On 27-07-2022 21:00, Tomasz Jeneralczyk wrote: > + (with-extensions (list mpv) IIUC, that's for using Guile modules defined in packages -- but mpv is not a Guile package, so I expect that the surrounding with-extensions can be dropped. > + (let* ((args (package-arguments opencv))) > + (assoc-set! args #:configure-flags > + (append (list "-DBUILD_opencv_python3=ON") > + (assoc-ref args #:configure-flags))) Look for substitute-keyword-arguments, which isn't stateful and hence there is less risk of accidentally modifying the arguments of the parent package.  Also, any reason for not adding this to the original package? (Possibly there is one). > + (replace 'check > + (lambda _ > + (setenv "DISPLAY" ":0") > + (setenv "XDG_CACHE_HOME" (getcwd)) > + (setenv "HOME" (getcwd)) > + (system "Xvfb &") > + (invoke "python" "test.py"))) Run "./pre-inst-env guix lint hydrus-network", it will have a remark about this.  Also, technically this is racy -- it's possible for python to start before Xvfb is ready though so far this doesn't seem to have caused trouble for other packages yet AFAIK -- I recommend "xvfb-run" "--" "python" "test.py" instead. (I just scrolled quickly through the patches, a more full review will have to come later.) Greetings, Maxime.