Discourage direct Lua file modification (#84)

gulpfile.js

@@ -5,6 +5,7 @@ const renderSvg = require('./tools/resvg');
 const minifyLua = require('./tools/luamin');
 const compileMoonscript = require('./tools/moonscript');
 const optimizeLua = require ('./tools/optimizations');
+const discourageLuaMod = require ('./tools/discourageLuaModification');
 
 const lastRunCache = new Map();
 function lastRunIgnoreErrors(task) {
@@ -67,6 +68,7 @@ function moon() {
 	return gulp.src('src/**/*.moon', { since: lastRunIgnoreErrors(moon) })
 		.pipe(compileMoonscript())
 		.pipe(optimizeLua())
+		.pipe(discourageLuaMod())
 		// .pipe(minifyLua())
 		.pipe(gulp.dest('dest', { mode: 0777 }));
 }

tools/discourageLuaModification.js

@@ -0,0 +1,54 @@
+const { Transform } = require('stream');
+
+const { streamToBuffer } = require('./util');
+
+const LUA_FILE_PREFIX =
+`-- !!! THIS FILE IS COMPILED !!!
+-- This gamemode is written in Moonscript, and its source code is available
+-- here: https://github.com/NotMyWing/GarrysModAmongUs
+-- The code you see here is the result of compiled code, and is probably not
+-- something you want to edit directly. Please consider editing the original
+-- gamemode source off GitHub instead.`;
+
+/**
+ * Discourage direct Lua file modification by notifying users where to find
+ * the uncompiled gamemode source code.
+ */
+class DiscourageLuaModificationTransform extends Transform {
+
+	constructor() {
+		super({ objectMode: true });
+	}
+
+	/**
+	 * Transforms a file.
+	 * @param {Object} file The file to process.
+	 * @param {string} encoding The encoding of the file.
+	 * @param {Function} next A callback function.
+	 */
+	_transform(file, encoding, next) {
+		if (file.isNull()) {
+			return next(null, file);
+		}
+
+		if (file.isStream()) {
+			streamToBuffer(file.contents, (err, contents) => {
+				if (err) this.emit('error', err);
+				else {
+					const code = contents.toString(encoding);
+					file.contents = Buffer.from(LUA_FILE_PREFIX + '\n\n' + code, encoding);
+					next(null, file);
+				}
+			});
+		}
+
+		if (file.isBuffer()) {
+			const code = file.contents.toString(encoding);
+			file.contents = Buffer.from(LUA_FILE_PREFIX + '\n\n' + code, encoding);
+			next(null, file);
+		}
+	}
+}
+
+module.exports = () => new DiscourageLuaModificationTransform();
+module.exports.DiscourageLuaModificationTransform = DiscourageLuaModificationTransform;