oci-as-buildroot

Fixes: rpm-software-management#1482

mock/py/mockbuild/config.py

@@ -31,7 +31,7 @@
                'ccache', 'selinux', 'package_state', 'chroot_scan',
                'lvm_root', 'compress_logs', 'sign', 'pm_request',
                'hw_info', 'procenv', 'showrc', 'rpkg_preprocessor',
-               'rpmautospec', 'buildroot_lock']
+               'rpmautospec', 'buildroot_lock', 'oci_as_buildroot']
 
 def nspawn_supported():
     """Detect some situations where the systemd-nspawn chroot code won't work"""
@@ -234,6 +234,8 @@ def setup_default_config_opts():
                 'process-distgit',
             ]
         },
+        'oci_as_buildroot_enable': True,
+        'oci_as_buildroot_opts': {},
     }
 
     config_opts['environment'] = {

mock/py/mockbuild/plugins/oci_as_buildroot.py

@@ -0,0 +1,51 @@
+"""
+Generate OCI from prepared build chroot.
+Use given OCI image as build chroot (TODO).
+"""
+
+import os
+import mockbuild.util
+from mockbuild.trace_decorator import getLog
+
+requires_api_version = "1.1"
+
+
+def init(plugins, conf, buildroot):
+    """ The obligatory plugin entry point """
+    OCIAsBuildroot(plugins, conf, buildroot)
+
+
+class OCIAsBuildroot:
+    """
+    OCIAsBuildroot plugin (class).
+    """
+    def __init__(self, plugins, conf, buildroot):
+        self.buildroot = buildroot
+        self.state = buildroot.state
+        self.conf = conf
+        plugins.add_hook("postdeps", self.produce_buildroot_image)
+
+    def do(self, cmd):
+        """ Execute command on host (as root) """
+        getLog().info("Executing %s", ' '.join(cmd))
+        mockbuild.util.do(cmd)
+
+    def _produce_image_as_root(self):
+        name = f"mock-container-{self.buildroot.config['root']}"
+        # TODO: chain build produces multiple buildroots
+        tarball = os.path.join(self.buildroot.resultdir, "buildroot-oci.tar")
+        chroot = self.buildroot.make_chroot_path()
+        self.do(["buildah", "from", "--name", name, "scratch"])
+        self.do(["buildah", "add", name, chroot, "/"])
+        self.do(["buildah", "commit", "--format", "oci", name,
+                 "oci-archive:" + tarball])
+        self.do(["buildah", "rm", name])
+
+    def produce_buildroot_image(self):
+        """ Generate OCI image from buildroot using Buildah """
+        try:
+            self.state.start("producing buildroot as OCI image")
+            with self.buildroot.uid_manager.elevated_privileges():
+                self._produce_image_as_root()
+        finally:
+            self.state.finish("producing buildroot as OCI image")