Niels Thykier: Language Server (LSP) support for debian/control
About a month ago, Otto Kek l inen asked for editor extensions for debian related
files on the debian-devel mailing list. In that thread, I concluded that what we
were missing was a "Language Server" (LSP) for our packaging files.
Last week, I started a prototype for such a LSP for the debian/control file as
a starting point based on the pygls
library. The initial prototype worked and I could do very basic diagnostics plus
completion suggestion for field names.
Current features
I got 4 basic features implemented, though I have only been able to test two of them in
emacs.
Despite its very limited feature set, I feel editing debian/control in emacs is now a much more pleasant experience. Coming back to the features that Otto requested, the above covers a grand total of zero. Sorry, Otto. It is not you, it is me.
- Diagnostics or linting of basic issues.
- Completion suggestions for all known field names that I could think of and values for some fields.
- Folding ranges (untested). This feature enables the editor to "fold" multiple lines. It is often used with multi-line comments and that is the feature currently supported.
- On save, trim trailing whitespace at the end of lines (untested). Might not be registered correctly on the server end.
Completion suggestions
For completion, all known fields are completed. Place the cursor at the start of the line
or in a partially written out field name and trigger the completion in your editor. In my
case, I can type R-R-R and trigger the completion and the editor will automatically
replace it with Rules-Requires-Root as the only applicable match. Your milage may
vary since I delegate most of the filtering to the editor, meaning the editor has the
final say about whether your input matches anything.
The only filtering done on the server side is that the server prunes out fields already used
in the paragraph, so you are not presented with the option to repeat an already used field,
which would be an error. Admittedly, not an error the language server detects at the moment,
but other tools will.
When completing field, if the field only has one non-default value such as Essential
which can be either no (the default, but you should not use it) or yes, then the
completion suggestion will complete the field along with its value.
This is mostly only applicable for "yes/no" fields such as Essential and Protected.
But it does also trigger for Package-Type at the moment.
As for completing values, here the language server can complete the value for simple fields
such as "yes/no" fields, Multi-Arch, Package-Type and Priority. I intend to add
support for Section as well - maybe also Architecture.
Diagnostics
On the diagnostic front, I have added multiple diagnostics:
Notable omission at this time:
- An error marker for syntax errors.
- An error marker for missing a mandatory field like Package or Architecture. This also includes Standards-Version, which is admittedly mandatory by policy rather than tooling falling part.
- An error marker for adding Multi-Arch: same to an Architecture: all package.
- Error marker for providing an unknown value to a field with a set of known values. As an example, writing foo in Multi-Arch would trigger this one.
- Warning marker for using deprecated fields such as DM-Upload-Allowed, or when setting a field to its default value for fields like Essential. The latter rule only applies to selected fields and notably Multi-Arch: no does not trigger a warning.
- Info level marker if a field like Priority duplicates the value of the Source paragraph.
- No errors are raised if a field does not have a value.
- No errors are raised if a field is duplicated inside a paragraph.
- No errors are used if a field is used in the wrong paragraph.
- No spellchecking of the Description field.
- No understanding that Foo and X[CBS]-Foo are related. As an example, XC-Package-Type is completely ignored despite being the old name for Package-Type.
- Quick fixes to solve these problems... :)
Trying it out
If you want to try, it is sadly a bit more involved due to things not being uploaded
or merged yet. Also, be advised that I will regularly rebase my git branches as I
revise the code.
The setup:
Obviously, the setup should get easier over time. The first three bullet points should eventually get resolved by merges and upload meaning you end up with an apt install command instead of them. For the editor part, I would obviously love it if we can add snippets for editors to make the automatically pick up the language server when the relevant file is installed.
- Build and install the deb of the main branch of pygls from https://salsa.debian.org/debian/pygls The package is in NEW and hopefully this step will soon just be a regular apt install.
- Build and install the deb of the rts-locatable branch of my python-debian fork from https://salsa.debian.org/nthykier/python-debian There is a draft MR of it as well on the main repo.
- Build and install the deb of the lsp-support branch of debputy from https://salsa.debian.org/debian/debputy
- Configure your editor to run debputy lsp debian/control as the language server for debian/control. This is depends on your editor. I figured out how to do it for emacs (see below). I also found a guide for neovim at https://neovim.io/doc/user/lsp. Note that debputy can be run from any directory here. The debian/control is a reference to the file format and not a concrete file in this case.
