7z-sys-provided: let user override paths

let the user override assumed paths via environment.
lib_dir is probed first from LD_LIBRARY_PATH.
7z executable is expected at lib_dir/7z but if not existing the PATH
variable is probed for the first best match.

With this patch it possible to run scancode is buildsystems like YOCTO,
which heaviily rely on overriding paths via environment to pick the
correct implementation from the build workspace

Signed-off-by: Konrad Weihmann <kweihmann@outlook.com>

Author: priv-kweihmann

builtins/extractcode_7z_system_provided/src/extractcode_7z/__init__.py

@@ -9,7 +9,9 @@
 
 
 import platform
+from os import environ
 from os import path
+from os import pathsep
 
 from plugincode.location_provider import LocationProviderPlugin
 
@@ -22,26 +24,34 @@ def get_locations(self):
         locations of the 7zip exe and shared libraries as installed on various
         Linux distros or on FreeBSD.
         """
-        mainstream_system = platform.system().lower()
-        if mainstream_system == 'linux':
-            distribution = platform.linux_distribution()[0].lower()
-            debian_based_distro = ['ubuntu', 'mint', 'debian']
-            rpm_based_distro = ['fedora', 'redhat']
-
-            if distribution in debian_based_distro:
-                lib_dir = '/usr/lib/p7zip'
-
-            elif distribution in rpm_based_distro:
-                lib_dir = '/usr/libexec/p7zip'
-
-            else:
-                raise Exception('Unsupported system: {}'.format(distribution))
-        elif mainstream_system == 'freebsd':
-            lib_dir = '/usr/local/libexec/p7zip'
+        lib_dir = environ.get('LD_LIBRARY_PATH')
+        if not lib_dir:
+            mainstream_system = platform.system().lower()
+            if mainstream_system == 'linux':
+                distribution = platform.linux_distribution()[0].lower()
+                debian_based_distro = ['ubuntu', 'mint', 'debian']
+                rpm_based_distro = ['fedora', 'redhat']
+
+                if distribution in debian_based_distro:
+                    lib_dir = '/usr/lib/p7zip'
+
+                elif distribution in rpm_based_distro:
+                    lib_dir = '/usr/libexec/p7zip'
+
+                else:
+                    raise Exception('Unsupported system: {}'.format(distribution))
+            elif mainstream_system == 'freebsd':
+                lib_dir = '/usr/local/libexec/p7zip'
+        lib_7z = path.join(lib_dir, '7z')
+        if not path.exists(lib_7z):
+            for element in environ.get('PATH', '').split(pathsep):
+                if path.exists(path.join(element, '7z')):
+                    lib_7z = path.join(element, '7z')
+                    break
 
         locations = {
             'extractcode.sevenzip.libdir': lib_dir,
-            'extractcode.sevenzip.exe': path.join(lib_dir, '7z'),
+            'extractcode.sevenzip.exe': lib_7z,
         }
 
         return locations