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<?xml version="1.0" encoding="UTF-8"?>
<guide self="ebuild-writing/eapi/">
<chapter>
<title>EAPI Usage and Description</title>
<body>
<p>
The <uri link="https://wiki.gentoo.org/wiki/Project:PMS">Package Manager
Specification (PMS)</uri> is a standardization effort to ensure that the
ebuild file format, the ebuild repository format (of which the Gentoo
repository is Gentoo's main incarnation) as well as behaviour of the package
managers interacting with these ebuilds is properly written down and agreed
upon.
</p>
<p>
EAPI is a version defined in ebuilds and other package manager related files
which informs the package manager about the file syntax and content. It is,
in effect, the version of the package manager specification (PMS) that the
file adheres to.
</p>
<p>
This section provides usage and descriptions of the different EAPIs.
</p>
</body>
<section>
<title>Usage of EAPIs</title>
<body>
<important>
An overview about the important features of each EAPI is provided in the
appendix of the Package Manager Specification. The two-page leaflet
can be printed out, consulted for reference and is available
as <c>app-doc/pms</c> in the main tree.
</important>
<p>
You must set the EAPI variable by specifying it at the top of the ebuild:
</p>
<codesample lang="ebuild">
# Copyright 1999-2021 Gentoo Authors
# Distributed under the terms of the GNU General Public License v2
EAPI=7
</codesample>
<note>
Most developers prefer to set the EAPI version without quotes. However, the PMS
allows single and double quotes as well.
</note>
<important>
EAPI must only be defined in ebuild files, not eclasses. (eclasses may have
EAPI-conditional code)
</important>
<p>
When writing new ebuilds developers can choose whatever EAPI they think
is the best. Using the features of the latest EAPI is encouraged.
</p>
</body>
<subsection>
<title>Upgrade path</title>
<body>
<p>
Gentoo policy is to support upgrades for installations at least a year old
with no/little intervention and up to two years old with minor intervention. To
achieve this, developers must avoid using the latest EAPI in ebuilds within
the <c>@system</c> set (see <uri link="::general-concepts/dependencies/#implicit-system-dependency"/>)
or its dependencies.
</p>
<p>
The Base System project has
<uri link="https://wiki.gentoo.org/wiki/Project:Base#Rules_and_limitations">rules</uri>
governing their use of newer EAPIs, as does the
<uri link="https://projects.gentoo.org/python/guide/package-maintenance.html#porting-packages-to-a-new-eapi">Python project</uri>.
</p>
<p>
It is also convention that blockers within ebuilds are retained for at least
2 years after the last ebuild matching the block is removed from the tree to
avoid file collisions for users upgrading older systems. <c>pkgcheck</c> has
a warning for this called <c>OutdatedBlocker</c> (or even
<c>NonexistentBlocker</c> for when the match is from pre-git times if using
a non-grafted repository).
</p>
</body>
</subsection>
</section>
<section>
<title>EAPIs 0 to 4</title>
<body>
<p>
EAPIs 0 to 4 are obsolete and must no longer be used. Refer to the Package
Manager Specification for details about them.
</p>
</body>
</section>
<section>
<title>EAPI 5</title>
<subsection>
<title>EAPI 5 Metadata</title>
<body>
<dl>
<dt>REQUIRED_USE supports new at-most-one-of operator</dt>
<dd>
The new <b>at-most-one-of</b> operator consists of the string <c>??</c>,
and is satisfied if zero or one (but no more) of its child elements is
matched.
</dd>
<dt>SLOT supports optional "sub-slot" part</dt>
<dd>
The <c>SLOT</c> variable may contain an optional <b>sub-slot</b> part that
follows the regular slot and is delimited by a <c>/</c> character.
The sub-slot must be a valid slot name. The sub-slot is used to represent
cases in which an upgrade to a new version of a package with a different
sub-slot may require dependent packages to be rebuilt. When the sub-slot
part is omitted from the SLOT definition, the package is considered to have
an implicit sub-slot which is equal to the regular slot.
