Renaming a folder doubles the folder name in file paths (console errors show /lib/lib/helper.js) #4365

p5.js version

2.3.4

What is your operating system?

Mac OS

Web browser and version

155.0.8059.40 (Official Build) (arm64)

Actual Behavior

After renaming a folder in the sidebar, the editor stores a wrong path for the
folder and every file inside it: the folder's own name is added twice. This shows
up in console errors. A script in a renamed folder lib reports its error at
/lib/lib/helper.js:1:1 instead of /lib/helper.js:1:1

When logged in, the wrong path only lasts until the next save (each save rebuilds
the paths). When logged out, nothing is saved to the server, so it stays wrong for
the whole session.

Cause: in client/modules/IDE/reducers/files.js, the UPDATE_FILE_NAME case loops
over the folder's children but passes action.id (the folder itself) instead of
childId to setFilePath:

updatedFile.children.forEach((childId) => {
  setFilePath(newState, action.id, childPath);
});

Expected Behavior

After renaming folder js to lib, files inside it should have the path
/lib/..., and the console should show at /lib/helper.js:1:1.

Steps to reproduce

1. Open editor.p5js.org while logged out.
2. Create a folder js, and inside it a file helper.js containing noSuchFunction();
3. In index.html, add <script src="js/helper.js"></script> above the sketch.js script tag.
4. Press Play and expand the error in the console: at /js/helper.js:1:1 (correct).
5. Rename the folder js to lib and change the script tag to lib/helper.js.
6. Press Play and expand the error: at /lib/lib/helper.js:1:1 (wrong).

Suggested fix: pass childId instead of action.id to setFilePath in the
UPDATE_FILE_NAME case. I've tested this locally with unit tests for the reducer
(top-level and nested folder renames); the existing tests in files.test.js only
cover deletion. I'd be happy to open a PR with the fix and tests if this is approved.

Related: #2186 (mutation in the files reducer), a different issue in the same file.