path: root/glep-0084.rst

---
GLEP: 84
Title: Standard format for package.mask files
Author: Arthur Zamarin <arthurzam@gentoo.org>
Type: Standards Track
Status: Final
Version: 1.0
Created: 2023-11-01
Last-Modified: 2024-09-26
Post-History: 2023-10-04, 2023-10-13, 2023-11-01
Content-Type: text/x-rst
---

Abstract
========

This GLEP specifies the format of ``package.mask`` files under profiles
directory.

Motivation
==========

At the moment of writing this GLEP, ``package.mask`` files didn't have a full
format specification. While PMS sections 4.4 [#PMS-4.4]_ and 5.2.8
[#PMS-5.2.8]_ specifies the raw format which the package manager must support
for correct behavior, it does not specify how comments must be formatted, how
entries must be grouped, how last-rite masks should be written, etc.

Various tools have been developed to handle that mask message. A non exhaustive
list includes ``lr-add-pmask`` [#lr-add-pmask]_, ``pkgdev mask`` [#pkgdev-mask]_,
and ``soko`` [#soko-mask]_. Those tools have different purposes, filing a new
mask message with all relevant information, and showing a nice rendered mask
message to users. Those tools are very complicated (since they need to handle
various edge cases of existing masks, and try to prepare for future mask
messages).

For a long time, ``profiles/package.mask`` had a special header [#CURR-MASK]_
whose purpose was to define the mask message formatting. While it has served
its purpose for a long time indeed, it still left a lot of wiggle room for the
message.

Therefore, the motivation for this GLEP is to provide unified, clear and
complete specification for package.mask entries across the repository.

Specification
=============

Header
------

As an opt-in GLEP for files, files which want to use this GLEP format should
define a special header line which tools should use to know the format of the
file. This line should appear as the first non empty line after the copyright
header. The line should be:

    # Uses GLEP 84 format

This header should come instead of the current very long header [#CURR-MASK]_,
as mentioning the GLEP is enough.

Files can decide to add some extra file documentation, in which case, the
entries start after the first separation line comment which begins and ends
with at least 5 "-", matching to the regex:

    # -{5,}.*-{5,}

All comments before the first occurrence of this separation line comment are
ignored, and should be considered as file documentation. Another separation
line may appear, after which all comments are also ignored. Those separation
lines are optional, and are not required for the file to conform to this GLEP.

Entries Grouping
----------------

Each mask entry consists of 2 parts: `comments block`_ and `packages list`_,
which aren't separated by a blank line between the 2 parts. Between entries, a
mandatory blank line must appear.

New entries added to the file must be inserted at the beginning, after the file
header.

Packages List
-------------

Must conform to PMS sections 4.4 [#PMS-4.4]_ and 5.2.8 [#PMS-5.2.8]_. This GLEP
further limits the syntax to one item per line, without any leading or trailing
whitespace, no comments inside the packages list. Blank lines between items are
allowed.

Comments Block
--------------

The lines in the comment block are prefixed with a "#" symbol. The comments
should be separated with single space from the "#", unless this is trailing
whitespace, in which case it should be removed (meaning blank lines in comments
block are just "#\\n").

The comments block consists of 2 mandatory parts (`author line`_ and
`explanation`_) and one optional part (`last-rite epilogue`_). A blank line to
separate the parts is optional. Trailing whitespace should be dropped.

The lines of the comments block should use column wrapping of 80 characters
(including the "#" prefix). The author line is excluded from this maximum
width.

For simplifying the explanation, we wouldn't mention the "#" prefix.
Implementations are advised to drop this prefix before further processing the
block.

Author Line
'''''''''''

A line of the format: ``${AUTHOR-NAME} <${EMAIL}> (${SINGLE-DATE})``. The author
name and email should correspond to the mask author, and should confirm to the
GLEP 76 rules. The date should be of RFC-3339 full-date format, meaning
``YYYY-MM-DD``. The date is recommended to use the date at UTC timezone at the
moment of commit push.

Explanation
'''''''''''

In this block the reasons for the mask should be listed, with extra explanation
where needed. If referencing bugs, use the `bugs list`_ format (mask rendering
tools should render mentioned bugs also in this part).

In this part, a paragraph separator is a blank line, similar to ReStructuredText
format. Using multiple blank lines between paragraphs is prohibited.

Last-Rite Epilogue
''''''''''''''''''

If the last paragraph starts with "Removal on", then this mask entry is
considered as last-rite mask, and the last paragraph must conform to the
last-rite epilogue format.

The paragraph should be of format ``Removal on {DATE}[.,]? +{BUGS-LIST}.?``,
where the date is RFC-3339 full-date format, meaning ``YYYY-MM-DD``, and the
bugs list is of the `bugs list`_ format. The listed bugs should include the
last-rite bug opened, and potentially more relevant bugs which weren't listed
in the explanation paragraphs.

Bugs List
'''''''''

A list of bugs should start with a word matching the regular expression
``"[Bb]ugs?"`` (Bug, Bugs, bug, bugs), a single space, and a comma-separated
list of bug numbers, where each bug number starts with "#" symbol. For example
``Bugs #667687, #667689``. Parsers for bugs list should handle bugs list
wrapping to multiple lines because of its length.

Rationale
=========

Not using a hard-coded format
-----------------------------

While using a hard coded format, of some key-value kind (for example TOML, XML,
INI), might be the correct path in the future, for the moment of writing this
GLEP, it is preferred to stay with a format resembling most of the masks. Also,
this GLEP prefers staying with a format close to an organized free-text.