</dd>
<dt>Slot operators and sub-slots in dependencies</dt>
<dd>
<p>
A slot dependency may contain an optional sub-slot part that follows the
regular slot and is delimited by a <c>/</c> character. This can be useful
for packages installing pre-built binaries that require a library with a
specific soname version which corresponds to the sub-slot. For example:
</p>
<codesample lang="ebuild">
RDEPEND="dev-libs/foo:0/3"
</codesample>
<p>
Package dependency specifications can use <b>slot operators</b> to clarify
what should happen if the slot and/or sub-slot of a runtime dependency
changes:
</p>
<ul>
<li>
<c>:*</c> Indicates that any slot value is acceptable. In addition,
for runtime dependencies, indicates that the package specifying the
dependency will not break if the package matching the dependency is
replaced by a different matching package with a different slot and/or
sub-slot.
</li>
<li>
<c>:=</c> Indicates that any slot value is acceptable. In addition,
for runtime dependencies, indicates that the package specifying the
dependency will break unless there is available a package matching
the dependency and whose slot and sub-slot are equal to the slot and
sub-slot of the best installed version that had matched this dependency
at the time when the package specifying this dependency had been
installed.
</li>
<li>
<p>
<c>:slot=</c> Indicates that only a specific slot value is acceptable,
and otherwise behaves identically to the <c>:=</c> operator.
</p>
<note>
use <c>:slot/subslot</c> without a <c>=</c> to depend on a specific
slot and sub-slot pair; it's a syntax error to use <c>:slot/subslot=</c>
in an ebuild.
</note>
</li>
</ul>
<p>
The <c>:slot</c> dependency syntax continues to behave like in EAPI=4 or
earlier, i.e. it indicates that only the specific slot value is acceptable,
but the package will not break when the version matching the runtime
dependency is replaced by a version with a different sub-slot.
</p>
<p>
For example:
</p>
<codesample lang="ebuild">
RDEPEND="dev-libs/foo:2=
>=dev-libs/bar-0.9:=
media-gfx/baz:*
x11-misc/wombat:0"
</codesample>
<p>
means that the package should be rebuilt when <c>foo:2</c> or
<c>>=bar-0.9</c> are upgraded to versions with different subslots,
but that changes in subslots of <c>baz</c> or <c>wombat:0</c> should be
ignored.
</p>
</dd>
</dl>
</body>
</subsection>
<subsection>
<title>EAPI 5 Profiles</title>
<body>
<dl>
<dt>Profile stable USE forcing and masking</dt>
<dd>
In profile directories with an EAPI supporting stable masking, new USE
configuration files are supported: <c>use.stable.mask</c>,
<c>use.stable.force</c>, <c>package.use.stable.mask</c> and
<c>package.use.stable.force</c>. These files behave similarly to previously
supported USE configuration files, except that they only influence packages
that are merged due to a stable keyword.
</dd>
</dl>
</body>
</subsection>
<subsection>
<title>EAPI 5 Helpers</title>
<body>
<dl>
<dt>econf adds --disable-silent-rules</dt>
<dd>
This option will automatically be passed if <c>--disable-silent-rules</c>
occurs in the output of <c>configure --help</c>.
</dd>
<dt>new* commands can read from standard input</dt>
<dd>
Standard input is read when the first parameter is <c>-</c> (a hyphen).
</dd>
<dt>New option --host-root for {has,best}_version</dt>
<dd>
This option <c>--host-root</c> will cause the query to apply to the host
root instead of ROOT.
</dd>
<dt>New doheader helper function</dt>
<dd>
Installs the given header files into <c>/usr/include/</c>. If option
<c>-r</c> is specified, descends recursively into any directories given.
</dd>
<dt>New usex helper function</dt>
<dd>
<!-- We probably need an example here -->
<pre>
USAGE: usex <USE flag> [true output] [false output] [true suffix] [false suffix]
DESCRIPTION:
If USE flag is set, echo [true output][true suffix] (defaults to "yes"),
otherwise echo [false output][false suffix] (defaults to "no").
</pre>
</dd>
</dl>
</body>
</subsection>
<subsection>
<title>EAPI 5 Phases</title>
<body>
<dl>
<dt>src_test supports parallel tests</dt>
<dd>
Unlike older EAPIs, the default <c>src_test</c> implementation will not
pass the -j1 option to emake.
