Ken I believe I've figured it out and there was an important bit I left out.
The test in CIDER was ensuring a buffer was named correctly based on the current project, and it set the current project's directory by setq'ing default-directory. This seems to be a big no-no as the default directory expects a well formed path. The doc string of default-directory being:
Name of default directory of current buffer.
It should be an absolute directory name; on GNU and Unix systems,
these names start with `/' or `~' and end with `/'.
To interactively change the default directory, use command `cd'.
So the "bug" can be reproduced by the following, which was the important bits of the test:
(let ((default-directory "made/up/project/location"))
* note this will freeze your emacs
I believe your change caused the behavior here but it seems like a reasonable change and CIDER is definitely not honoring the assumptions in `default-directory`. We had some careless usages of this variable in our tests and it seems like it has finally caught up to us. Unless you consider this an edge case to watch for (and I can't imagine you do) it seems like this should be closed.
Sorry for the noise and thanks for your help