Packaging:AutoProvidesAndRequiresFiltering

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Contents

Summary

RPM has no general, standard mechanism to enable filtering of auto-generated requires and provides; this guideline describes how Fedora has implemented such a system.

  • MUST: Packages must not provide RPM dependencies things that are not global in nature, or are otherwise indicated (e.g. through a virtual provides system). e.g. a plugin package containing a binary shared library must not "provide" that library unless it is accessible through the system library paths.
  • MUST: Where filtering automatically generated RPM dependency information, the filtering system implemented by Fedora must be used, except where there is a compelling reason to deviate from it.

Rationale

RPM has no general mechanism to enable filtering of auto-generated requires and provides; this feature aims to implement one.

The auto requires and provides system contained in RPM is quite useful; however, it often picks up "private" package capabilities that shouldn't be advertised as global, things that are "just wrong", or things prohibited by policy (e.g. deps from inside %{_docdir}).

For example:

  • Various "plugin" packages (e.g. Pidgin, Perl, Apache, KDE) are marked as "providing" private shared libraries outside the system path.
  • Files in %{_docdir} are routinely scanned, and can trigger prov/req when this is explicitly forbidden by policy.

As it stands, filtering these auto-generated requires and provides is difficult and messy at best, and horribly deep magic in many cases; with little guidance on how to do it.[1] This feature aims to make the following tasks easy:

  • preventing files/directories from being scanned for requires (pre-scan filtering)
  • preventing files/directories from being scanned for provides (pre-scan filtering)
  • removing items from the requires stream (post-scan filtering)
  • removing items from the provides stream (post-scan filtering)

Macros defining the filtering system: macros.filtering

Examples

e.g. to ensure an arch-specific perl-* package won't provide or require things that it shouldn't, we could use an invocation as such:

# we don't want to provide private Perl extension libs
%filter_provides_in %{perl_vendorarch}/.*\\.so$ 
%filter_provides_in -P %{perl_archlib}/(?!CORE/libperl).*\\.so$ 

# we don't want to either provide or require anything from _docdir, per policy
%filter_provides_in %{_docdir} 
%filter_requires_in %{_docdir}

# actually set up the filtering
%filter_setup

%description
...

Or better yet, have all that centralized, so any package providing a Perl extension[2] can easily invoke the correct filtering incantations:

%{?perl_default_filter}

%description
...

A brief comparison of other auto req/prov filtering systems.

Usage

Location of macros

It's strongly recommended that these filtering macros be invoked before %description, but after any other definitions.

Preventing files/directories from being scanned for provides (pre-scan filtering)

The %filter_provides_in macro is used to define the files or directories that should not be scanned for any "provides" information. This macro may be safely invoked multiple times, and can handle regular expressions. (The -P flag can be passed to specify that a PCRE is being used.)

We can filter by regex:

# we don't want to provide private Perl extension libs
%filter_provides_in %{perl_vendorarch}/.*\\.so$ 
%filter_provides_in -P %{perl_archlib}/(?!CORE/libperl).*\\.so$ 

Or by anything matching, say, a directory:

# we don't want to either provide or require anything from _docdir, per policy
%filter_provides_in %{_docdir}

Preventing files/directories from being scanned for requires (pre-scan filtering)

The %filter_requires_in macro is used to define the files or directories that should not be scanned for any "requires" information; it does for requires what the %filter_provides_in macro does for provides.

Removing items from the requires stream (post-scan filtering)

Removing items from the provides stream (post-scan filtering)

General filter setup

The %{filter_setup} macro must be invoked after defining any specific overrides; this macro does all the heavy lifting of implementing the filtering desired:

# ... filtering defines here
%filter_setup