add support for loading loaders via import()

.travis.yml

@@ -4,6 +4,8 @@ node_js:
   - "6"
   - "8"
   - "10"
+  - "12"
+  - "14"
   - node
 script: npm run travis
 

lib/LoaderRunner.js

@@ -72,9 +72,10 @@ function createLoaderObject(loader) {
 				obj.ident = undefined;
 			} else {
 				if(!value.loader)
-					throw new Error("request should be a string or object with loader and object (" + JSON.stringify(value) + ")");
+					throw new Error("request should be a string or object with loader and options (" + JSON.stringify(value) + ")");
 				obj.path = value.loader;
 				obj.fragment = value.fragment || "";
+				obj.type = value.type;
 				obj.options = value.options;
 				obj.ident = value.ident;
 				if(obj.options === null)

lib/loadLoader.js

@@ -1,23 +1,42 @@
 var LoaderLoadingError = require("./LoaderLoadingError");
+var url;
 
 module.exports = function loadLoader(loader, callback) {
-	try {
-		var module = require(loader.path);
-	} catch(e) {
-		// it is possible for node to choke on a require if the FD descriptor
-		// limit has been reached. give it a chance to recover.
-		if(e instanceof Error && e.code === "EMFILE") {
-			var retry = loadLoader.bind(null, loader, callback);
-			if(typeof setImmediate === "function") {
-				// node >= 0.9.0
-				return setImmediate(retry);
-			} else {
-				// node < 0.9.0
-				return process.nextTick(retry);
+	if(loader.type === "module") {
+		try {
+			if(url === undefined) url = require("url");
+			var loaderUrl = url.pathToFileURL(loader.path);
+			var modulePromise = eval("import(" + JSON.stringify(loaderUrl.toString()) + ")");
+			modulePromise.then(function(module) {
+				handleResult(loader, module, callback);
+			}, callback);
+			return;
+		} catch(e) {
+			callback(e);
+		}
+	} else {
+		try {
+			var module = require(loader.path);
+		} catch(e) {
+			// it is possible for node to choke on a require if the FD descriptor
+			// limit has been reached. give it a chance to recover.
+			if(e instanceof Error && e.code === "EMFILE") {
+				var retry = loadLoader.bind(null, loader, callback);
+				if(typeof setImmediate === "function") {
+					// node >= 0.9.0
+					return setImmediate(retry);
+				} else {
+					// node < 0.9.0
+					return process.nextTick(retry);
+				}
 			}
+			return callback(e);
 		}
-		return callback(e);
+		return handleResult(loader, module, callback);
 	}
+};
+
+function handleResult(loader, module, callback) {
 	if(typeof module !== "function" && typeof module !== "object") {
 		return callback(new LoaderLoadingError(
 			"Module '" + loader.path + "' is not a loader (export function or es6 module)"
@@ -32,4 +51,4 @@ module.exports = function loadLoader(loader, callback) {
 		));
 	}
 	callback();
-};
+}

test/fixtures/esm-loader.mjs

@@ -0,0 +1,3 @@
+export default function(source) {
+	return source + "-esm";
+};

test/runLoaders.js

@@ -607,6 +607,28 @@ describe("runLoaders", function() {
 		});
 		delete global.System;
 	});
+	if(+process.versions.modules >= 83) {
+		it("should load a loader using import()", function(done) {
+			runLoaders({
+				resource: path.resolve(fixtures, "resource.bin"),
+				loaders: [
+					{
+						loader: path.resolve(fixtures, "esm-loader.mjs"),
+						type: "module"
+					}
+				]
+			}, function(err, result) {
+				if(err) return done(err);
+				result.result.should.be.eql(["resource-esm"]);
+				result.cacheable.should.be.eql(true);
+				result.fileDependencies.should.be.eql([
+					path.resolve(fixtures, "resource.bin")
+				]);
+				result.contextDependencies.should.be.eql([]);
+				done();
+			});
+		});
+	}
 	describe("getContext", function() {
 		var TESTS = [
 			["/", "/"],