+  testEnvironment: 'node',
+};

packages/gatsby-plugin-vercel-builder/package.json

@@ -14,6 +14,8 @@
   },
   "scripts": {
     "build": "node ../../utils/build-builder.mjs",
+    "test": "jest --reporters=default --reporters=jest-junit --env node --verbose --bail --runInBand",
+    "test-unit": "pnpm test test/unit.*test.*",
     "type-check": "tsc --noEmit"
   },
   "dependencies": {
@@ -27,6 +29,7 @@
   "devDependencies": {
     "@types/etag": "1.8.0",
     "@types/fs-extra": "11.0.1",
+    "@types/jest": "27.5.1",
     "@types/node": "14.18.33",
     "@types/react": "18.0.26",
     "jest-junit": "16.0.0",

packages/gatsby-plugin-vercel-builder/src/handlers/build.ts

@@ -17,9 +17,11 @@ import type {
 export const writeHandler = async ({
   outDir,
   handlerFile,
+  prefix = '',
 }: {
   outDir: string;
   handlerFile: string;
+  prefix?: string;
 }) => {
   const { major } = await getNodeVersion(process.cwd());
 
@@ -35,6 +37,7 @@ export const writeHandler = async ({
       minify: true,
       define: {
         'process.env.NODE_ENV': "'production'",
+        vercel_pathPrefix: JSON.stringify(prefix),
       },
     });
   } catch (e: any) {

packages/gatsby-plugin-vercel-builder/src/helpers/functions.ts

@@ -37,7 +37,7 @@ export async function createServerlessFunctions(
         await ensureDir(functionDir);
 
         await Promise.all([
-          writeHandler({ outDir: functionDir, handlerFile }),
+          writeHandler({ outDir: functionDir, handlerFile, prefix }),
           copyFunctionLibs({ functionDir }),
           copyHTMLFiles({ functionDir }),
           writeVCConfig({ functionDir }),

packages/gatsby-plugin-vercel-builder/templates/ssr-handler.js

@@ -1,8 +1,8 @@
 import os from 'os';
 import etag from 'etag';
-import { parse } from 'url';
+import { join } from 'path';
 import { copySync, existsSync } from 'fs-extra';
-import { join, dirname, basename } from 'path';
+import { getPageName } from './utils';
 
 const TMP_DATA_PATH = join(os.tmpdir(), 'data/datastore');
 const CUR_DATA_PATH = join(__dirname, '.cache/data/datastore');
@@ -25,34 +25,14 @@ async function getPageSSRHelpers() {
 }
 
 export default async function handler(req, res) {
-  let pageName;
-  const pathname = parse(req.url).pathname || '/';
-  const isPageData = pathname.startsWith('/page-data/');
-  if (isPageData) {
-    // /page-data/index/page-data.json
-    // /page-data/using-ssr/page-data.json
-    pageName = basename(dirname(pathname));
-    if (pageName === 'index') {
-      pageName = '/';
-    }
-  } else {
-    // /using-ssr
-    // /using-ssr/
-    // /using-ssr/index.html
-    pageName = basename(pathname);
-    if (pageName === 'index.html') {
-      pageName = basename(dirname(pathname));
-    }
-    if (!pageName) {
-      pageName = '/';
-    }
-  }
+  // eslint-disable-next-line no-undef
+  const { pathName, isPageData } = getPageName(req.url, vercel_pathPrefix);
 
   const [graphqlEngine, { getData, renderHTML, renderPageData }] =
     await Promise.all([getGraphQLEngine(), getPageSSRHelpers()]);
 
   const data = await getData({
-    pathName: pageName,
+    pathName,
     graphqlEngine,
     req,
   });

packages/gatsby-plugin-vercel-builder/templates/utils.ts

@@ -0,0 +1,29 @@
+import { parse } from 'url';
+import { basename, dirname } from 'path';
+
+export function getPageName(url: string, pathPrefix = '') {
+  let pathName = (parse(url).pathname || '/').slice(pathPrefix.length);
+  const isPageData = pathName.startsWith('/page-data/');
+  if (isPageData) {
+    // "/page-data/index/page-data.json" -> "/"
+    // "/page-data/using-ssr/page-data.json" -> "using-ssr"
+    // "/page-data/foo/bar/ssr/page-data.json" -> "foo/bar/ssr"
+    pathName = pathName.split('/').slice(2, -1).join('/');
+    if (pathName === 'index') {
+      pathName = '/';
+    }
+  } else {
+    // "/using-ssr" -> "using-ssr"
+    // "/using-ssr/" -> "using-ssr"
+    // "/using-ssr/index.html" -> "using-ssr"
+    // "/foo/bar/ssr" -> "foo/bar/ssr"
+    if (basename(pathName) === 'index.html') {
+      pathName = dirname(pathName);
+    }
+    if (pathName !== '/') {
+      // Remove leading and trailing "/"
+      pathName = pathName.replace(/(^\/|\/$)/g, '');
+    }
+  }
+  return { isPageData, pathName };
+}

