feat(pages)!: explicitly allow optional params with [[ (#4537)

docs/content/2.guide/3.directory-structure/10.pages.md

@@ -95,6 +95,8 @@ Here are some examples to illustrate what a page with a single root element look
 
 If you place anything within square brackets, it will be turned into a [dynamic route](https://router.vuejs.org/guide/essentials/dynamic-matching.html) parameter. You can mix and match multiple parameters and even non-dynamic text within a file name or directory.
 
+If you want a parameter to be _optional_, you must enclose it in double square brackets - for example, `~/pages/[[slug]]/index.vue` or `~/pages/[[slug]].vue` will match both `/` and `/test`.
+
 ### Example
 
 ```bash

packages/nuxt/src/pages/utils.ts

@@ -10,12 +10,14 @@ enum SegmentParserState {
   initial,
   static,
   dynamic,
+  optional,
   catchall,
 }
 
 enum SegmentTokenType {
   static,
   dynamic,
+  optional,
   catchall,
 }
 
@@ -67,7 +69,6 @@ export function generateRoutesFromFiles (files: string[], pagesDir: string): Nux
       const tokens = parseSegment(segment)
       const segmentName = tokens.map(({ value }) => value).join('')
       const isSingleSegment = segments.length === 1
-      const isLastSegment = i === segments.length - 1
 
       // ex: parent/[slug].vue -> parent-slug
       route.name += (route.name && '-') + segmentName
@@ -83,9 +84,6 @@ export function generateRoutesFromFiles (files: string[], pagesDir: string): Nux
         route.path += '/'
       } else if (segmentName !== 'index') {
         route.path += getRoutePath(tokens)
-        if (isLastSegment && tokens.length === 1 && tokens[0].type === SegmentTokenType.dynamic) {
-          route.path += '?'
-        }
       }
     }
 
@@ -99,7 +97,9 @@ function getRoutePath (tokens: SegmentToken[]): string {
   return tokens.reduce((path, token) => {
     return (
       path +
-      (token.type === SegmentTokenType.dynamic
+      (token.type === SegmentTokenType.optional
+        ? `:${token.value}?`
+        : token.type === SegmentTokenType.dynamic
           ? `:${token.value}`
           : token.type === SegmentTokenType.catchall
             ? `:${token.value}(.*)*`
@@ -131,6 +131,8 @@ function parseSegment (segment: string) {
           ? SegmentTokenType.static
           : state === SegmentParserState.dynamic
             ? SegmentTokenType.dynamic
+            : state === SegmentParserState.optional
+              ? SegmentTokenType.optional
               : SegmentTokenType.catchall,
       value: buffer
     })
@@ -163,11 +165,15 @@ function parseSegment (segment: string) {
 
       case SegmentParserState.catchall:
       case SegmentParserState.dynamic:
+      case SegmentParserState.optional:
         if (buffer === '...') {
           buffer = ''
           state = SegmentParserState.catchall
         }
-        if (c === ']') {
+        if (c === '[' && state === SegmentParserState.dynamic) {
+          state = SegmentParserState.optional
+        }
+        if (c === ']' && (state !== SegmentParserState.optional || buffer[buffer.length - 1] === ']')) {
           if (!buffer) {
             throw new Error('Empty param')
           } else {

packages/nuxt/test/pages.test.ts

@@ -97,26 +97,48 @@ describe('pages:generateRoutesFromFiles', () => {
       description: 'should generate correct dynamic routes',
       files: [
           `${pagesDir}/[slug].vue`,
+          `${pagesDir}/[[foo]]`,
+          `${pagesDir}/[[foo]]/index.vue`,
+          `${pagesDir}/[bar]/index.vue`,
           `${pagesDir}/sub/[slug].vue`,
-          `${pagesDir}/[sub]/route-[slug].vue`
+          `${pagesDir}/[[sub]]/route-[slug].vue`
       ],
       output: [
         {
           name: 'slug',
-          path: '/:slug?',
+          path: '/:slug',
           file: `${pagesDir}/[slug].vue`,
           children: []
         },
+        {
+          children: [
+            {
+
+              name: 'foo',
+              path: '',
+              file: `${pagesDir}/[[foo]]/index.vue`,
+              children: []
+            }
+          ],
+          file: 'pages/[[foo]]',
+          path: '/:foo?'
+        },
+        {
+          children: [],
+          name: 'bar',
+          file: 'pages/[bar]/index.vue',
+          path: '/:bar'
+        },
         {
           name: 'sub-slug',
-          path: '/sub/:slug?',
+          path: '/sub/:slug',
           file: `${pagesDir}/sub/[slug].vue`,
           children: []
         },
         {
           name: 'sub-route-slug',
-          path: '/:sub/route-:slug',
-          file: `${pagesDir}/[sub]/route-[slug].vue`,
+          path: '/:sub?/route-:slug',
+          file: `${pagesDir}/[[sub]]/route-[slug].vue`,
           children: []
         }
       ]
@@ -150,32 +172,32 @@ describe('pages:generateRoutesFromFiles', () => {
       files: [
           `${pagesDir}/[a1_1a].vue`,
           `${pagesDir}/[b2.2b].vue`,
-          `${pagesDir}/[c3@3c].vue`,
-          `${pagesDir}/[d4-4d].vue`
+          `${pagesDir}/[[c3@3c]].vue`,
+          `${pagesDir}/[[d4-4d]].vue`
       ],
       output: [
         {
           name: 'a1_1a',
-          path: '/:a1_1a?',
+          path: '/:a1_1a',
           file: `${pagesDir}/[a1_1a].vue`,
           children: []
         },
         {
           name: 'b2.2b',
-          path: '/:b2.2b?',
+          path: '/:b2.2b',
           file: `${pagesDir}/[b2.2b].vue`,
           children: []
         },
         {
           name: 'c33c',
           path: '/:c33c?',
-          file: `${pagesDir}/[c3@3c].vue`,
+          file: `${pagesDir}/[[c3@3c]].vue`,
           children: []
         },
         {
           name: 'd44d',
           path: '/:d44d?',
-          file: `${pagesDir}/[d4-4d].vue`,
+          file: `${pagesDir}/[[d4-4d]].vue`,
           children: []
         }
       ]