From Fedora Project Wiki

Dynamic BuildRequires

Summary

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

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.

Changes in tooling

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

Example

Probably easiest demonstration how this works is to show example. First, let's make necessary changes in our spec file (I'm taking rust-rpick). 

diff --git a/rust-rpick.spec b/rust-rpick.spec
index 716a185..01a6d35 100644
--- a/rust-rpick.spec
+++ b/rust-rpick.spec
@@ -16,12 +16,6 @@ Source:         %{crates_source}
 ExclusiveArch:  %{rust_arches}
 
 BuildRequires:  rust-packaging
-BuildRequires:  (crate(dirs/default) >= 1.0.0 with crate(dirs/default) < 2.0.0)
-BuildRequires:  (crate(rand/default) >= 0.6.0 with crate(rand/default) < 0.7.0)
-BuildRequires:  (crate(serde/default) >= 1.0.0 with crate(serde/default) < 2.0.0)
-BuildRequires:  (crate(serde/derive) >= 1.0.0 with crate(serde/derive) < 2.0.0)
-BuildRequires:  (crate(serde_yaml/default) >= 0.8.0 with crate(serde_yaml/default) < 0.9.0)
-BuildRequires:  (crate(structopt/default) >= 0.2.0 with crate(structopt/default) < 0.3.0)
 
 %global _description \
 Helps you pick items from a list by various algorithms. Example uses: pick a\
@@ -69,6 +63,9 @@ which use "default" feature of "%{crate}" crate.
 %autosetup -n %{crate}-%{version_no_tilde} -p1
 %cargo_prep
 
+%generate_buildrequires
+%cargo_generate_buildrequires
+
 %build
 %cargo_build

Then let's try to build package (I will skip parts like rustc executions because it is irrelevant). 

