Improve chroot guessing with availability hints

Copr can provide available chroots when a repository is not found. When
a user hasn't provided the chroot, we can improve our guessing.

The result is that it'll always prefer epel, but can also use the
centos-stream or rhel buildroot when available. This makes it easier for
projects that build without EPEL.

This is an alternative take on 313470b.

Author: ekohl

plugins/copr.py

@@ -78,6 +78,13 @@ def linux_distribution():
     from ConfigParser import ConfigParser, NoOptionError, NoSectionError
     from urllib2 import urlopen, HTTPError, URLError
 
+
+class RepoNotFoundError(dnf.exceptions.Error):
+    def __init__(self, message, available_chroots=None):
+        super(RepoNotFoundError, self).__init__(message)
+        self.available_chroots = available_chroots
+
+
 @dnf.plugin.register_command
 class CoprCommand(dnf.cli.Command):
     """ Copr plugin for DNF """
@@ -454,7 +461,7 @@ def _need_root(cls):
             raise dnf.exceptions.Error(
                 _('This command has to be run under the root user.'))
 
-    def _guess_chroot(self):
+    def _guess_chroot(self, available_chroots=None):
         """ Guess which chroot is equivalent to this machine """
         # FIXME Copr should generate non-specific arch repo
         dist = self.chroot_config
@@ -490,7 +497,20 @@ def _guess_chroot(self):
         elif "Amazon Linux" in dist[0]:
             chroot = "amazonlinux-{}-{}".format(dist[1], distarch if distarch else "x86_64")
         else:
-            chroot = ("epel-{}-{}".format(dist[1].split(".", 1)[0], distarch if distarch else "x86_64"))
+            releasever = dist[1].split(".", 1)[0]
+            arch = distarch if distarch else "x86_64"
+
+            if available_chroots:
+                guesses = ['epel', 'rhel']
+                if "CentOS Stream" in dist:
+                    guesses.insert(1, 'centos-stream')
+                for guess in guesses:
+                    chroot = "{}-{}-{}".format(guess, releasever, arch)
+                    if chroot in available_chroots:
+                        return chroot
+                return None
+            else:
+                chroot = "epel-{}-{}".format(releasever, arch)
         return chroot
 
     def _download_repo_file(self, project_name, chroot):
@@ -509,17 +529,18 @@ def _download_repo_file(self, project_name, chroot):
                 error_data_decoded = json.loads(error_data_decoded)
                 error_msg += _("Repository '{0}' does not exist in project '{1}'.").format(
                     chroot, project_name)
-                if error_data_decoded.get("available chroots"):
+                available_chroots = error_data_decoded.get("available chroots")
+                if available_chroots:
                     error_msg += _("\nAvailable repositories: ") + ', '.join(
-                        "'{}'".format(x) for x in error_data_decoded["available chroots"])
+                        "'{}'".format(x) for x in available_chroots)
                     error_msg += _("\n\nIf you want to enable a non-default repository, use the following command:\n"
                                    "  'dnf copr enable {0} <repository>'\n"
                                    "But note that the installed repo file will likely need a manual "
                                    "modification.").format(project_name)
-                raise dnf.exceptions.Error(error_msg)
+                raise RepoNotFoundError(error_msg, available_chroots)
             else:
                 error_msg += _("Project {0} does not exist.").format(project_name)
-                raise dnf.exceptions.Error(error_msg)
+                raise RepoNotFoundError(error_msg)
         except URLError as e:
             error_msg = _("Failed to connect to {0}: {1}").format(self.copr_url + api_path, e.reason.strerror)
             raise dnf.exceptions.Error(error_msg)
@@ -529,7 +550,17 @@ def _download_repo_file(self, project_name, chroot):
     def _download_repo(self, project_name, repo_filename, chroot=None):
         _chroot = chroot or self._guess_chroot()
 
-        response = self._download_repo_file(project_name, _chroot)
+        try:
+            response = self._download_repo_file(project_name, _chroot)
+        except RepoNotFoundError as e:
+            # If a chroot was given or none are available we shouldn't guess again
+            if chroot or not e.available_chroots:
+                raise
+
+            new_guess = self._guess_chroot(e.available_chroots)
+            if not new_guess or new_guess == _chroot:
+                raise
+            response = self._download_repo_file(project_name, new_guess)
 
         if os.path.exists(repo_filename):
             os.remove(repo_filename)