Collect text usage during build step

ts-collect-textkeys.js

var es = require('event-stream');
var fs = require('fs');
var mkdirp = Promise.denodeify(require('mkdirp'));
var path = require('path');
var plumber = require('gulp-plumber');
var Promise = require('promise');
var ts = require('typescript');
var typescript = require('gulp-typescript');

var paths = {
  source: "../src",
  output: "../dist",
  textkeys: "../build/META-INF/frontend-textkeys.conf"
};

var typescriptCompiler = typescriptCompiler || null;

gulp.task('build-typescript', function() {
	if (!typescriptCompiler) {
		typescriptCompiler = typescript.createProject('tsconfig.json', {
			typescript: ts
		});
	}

	return gulp.src(paths.source)
			.pipe(plumber())
			.pipe(sourcemaps.init({loadMaps: true}))
			.pipe(collectTextUsage())
			.pipe(typescript(typescriptCompiler))
			.pipe(sourcemaps.write({includeContent: true}))
			.pipe(gulp.dest(paths.output));
});

function collectTextUsage() {
	var textkeys = new Set();

	return es.through(function(file) {
		this.emit('data', file);

		var fileSource = file.contents.toString();
		var fileNode = ts.createSourceFile(file.path, fileSource, ts.ScriptTarget.ES5, false);

		function extractTextKeys(node) {
			if (node.kind === ts.SyntaxKind.StringLiteral) {
				textkeys.add(node.text);
			}
			ts.forEachChild(node, extractTextKeys);
		}
		function checkNode(node) {
			if (node.kind === ts.SyntaxKind.Decorator) {
				var code = fileSource.substring(node.pos, node.end).trim();
				if (code.match(/^@text(Promise)?\(/)) {
					extractTextKeys(node);
				}
			} else {
				ts.forEachChild(node, checkNode);
			}
		}

		checkNode(fileNode);

	}, function() {
		var textArray = Array.from(textkeys.values());
		textArray.sort();
		mkdirp(path.dirname(paths.textkeys), function() {
			var fileHandle = fs.openSync(paths.textkeys, "w");
			fs.writeSync(fileHandle, textArray.join("\n"));
			fs.closeSync(fileHandle);
			this.emit('end');
		}.bind(this));
	});
}