packages/gatsby-plugin-vercel-builder/test/tsconfig.json

@@ -0,0 +1,7 @@
+{
+  "compilerOptions": {
+    "sourceMap": true
+  },
+  "extends": "../tsconfig.json",
+  "include": ["*.test.ts"]
+}

packages/gatsby-plugin-vercel-builder/test/unit.get-page-name.test.ts

@@ -0,0 +1,64 @@
+import { getPageName } from '../templates/utils';
+
+describe('getPageName()', () => {
+  it.each([
+    {
+      input: '/page-data/index/page-data.json',
+      pageName: '/',
+      isPageData: true,
+    },
+    {
+      input: '/page-data/using-ssr/page-data.json',
+      pageName: 'using-ssr',
+      isPageData: true,
+    },
+    { input: '/', pageName: '/', isPageData: false },
+    { input: '/index.html', pageName: '/', isPageData: false },
+    { input: '/using-ssr', pageName: 'using-ssr', isPageData: false },
+    { input: '/using-ssr/', pageName: 'using-ssr', isPageData: false },
+    {
+      input: '/using-ssr/index.html',
+      pageName: 'using-ssr',
+      isPageData: false,
+    },
+    { input: '/foo/bar/ssr', pageName: 'foo/bar/ssr', isPageData: false },
+    {
+      input: '/page-data/foo/bar/ssr/page-data.json',
+      pageName: 'foo/bar/ssr',
+      isPageData: true,
+    },
+
+    { input: '/foo/', pathPrefix: '/foo', pageName: '/', isPageData: false },
+    {
+      input: '/foo/index.html',
+      pathPrefix: '/foo',
+      pageName: '/',
+      isPageData: false,
+    },
+    {
+      input: '/foo/bar/ssr',
+      pathPrefix: '/foo/',
+      pageName: 'bar/ssr',
+      isPageData: false,
+    },
+    {
+      input: '/foo/page-data/index/page-data.json',
+      pathPrefix: '/foo',
+      pageName: '/',
+      isPageData: true,
+    },
+    {
+      input: '/foo/page-data/bar/ssr/page-data.json',
+      pathPrefix: '/foo',
+      pageName: 'bar/ssr',
+      isPageData: true,
+    },
+  ])(
+    'Should return "$pageName" for "$input"',
+    ({ input, pathPrefix, pageName, isPageData }) => {
+      const actual = getPageName(input, pathPrefix);
+      expect(actual.pathName).toEqual(pageName);
+      expect(actual.isPageData).toEqual(isPageData);
+    }
+  );
+});

packages/static-build/test/fixtures/gatsby-v5-pathPrefix/probes.json

@@ -12,6 +12,10 @@
     {
       "path": "/foo/x/y/z",
       "mustContain": "<h1>Page not found</h1>"
+    },
+    {
+      "path": "/foo/foo/bar/ssr/",
+      "mustContain": "<h1>This page is <!-- -->rendered server side (nested)</h1>"
     }
   ]
 }

packages/static-build/test/fixtures/gatsby-v5-pathPrefix/src/pages/foo/bar/ssr.js

@@ -0,0 +1,21 @@
+import * as React from 'react';
+
+const UsingSSR = ({ serverData }) => {
+  return (
+    <>
+      <h1>
+        This page is {serverData.message}
+      </h1>
+    </>
+  );
+};
+
+export const Head = () => <title>SSR Gatsby</title>;
+
+export default UsingSSR;
+
+export async function getServerData() {
+  return {
+    props: { message: 'rendered server side (nested)' },
+  }
+}

packages/static-build/test/fixtures/gatsby-v5/probes.json

@@ -20,6 +20,10 @@
     {
       "path": "/x/y/z",
       "mustContain": "<h1>Page not found</h1>"
+    },
+    {
+      "path": "/foo/bar/ssr/",
+      "mustContain": "<h1>This page is <!-- -->rendered server side (nested)</h1>"
     }
   ]
 }

packages/static-build/test/fixtures/gatsby-v5/src/pages/foo/bar/ssr.js

@@ -0,0 +1,21 @@
+import * as React from 'react';
+
+const UsingSSR = ({ serverData }) => {
+  return (
+    <>
+      <h1>
+        This page is {serverData.message}
+      </h1>
+    </>
+  );
+};
+
+export const Head = () => <title>SSR Gatsby</title>;
+
+export default UsingSSR;
+
+export async function getServerData() {
+  return {
+    props: { message: 'rendered server side (nested)' },
+  }
+}

pnpm-lock.yaml

@@ -969,6 +969,9 @@ importers:
       '@types/fs-extra':
         specifier: 11.0.1
         version: 11.0.1
+      '@types/jest':
+        specifier: 27.5.1
+        version: 27.5.1
       '@types/node':
         specifier: 14.18.33
         version: 14.18.33