Use rpmdev-vercmp as a fallback for version comparison on RHEL5

salt/modules/rpm.py

@@ -586,20 +586,76 @@ def version_cmp(ver1, ver2):
         salt '*' pkg.version_cmp '0.2-001' '0.2.0.1-002'
     '''
     try:
+        cmp_func = None
         if HAS_RPM:
-            cmp_func = rpm.labelCompare
-        elif HAS_RPMUTILS:
-            cmp_func = rpmUtils.miscutils.compareEVR
+            try:
+                cmp_func = rpm.labelCompare
+            except AttributeError:
+                # Catches corner case where someone has a module named "rpm" in
+                # their pythonpath.
+                log.debug(
+                    'rpm module imported, but it does not have the '
+                    'labelCompare function. Not using rpm.labelCompare for '
+                    'version comparison.'
+                )
+        if cmp_func is None and HAS_RPMUTILS:
+            try:
+                cmp_func = rpmUtils.miscutils.compareEVR
+            except AttributeError:
+                log.debug('rpmUtils.miscutils.compareEVR is not available')
+
+        if cmp_func is None:
+            if salt.utils.which('rpmdev-vercmp'):
+                # rpmdev-vercmp always uses epochs, even when zero
+                def _ensure_epoch(ver):
+                    def _prepend(ver):
+                        return '0:{0}'.format(ver)
+
+                    try:
+                        if ':' not in ver:
+                            return _prepend(ver)
+                    except TypeError:
+                        return _prepend(ver)
+                    return ver
+
+                ver1 = _ensure_epoch(ver1)
+                ver2 = _ensure_epoch(ver2)
+                result = __salt__['cmd.run'](['rpmdev-vercmp', ver1, ver2],
+                                             python_shell=False,
+                                             ignore_retcode=True).strip()
+                if result.endswith('equal'):
+                    return 0
+                elif 'is newer' in result:
+                    newer_version = result.split()[0]
+                    if newer_version == ver1:
+                        return 1
+                    elif newer_version == ver2:
+                        return -1
+                log.warning(
+                    'Failed to interpret results of rpmdev-vercmp output: %s',
+                    result
+                )
+            else:
+                # We'll need to fall back to salt.utils.version_cmp()
+                log.warning(
+                    'rpmdevtools is not installed, please install it for '
+                    'more accurate version comparisons'
+                )
         else:
-            cmp_func = None
-        cmp_result = cmp_func is None and 2 or cmp_func(salt.utils.str_version_to_evr(ver1),
-                                                        salt.utils.str_version_to_evr(ver2))
-        if cmp_result not in (-1, 0, 1):
-            raise Exception("Comparison result '{0}' is invalid".format(cmp_result))
+            cmp_result = cmp_func(salt.utils.str_version_to_evr(ver1),
+                                  salt.utils.str_version_to_evr(ver2))
+            if cmp_result not in (-1, 0, 1):
+                raise CommandExecutionError(
+                    'Comparison result \'{0}\' is invalid'.format(cmp_result)
+                )
+
+            return cmp_result
 
-        return cmp_result
     except Exception as exc:
-        log.warning("Failed to compare version '{0}' to '{1}' using RPM: {2}".format(ver1, ver2, exc))
+        log.warning(
+            'Failed to compare version \'%s\' to \'%s\' using RPM: %s',
+            ver1, ver2, exc
+        )
 
     return salt.utils.version_cmp(ver1, ver2)