fix(experimental): repeatable params in subsegments

posva · posva · commit 846640e4b500 · 2026-05-27T18:02:00.000+02:00
diff --git a/packages/router/src/experimental/route-resolver/matchers/matcher-pattern.spec.ts b/packages/router/src/experimental/route-resolver/matchers/matcher-pattern.spec.ts
@@ -6,6 +6,7 @@ import {
 import { MatcherPatternPathStar } from './matcher-pattern-path-star'
 import { miss } from './errors'
 import { definePathParamParser } from './param-parsers'
+import { mockWarn } from '../../../../__tests__/vitest-mock-warn'
 
 describe('MatcherPatternPathStatic', () => {
   describe('match()', () => {
@@ -129,6 +130,8 @@ describe('MatcherPatternPathStar', () => {
 })
 
 describe('MatcherPatternPathDynamic', () => {
+  mockWarn()
+
   it('single param', () => {
     const pattern = new MatcherPatternPathDynamic(
       /^\/teams\/([^/]+?)\/b$/i,
@@ -376,6 +379,48 @@ describe('MatcherPatternPathDynamic', () => {
     )
   })
 
+  it('repeatable param in a sub segment', () => {
+    // produced by file-based routing for `set.[ids]+.other`
+    const pattern = new MatcherPatternPathDynamic(
+      /^\/set\/(.+?)\/other$/,
+      {
+        ids: [{}, true],
+      },
+      [['set/', 1, '/other']]
+    )
+
+    expect(pattern.match('/set/123/other')).toEqual({ ids: ['123'] })
+    expect(pattern.match('/set/123/456/other')).toEqual({
+      ids: ['123', '456'],
+    })
+    expect(pattern.build({ ids: ['123'] })).toBe('/set/123/other')
+    expect(pattern.build({ ids: ['123', '456'] })).toBe('/set/123/456/other')
+  })
+
+  it('multiple repeatable params in a sub segment', () => {
+    // produced by file-based routing for `before.[ids]+.middle.[other]+.after`
+    const pattern = new MatcherPatternPathDynamic(
+      /^\/before\/(.+?)\/middle\/(.+?)\/after$/,
+      {
+        ids: [{}, true],
+        other: [{}, true],
+      },
+      [['before/', 1, '/middle/', 1, '/after']]
+    )
+
+    expect(pattern.match('/before/a/middle/c/after')).toEqual({
+      ids: ['a'],
+      other: ['c'],
+    })
+    expect(pattern.match('/before/a/b/middle/c/d/after')).toEqual({
+      ids: ['a', 'b'],
+      other: ['c', 'd'],
+    })
+    expect(pattern.build({ ids: ['a', 'b'], other: ['c', 'd'] })).toBe(
+      '/before/a/b/middle/c/d/after'
+    )
+  })
+
   it('can have a trailing slash after a single param', () => {
     const pattern = new MatcherPatternPathDynamic(
       /^\/teams\/([^/]+?)\/$/i,
diff --git a/packages/router/src/experimental/route-resolver/matchers/matcher-pattern.ts b/packages/router/src/experimental/route-resolver/matchers/matcher-pattern.ts
@@ -272,17 +272,12 @@ export class MatcherPatternPathDynamic<
                 ;[parser, repeatable, optional] = this.params[paramName]
                 value = (parser?.set || identityFn)(params[paramName])
 
-                // param cannot be repeatable when in a sub segment
-                if (__DEV__ && repeatable) {
-                  warn(
-                    `Param "${String(paramName)}" is repeatable, but used in a sub segment of the path: "${this.pathParts.join('')}". Repeated params can only be used as a full path segment: "/file/[ids]+/something-else". This will break in production.`
-                  )
-                  return Array.isArray(value)
-                    ? value.map(encodeParam).join('/')
-                    : encodeParam(value)
-                }
-
-                return encodeParam(value as string | null | undefined)
+                // a repeatable param in a sub segment joins its values with `/`
+                // so file-based routes like `rep.[ids]+` (sub segment
+                // ['rep/', 1]) and `set.[ids]+.other` round-trip correctly
+                return Array.isArray(value)
+                  ? value.map(encodeParam).join('/')
+                  : encodeParam(value as string | null | undefined)
               })
               .join('')
           }