⋊> ~/P/s/r/rust-rpick on master ⨯ fedpkg mockbuild --mock-config $PWD/fedora-rawhide-x86_64-buildreqs.cfg
Wrote: /home/brain/Projects/src.fedoraproject.org/rpms/rust-rpick/rust-rpick-0.3.0-1.fc31.src.rpm
INFO: mock.py version 1.4.14 starting (python version = 3.7.3)...
[…]
INFO: Start(/home/brain/Projects/src.fedoraproject.org/rpms/rust-rpick/rust-rpick-0.3.0-1.fc31.src.rpm)  Config(fedora-rawhide-x86_64-buildreqs)
[…]
Start: build phase for rust-rpick-0.3.0-1.fc31.src.rpm
Start: build setup for rust-rpick-0.3.0-1.fc31.src.rpm
Building target platforms: x86_64
Building for target x86_64
Wrote: /builddir/build/SRPMS/rust-rpick-0.3.0-1.fc31.src.rpm
Repository 'kkt' is missing name in configuration, using id.
fedora                                           21 kB/s |  19 kB     00:00    
kkt                                             2.6 MB/s | 3.0 kB     00:00    
Dependencies resolved.
================================================================================
 Package                    Arch     Version                     Repo      Size
================================================================================
Installing:
 rust-packaging             x86_64   6-28.fc31+buildreqs         kkt       13 k
Installing dependencies:
[…]
Finish: build setup for rust-rpick-0.3.0-1.fc31.src.rpm
Start: rpmbuild rust-rpick-0.3.0-1.fc31.src.rpm
Start: Outputting list of installed packages
Finish: Outputting list of installed packages
Building target platforms: x86_64
Building for target x86_64
Executing(%prep): /bin/sh -e /var/tmp/rpm-tmp.0m57Wu
+ umask 022
+ cd /builddir/build/BUILD
+ cd /builddir/build/BUILD
+ rm -rf rpick-0.3.0
+ /usr/bin/gzip -dc /builddir/build/SOURCES/rpick-0.3.0.crate
+ /usr/bin/tar -xof -
+ STATUS=0
+ '[' 0 -ne 0 ']'
+ cd rpick-0.3.0
+ /usr/bin/chmod -Rf a+rX,u+w,g-w,o-w .
+ set -eu
+ /usr/bin/mkdir -p .cargo
+ cat
+ /usr/bin/rm -f Cargo.lock
+ exit 0
Executing(buildreqs): /bin/sh -e /var/tmp/rpm-tmp.LooeBv
+ umask 022
+ cd /builddir/build/BUILD
+ cd /builddir/build/BUILD
+ cd rpick-0.3.0
+ /usr/bin/cargo-inspector -BR Cargo.toml
+ /usr/bin/cargo-inspector -TR Cargo.toml
+ exit 0
Wrote: /builddir/build/SRPMS/rust-rpick-0.3.0-1.fc31.buildreqs.nosrc.rpm
INFO: Dynamic buildrequires detected
Repository 'kkt' is missing name in configuration, using id.
fedora                                           17 kB/s |  19 kB     00:01    
kkt                                             2.8 MB/s | 3.0 kB     00:00    
Package rust-packaging-6-28.fc31+buildreqs.x86_64 is already installed.
Dependencies resolved.
================================================================================
 Package                                  Arch    Version         Repo     Size
================================================================================
Installing:
 rust-dirs+default-devel                  noarch  1.0.5-1.fc31    fedora  7.6 k
 rust-rand+default-devel                  noarch  0.6.5-3.fc31    fedora  8.4 k
 rust-serde+default-devel                 noarch  1.0.90-1.fc31   fedora   12 k
 rust-serde+derive-devel                  noarch  1.0.90-1.fc31   fedora   12 k
 rust-serde_yaml+default-devel            noarch  0.8.8-2.fc30    fedora  8.3 k
 rust-structopt+default-devel             noarch  0.2.15-2.fc31   fedora  8.2 k
Installing dependencies:
[…]
Building target platforms: x86_64
Building for target x86_64
Executing(%prep): /bin/sh -e /var/tmp/rpm-tmp.l2cC5s
+ umask 022
+ cd /builddir/build/BUILD
+ cd /builddir/build/BUILD
+ rm -rf rpick-0.3.0
+ /usr/bin/gzip -dc /builddir/build/SOURCES/rpick-0.3.0.crate
+ /usr/bin/tar -xof -
+ STATUS=0
+ '[' 0 -ne 0 ']'
+ cd rpick-0.3.0
+ /usr/bin/chmod -Rf a+rX,u+w,g-w,o-w .
+ set -eu
+ /usr/bin/mkdir -p .cargo
+ cat
+ /usr/bin/rm -f Cargo.lock
+ exit 0
Executing(buildreqs): /bin/sh -e /var/tmp/rpm-tmp.cvhwuw
+ umask 022
+ cd /builddir/build/BUILD
+ cd /builddir/build/BUILD
+ cd rpick-0.3.0
+ /usr/bin/cargo-inspector -BR Cargo.toml
+ /usr/bin/cargo-inspector -TR Cargo.toml
+ exit 0
Executing(%build): /bin/sh -e /var/tmp/rpm-tmp.dlI3ax
+ umask 022
+ cd /builddir/build/BUILD
+ cd rpick-0.3.0
+ /usr/bin/env CARGO_HOME=.cargo RUSTC_BOOTSTRAP=1 /usr/bin/cargo build -j8 -Z avoid-dev-deps --release
[…]
Finish: build phase for rust-rpick-0.3.0-1.fc31.src.rpm
INFO: Done(/home/brain/Projects/src.fedoraproject.org/rpms/rust-rpick/rust-rpick-0.3.0-1.fc31.src.rpm) Config(fedora-rawhide-x86_64-buildreqs) 2 minutes 9 seconds
INFO: Results and/or logs in: /home/brain/Projects/src.fedoraproject.org/rpms/rust-rpick/results_rust-rpick/0.3.0/1.fc31
INFO: Cleaning up build root ('cleanup_on_success=True')
Start: clean chroot
Finish: clean chroot
Finish: run

Let's check dependencies of src.rpm. 

⋊> ~/P/s/r/rust-rpick on master ⨯ rpm -qpR $PWD/results_rust-rpick/0.3.0/1.fc31/rust-rpick-0.3.0-1.fc31.src.rpm
(crate(dirs/default) >= 1.0.0 with crate(dirs/default) < 2.0.0)
(crate(rand/default) >= 0.6.0 with crate(rand/default) < 0.7.0)
(crate(serde/default) >= 1.0.0 with crate(serde/default) < 2.0.0)
(crate(serde/derive) >= 1.0.0 with crate(serde/derive) < 2.0.0)
(crate(serde_yaml/default) >= 0.8.0 with crate(serde_yaml/default) < 0.9.0)
(crate(structopt/default) >= 0.2.0 with crate(structopt/default) < 0.3.0)
rpmlib(CompressedFileNames) <= 3.0.4-1
rpmlib(DynamicBuildRequires) <= 4.15.0-1
rpmlib(FileDigests) <= 4.6.0-1
rpmlib(RichDependencies) <= 4.12.0-1
rust-packaging

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
  • 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

  1. Make sure you have new rpm-build (OPTION 1) or mock (OPTION 2).
  2. Add %generate_buildrequires script into spec file which prints dependencies, remove static BuildRequires
  3. Build package
    1. OPTION1: Run rpmbuild -ba with your usual workflow
    2. OPTION2: Run mock -r fedora-rawhide-x86_64 with your usual workflow
  4. 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

TBD.

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