</dd>
</dl>
</body>
</subsection>
<subsection>
<title>EAPI 5 Variables</title>
<body>
<dl>
<dt>EBUILD_PHASE_FUNC</dt>
<dd>
During execution of an ebuild phase function (such as <c>pkg_setup</c> or
<c>src_unpack</c>), the <c>EBUILD_PHASE_FUNC</c> variable will contain the
name of the phase function that is currently executing.
</dd>
</dl>
</body>
</subsection>
</section>
<section>
<title>EAPI 6</title>
<subsection>
<title>EAPI 6 Bash version</title>
<body>
<dl>
<dt>Bash version</dt>
<dd>
Ebuilds can use features of Bash version 4.2 (was 3.2 before).
</dd>
</dl>
</body>
</subsection>
<subsection>
<title>EAPI 6 Ebuild Environment</title>
<body>
<dl>
<dt>Locale settings</dt>
<dd>
Behaviour of case modification and collation order (<c>LC_CTYPE</c> and
<c>LC_COLLATE</c>) are guaranteed to be the same as in the C locale, as far
as characters in the ASCII range are concerned.
</dd>
<dt><c>failglob</c> enabled</dt>
<dd>
For <c>EAPI=6</c>, the <c>failglob</c> option of bash is set in the global
scope of ebuilds. If set, failed pattern matches during filename expansion
result in an error when the ebuild is being sourced.
</dd>
</dl>
</body>
</subsection>
<subsection>
<title>EAPI 6 Phases</title>
<body>
<dl>
<dt>Update default implementation of <c>src_prepare</c></dt>
<dd>
<p>
This phase is no longer a no-op, it supports applying patches via the
<c>PATCHES</c> variable and applying user patches via <c>eapply_user</c>.
The default <c>src_prepare</c> looks like this:
</p>
<codesample lang="ebuild">
src_prepare() {
if [[ $(declare -p PATCHES 2>/dev/null) == "declare -a"* ]]; then
[[ -n ${PATCHES[@]} ]] && eapply "${PATCHES[@]}"
else
[[ -n ${PATCHES} ]] && eapply ${PATCHES}
fi
eapply_user
}
</codesample>
</dd>
<dt>New <c>src_install</c> Phase Function</dt>
<dd>
<p>
This phase uses the new <c>einstalldocs</c> function for installation of
documentation. The default <c>src_install</c> looks like this:
</p>
<codesample lang="ebuild">
src_install() {
if [[ -f Makefile ]] || [[ -f GNUmakefile ]] || [[ -f makefile ]]; then
emake DESTDIR="${D}" install
fi
einstalldocs
}
</codesample>
</dd>
</dl>
</body>
</subsection>
<subsection>
<title>EAPI 6 Helpers</title>
<body>
<dl>
<dt><c>einstall</c> banned</dt>
<dd>
The <c>einstall</c> helper has been banned with <c>EAPI=6</c>.
</dd>
<dt><c>dohtml</c> deprecated</dt>
<dd>
The <c>dohtml</c> helper has been deprecated with <c>EAPI=6</c>.
</dd>
<dt><c>nonfatal die</c></dt>
<dd>
When <c>die</c> or <c>assert</c> are called under the <c>nonfatal</c>
command and with the <c>-n</c> option, they will not abort the build
process but return with an error.
</dd>
<dt><c>eapply</c> support</dt>
<dd>
The <c>eapply</c> command is a simplified substitute for <c>epatch</c>
(from <c>eutils.eclass</c>), implemented in the package manager.
The patches from its file or directory arguments are applied using patch
<c>-p1</c>, but it accepts <c>patch(1)</c> options from GNU patch to
override default behavior.
</dd>
<dt><c>eapply_user</c> support</dt>
<dd>
<p>
The <c>eapply_user</c> command permits the package manager to apply
user-provided patches. It must be called from every <c>src_prepare</c>
function.
</p>
<note>
<c>eapply_user</c> doesn't need to be called explicitly when default
<c>src_prepare</c> is called.
</note>
</dd>
<dt><c>econf</c> adds <c>--docdir</c> and <c>--htmldir</c></dt>
<dd>
Options <c>--docdir</c> and <c>--htmldir</c> are passed to
<c>configure</c>, in addition to the existing options.
</dd>
<dt><c>in_iuse</c> support</dt>
<dd>
The <c>in_iuse</c> function returns <c>true</c> if the given parameter is
available in the ebuilds <c>USE</c>.
</dd>
<dt><c>unpack</c> changes</dt>
<dd>
<ul>
<li>
<c>unpack</c> supports relative paths without leading <c>./</c>
(<c>unpack foo/bar.tar.gz</c> is valid as relative path).
</li>
<li><c>unpack</c> supports <c>.txz</c> (xz compressed tarball).</li>
<li><c>unpack</c> matches filename extensions case-insensitively.</li>
</ul>
</dd>
<dt><c>einstalldocs</c> support</dt>
<dd>
The <c>einstalldocs</c> function will install the files specified by the
<c>DOCS</c> variable (or a default set of files if <c>DOCS</c> is unset)
and by the <c>HTML_DOCS</c> variable.
</dd>
<dt><c>get_libdir</c> support</dt>
<dd>
The <c>get_libdir</c> command outputs the <c>lib*</c> directory basename
suitable for the current ABI.
</dd>
</dl>
</body>
</subsection>
</section>
<section>
<title>EAPI 7</title>
<subsection>
<title>EAPI 7 Terminology</title>
<body>
<p>
Documents may use the following terms to better describe dependency and
installation targets.
</p>
<dl>
<dt><c>CHOST</c></dt>
<dd>
The system that will be running the installed package.
</dd>
<dt><c>CBUILD</c></dt>
<dd>
The system used to build packages. When not cross-compiling,
CBUILD == CHOST.
</dd>
<dt><c>CTARGET</c></dt>
<dd>
Used in certain cross-compilations, often empty value.
</dd>
</dl>
</body>
</subsection>
<subsection>
<title>EAPI 7 Variables</title>
<body>
<dl>
<dt><c>PORTDIR</c> and <c>ECLASSDIR</c> are removed</dt>
<dd>
<c>PORTDIR</c> and <c>ECLASSDIR</c> are no longer defined and cannot be
used in ebuilds to access these directories.
</dd>
<dt><c>DESTTREE</c> and <c>INSDESTTREE</c> are removed</dt>
<dd>
The unintended exported variables <c>PORTDIR</c> and <c>ECLASSDIR</c>
cannot be used in ebuilds to manipulate installation paths. Use <c>into</c>
or <c>insinto</c>, respectively, instead.
</dd>
<dt><c>D</c>, <c>ED</c>, <c>ROOT</c>, and <c>EROOT</c> modified</dt>
<dd>
These variables no longer contain a trailing slash with <c>EAPI=7</c>.
</dd>
<dt><c>BDEPEND</c> added</dt>
<dd>
Previously, all build-time tools and libraries went into the <c>DEPEND</c>.
Now, built-time dependencies are split into <c>DEPEND</c> and
<c>BDEPEND</c>. The difference is simply that <c>BDEPEND</c> are
dependencies to be executed on the CBUILD. <c>DEPEND</c> remains for other
dependencies, such as libraries, for the CHOST. This improves the
cross-compilation support.
</dd>
<dt><c>BROOT</c> added</dt>
<dd>
<c>BROOT</c> is the absolute path to the root directory, including any
prefix, containing build dependencies satisfied by BDEPEND, typically
executable build tools.
</dd>
<dt><c>SYSROOT</c> and <c>ESYSROOT</c> added</dt>
<dd>
<c>SYSROOT</c> is the location of where dependencies in <c>DEPEND</c> are
installed. <c>ESYSROOT</c> is <c>SYSROOT</c> with <c>EPREFIX</c> appended.
</dd>
<dt><c>ENV_UNSET</c> added</dt>
<dd>
A whitespace delimited list of variables to be removed from the build
environment.
</dd>
</dl>
</body>
</subsection>
<subsection>
<title>EAPI 7 Metadata</title>
<body>
<dl>
<dt>Empty groupings are banned</dt>
<dd>
Groupings which are empty, such as <c>DEPEND="|| ( ${empty_var} )"</c>
will now generate an error. Furthermore, conditions within groupings are
more strictly enforced. For example, <c>REQUIRED_USE="|| ( foo? ( bar )
baz? ( zoinks )"</c> would previously work with <c>USE="-foo -baz"</c>
now requires either <c>USE="foo bar"</c> or <c>USE="baz zoinks"</c>.
