Drop support for custom extensions

Also, simplify the extensions logic

Author: moonglum

lib/bundle/babel.js

@@ -7,7 +7,6 @@ module.exports = function generateTranspiler({ esnext, jsx, exclude }, { browser
 		babelHelpers: "bundled"
 	};
 	let plugins = [];
-	let extensions = [];
 
 	if(exclude) {
 		settings.exclude = exclude.map(pkg => {
@@ -32,7 +31,6 @@ module.exports = function generateTranspiler({ esnext, jsx, exclude }, { browser
 	}
 
 	if(jsx) {
-		extensions.push(".jsx");
 		let { pragma, pragmaFrag } = jsx;
 		plugins.push(["@babel/plugin-transform-react-jsx",
 			{ pragma, pragmaFrag }]);
@@ -45,7 +43,6 @@ module.exports = function generateTranspiler({ esnext, jsx, exclude }, { browser
 	let babel = loadExtension("@rollup/plugin-babel",
 			"failed to activate ESNext transpiler", "faucet-pipeline-esnext");
 	return {
-		plugin: babel.default(settings),
-		extensions
+		plugin: babel.default(settings)
 	};
 };

lib/bundle/config.js

@@ -21,8 +21,6 @@ let NAMELESS_MODULES = new Set(["es", "amd", "cjs"]); // NB: Rollup identifiers
 module.exports = generateConfig;
 
 // generates Rollup configuration
-// * `extensions` is a list of additional file extensions for loading modules
-//   (e.g. `[".jsx"]`)
 // * `externals` determines which modules/packages to exclude from the bundle
 //   (e.g. `{ jquery: "jQuery" }` - the key refers to the respective
 //   module/package name, the value refers to a corresponding global variable)
@@ -47,19 +45,20 @@ module.exports = generateConfig;
 // * `sourcemaps`, if truthy, activates inline source-map generation
 // * `compact`, if truthy, compresses the bundle's code - see `determineCompacting`
 //    for compression levels, determined by the respective value
-function generateConfig({ extensions = [], // eslint-disable-next-line indent
-		externals, format, exports, // eslint-disable-next-line indent
+function generateConfig({ externals, format, exports, // eslint-disable-next-line indent
 		esnext, jsx, typescript, // eslint-disable-next-line indent
 		sourcemaps, compact }, { browsers }) {
 	let cfg = { sourcemap: sourcemaps };
 	let plugins = [];
+	let extensions = [".js"];
 
 	if(esnext || jsx) {
 		let transpiler = Object.assign({}, esnext, jsx);
 		if(esnext) {
 			transpiler.esnext = true;
 		}
 		if(jsx) {
+			extensions.push(".jsx");
 			// just to be safe, discard JSX-specifics on parent object
 			delete transpiler.pragma;
 			delete transpiler.fragment;
@@ -76,8 +75,7 @@ function generateConfig({ extensions = [], // eslint-disable-next-line indent
 			console.error("transpiling JavaScript for", browsers.join(", "));
 		}
 
-		let { plugin, extensions: ext } = generateTranspiler(transpiler, { browsers });
-		extensions = ext.concat(extensions);
+		let { plugin } = generateTranspiler(transpiler, { browsers });
 		plugins.push(plugin);
 	}
 	if(typescript) {
@@ -88,13 +86,8 @@ function generateConfig({ extensions = [], // eslint-disable-next-line indent
 		plugins.push(typescript === true ? ts() : ts(typescript));
 	}
 
-	let resolve = {};
-	if(extensions.length) {
-		resolve.extensions = [".js"].concat(extensions);
-	}
-
 	plugins = plugins.concat([
-		nodeResolve(resolve),
+		nodeResolve({ extensions }),
 		commonjs({ include: "node_modules/**" })
 	]);
 	if(compact) {

test/unit/test_bundling.js

@@ -118,27 +118,6 @@ console.log("[\\u2026] ".concat(MYLIB)); // eslint-disable-line no-console
 			});
 	});
 
-	it("should support custom file extensions", () => {
-		let config = [{
-			source: "./src/index.coffee",
-			target: "./dist/bundle.js",
-			extensions: [".coffee"]
-		}];
-		let assetManager = new MockAssetManager(FIXTURES_DIR);
-
-		return faucetJS(config, assetManager, DEFAULT_OPTIONS)().
-			then(_ => {
-				assetManager.assertWrites([{
-					filepath: path.resolve(FIXTURES_DIR, "./dist/bundle.js"),
-					content: makeBundle(`
-var helper = { foo: "lorem", bar: "ipsum" };
-
-console.log(\`[…] $\{helper}\`); // eslint-disable-line no-console
-					`)
-				}]);
-			});
-	});
-
 	it("should support customizing bundle's API", () => {
 		let config = [{
 			source: "./src/lib.js",