Dynamic BuildRequires

Summary

Add possibility to generate build-time dependencies within RPM spec file and teach RPM and mock how to handle this.

Owner

Name: Igor Gnatenko, Florian Festi, Miroslav Suchý
Email: ignatenkobrain@fedoraproject.org, ffesti@redhat.com, miroslav@suchy.cz
Release notes owner:

Current status

Targeted release: Fedora 31
Last updated: 2019-04-12
Tracker bug: <will be assigned by the Wrangler>

Detailed Description

For many languages (Rust, Golang, Node.Js, Ruby, Python), BuildRequires can be automatically generated. All it takes, run some special tool which will output dependencies in RPM format.

rpmbuild

New %generate_buildrequires section ("script" later in text) in spec file
New option -br which will run script, check dynamic BuildRequires
- If all of them are satisfied, generate src.rpm
- If some of them are not satisfied or --nodeps is present, generate buildreqs.nosrc.rpm
src.rpm produced by rpmbuild -ba will contain dynamic BuildRequires
Option -bs does not change behavior

mock

New option in config dynamic_buildrequires which controls support of new features
Support for rpmbuild changes if this option enabled

Benefit to Fedora

Packagers won't have to pre-generate BuildRequires in the spec file which means it will be always updated (and correct) :

Packagers can focus of making their packages better instead of spending all their packaging time copying BuildRequires from documentation and third party tools.
BuildRequires are dropped as soon as they're no longer necessary
Packages can be easily bumped without requiring a manual BuildRequires refresh
BuildRequires and Requires generation can use similar utilities, making sure that the deps packages declare can also be used for second-level building. Packages no longer need to declare the deps of their second and n-th dependencies because someone forgot to declare them in the correct package.

Scope

Proposal owners: Implement support for a feature in RPM and mock. Make use of it in interested ecosystems.
Other developers: Maintainers of language stacks are advised to use this feature.
Release engineering: #8129
- List of deliverables: N/A
Policies and guidelines: Packaging Guidelines need to be updated with instructions how to use this feature.
Trademark approval: N/A (not needed for this Change)

Upgrade/compatibility impact

Packagers and users who use repoquery might be affected (src.rpm might not contain generated dependencies).

How To Test

0. Make sure you have new rpm-build (OPTION 1) or mock (OPTION 2). 1. Add %generate_buildrequires script into spec file which prints dependencies, remove static BuildRequires 2. OPTION1: Run rpmbuild -ba with your usual workflow 2. OPTION2: Run mock -r fedora-rawhide-x86_64 with your usual workflow 3. Check that your package builds fine, dependencies are getting checked/installed and final src.rpm contains generated BuildRequires

User Experience

Users won't notice differences.

Dependencies

Required feature needs to be implemented in RPM and mock.

Contingency Plan

Contingency mechanism: (What to do? Who will do it?) Proposal Owners might still ship feature disabled for Fedora buildsystem but have it available for end-users, and move full completion to the next release.
Contingency deadline: Beta Freeze
Blocks release? No.
Blocks product? No.

Documentation

TBD.

Release Notes