</dd>
</dl>
</body>
</subsection>
<subsection>
<title>EAPI 7 Profiles</title>
<body>
<dl>
<dt><c>package.provided</c> banned</dt>
<dd>
Profiles may no longer contain a <c>package.provided</c> file with
<c>EAPI=7</c>.
</dd>
</dl>
</body>
</subsection>
<subsection>
<title>EAPI 7 Helpers</title>
<body>
<dl>
<dt><c>dohtml</c> banned</dt>
<dd>
The <c>dohtml</c> helper has been banned with <c>EAPI=7</c>.
</dd>
<dt><c>dolib</c> and <c>libopts</c> banned</dt>
<dd>
The <c>dolib</c> helper and the associated <c>libopts</c> have been banned
with <c>EAPI=7</c>.
</dd>
<dt><c>has_version</c> and <c>best_version</c> changes</dt>
<dd>
<p>
<c>has_version</c> and <c>best_version</c> now support an optional switch
to determine which type of dependencies to check.
</p>
<ul>
<li><c>-r</c> (the default) will check runtime dependencies (RDEPEND)</li>
<li><c>-d</c> will check CHOST build-time dependencies (DEPEND)</li>
<li><c>-b</c> will check CBUILD build-time dependencies (BDEPEND)</li>
</ul>
</dd>
<dt>Version manipulation and comparison commands</dt>
<dd>
<p>
EAPI=7 introduced three commands for common version number operations.
</p>
<ul>
<li><c>ver_cut</c> obtains substrings of a version string</li>
<li><c>ver_rs</c> replaces separators in a version string</li>
<li><c>ver_test</c> compares two versions</li>
</ul>
<p>
See <uri link="::ebuild-writing/variables/#Version and Name Formatting Issues"/>
for examples of common uses or
<uri link="https://dev.gentoo.org/~mgorny/articles/the-ultimate-guide-to-eapi-7.html#version-manipulation-and-comparison-commands">
an in-depth look</uri>
</p>
</dd>
<dt>New function <c>eqawarn</c></dt>
<dd>
The <c>eqawarn</c> helper has been added with <c>EAPI=7</c>. This function
is to alert developers to a deprecated feature. Previously, this was
contained in <c>eutils</c> eclass which is no longer necessary.
</dd>
<dt>New function <c>dostrip</c></dt>
<dd>
The <c>dostrip</c> helper has been added with <c>EAPI=7</c>. This function
controls whether or not to strip a binary. <c>dostrip -x [file]</c> will
exclude a binary from being stripped. Conversely, when combined with
RESTRICT=strip, <c>dostrip [file]</c> selects a binary file to be stripped.
</dd>
<dt><c>die</c> and <c>assert</c> changes</dt>
<dd>
These commands are now safe to use in a subshell and act as if they were
called in the main process.
</dd>
<dt><c>nonfatal</c> changes</dt>
<dd>
The <c>nonfatal</c> command now works for shell functions and subprocesses.
</dd>
<dt><c>domo</c> behaviour changed</dt>
<dd>
<c>domo</c> (for localizations) now ignores the <c>into</c> directives.
This follows similar commands like <c>doinfo</c> and <c>doman</c>.
</dd>
<dt><c>econf</c> changes</dt>
<dd>
The cross-compilation options <c>--build</c> and <c>--target</c> options
to specify <c>CBUILD</c> and <c>CTARGET</c> respectively have been added
and are retro-active to all EAPIs. In addition, if the build supports
<c>--with-sysroot</c>, the correct value will be passed such that normal
and cross-compilations succeed.
</dd>
</dl>
</body>
</subsection>
</section>
<section>
<title>EAPI 8</title>
<body>
<note>
This section is based on
<uri link="https://mgorny.pl/articles/the-ultimate-guide-to-eapi-8.html">
The ultimate guide to EAPI 8</uri> by Michał Górny.
</note>
</body>
<subsection>
<title>EAPI 8 tree layout</title>
<body>
<dl>
<dt>Less strict naming rules for updates directory</dt>
<dd>
<p>
Up to EAPI 7, the files in the <c>profiles/updates</c> directory had to
follow strict naming by quarters like <c>2Q-2021</c>, indicating the
quarter and the year when they were added. Such a choice of name had the
side effect that lexical sorting of filenames was unsuitable.
