Over rated vs under rated: ReasonReact

Over rated vs under rated” is a game the economist Tyler Cowen plays at the end of his podcast. I recently built a simple wizard app using ReasonReact. The app walks you through a Cognitive Behavioral Therapy (CBT) technique to make decisions. This post is my hot take on what is “over rated/under rated” in ReasonReact. This is not a hot take on ReasonML the language.

Under rated

  1. The type inference: I did not provide any type annotations. The type checker inferred everything. It inferred the correct types and found bugs in my code. Compared to Flow, the JS type thing I have used, this was delightful. Not providing type annotations but still getting type checking is extremely under rated.

  2. Compiler errors: The error messages when compiling code were spot on. ReasonML has the most helpful spot on obvious error messages amongst all the programming languages I have used. I did not have to look up what a particular error message meant. This is huge for a programming language I am using for the first time.

  3. Automatic module resolution: My code is not littered with the noise of import/export statements. The compiler figures out the modules or tells me politely when it cannot. Half my JS code is usually import/export statements. Specifically the filenames have to be unique across the whole project in a ReasonML app. This abstracts away the file system and allows you to move files around without changing code.

  4. File local modules: To start a new scope within a file, I can use module ChildComponent { syntax. In this scope I can have a local type called state or a variable called component. My Flow/JS code when creating child components within the same file would have names with a noisy prefix type ChildSubcomponentFooState = ….. Local modules solves this problem elegantly.

  5. Built in reducer: The built in reducer forces code modularity, by pushing most of the business logic to the reducers. This makes it easy for most of my components to be stateless.

  6. Miscellaneous: Builds are fast. The switch statements are ergonomic. It is React adjacent, learning ReasonReact is easy if you know React. The robust Ocaml standard library available in ReasonML has most things I need.

Over rated

  1. JSX support: I had to annotate every string inside JSX with ReasonReact.string . I can see why the type-system needs it but, it was a buzzkill when writing a lot of layout jsx.

  2. Styles: The current way of doing styles via a styles object is extremely verbose. The API is type safe but it makes it cumbersome to use. The community is working on fixing the styles story.

  3. No dynamic imports: There is no story around code-splitting a big ReasonApp yet. There is an open issue to support dynamic imports. I loved ReasonML. It made programming joyful again. It was verbose than expected. The language and tooling seem quite well polished.

I am sheki and I approve of ReasonML.