mock: fix dynamic buildrequires unnecesarry loop

per discussion here: rpm-software-management/rpm#963
Mock should accept return code 0 from rpm.

Relates: rpm-software-management#434

mock/py/mockbuild/backend.py

@@ -180,24 +180,26 @@ def remove(self, *rpms):
         self.buildroot.root_log.info(output)
 
     @traceLog()
-    def installSrpmDeps(self, *srpms):
+    def installSrpmDeps(self, *srpms, ignored_deps = None):
         """Figure out deps from srpm. Call package manager to install them"""
         try:
             self.uid_manager.becomeUser(0, 0)
 
             # first, install pre-existing deps and configured additional ones
-            deps = list(self.buildroot.preexisting_deps)
+            deps = set(self.buildroot.preexisting_deps)
             for hdr in util.yieldSrpmHeaders(srpms, plainRpmOk=1):
                 # get text buildreqs
-                deps.extend(util.getAddtlReqs(hdr, self.more_buildreqs))
-            if deps:
+                deps.update(util.getAddtlReqs(hdr, self.more_buildreqs))
+            if deps > ignored_deps:
                 self.buildroot.pkg_manager.install(*deps, check=True)
 
             # install actual build dependencies
             self.buildroot.pkg_manager.builddep(*srpms, check=True)
         finally:
             self.uid_manager.restorePrivs()
 
+        return deps
+
     @traceLog()
     def installSpecDeps(self, spec_file):
         try:
@@ -693,13 +695,13 @@ def get_command(mode):
         bd_out = self.make_chroot_path(self.buildroot.builddir)
         max_loops = int(self.config.get('dynamic_buildrequires_max_loops'))
         success = False
+        deps = set()
         if dynamic_buildrequires and self.config.get('dynamic_buildrequires'):
             while not success and max_loops > 0:
                 # run rpmbuild+installSrpmDeps until
                 # * it fails
                 # * installSrpmDeps does nothing
                 # * or we run out of dynamic_buildrequires_max_loops tries
-                packages_before = self.buildroot.all_chroot_packages()
                 try:
                     self.buildroot.doChroot(get_command(['-br']),
                                             shell=False, logger=self.buildroot.build_log, timeout=timeout,
@@ -708,18 +710,19 @@ def get_command(mode):
                                             nspawn_args=self._get_nspawn_args(),
                                             unshare_net=self.private_network,
                                             printOutput=self.config['print_main_output'])
-                    success = True
                 except Error as e:
                     if e.resultcode != 11:
                         raise e
+                finally:
                     max_loops -= 1
                     self.buildroot.root_log.info("Dynamic buildrequires detected")
                     self.buildroot.root_log.info("Going to install missing buildrequires")
                     buildreqs = glob.glob(bd_out + '/SRPMS/*.buildreqs.nosrc.rpm')
-                    self.installSrpmDeps(*buildreqs)
-                    packages_after = self.buildroot.all_chroot_packages()
-                    if packages_after == packages_before:
+                    new_deps = self.installSrpmDeps(*buildreqs, deps)
+                    if new_deps <= deps:
                         success = True
+                    else:
+                        deps = new_deps
                     for f_buildreqs in buildreqs:
                         os.remove(f_buildreqs)
                     if not sc: