fix(router): treat /application as outside base="/app"

[damiengrandi]

Description

Router with base="/app" treated /application as in-base (lication) because relativePath used a string prefix (indexOf === 0), not a path segment.

It now matches only when the path is the base, or continues with / / %2F (decodeURI leaves %2F encoded, so /app%2Fusers still yields %2Fusers).

To reproduce

Save as repro.mjs at the repo root, then run without this PR:

node repro.mjs

import { relativePath } from "./packages/wouter/src/paths.js";

const cases = [
  {
    base: "/app",
    path: "/app/users",
    expected: "/users",
    note: "real child of /app — should stay in-base",
  },
  {
    base: "/app",
    path: "/application",
    expected: "~/application",
    note: "different path that only shares the /app prefix",
  },
  {
    base: "/app",
    path: "/apple",
    expected: "~/apple",
    note: "same prefix collision",
  },
  {
    base: "/MyApp",
    path: "/MyOtherApp",
    expected: "~/MyOtherApp",
    note: "already OK — not a string prefix",
  },
];

for (const { base, path, expected, note } of cases) {
  const got = relativePath(base, path);
  const ok = got === expected;

  console.log(ok ? "ok  " : "FAIL");
  console.log(`  base=${base}  path=${path}`);
  console.log(`  expected ${JSON.stringify(expected)}`);
  console.log(`  got      ${JSON.stringify(got)}`);
  console.log(`  ${note}`);
  console.log("");
}

2/4 fail

To test the fix

• Run bun test packages/wouter/test/path-normalization.test.tsx
• Execute node repro.mjs again: no fail

Screenshots

bun test after the fix:

[bolt-new-by-stackblitz]

Run & review this pull request in StackBlitz Codeflow.

[molefrog]

Thanks, the fix is correct and brings Router base in line with how <Route nest> already matches (regexparam's loose (?=$|\/) lookahead). Full suite, lint and size pass here.

One request before merging: drop the %2f branch. %2F is a literal slash inside a single segment, so /app%2Fusers is not a child of /app, and regexparam already treats it that way. The extra branch also costs ~30 B in a file with 69 B of headroom. This keeps the bundle at its current size:

return !base ||
  (path.toLowerCase() + "/").startsWith(base.toLowerCase() + "/")
  ? path.slice(base.length) || "/"
  : "~" + path;

Then flip the existing expectation to ["/app", "/app%2Fusers", "~/app%2Fusers"], which still verifies that %2F is not decoded. Tests, lint and size are green with this applied.

---

Generated by Claude Code

[molefrog]

Hey @damiengrandi thank you for your PR. sorry for the AI-generated reply, I just asked Claude to review it. And I think it's a good point and we should drop that check. Could you please update it? I'd be happy to merge this once this fix lands.

Alexey.

[damiengrandi]

Hi @molefrog, it's done!

[molefrog]

Published in v3.11.1