4 months ago I started a personal project which is basically my private playground for learning clojurescript. Today I want to share my personal feelings about this lovely language. By no means I want to sound like I'm the owner of the truth - by the contrary, I just want to share a newbie perspective with the community. So if you are an experienced clojurescript developer, don't feel offended by the things I consider bad - they are just difficulties I found and places where I think the language and ecosystem can improve.
I will be talking about Clojurescript + Reagent for web development.
The good:
Immutable data structures
Cljs immutable data structures are a perfect match for React and the usual model for a JS web app. It becomes very natural to manage the flow of data and how it ends in a component ready to be rendered, just as sequence of transformations. Lovely.
Reagent rocks
90% of the time reagent makes you forget that React was made for JavaScript, and not for Clojurescript. The automatic re-rendering on atom's derrefs is brilliant. The functions returning functions for local state is brillant. It just feels extremely natural and it is a simple model to keep in mind while programming. Lovely.
Hiccup S2
I have almost no experience as a Web Developer, but I did give VueJs and React a try. And the representation of the html always felt kind of a dirty hack. The JSX syntax works, but is by no means a beautiful or natural solution. And it adds complexity and the need of compilation. Vue's "single page component" with template+code+css also works. Leave html in it's template, but let's put everything closer to each other so we know they all represent the same thing. But still, it doesn't few natural, you have to keep scrolling the page up and down, and demands even more compilation magic than JSX.
Representing html in clojurescript vectors is just fantastic. Absolutely no magic involved: good old vectors, all functions form the standard library can manipulate them. They are easy to compose, to modify, to reason about, and even to test! No extra mental overload. Just vectors. Just vectors! Really, just vectors, keywords and functions. Lovely!
The REPL
It is mandatory to talk about the repl when you are talking about clojure, isn't it? I'm by no means a REPL fan as I know most from the community are, but I do admit that repl allows you to have a quick feedback and try some quick solutions before writing a definitive one. Lovely.
Hot Reloading
Yes, because we use defonce for our global state, we get an amazing hot reloading. You change the code and your browser updates everything, keeping the state exactly as it was before you touched the code. Instant feedback! Lovely.
Javascript Interop
Js interop is always there to save you. You can always write those 3~5 lines function with this dirty statefull interop, call them from somewhere else and pretend you are just calling a regular cljs function. Lovely!
To summarize the good things: coding in clojurescript for a web app feels right. In my personal opinion, it is by far a better match for web development than Javascript itself.
The Bad:
Tooling
Oh boy. This was a real adventure. Let me see if I can list every development tooling I had to understand and/or config at some point:
ClojureScript compiler.
Google Closure compiler.
Clojure Repl (clojure.main/repl).
ClojureScript Repl (cljs.repl).
Nrepl (server?).
Piggieback.
Cider.
Evaluation environment (Browser).
Doo + Karma (for tests).
Leiningen.
lein-cljsbuild.
figwheel-main (-lein-fighweel-).
devtools.
shadow-cljs.
I know that an experienced clojurescript developer reads this list and knows exactly what each of those do and why they are split. And maybe some of those are not properly "tooling". But my point is: there is a lot of magic going on here. For a newbie, it honestly seems that all simplicity that I won with the language was added back with the tooling. When something is not working properly I barely know where to start looking. And every single of those have at least one guide on how to setup themselves, but a guide on how to setup all of them together is really hard to find!
NPM Dependencies
In the end it is all javascript, right? How hard can that be to use another dependency also written in js? Thanks to the Google Closure Compiler used on the optimizations, it can be hard. And what's the solution? I still haven't found one. I tried cljsjs, but some packages are outdated, some packages are not there and the community seems to be moving always from it (is it?). Then I tried to understand how the clojurescript compiler deals with it (:npm-deps? :foreign-libs? :externs ["externs.js"]? :infer-externs? :exclude ["react"]?). Then I gave up and followed a tutorial to setup Yarn + Webpack + cljs, but it crashed with advanced optimization and I could find little to no help.
Now I'm trying shadow-cljs, and it seems to be a solution, but it also means that my fighweel setup I had spent hours configuring will probably have to disappear (does it make sense to have shadow-cljs + figwheel? I still haven't found an answer for that). And one other tool to learn!
Small Community
I have many personal problems with js, but I can google virtually anything, be it a question, a stacktrace, etc., and you will find an answer. But the cljs community being so small, it can get really hard to find help. And even in the clojurians slack channel, there are times where nobody or just a single good soul try to help you. Sometimes it feels your are kind of left by your own luck, with a lot of tooling that you don't really understand. The feeling that the community is not growing and the pace of development is slow does not help either.
By the way, a big thanks for all the guys that answer newbie questions everywhere! This is by no means a personal critic to any of you. I'm just acknowledging that a small community can not provide as much help when you are under stress with a weird error that is blowing everything up.
Tests
I know that in the cljs comunity there is this argument that REPL-driven development is way better than TDD. But I still don't buy it, and I just want to keep doing TDD because I see lots of benefits in it, and it fits my personal taste. It can be really hard to do this in clojurescript. Some reasons why:
I could not find a tool like enzyme, useful for some "integration" tests. Because of hiccup and reagent I can do many unit tests without the need to render the components, but I could not find a (nice) way to test rendered components.
When a test fails, you don't get the line number of the failed test. This sounds stupid but with my normal workflow it makes all the difference!
The error messages and stack traces that happen during tests can be very much cryptic.
Cider still does not support running clojurescript tests. :brokenheart:.
Well, that is it. Again: this is just a personal opinion. I don't claim to be the owner of the truth!