Specific format for bugs list
-----------------------------

It is preferable to specify the exact expected format for the bugs list, so
rendering tools (such as ``soko``) can render the bugs numbers as links. Other
use-cases for extracting the bug numbers exist, for example a new tool for
tree-cleaning last-rited packages.

UTC time zone for dates
-----------------------

Specifying a time zone is quite sensible for an international project such as
Gentoo. While a difference in a date-only timestamp because of time zone is
quite unlikely, the main purpose of standardizing on UTC is to prevent the case
of new entries having a date prior to existing one. Since creating a mask entry
using tools (such as pkgdev mask) is recommended, the tool should generate the
correct date, which should be transparent to the user.

Disallow "removal in X days"
----------------------------

Another existing variant of last-rite epilogue is using "removal in X days". It
complicates the knowledge of the last date, since the user needs to compute
what is the correct date (consider the amount of days in the same month). The
existence of tools helping to file mask entries means that computing the
removal date is simple for the writer. No gain is seen from allowing "removal
in X days" format.

Backwards Compatibility
=======================

This specification does not break the raw entries format specified in PMS,
meaning all existing package managers implementations confirming to PMS will
also support this new specification.

However, multiple existing entries would need to be manually updated to conform
to the new specification, so the updated tools can parse and work with all
existing entries. Only after fixing all entries, the special header should be
added, opting in the new format. Tools which might be used for overlays are
recommended to not crash upon non-confirming entries, and verify the existence
of this special header.

Reference Implementation
========================

..
    TODO: add reference implementations for:
    1. pkgcheck check for confirming format
    2. pkgdev updated for new format
    3. soko updated to use new format

BNF Grammar
-----------

.. code:: bnf

    BUGS-LIST    ::= [Bb]ugs? #\d+(,? #\d+)*
                 ::= [Bb]ugs? +#\d+(,? +#\d+)*
    DATE         ::= YYYY-MM-DD
    LAST-RITE    ::= Removal on {DATE}[.,]? +{BUGS-LIST}.?
    AUTHOR-LINE  ::= {AUTHOR-NAME} <{AUTHOR-EMAIL}> ({DATE})
    PARAGRAPH    ::= # [^\n]+(\n# [^\n]+)*
    EXPLANATION  ::= {PARAGRAPH}(\n#\n{PARAGRAPH})*
    MASK-COMMENT ::= # {AUTHOR-LINE}\n{EXPLANATION}
                 ::= # {AUTHOR-LINE}\n{EXPLANATION}\n# {LAST-RITE}
    PKGS_GROUP   ::= {DEP}(\n{DEP})*
    MASK-PKGS    ::= {PKGS_GROUP}(\n+{PKGS_GROUP})*
    ENTRY        ::= {MASK-COMMENT}\n{MASK-PKGS}
    ENTRIES      ::= {ENTRY}(\n\n{ENTRY})*
    GLEP-HEADER  ::= # Uses GLEP 84 format
    SEPARATION   ::= # -{5,}.*-{5,}
    FILE         ::= {COPYRIGHT}\n+{GLEP-HEADER}\n{ENTRIES}
                 ::= {COPYRIGHT}\n+{GLEP-HEADER}\n+{COMMENTS}\n+{SEPARATION}\n{ENTRIES}
                 ::= {COPYRIGHT}\n+{GLEP-HEADER}\n+{COMMENTS}\n+{SEPARATION}\n{ENTRIES}\n{SEPARATION}\n+{COMMENTS}

Example Entries
---------------

.. code::

    # Arthur Zamarin <arthurzam@gentoo.org> (2023-09-21)
    # Very broken, no idea why packaged, need to drop ASAP. The project
    # is done with supporting this package. See for history bug #667889.
    #
    # As a better plan, you should migrate to dev-lang/perl, which has
    # better compatibility with dev-lang/ruby when used with dev-lang/lua
    # bindings.
    # Removal on 2023-10-21.  Bugs #667687, #667689.
    dev-lang/python

    # Arthur Zamarin <arthurzam@gentoo.org> (2023-09-20)
    # Normal mask for testing
    dev-lang/lua:5.1

References and Footnotes
========================

.. [#PMS-4.4] "PMS section 4.4"
   (https://projects.gentoo.org/pms/8/pms.html#x1-320004.4)

.. [#PMS-5.2.8] "PMS section 5.2.8"
   (https://projects.gentoo.org/pms/8/pms.html#x1-510005.2.8)

.. [#CURR-MASK] "Existing ``packages.mask`` header before this GLEP"
   (https://gitweb.gentoo.org/repo/gentoo.git/tree/profiles/package.mask?id=9acaae3e1a70ec6bd72e3c324b115bae1a05ed5f)

.. [#lr-add-pmask] https://github.com/projg2/mgorny-dev-scripts/blob/52ceab3a579b35fb0d92f7a1f060cd7d4659f24f/lr-add-pmask

.. [#pkgdev-mask] https://gitweb.gentoo.org/proj/pkgcore/pkgdev.git/tree/src/pkgdev/scripts/pkgdev_mask.py?h=v0.2.8

.. [#soko-mask] https://gitweb.gentoo.org/sites/soko.git/tree/pkg/portage/repository/mask.go?h=v1.0.3

Copyright
=========

This work is licensed under the Creative Commons Attribution-ShareAlike 4.0
International License.  To view a copy of this license, visit
https://creativecommons.org/licenses/by-sa/4.0/.