Re: Package critique: modeline for air quality information

[tpeplt <tpeplt@gmail.com>]

The following message is a courtesy copy of an article
that has been posted to gnu.emacs.help as well.

John Haman <mail@johnhaman.org> writes:

> I wrote a package that adds local air quality statistics to the
> mode-line. Here it is:
>
> https://github.com/jthaman/air-quality/blob/main/air-quality.el
>
> If you are so inclined, I'd like some thoughts on the code. It's
> short, but I'm trying to get better at Emacs Lisp (at least this week,
> while I'm on vacation...)
>
> --

Some good practices to follow:

1. Byte-compile the source to locate and resolve many types of problems.
Byte compilation is available as a command (‘emacs-lisp-byte-compile’)
or via the Emacs-Lisp menu when editing a .el file.  With your
‘air-quality.el’ (version 0.1 from the git repository), it yields the
following message:

> In air-quality--get-update:
> air-quality.el:125:17: Warning: reference to free variable
> ‘url-http-end-of-headers’

2. Emacs Lisp also has a ‘lint’ available via the Emacs-Lisp menu.  This
can be helpful, but it can also find spurious (non-existent) problems
that are due to its limitations.  For ‘air-quality.el’, it yields:

> In function air-quality--get-update:
> air-quality.el:118:Warning: Reference to unbound symbol:
> url-http-end-of-headers
>
> Linting finished.

3. ‘Checkdoc’ can help identify good practices, such as doc-string
standards, so that you (and others) will have usable descriptions of
procedures and data structures.  It looks as though you have run it on
air-quality.el because it gives no warnings or errors.

4. Consider adding the code as an ELPA package that can be installed via
the Emacs menu Options/Manage Emacs Packages (or the command
‘list-packages’) once it has reached a level of maturity that you
consider acceptable.

--