The bsconfig.json file

The bsconfig.json file is a required file for all BuckleScript projects. Let's explore it:

// This is the configuration file used by BuckleScript's build system bsb. Its documentation lives here: http://bucklescript.github.io/bucklescript/docson/#build-schema.json
// BuckleScript comes with its own parser for bsconfig.json, which is normal JSON, with the extra support of comments and trailing commas.
{
  "name": "my-first-app",
  "version": "0.1.0",
  "sources": {
    "dir" : "src",
    "subdirs" : true
  },
  "package-specs": {
    "module": "commonjs",
    "in-source": true
  },
  "suffix": ".bs.js",
  "bs-dependencies": [
      // add your dependencies here. You'd usually install them normally through `npm install my-dependency`. If my-dependency has a bsconfig.json too, then everything will work seamlessly.
  ],
  "warnings": {
    "error" : "+101"
  },
  "namespace": true,
  "refmt": 3
}

We'll soon be changing some of these defaults to get more comfortable with BuckleScript's configuration file. Let's first add the following code to Demo.re:

type decision =
  | Yes
  | No
  | Maybe;

let decision = Maybe;

let response =
  switch (decision) {
  | Yes => "Yes!"
  | No => "I'm afraid not."
  };

Js.log(response);

As you can see, the switch expression isn't handling all possible cases of decision. Running npm run build results in the following output:

ninja: Entering directory `lib/bs'
[3/3] Building src/Demo.mlast.d
[1/1] Building src/Demo-MyFirstApp.cmj

  Warning number 8
  .../Demo.re 9:3-12:3
  
   7 │ 
   8 │ let response =
   9 │ switch (decision) {
  10 │ | Yes => "Yes!"
  11 │ | No => "I'm afraid not."
  12 │ };
  13 │ 
  14 │ Js.log(response);
  
  You forgot to handle a possible value here, for example: 
Maybe