Slot and subslot deps

Signed-off-by: Michał Górny <mgorny@gentoo.org>

1 files changed, 35 insertions, 0 deletions

diff --git a/dependencies.rst b/dependencies.rst
index 2b63f7f..5334eee 100644
--- a/dependencies.rst
+++ b/dependencies.rst
@@ -30,4 +30,39 @@ This is especially important for packages that take long time to build.
    by the Council but no reference implementation has been written.
 
 
+.. index:: RDEPEND; slot and subslot deps
+.. index:: Slot; dependencies
+.. index:: Subslot; dependencies
+
+Slot and subslot dependencies
+-----------------------------
+:Source: QA
+:Reference: https://archives.gentoo.org/gentoo-portage-dev/message/9cae3a92412a007febe7ac0612d50f5f
+:Reported: by repoman and pkgcheck
+
+Whenever a package dependency specification matches a range of versions
+that span different slots or subslots, the package must explicitly
+include slot specification.  If the ``:=`` operator is not applicable
+and any slot is acceptable, explicit ``:*`` operator must be used.
+If the ``:<slot>=`` operator is not applicable and only a specific slot
+can be used, ``:<slot>`` value must be explicitly specified.
+
+Package dependency specification without explicit slot specifier can
+be used on packages that are not slotted nor subslotted at the moment.
+
+*Rationale*: this policy aims to help detecting missing slot operators
+when dependencies start using slots or subslots.  It uses the fact that
+the explicit ``:*`` operator is equivalent to no slot specification,
+and therefore can be used interchangeably.  In this case, we assume
+that the latter means 'dependency not verified yet', while the former
+means 'verified that any slot is acceptable'.
+
+.. Note::
+
+   The Paludis_ package manager applies different logic when no slot
+   is specified on the dependency.  It pulls in the slot corresponding
+   to the newest package version available.
+
+
 .. _GLEP 62: https://www.gentoo.org/glep/glep-0062.html
+.. _Paludis: https://paludis.exherbo.org/