Add Reason asset type

package.json

@@ -14,6 +14,7 @@
     "babylon": "^6.17.4",
     "babylon-walk": "^1.0.2",
     "browser-resolve": "^1.11.2",
+    "bsb-js": "^1.0.1",
     "chalk": "^2.1.0",
     "chokidar": "^1.7.0",
     "commander": "^2.11.0",

src/Parser.js

@@ -12,6 +12,8 @@ class Parser {
     this.registerExtension('es6', './assets/JSAsset');
     this.registerExtension('jsm', './assets/JSAsset');
     this.registerExtension('mjs', './assets/JSAsset');
+    this.registerExtension('ml', './assets/ReasonAsset');
+    this.registerExtension('re', './assets/ReasonAsset');
     this.registerExtension('ts', './assets/TypeScriptAsset');
     this.registerExtension('tsx', './assets/TypeScriptAsset');
     this.registerExtension('coffee', './assets/CoffeeScriptAsset');

src/assets/ReasonAsset.js

@@ -0,0 +1,28 @@
+const bsb = require('bsb-js');
+const fs = require('fs');
+const JSAsset = require('./JSAsset');
+const promisify = require('../utils/promisify');
+const readFile = promisify(fs.readFile);
+
+class ReasonAsset extends JSAsset {
+  async parse(code) {
+    // This runs BuckleScript - the Reason to JS compiler.
+    // Other Asset types use `localRequire` but the `bsb-js` package already
+    // does that internally. This should also take care of error handling in
+    // the Reason compilation process.
+    if (process.env.NODE_ENV !== 'test') {
+      await bsb.runBuild();
+    }
+
+    // This is a simplified use-case for Reason - it only loads the recommended
+    // BuckleScript configuration to simplify the file processing.
+    const outputFile = this.name.replace(/\.(re|ml)$/, '.bs.js');
+    const outputContent = await readFile(outputFile);
+    this.contents = outputContent.toString();
+
+    // After loading the compiled JS source, use the normal JS behavior.
+    return await super.parse(this.contents);
+  }
+}
+
+module.exports = ReasonAsset;

test/integration/reason/index.js

@@ -0,0 +1,5 @@
+var local = require('./local.re');
+
+module.exports = function () {
+  return local.a + local.b;
+};

test/integration/reason/local.re

@@ -0,0 +1,3 @@
+let a = 1;
+
+let b = 2;

test/reason.js

@@ -0,0 +1,16 @@
+const assert = require('assert');
+const fs = require('fs');
+const {bundle, run, assertBundleTree} = require('./utils');
+
+describe('reason', function() {
+  it('should produce a bundle', async function() {
+    let b = await bundle(__dirname + '/integration/reason/index.js');
+
+    assert.equal(b.assets.size, 2);
+    assert.equal(b.childBundles.size, 0);
+
+    let output = run(b);
+    assert.equal(typeof output, 'function');
+    assert.equal(output(), 3);
+  });
+});