added experimental TypeScript support

caveats:
* there's barely any abstraction here (cf. inline comment), so the only
  reason not to use TypeScript directly is module bundling via Rollup
* this plugin is getting a little bloaty, but that seems inevitable
  unless we wanna make some separate TypeScript plugin fork it or
  include hooks for a `generateTranspiler` equivalent; YAGNI for now
* more significantly, stuffing everything into the `js` config section
  seems a little risky WRT avoiding breaking changes in future evolution
* the test's sample code seems pretty silly

based on earlier efforts by @tillsc

lib/bundle/config.js

@@ -32,10 +32,12 @@ module.exports = generateConfig;
 //     * `jsx.pragma` determines the function to use for JSX expressions
 //       (e.g. `jsx: { pragma: "createElement" }`)
 //     * additionally accepts the same options as `esnext`
+// * `typescript`, if truthy, activates TypeScript transpilation - anything
+//   other than `true` will be passed through as TypeScript compiler options
 // * `compact`, if truthy, compresses the bundle's code while retaining the
 //   source code's original structure
 function generateConfig({ extensions = [], // eslint-disable-next-line indent
-		externals, format, moduleName, esnext, jsx, compact }, { browsers }) {
+		externals, format, moduleName, esnext, jsx, typescript, compact }, { browsers }) {
 	let plugins = [];
 	if(esnext || jsx) {
 		let transpiler = Object.assign({}, esnext, jsx);
@@ -54,6 +56,13 @@ function generateConfig({ extensions = [], // eslint-disable-next-line indent
 		extensions = ext.concat(extensions);
 		plugins.push(plugin);
 	}
+	if(typescript) {
+		let ts = requireOptional("rollup-plugin-typescript2",
+				"failed to activate TypeScript", "faucet-pipeline-typescript");
+		extensions.push(".ts");
+		// TODO: provide defaults and abstractions for low-level options?
+		plugins.push(typescript === true ? ts() : ts(typescript));
+	}
 
 	let resolve = { jsnext: true };
 	if(extensions.length) {

package.json

@@ -36,6 +36,7 @@
 		"eslint-config-fnd-jsx": "^1.1.0",
 		"faucet-pipeline-esnext": "file:pkg/faucet-pipeline-esnext",
 		"faucet-pipeline-jsx": "file:pkg/faucet-pipeline-jsx",
+		"faucet-pipeline-typescript": "file:pkg/faucet-pipeline-typescript",
 		"json-diff": "^0.5.2",
 		"mocha": "^5.0.1",
 		"npm-run-all": "^4.1.2",

pkg/faucet-pipeline-typescript/package.json

@@ -0,0 +1,23 @@
+{
+	"name": "faucet-pipeline-typescript",
+	"version": "1.0.0-beta.1",
+	"description": "TypeScript for faucet-pipeline",
+	"author": "FND",
+	"contributors": [
+		"Till Schulte-Coerne <[email protected]>"
+	],
+	"license": "Apache-2.0",
+	"homepage": "https://github.com/faucet-pipeline/faucet-pipeline-js",
+	"repository": {
+		"type": "git",
+		"url": "https://github.com/faucet-pipeline/faucet-pipeline-js.git"
+	},
+	"bugs": {
+		"url": "https://github.com/faucet-pipeline/faucet-pipeline-js/issues"
+	},
+	"dependencies": {
+		"faucet-pipeline-js": "1.0.0-beta.1",
+		"rollup-plugin-typescript2": "^0.11.1",
+		"typescript": "^2.7.2"
+	}
+}

test/cli/run

@@ -32,6 +32,12 @@ begin "$root/test_jsx"
 	assert_identical "./dist/bundle.js" "./expected.js"
 end
 
+begin "$root/test_typescript"
+	faucet
+	assert_identical "./dist/bundle.js" "./expected.js"
+	rm -r "./.rpt2_cache"
+end
+
 begin "$root/test_browserslist"
 	faucet
 	assert_identical "./dist/bundle.js" "./expected.js"

test/cli/test_typescript/expected.js

@@ -0,0 +1,39 @@
+(function () {
+'use strict';
+
+if(typeof global === "undefined" && typeof window !== "undefined") {
+	window.global = window;
+}
+
+var LogLevel;
+(function (LogLevel) {
+    LogLevel[LogLevel["Debug"] = 0] = "Debug";
+    LogLevel[LogLevel["Info"] = 1] = "Info";
+    LogLevel[LogLevel["Critical"] = 2] = "Critical";
+})(LogLevel || (LogLevel = {}));
+function log(level, msg) {
+    if (level === LogLevel.Critical) {
+        console.error(msg);
+    }
+    else {
+        console.log(msg);
+    }
+}
+
+var generateArticle = function (params) {
+    var title = params.title, authors = params.authors;
+    if (typeof title !== "string") {
+        log(LogLevel.Debug, "auto-generating title");
+        title = title.main + ": " + title.sub;
+    }
+    return title + "\n" + authors.join(", ");
+};
+generateArticle({
+    title: {
+        main: "Hello World",
+        sub: "sup"
+    },
+    authors: ["foo", "bar"]
+});
+
+}());

test/cli/test_typescript/faucet.config.js

@@ -0,0 +1,14 @@
+"use strict";
+
+let path = require("path");
+
+module.exports = {
+	js: [{
+		source: "./src/index.ts",
+		target: "./dist/bundle.js",
+		typescript: true
+	}],
+	plugins: {
+		js: path.resolve(__dirname, "../../..")
+	}
+};

test/cli/test_typescript/src/index.ts

@@ -0,0 +1,28 @@
+import { log, LogLevel } from "./util";
+
+interface ComplexTitle {
+	main: string;
+	sub: string;
+}
+
+interface ArticleInterface {
+	title: string | ComplexTitle;
+	authors: string[];
+}
+
+let generateArticle = (params: ArticleInterface) => {
+	let { title, authors } = params;
+	if(typeof title !== "string") {
+		log(LogLevel.Debug, "auto-generating title");
+		title = `${title.main}: ${title.sub}`;
+	}
+	return title + "\n" + authors.join(", ");
+};
+
+generateArticle({
+	title: {
+		main: "Hello World",
+		sub: "sup"
+	},
+	authors: ["foo", "bar"]
+});

test/cli/test_typescript/src/util.ts

@@ -0,0 +1,9 @@
+export enum LogLevel { Debug, Info, Critical }
+
+export function log(level: LogLevel, msg: string) {
+	if(level === LogLevel.Critical) {
+		console.error(msg);
+	} else {
+		console.log(msg);
+	}
+}