Document base initialization for API users including reading config and variables

[xylle]

Hello,
I work with "Rocky Linux 9.0 (Blue Onyx)", python 3.9.10 and dnf 4.10.0
I make a plugin for dnf, and it's work an expected

import dnf
import json
from dnfpluginscore import _, logger

@dnf.plugin.register_command
class JsonUpdatesCommand(dnf.cli.Command):
    aliases = ('json-updates',)
    summary = _('Lister les mises à jour disponibles en JSON')

    def __init__(self, cli):
        super(JsonUpdatesCommand, self).__init__(cli)

    def configure(self):
        pass

    def run(self):
        self.base.fill_sack(load_system_repo=True, load_available_repos=True)
        query = self.base.sack.query().upgrades()

        updates = []
        for pkg in query:
            installed_query = self.base.sack.query().installed().filter(name=pkg.name)
            installed_pkg = next(iter(installed_query), None)
            if installed_pkg:
                installed_version = f"{installed_pkg.version}-{installed_pkg.release}"
            else:
                installed_version = "Non installé"
            updates.append({
                'paquet': pkg.name,
                'version_installee': installed_version,
                'version_disponible': f'{pkg.version}-{pkg.release}'
            })

        print(json.dumps(updates, indent=2))


def load_commands():
    return [JsonUpdatesCommand]

Partial output :

[
  {
    "paquet": "yum",
    "version_installee": "4.10.0-5.el9_0",
    "version_disponible": "4.14.0-17.el9"
  },
  {
    "paquet": "python3-dnf",
    "version_installee": "4.10.0-5.el9_0",
    "version_disponible": "4.14.0-17.el9"
  },
....

When I want to make a python script for the same thing, he doesn't work

#!/usr/bin/env python3

import dnf

base = dnf.Base()
base.fill_sack(load_system_repo=True, load_available_repos=True)
q = base.sack.query()
i = q.upgrades()

packages = list(i)
print("Installed package:")
for pkg in i:
    print(pkg, pkg.reponame)

The list of pkg update are empty on the same server
When I try i = q.installed() in place of i = q.upgrades(), I have the list of installed package.

[m-blaha]

I think you miss loading repository configurations in your example. You need to add base.read_all_repos() before the base.fill_sack() step:

...
base = dnf.Base()
base.read_all_repos()
base.fill_sack(load_system_repo=True, load_available_repos=True)
...

Without it, there are no repositories available (except for the "system repo" loaded from the rpmdb), thus no upgrades available.

[xylle]

Thanks, the first time I try :

...
base = dnf.Base()
base.read_all_repos()
base.fill_sack()
...

I have some error missing file in cache

...
base = dnf.Base()
base.read_all_repos()
base.fill_sack(load_system_repo=True, load_available_repos=True)
...

With this, it's works as expected.
it's possible to put this into documentation ?

[xylle]

I have some error in repo file : mirrorlist line finish with $rltype

[baseos]
name=Rocky Linux $releasever - BaseOS
mirrorlist=https://mirrors.rockylinux.org/mirrorlist?arch=$basearch&repo=BaseOS-$releasever$rltype
#baseurl=http://dl.rockylinux.org/$contentdir/$releasever/BaseOS/$basearch/os/
gpgcheck=1
enabled=1
countme=1
metadata_expire=6h
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-Rocky-9

When I make dnf check-update I have no error, but with the script I have 404 error.
If I remove $rltype, it's work with cli and script

[m-blaha]

Regarding the fill_sack parameters - that's strange since True is the default value for both parameters, and I'd have expected both lines to behave the same.

And regarding the "error" in the repo file - you need to read the variable definitions (then DNF would correctly substitute the $rltype string with its actual value). You should probably also read the configuration file:

...
base = dnf.Base()
# read the configuration from /etc/dnf/dnf.conf
base.conf.read(priority=dnf.conf.PRIO_MAINCONFIG)
# update variable substitutions from /etc/dnf/vars (or other location configured via varsdir)
base.conf.substitutions.update_from_etc(base.conf.installroot, varsdir=base.conf.varsdir)
base.read_all_repos()
base.fill_sack(load_system_repo=True, load_available_repos=True)
...

I guess the DNF API usage should be better documented...

[xylle]

Thank you, it's working with $rltype.
I put the code for future research

    base = dnf.Base()
    # base.conf.read()
    
    # read the configuration from /etc/dnf/dnf.conf
    base.conf.read(priority=dnf.conf.PRIO_MAINCONFIG)
    # update variable substitutions from /etc/dnf/vars (or other location configured via varsdir)
    base.conf.substitutions.update_from_etc(base.conf.installroot, varsdir=base.conf.varsdir)

    # Charge les dépôts système ET disponibles pour obtenir les upgrades
    base.read_all_repos()
    base.fill_sack(load_system_repo=True, load_available_repos=True)
    
    upgrades = base.sack.query().upgrades()

Could you please add this code to the example in the documentation?