New mode --calculate-build-dependencies

When specified, the ".buildreqs.nosrc.rpm" file is provided in the
results directory.

Fixes: rpm-software-management#1358

mock/py/mock.py

@@ -120,6 +120,9 @@ def command_parse():
     parser.add_option("--rebuild", action="store_const", const="rebuild",
                       dest="mode", default='__default__',
                       help="rebuild the specified SRPM(s)")
+    parser.add_option("--calculate-build-dependencies", action="store_const",
+                      const="calculatedeps", dest="mode",
+                      help="Resolve static and dynamic build dependencies")
     parser.add_option("--chain", action="store_const", const="chain",
                       dest="mode",
                       help="build multiple RPMs in chain loop")
@@ -402,6 +405,11 @@ def command_parse():
         else:
             options.mode = 'rebuild'
 
+    options.calculatedeps = None
+    if options.mode == "calculatedeps":
+        options.mode = "rebuild"
+        options.calculatedeps = True
+
     # Optparse.parse_args() eats '--' argument, while argparse doesn't.  Do it manually.
     if args and args[0] == '--':
         args = args[1:]

mock/py/mockbuild/backend.py

@@ -300,6 +300,7 @@ def build(self, srpm, timeout, check=True, spec=None):
                             ' See "dynamic_buildrequires" in config_opts.')
 
             self.install_external(requires)
+            # install the (static) BuildRequires
             self.installSrpmDeps(rebuilt_srpm)
             self.state.finish(buildsetup)
             buildsetup_finished = True
@@ -720,6 +721,7 @@ def rebuild_package(self, spec_path, timeout, check, dynamic_buildrequires):
         # --nodeps because rpm in the root may not be able to read rpmdb
         # created by rpm that created it (outside of chroot)
         check_opt = []
+        depsonly = self.config["calculatedeps"]
         if not check:
             # this is because EL5/6 does not know --nocheck
             # when EL5/6 targets are not supported, replace it with --nocheck
@@ -781,7 +783,9 @@ def get_command(mode, checkdeps=False):
                 if packages_after == packages_before:
                     success = True
                 for f_buildreqs in buildreqs:
-                    os.remove(f_buildreqs)
+                    if not (success and depsonly):
+                        # we want to keep the nosrc.rpm file
+                        os.remove(f_buildreqs)
                 # The first rpmbuild -br already did %prep, so we don't need waste time
                 if '--noprep' not in br_mode:
                     br_mode += ['--noprep']
@@ -803,14 +807,16 @@ def get_command(mode, checkdeps=False):
         # Unfortunately, we can only do this when using a bootstrap chroot,
         # because the rpm in the chroot might not understand the rpmdb otherwise.
         # See https://github.com/rpm-software-management/mock/issues/1246
-        checkdeps = dynamic_buildrequires and self.bootstrap_buildroot is not None
-        self.buildroot.doChroot(get_command(mode, checkdeps=checkdeps),
-                                shell=False, logger=self.buildroot.build_log, timeout=timeout,
-                                uid=self.buildroot.chrootuid, gid=self.buildroot.chrootgid,
-                                user=self.buildroot.chrootuser,
-                                nspawn_args=self._get_nspawn_args(),
-                                unshare_net=self.private_network,
-                                printOutput=self.config['print_main_output'])
+
+        if not depsonly:
+            checkdeps = dynamic_buildrequires and self.bootstrap_buildroot is not None
+            self.buildroot.doChroot(get_command(mode, checkdeps=checkdeps),
+                                    shell=False, logger=self.buildroot.build_log, timeout=timeout,
+                                    uid=self.buildroot.chrootuid, gid=self.buildroot.chrootgid,
+                                    user=self.buildroot.chrootuser,
+                                    nspawn_args=self._get_nspawn_args(),
+                                    unshare_net=self.private_network,
+                                    printOutput=self.config['print_main_output'])
         results = glob.glob(bd_out + '/RPMS/*.rpm')
         results += glob.glob(bd_out + '/SRPMS/*.rpm')
         self.buildroot.final_rpm_list = [os.path.basename(result) for result in results]

mock/py/mockbuild/config.py

@@ -386,6 +386,8 @@ def setup_default_config_opts():
 
     config_opts["recursion_limit"] = 5000
 
+    config_opts["calculatedeps"] = None
+
     return config_opts
 
 
@@ -637,6 +639,8 @@ def set_config_opts_per_cmdline(config_opts, options, args):
     # which though affects root_cache).
     config_opts["additional_packages"] = options.additional_packages
 
+    config_opts["calculatedeps"] = options.calculatedeps
+
 
 def check_config(config_opts):
     if 'root' not in config_opts: