Parent clientLoader doesn't revalidate when a child route is changed

[stevan-borus]

I'm using React Router as a...

framework

Reproduction

stackblitz repro

System Info

System:
    OS: macOS 15.3.2
    CPU: (8) arm64 Apple M1 Pro
    Memory: 216.94 MB / 16.00 GB
    Shell: 5.9 - /bin/zsh
Binaries:
    Node: 20.12.2 - ~/.nvm/versions/node/v20.12.2/bin/node
    npm: 10.9.0 - ~/.nvm/versions/node/v20.12.2/bin/npm
    pnpm: 10.5.0 - ~/Library/pnpm/pnpm
    Watchman: 2024.08.26.00 - /opt/homebrew/bin/watchman
Browsers:
    Chrome: 134.0.6998.89
    Edge: 134.0.3124.68
    Safari: 18.3.1
npmPackages:
    @react-router/dev: ^7.4.0 => 7.4.0 
    @react-router/node: ^7.4.0 => 7.4.0 
    react-router: ^7.4.0 => 7.4.0 
    vite: ^6.2.2 => 6.2.2

Used Package Manager

pnpm

Expected Behavior

The parent clientLoader should always revalidate when its child route is changed, without setting shouldRevalidate = () => true;

Actual Behavior

In the repro, v7.1.5 is set and for that version, the parent clientLoader revalidates when the child route is changed by clicking on one of the links in the parent component, so the selected link which is set in the parent clientLoader can also change

In later versions, the parent clientLoader only revalidates when shouldRevalidate is explicitly set to true
shouldRevalidate = () => true;

This is happening when ssr: false

[brophdawg11]

This is expected behavior for "SPA Mode" apps and matches the original pre-Single-Fetch behavior for revalidations, where routes only revalidate if their params change or after a submission. A GET navigation between child routes should not be mutating any data so the loader should not need to re-run by default.

The behavior in 7.00 -> 7.1.5 was incorrect because the "single fetch" de-optimization of revalidating reused loaders on GET navigations was being incorrectly applied to SPA mode where there is no running server, and thus no "single fetch" HTTP call to make. We fixed this and removed the de-optimization for SPA Mode apps in 7.2.0 via #12948.