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GLEP 84: Standard format for package.mask files

Author Arthur Zamarin <[email protected]>
Type Standards Track
Status Final
Version 1.0
Created 2023-11-01
Last modified 2024-09-26
Posting history 2023-10-04, 2023-10-13, 2023-11-01
GLEP source glep-0084.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 [1] and 5.2.8 [2] 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 [4], pkgdev mask [5], and soko [6]. 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 [3] 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

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 [1] and 5.2.8 [2]. 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

BNF Grammar

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

# 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