Build Cache wrapper for minifying CSS files
An NDCODE project.
Overview
The less_css_cache package exports a single constructor
LessCSSCache(diag)
which must be called with the new operator. The resulting cache object stores
the utf-8-encoded text of CSS files loaded from disk and minified.
See the build_cache, disk_build, and less packages for more information.
The LessCSSCache object is essentially a wrapper object which routes the
request between these packages, to ensure that the minified CSS text is either
retrieved from RAM or minified from a source file as required.
Calling API
Suppose one has a LessCSSCache instance named lcc. It behaves somewhat like
an ES6 Map object, except that it only has the lcc.get() function, because
new objects are added to the cache by attempting to get them.
The interface for the LessCSSCache-provided instance function lcc.get() is:
await lcc.get(key) — retrieves the object stored under key, where
key is the on-disk pathname to a CSS file. A Buffer object is returned,
containing the utf-8-encoded text resulting from running clean-css on the
source file. The pathname and the returned result are cached for future reuse.
Before returning the cached copy, the existence and modification times of the
main CSS file and all dependents on disk are checked to make sure that the
cache is up-to-date. The dependencies are discovered the first time the main
file is compiled, and saved in a separate (hidden) dependency file, alongside
the (hidden) output file. If the main CSS file doesn't exist or it includes a
source file that doesn't exist (possibly a source file whose deletion triggered
recompilation), an ENOENT exception is thrown, or if the file and all current
dependencies exist with valid syntax, they are compiled and the cache updated.
If the file is not in cache but the disk output is up-to-date, it is reloaded.
About diagnostics
The diag argument to the constructor is a bool, which if true causes
messages to be printed via console.log() for all activities except for the
common case of retrieval when the object is already up-to-date. A diag value
of undefined is treated as false, thus it can be omitted in the usual case.
To be implemented
The less package is called with standard NDCODE options. This is part of the
reason to have less_css_cache, so as to provide a consistent interface to
minifiers or compilers for Javascript, CSS, SVG, etc. However, if some control
of the underlying compiler is needed in future, we could add an options
object to pass through, in which we'd inject our NDCODE options where not
overridden.
It is intended that we will shortly add a timer function (or possibly just a
function that the user should call periodically) to flush built templates from
the cache after a stale time. There is otherwise no way to delete an object
from the cache, except by first deleting it on disk, then trying to get it.
GIT repository
The development version can be cloned, downloaded, or browsed with gitweb at:
https://git.ndcode.org/public/less_css_cache.git
License
All of our NPM packages are MIT licensed, please see LICENSE in the repository.
Contributions
The caching system is under active development (and is part of a larger project that is also under development) and thus the API is tentative. Please go ahead and incorporate the system into your project, or try out our example webserver built on the system, subject to the caution that the API could change. Please send us your experience and feedback, and let us know of improvements you make.
Contact: Nick Downing nick@ndcode.org