projectile-complementary-dir mangles casing

[Lenbok]

I have defined a projectile type for R projects, which typically have their source code under a directory called R/, and unit tests in a directory called tests/testthat/.

I have added a project type like this:

  (projectile-register-project-type 'my-ess-r '("R")
                                    :compile "make"
                                    :test "make test"
                                    :src-dir "R/"
                                    :test-dir "tests/testthat/"
                                    :test-prefix "test_")

I want to use the functionality to toggle between impl and test, but it is broken.

Expected behavior

Jumping from impl R/foo.R should take me to tests/testthat/test_foo.R

Actual behavior

Jumping from impl R/foo.R takes me to TESTS/TESTTHAT/test_foo.R

Steps to reproduce the problem

Create file structure:

R
R/foo.R
tests/testthat/test_foo.R

Projectile version information

Projectile 2.8.0-snapshot

Emacs version

GNU Emacs 29.0.90

Operating system

Linux Mint.