Clay

Recently I've used babashka/fs a little bit, here are some quick notes for it:

• Path vs File. Use Path whenever possible, according to this SO answer to "Java: Path vs File". This is actually Java related.
• It's ok to use a path as a key for a clojure map. At my first try, I somehow came to the conclusion that it's not ok, while I was refactoring the live reload for clay. And later I found that it's totally fine to use it as a key. 😞
• Use fs/path to construct file/directory paths, for example, (fs/path "/tmp" "foo" "bar" "baz.clj") will result in a path object for /tmp/foo/bar/baz.clj on linux. If you're coming from Python, it might remind you of os.path.join(path, *paths).
• Use fs/createdirs for mkdir -p, though its name is a bit misleading, I first thought it's for creating a few dirs.
• fs/with-temp-dir is convenient for creating tests.

While refactoring the live reload feature of Clay, I realized I'd better break long functions into smaller and functional ones (as many as I can), which is also a common practice in the clojure community.

Small pure functions not only are easy to verify on the development process (using a REPL), but also are easy to test. And unit tests are easy to write in clojure, just use deftest from clojure.test, a very basic one looks like this:

While developing the live reload feature for Clay, a minimalistic Clojure tool for data visualization and literate programming, I found that it constantly takes ~1 minute for beholder to watch a directory. After some code inspect, I was still having no idea why it happened.

So I decided to use a profiler to find out what's going one under the hood, and Google immediately took me to clj-async-profiler. It's easy to set up following its basic usage docs: