[bug#65911] [PATCH 3/4] gnu: python-pyusb: Add libusb-compat backend.

[Jean-Pierre De Jesus DIAZ via Guix-patches via <guix-patches@gnu.org>]

* gnu/packages/libusb.scm (python-pyusb) <arguments>: Do not hard-code
  libusb1 library for all back-ends, and allow to use libusb0 as a
  back-end.  Also enabled tests as the package does have a test suite.

* gnu/packages/libusb.scm (python-pyusb) <inputs>: Add libusb-compat.

Signed-off-by: Jean-Pierre De Jesus DIAZ <jean@foundationdevices.com>
---
 gnu/packages/libusb.scm | 52 +++++++++++++++++++++++++++++++----------
 1 file changed, 40 insertions(+), 12 deletions(-)

diff --git a/gnu/packages/libusb.scm b/gnu/packages/libusb.scm
index 469882e871..d15e561668 100644
--- a/gnu/packages/libusb.scm
+++ b/gnu/packages/libusb.scm
@@ -288,28 +288,56 @@ (define-public python-pyusb
          "1fg7knfzybzija2b01pzrzhzsj989scl12sb2ra4f503l8279k54"))))
     (build-system python-build-system)
     (arguments
-     (list #:tests? #f                      ; no tests
-           #:modules '((srfi srfi-1)
+     (list #:modules '((srfi srfi-1)
                        (srfi srfi-26)
                        (guix build utils)
                        (guix build python-build-system))
            #:phases
            #~(modify-phases %standard-phases
+               ;; Repurpose the candidates parameter to be the path to the
+               ;; library, then on each backend we substitute the candidates
+               ;; with the full path to the .so library or with None if not
+               ;; supported.
+               ;;
+               ;; While most applications could use a single back-end this
+               ;; library allows to manually select the back-end so it is
+               ;; appropriate to provide as much back-ends as possible.
                (add-after 'unpack 'fix-libusb-reference
                  (lambda* (#:key inputs #:allow-other-keys)
-                   (substitute* "usb/libloader.py"
-                     (("lib = locate_library\\(candidates, find_library\\)")
-                      (string-append
-                       "lib = \""
-                       (find (negate symbolic-link?)
-                             (find-files (assoc-ref inputs "libusb")
-                                         "^libusb-.*\\.so\\..*"))
-                       "\""))))))))
-
+                   (let ((libusb0 (find
+                                    (negate symbolic-link?)
+                                    (find-files (assoc-ref inputs "libusb-compat")
+                                                "^libusb-.*\\.so\\..*")))
+                         (libusb1 (find
+                                    (negate symbolic-link?)
+                                    (find-files (assoc-ref inputs "libusb")
+                                                "^libusb-.*\\.so\\..*"))))
+                     (substitute* "usb/libloader.py"
+                       (("lib = locate_library\\(candidates, find_library\\)")
+                        "lib = candidates"))
+                     (substitute* "usb/backend/libusb0.py"
+                       (("\\('usb-0\\.1', 'usb', 'libusb0'\\)")
+                        (format #f "~s" libusb0)))
+                     (substitute* "usb/backend/libusb1.py"
+                       (("\\('usb-1\\.0', 'libusb-1\\.0', 'usb'\\)")
+                        (format #f "~s" libusb1)))
+                     ;; FIXME: OpenUSB is not packaged for GNU Guix.
+                     (substitute* "usb/backend/openusb.py"
+                       (("\\('openusb',\\)") "None")))))
+               ;; Note: tests seems to succeed with libusb-compat as libusb
+               ;; fails because it doesn't have a usbfs present in the build
+               ;; environment.
+               (replace 'check
+                 (lambda* (#:key tests? #:allow-other-keys)
+                   (when tests?
+                     (with-directory-excursion "tests"
+                       (setenv "PYUSB_DEBUG" "debug")
+                       (setenv "LIBUSB_DEBUG" "4")
+                       (invoke "python" "testall.py"))))))))
     (native-inputs
      (list python-setuptools-scm))
     (inputs
-     (list libusb))
+     (list libusb libusb-compat))
     (home-page "https://pyusb.github.io/pyusb/")
     (synopsis "Python bindings to the libusb library")
     (description
-- 
2.34.1