Using the debputy LSP in emacs
The guide I found so far relies on eglot. The guide below assumes you have the
elpa-dpkg-dev-el package installed for the debian-control-mode. Though it should
be a trivially matter to replace debian-control-mode with a different mode if you
use a different mode for your debian/control file.
In your emacs init file (such as ~/.emacs or ~/.emacs.d/init.el), you add the
follow blob.
Once you open the debian/control file in emacs, you can type M-x eglot to
activate the language server. Not sure why that manual step is needed and if someone
knows how to automate it such that eglot activates automatically on opening
debian/control, please let me know.
For testing completions, I often have to manually activate them (with C-M-i or
M-x complete-symbol). Though, it is a bit unclear to me whether this is an
emacs setting that I have not toggled or something I need to do on the language server
side.
(with-eval-after-load 'eglot
(add-to-list 'eglot-server-programs
'(debian-control-mode . ("debputy" "lsp" "debian/control"))))
From here
As next steps, I will probably look into fixing some of the "known missing" items under
diagnostics. The quick fix would be a considerable improvement to assisting users.
In the not so distant future, I will probably start to look at supporting other files
such as debian/changelog or look into supporting configuration, so I can cover
formatting features like wrap-and-sort.
I am also very much open to how we can provide integrations for this feature into
editors by default. I will probably create a separate binary package for specifically
this feature that pulls all relevant dependencies that would be able to provide editor
integrations as well.
Debian Public Statement about the EU Cyber Resilience Act and the Product Liability Directive
The European Union is currently preparing a regulation "on horizontal
cybersecurity requirements for products with digital elements" known as the
Cyber Resilience Act (CRA). It is currently in the final "trilogue" phase of
the legislative process. The act includes a set of essential cybersecurity and
vulnerability handling requirements for manufacturers. It will require products
to be accompanied by information and instructions to the user. Manufacturers
will need to perform risk assessments and produce technical documentation and,
for critical components, have third-party audits conducted. Discovered security
issues will have to be reported to European authorities within 25 hours (1).
The CRA will be followed up by the Product Liability Directive (PLD) which will
introduce compulsory liability for software.
While a lot of these regulations seem reasonable, the Debian project believes
that there are grave problems for Free Software projects attached to them.
Therefore, the Debian project issues the following statement:
Check it out 
Dormitory room in Zostel Ernakulam, Kochi.
Beds in Zostel Ernakulam, Kochi.
Onam sadya menu from Brindhavan restaurant.
Sadya lined up for serving
Sadya thali served on banana leaf.
We were treated with such views during the Wayanad trip.
A road in Rippon.
Entry to Kanthanpara Falls.
Kanthanpara Falls.
A view of Zostel Wayanad.
A map of Wayanad showing tourist places.
A view from inside the Zostel Wayanad property.
Terrain during trekking towards the Chembra peak.
Heart-shaped lake at the Chembra peak.
Me at the heart-shaped lake.
Views from the top of the Chembra peak.
View of another peak from the heart-shaped lake.
I m one of the few folks left who run and maintain mail servers. Recently I had major troubles receiving mails from the mail servers used by a bank, and when 
Some time ago, I decided to make a small banner with the 
So, with the encouragement of a few friends who were in the secret, this happened. In two copies, because the first attempt at the print had issues.
And yesterday we finally met that friend again, gave him all of the banners, and no violence happened, but he liked them :D
Edited 2023-09-01 00:58 +01:00 to fix the link to the Debconf policy.
But I m drifting from the topic/movie. 
I'm really
puzzled why someone invests lifetime to dig into company internal history
to try get something right, do a lengthy explanation to the whole team,
use the time of others, even mention that there was no explanation of
why it's not the default value anymore it should be, and repeat the same
mistake by not writing down anything in the commit message.
For the current company I'm inclined to propose a commit message validator.
For a potential future company I might join, I guess I ask for real world
git logs from repositories I should contribute to. Seems that this is another
valuable source of information to qualify the company culture. Next up to
the existence of whiteboards in the office.
I'm really happy that at least a majority of the people contributing to Debian
writes somewhat decent commit messages and changelogs. Let that be a reminder
to myself to improve in that area the next time I've to change something.
Icy morning Witch Wells Az
This post marks the beginning my yearly roundups of the favourite books and movies that I read and watched in 2022 that I plan to publish over the next few days.
Just as I did for 
