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Bug 1696204

Summary: dnf should enable parent-required-modules if user specify exact module version to install. Or print missing installed modules.
Product: Red Hat Enterprise Linux 8 Reporter: Andrei Stepanov <astepano>
Component: dnfAssignee: Jaroslav Mracek <jmracek>
Status: CLOSED ERRATA QA Contact: Jan Blazek <jblazek>
Severity: unspecified Docs Contact:
Priority: medium
Version: 8.2CC: amatej, james.antill, ppisar, psabata
Target Milestone: rcKeywords: FutureFeature, Reopened, Triaged
Target Release: 8.0Flags: pm-rhel: mirror+
Hardware: Unspecified
OS: Unspecified
Whiteboard:
dnf-4.2.17-1.el8 If docs needed, set a value
---
2020-04-28 16:47:40 UTC Bug
--- ---
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--- RHEL 7.3 requirements from Atomic Host:
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Description Andrei Stepanov 2019-04-04 10:35:34 UTC 
Suppose user enabled module perl-DBD-SQLite:1.58

# dnf module reset perl-DBD-SQLite
# dnf module enable perl-DBD-SQLite

At this point user enabled all modules: "perl-DBD-SQLite" that have stream "1.58"

Next user wants to install specific version of module "perl-DBD-SQLite" specifying: NSVC

# dnf module install perl-DBD-SQLite:1.58:8010020190322125518:e74546ca

Remember? Module is enabled.

But this command will fail. Because required modules are not installed:

Modulemd for perl-DBD-SQLite:1.58:8010020190322125518:e74546ca has:

 requires:
 perl: [5.24]
 perl-DBI: [1.641]
 platform: [el8]

DNF doesn't print any understanding explanation, why NSVC cannot be installed. However, module is enabled.

Currently user must also do:

# dnf module reset perl
# dnf module enable perl:5.24

This is not obvious. Child-module-expansion must install required parent-modules.

Otherwise, user cannot understand why module is enabled but is not installable.
I doubt that user will go and read read modulemd for perl-DBD-SQLite what it requires.

If you do not want to do this, than please, just print some useful info such as:

Requirements to install perl-DBD-SQLite:1.58:8010020190322125518:e74546ca is not satisfied.

Missing required installed modules: 
perl: 5.24
Comment 1 Jaroslav Mracek 2019-04-09 10:14:52 UTC 
I investigated the issue, and I found that the problem is caused by preferring of a context using default stream. This is more restrictive behaviorDue to latest changes that should not allow stream switch I would not recommend to change the behavior.

The issue could be resolved enabling perl:5.24 manually.
Comment 2 Andrei Stepanov 2019-04-09 10:30:15 UTC 
Jaroslav, hi.

I agree that "The issue could be resolved enabling perl:5.24 manually."

But, problem is users doesn't know that he needs enable perl:5.24 manually. Or Perl:5.26 or perl:6.01

DNF doesn't give any clue/hint why it fails.

There should be some meaningful info from DNF. something like: this NSVC has next requires:

 ------------------------
| |
| # DEPENDENCY |
| |
| Modules to be enabled: |
| |
| * perl:5.24 |
| * perl-DBI:1.641 |
| |
------------------------

Otherwise:
1. user will blame DNF.
2. user mast manually inspect md file to figure out why it fails.

Now DNF fails in very unfriendly manner.

Hope for your understanding.
Comment 3 Jaroslav Mracek 2019-04-09 12:42:50 UTC 
We need an opinion about required behavior from Modularity team.
Comment 5 Petr Šabata 2019-07-31 11:07:49 UTC 
I agree the current behavior is a consequence of the restrictive stream switching behavior and should be kept.
However, I also agree DNF should provide some more information to guide the user in the right direction; even if just by saying that the required context is available but couldn't be installed because of unment module-level dependencies. Would that be possible?
Comment 6 Jaroslav Mracek 2019-11-14 10:05:22 UTC 
I enhanced the error message (see output bellow) - https://github.com/rpm-software-management/dnf/pull/1532. Please do you agree with proposed solution?


# dnf module install perl-DBI:1.641:820190116185335:082fdf2f
All matches for argument 'perl-DBI:1.641:820190116185335:082fdf2f' in module 'perl-DBI:1.641' are not active
Error: Problems in request:
broken groups or modules: perl-DBI:1.641:820190116185335:082fdf2f
Comment 7 Andrei Stepanov 2019-11-14 10:23:29 UTC 
Jaroslav Mracek 
It looks match better now. Thank you.
Comment 15 errata-xmlrpc 2020-04-28 16:47:40 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2020:1823