</p>
<p>
In EAPI 8, the naming requirement is removed. Eventually, this will allow
switching to a more convenient scheme sorted by year. Different lengths
of time periods will also be possible.
</p>
<p>
Note that this change actually requires changing the repository EAPI
(found in <c>profiles/eapi</c>), so it will not affect Gentoo for at least
the next two years.
</p>
</dd>
</dl>
</body>
</subsection>
<subsection>
<title>EAPI 8 ebuild format</title>
<body>
<dl>
<dt>Bash version is now 5.0</dt>
<dd>
<p>
The Bash version used for ebuilds is changed from 4.2 to 5.0. This means
not only that ebuilds are now permitted to use features provided by the new
Bash version but also the <c>BASH_COMPAT</c> value used for the ebuild
environment is updated, switching the shell behaviour.
</p>
<p>
The only really relevant difference in behaviour is:
</p>
<ul>
<li>
<p>
Quotes are now removed from the RHS argument of a
<c>"${var/.../"..."}"</c> substitution:
</p>
<pre>
var=foo
echo "${var/foo/"bar"}"
</pre>
<p>
The above snippet yields <c>"bar"</c> in Bash 4.2 but just <c>bar</c>
in 4.3+.
</p>
</li>
</ul>
<p>
Potentially interesting new features include:
</p>
<ul>
<li>
<p>
Negative subscripts can now be used to set and unset array elements
(Bash 4.3+):
</p>
<pre>
$ foo=( 1 2 3 )
$ foo[-1]=4
$ unset 'foo[-2]'
$ declare -p foo
declare -a foo=([0]="1" [2]="4")
</pre>
</li>
<li>
<p>
Nameref variables are introduced that work as references to other
variables (4.3+):
</p>
<pre>
$ foo=( 1 2 3 )
$ declare -n bar=foo
$ echo "${bar[@]}"
1 2 3
$ bar[0]=4
$ echo "${foo[@]}"
4 2 3
$ declare -n baz=foo[1]
$ echo "${baz}"
2
$ baz=100
$ echo "${bar[@]}"
4 100 3
</pre>
</li>
<li>
<p>
The <c>[[ -v ... ]]</c> test operator can be used with array indices
to test for array elements being set (4.3+). The two following lines
are now equivalent:
</p>
<pre>
[[ -n ${foo[3]+1} ]]
[[ -v foo[3] ]]
</pre>
</li>
<li>
<p>
<c>mapfile</c> (AKA <c>readarray</c>) now accepts a delimiter via
<c>-d</c>, with a <c>-t</c> option to strip it from read data
(Bash 4.4+). The two following solutions to grab output from
<c>find(1)</c> are now equivalent:
</p>
<pre>
# old solution
local x files=()
while read -d '' -r x; do
files+=( "${x}" )
done < <(find -print0)
# new solution
local files=()
mapfile -d '' -t files < <(find -print0)
</pre>
</li>
<li>
<p>
A new set of transformations is available via <c>${foo@...}</c>
parameter expansion (4.4+), e.g. to print a value with necessary
quoting:
</p>
<pre>
$ var="foo 'bar' baz"
$ echo "${var@Q}"
'foo '\''bar'\'' baz'
</pre>
<p>
For more details, see: <c>info bash</c> or the
<uri link="https://www.gnu.org/software/bash/manual/html_node/Shell-Parameter-Expansion.html">
Bash reference manual</uri>.
</p>
</li>
<li>
<p>
<c>local -</c> can be used to limit single-letter (mangled via
<c>set</c>) shell option changes to the scope of the function, and
restore them upon returning from it (4.4+). The following two functions
are now equivalent:
</p>
<pre>
# old solution
func() {
local prev_shopt=$(shopt -p -o noglob)
set -o noglob
${prev_shopt}
}
# new solution
func() {
local -
set -o noglob
}
</pre>
<p>
The complete information on all changes and new features can be found
in the
<uri link="https://git.savannah.gnu.org/cgit/bash.git/tree/NEWS?h=bash-5.0">
Bash 5.0 (and earlier) release notes</uri>.
