generatePath changed behavior v6 bug

[brunouber]

Reproduction

https://codesandbox.io/p/sandbox/lfym8r

System Info

System:
    OS: macOS 15.3.1
    CPU: (11) arm64 Apple M3 Pro
    Memory: 123.61 MB / 18.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 20.2.0 - ~/.nvm/versions/node/v20.2.0/bin/node
    npm: 9.6.6 - ~/.nvm/versions/node/v20.2.0/bin/npm
    pnpm: 10.8.0 - ~/.nvm/versions/node/v20.2.0/bin/pnpm
  Browsers:
    Brave Browser: 137.1.79.123
    Chrome: 138.0.7204.158
    Chrome Canary: 140.0.7303.0
    Safari: 18.3

Used Package Manager

npm

Expected Behavior

generatePath should interpolate parameter separated by ".", as in version 6.8.2. This behavior changed unexpectedly in version 6.9.0.

Actual Behavior

generatePath("/books/:id.json", { id: "42" });

Expected: /books/42.json

Output: /books/:id.json ❌