Package: lektor-limit-dependencies
Lektor Limit DependenciesThis is an experimentalLektorplugin which aims to provide tools (or,
at least, a tool) to help keep Lektor’s dependency tracking under
control.IntroductionMotivating ExampleSuppose that you would like to list the three most recent blog posts
in the sidebar of your Lektor-based site.  This can be done by adding
something like to your site base template:<h3>Recent Posts</h3><ul>{%forpostinsite.query('/blog').order_by('-pub_date').limit(3)%}<li><ahref="{{post|url}}">{{post.title}}</a></li>{%endfor%}</ul>This is not without drawbacks, however.  To sort the post query by
date, Lektor iterates throughallof the blog’s posts, then sorts
them.  In so doing, it records all of the blog posts as dependenciesof every page on which this most-recent-post query is used.  If this
is in the sidebar of every page on your site,now every page on your
site will be rebuilt whenever any blog post at all(not just one of
the three most recent posts)is edited.Technically, it is true that all pages now depend on all posts.  You
might well edit thepub_dateof one of your older posts, such that
it should now appear in the most-recent listing.  However, it is not
true that all pages need to be rebuilt foranyedit of any post.
Unfortunately, Lektor’s dependency tracking system is not elaborate
enough to be able to express details abouthowpages are
dependent on other pages; it only records that theyaredependent, so Lektor has no option but to rebuild everything.A Solution?This plugin introduces a Jinja filter,limit_dependencies.  It
expects, as input, a Lektorqueryinstance.  It iterates through the
input query, and returns a new query instance which will yield the
same results.  While it is doing its iteration, it — essentially —
monkey-patches Lektor’s dependency tracking machinery to prevent it
from recording any dependencies.At the end,limit_dependenciesrecords one dependency on avirtual
source objectwhich depends only on the sequence of the identities
of the records in the query result.  (Lektor provides a means by which
virtual source objects can report checksums.  The
dependency tracking mechanism records those checksums, and will
trigger a rebuild should the checksum change.Limit_dependenciesgenerates a virtual source object whose checksum depends on the
sequence of identities in the query result.)In the above example, this is exactly what we want.  We only want to
trigger a rebuild if the order or composition of the most-recent three
posts changes.  (Or if any of their titles change.  Note that this
gets covered, too, since when the resulting query is iterated over in
the{% for %}loop, dependencies will be recorded on the three
most-recent posts.)Thus, the example above, if replaced by:<h3>Recent Posts</h3><ul>{%forpostinsite.query('/blog').order_by('-pub_date').limit(3)|limit_dependencies%}<li><ahref="{{post|url}}">{{post.title}}</a></li>{%endfor%}</ul>will work in a much more efficient and sane manner.  Pages will be
rebuilt only if there are changes in the order, composition or content
of the three most recent posts.InstallationAdd lektor-limit-dependencies to your project from command line:lektor plugins add lektor-limit-dependenciesSeethe Lektor plugin documentationfor more information.AuthorJeff Dairikidairiki@dairiki.orgChangelogRelease 1.0.0 (2023-01-31)No code changes from 1.0.0b1.Test under python 3.11.Release 1.0.0b1 (2021-03-29)Drop support for python<3.7 and lektor<3.3.Release 0.1 (2021-02-05)No code changes.Update development status classifier to "stable".Test under python 3.9.  Stop testing under 3.5.Release 0.1a1 (2020-05-19)Initial release.