</p>
</li>
</ul>
</dd>
</dl>
</body>
</subsection>
<subsection>
<title>EAPI 8 variables</title>
<body>
<dl>
<dt>Selective fetch/mirror restriction</dt>
<dd>
<p>
Before EAPI 8, fetch and mirror restrictions applied globally. That is,
if you needed to apply the respective restriction to at least one distfile,
you had to apply it to them all. However, sometimes packages used a
combination of proprietary and free distfiles, the latter including e.g.
third party patches, artwork. Until now, they had to be mirror-restricted
completely.
</p>
<p>
EAPI 8 allows undoing fetch and mirror restriction for individual files.
To use this, set <c>RESTRICT</c> as before, then use the special
<c>fetch+</c> prefix to specify URLs that can be fetched from, or the
<c>mirror+</c> prefix to reenable mirroring of individual files.
</p>
<p>
Similarly to how the <c>fetch</c> restriction implies a <c>mirror</c>
restriction, the <c>mirror</c> override implies a <c>fetch</c> override.
</p>
<codesample lang="ebuild">
EAPI=8
SRC_URI="
${P}.tgz
fetch+https://example.com/${P}-patch-1.tgz
mirror+https://example.com/${P}-fanstuff.tgz"
RESTRICT="fetch"
</codesample>
<p>
The following table summarises the new behaviour:
</p>
<table>
<tr>
<th><c>RESTRICT</c></th>
<th>URI prefix</th>
<th>Fetching</th>
<th>Mirroring</th>
</tr>
<tr>
<ti>(none)</ti>
<ti>(any)</ti>
<ti>allowed</ti>
<ti>allowed</ti>
</tr>
<tr>
<ti rowspan="2">mirror</ti>
<ti>(none) / fetch+</ti>
<ti>allowed</ti>
<ti>prohibited</ti>
</tr>
<tr>
<ti>mirror+</ti>
<ti>allowed</ti>
<ti>allowed</ti>
</tr>
<tr>
<ti rowspan="3">fetch</ti>
<ti>(none)</ti>
<ti>prohibited</ti>
<ti>prohibited</ti>
</tr>
<tr>
<ti>fetch+</ti>
<ti>allowed</ti>
<ti>prohibited</ti>
</tr>
<tr>
<ti>mirror+</ti>
<ti>allowed</ti>
<ti>allowed</ti>
</tr>
</table>
</dd>
<dt>Install-time dependencies (<c>IDEPEND</c>)</dt>
<dd>
<p>
The primary use for install-time dependencies is to specify dependencies
that are needed during the <c>pkg_postinst</c> phase and that can be
unmerged afterwards. That's pretty much the same as <c>RDEPEND</c>, except
for the unmerging part <d/> and uninstalling a few tools did not seem a
goal justifying another dependency type.
</p>
<p>
With cross-compilation support in EAPI 7, a new dependency type focused
on the build host (<c>CBUILD</c>) tools was added <d/> <c>BDEPEND</c>.
Unfortunately, this had missed the important use case of running
executables installed to the target system when cross-compiling.
<c>RDEPEND</c> was no longer a suitable method of pulling in tools for
<c>pkg_postinst</c>; and since <c>BDEPEND</c> is not used when installing
from a binary package, something new was needed.
</p>
<p>
This is where <c>IDEPEND</c> comes in. It is roughly to <c>RDEPEND</c> what
<c>BDEPEND</c> is to <c>DEPEND</c>. Similarly to <c>BDEPEND</c>,
it specifies packages that must be built for the <c>CBUILD</c> triplet
and installed into <c>BROOT</c> (and therefore queried using
<c>has_version -b</c>). However, similarly to <c>RDEPEND</c>, it is used
when the package is being merged rather than built from source.
It is guaranteed to be satisfied throughout <c>pkg_preinst</c> and
<c>pkg_postinst</c>, and it can be uninstalled afterwards.
</p>
<codesample lang="ebuild">
EAPI=8
inherit xdg-utils
IDEPEND="dev-util/desktop-file-utils"
pkg_postinst() {
xdg_desktop_database_update
}
pkg_postrm() {
xdg_desktop_database_update
}
</codesample>
<p>
In the example provided above, the ebuild needs to be update the icon cache
upon being installed or uninstalled. By placing the respective tool in
<c>IDEPEND</c>, the ebuild requests it to be available at the time of
<c>pkg_postinst</c>. When cross-compiling, the tool will be built for