Screeps: How do I set up source map using TypeScript and Webpack?

Question

I'm trying to set my new Screeps (the game) project from scratch using TypeScript (^2.9.2) and Webpack (^4.12.1). How do I properly set up source maps? What I did:

1. Set "sourceMap": true, in tsconfig.json
2. Set devtool: 'inline-source-map', in webpack.config.js. I imagine inline is a must for Screeps?
3. Set loader: "source-map-loader", for test: /\.ts$/, enforce: 'pre', in webpack config to not loose TS source maps.

In my main.ts, which right now is just console.log(foo); results in:

ReferenceError: foo is not defined
    at Object../src/main.ts:98:13
    at __webpack_require__:20:30
    at eval:84:18
    at main:87:10
    at eval:105:4
    at Object.<anonymous>:2:143759
    at Object.r.run:2:144268```

This is the case in the Screeps client console. In Firefox I only see foo is not defined without any more specific information.

Is there any way I would get /src/main.ts:1:13 (proper line number) somewhere in the stacktrace? This looks like there would be no source map whatsoever, but there is one in the main.js build at the bottom:

//# sourceMappingURL=data:application/json;charset=utf-8;base64,eyJ2ZXJzaW9uIjozLCJzb3VyY2VzIjpbIndlYnBhY2s6Ly8vd2VicGFjay9ib290c3RyYXAiLCJ3ZWJwYWNrOi8vLy4vc3JjL21haW4udHMiXSwibmFtZXMiOltdLCJtYXBwaW5ncyI6IjtBQUFBO0FBQ0E7O0FBRUE7QUFDQTs7QUFFQTtBQUNBO0FBQ0E7QUFDQTtBQUNBO0FBQ0E7QUFDQTtBQUNBO0FBQ0E7QUFDQTs7QUFFQTtBQUNBOztBQUVBO0FBQ0E7O0FBRUE7QUFDQTtBQUNBOzs7QUFHQTtBQUNBOztBQUVBO0FBQ0E7O0FBRUE7QUFDQTtBQUNBO0FBQ0Esa0RBQTBDLGdDQUFnQztBQUMxRTtBQUNBOztBQUVBO0FBQ0E7QUFDQTtBQUNBLGdFQUF3RCxrQkFBa0I7QUFDMUU7QUFDQSx5REFBaUQsY0FBYztBQUMvRDs7QUFFQTtBQUNBO0FBQ0E7QUFDQTtBQUNBO0FBQ0E7QUFDQTtBQUNBO0FBQ0E7QUFDQTtBQUNBO0FBQ0EsaURBQXlDLGlDQUFpQztBQUMxRSx3SEFBZ0gsbUJBQW1CLEVBQUU7QUFDckk7QUFDQTs7QUFFQTtBQUNBO0FBQ0E7QUFDQSxtQ0FBMkIsMEJBQTBCLEVBQUU7QUFDdkQseUNBQWlDLGVBQWU7QUFDaEQ7QUFDQTtBQUNBOztBQUVBO0FBQ0EsOERBQXNELCtEQUErRDs7QUFFckg7QUFDQTs7O0FBR0E7QUFDQTs7Ozs7Ozs7Ozs7Ozs7QUNsRkEsT0FBTyxDQUFDLEdBQUcsQ0FBQyxVQUFVLENBQUMsQ0FBQyIsImZpbGUiOiJtYWluLmpzIiwic291cmNlc0NvbnRlbnQiOlsiIFx0Ly8gVGhlIG1vZHVsZSBjYWNoZVxuIFx0dmFyIGluc3RhbGxlZE1vZHVsZXMgPSB7fTtcblxuIFx0Ly8gVGhlIHJlcXVpcmUgZnVuY3Rpb25cbiBcdGZ1bmN0aW9uIF9fd2VicGFja19yZXF1aXJlX18obW9kdWxlSWQpIHtcblxuIFx0XHQvLyBDaGVjayBpZiBtb2R1bGUgaXMgaW4gY2FjaGVcbiBcdFx0aWYoaW5zdGFsbGVkTW9kdWxlc1ttb2R1bGVJZF0pIHtcbiBcdFx0XHRyZXR1cm4gaW5zdGFsbGVkTW9kdWxlc1ttb2R1bGVJZF0uZXhwb3J0cztcbiBcdFx0fVxuIFx0XHQvLyBDcmVhdGUgYSBuZXcgbW9kdWxlIChhbmQgcHV0IGl0IGludG8gdGhlIGNhY2hlKVxuIFx0XHR2YXIgbW9kdWxlID0gaW5zdGFsbGVkTW9kdWxlc1ttb2R1bGVJZF0gPSB7XG4gXHRcdFx0aTogbW9kdWxlSWQsXG4gXHRcdFx0bDogZmFsc2UsXG4gXHRcdFx0ZXhwb3J0czoge31cbiBcdFx0fTtcblxuIFx0XHQvLyBFeGVjdXRlIHRoZSBtb2R1bGUgZnVuY3Rpb25cbiBcdFx0bW9kdWxlc1ttb2R1bGVJZF0uY2FsbChtb2R1bGUuZXhwb3J0cywgbW9kdWxlLCBtb2R1bGUuZXhwb3J0cywgX193ZWJwYWNrX3JlcXVpcmVfXyk7XG5cbiBcdFx0Ly8gRmxhZyB0aGUgbW9kdWxlIGFzIGxvYWRlZFxuIFx0XHRtb2R1bGUubCA9IHRydWU7XG5cbiBcdFx0Ly8gUmV0dXJuIHRoZSBleHBvcnRzIG9mIHRoZSBtb2R1bGVcbiBcdFx0cmV0dXJuIG1vZHVsZS5leHBvcnRzO1xuIFx0fVxuXG5cbiBcdC8vIGV4cG9zZSB0aGUgbW9kdWxlcyBvYmplY3QgKF9fd2VicGFja19tb2R1bGVzX18pXG4gXHRfX3dlYnBhY2tfcmVxdWlyZV9fLm0gPSBtb2R1bGVzO1xuXG4gXHQvLyBleHBvc2UgdGhlIG1vZHVsZSBjYWNoZVxuIFx0X193ZWJwYWNrX3JlcXVpcmVfXy5jID0gaW5zdGFsbGVkTW9kdWxlcztcblxuIFx0Ly8gZGVmaW5lIGdldHRlciBmdW5jdGlvbiBmb3IgaGFybW9ueSBleHBvcnRzXG4gXHRfX3dlYnBhY2tfcmVxdWlyZV9fLmQgPSBmdW5jdGlvbihleHBvcnRzLCBuYW1lLCBnZXR0ZXIpIHtcbiBcdFx0aWYoIV9fd2VicGFja19yZXF1aXJlX18ubyhleHBvcnRzLCBuYW1lKSkge1xuIFx0XHRcdE9iamVjdC5kZWZpbmVQcm9wZXJ0eShleHBvcnRzLCBuYW1lLCB7IGVudW1lcmFibGU6IHRydWUsIGdldDogZ2V0dGVyIH0pO1xuIFx0XHR9XG4gXHR9O1xuXG4gXHQvLyBkZWZpbmUgX19lc01vZHVsZSBvbiBleHBvcnRzXG4gXHRfX3dlYnBhY2tfcmVxdWlyZV9fLnIgPSBmdW5jdGlvbihleHBvcnRzKSB7XG4gXHRcdGlmKHR5cGVvZiBTeW1ib2wgIT09ICd1bmRlZmluZWQnICYmIFN5bWJvbC50b1N0cmluZ1RhZykge1xuIFx0XHRcdE9iamVjdC5kZWZpbmVQcm9wZXJ0eShleHBvcnRzLCBTeW1ib2wudG9TdHJpbmdUYWcsIHsgdmFsdWU6ICdNb2R1bGUnIH0pO1xuIFx0XHR9XG4gXHRcdE9iamVjdC5kZWZpbmVQcm9wZXJ0eShleHBvcnRzLCAnX19lc01vZHVsZScsIHsgdmFsdWU6IHRydWUgfSk7XG4gXHR9O1xuXG4gXHQvLyBjcmVhdGUgYSBmYWtlIG5hbWVzcGFjZSBvYmplY3RcbiBcdC8vIG1vZGUgJiAxOiB2YWx1ZSBpcyBhIG1vZHVsZSBpZCwgcmVxdWlyZSBpdFxuIFx0Ly8gbW9kZSAmIDI6IG1lcmdlIGFsbCBwcm9wZXJ0aWVzIG9mIHZhbHVlIGludG8gdGhlIG5zXG4gXHQvLyBtb2RlICYgNDogcmV0dXJuIHZhbHVlIHdoZW4gYWxyZWFkeSBucyBvYmplY3RcbiBcdC8vIG1vZGUgJiA4fDE6IGJlaGF2ZSBsaWtlIHJlcXVpcmVcbiBcdF9fd2VicGFja19yZXF1aXJlX18udCA9IGZ1bmN0aW9uKHZhbHVlLCBtb2RlKSB7XG4gXHRcdGlmKG1vZGUgJiAxKSB2YWx1ZSA9IF9fd2VicGFja19yZXF1aXJlX18odmFsdWUpO1xuIFx0XHRpZihtb2RlICYgOCkgcmV0dXJuIHZhbHVlO1xuIFx0XHRpZigobW9kZSAmIDQpICYmIHR5cGVvZiB2YWx1ZSA9PT0gJ29iamVjdCcgJiYgdmFsdWUgJiYgdmFsdWUuX19lc01vZHVsZSkgcmV0dXJuIHZhbHVlO1xuIFx0XHR2YXIgbnMgPSBPYmplY3QuY3JlYXRlKG51bGwpO1xuIFx0XHRfX3dlYnBhY2tfcmVxdWlyZV9fLnIobnMpO1xuIFx0XHRPYmplY3QuZGVmaW5lUHJvcGVydHkobnMsICdkZWZhdWx0JywgeyBlbnVtZXJhYmxlOiB0cnVlLCB2YWx1ZTogdmFsdWUgfSk7XG4gXHRcdGlmKG1vZGUgJiAyICYmIHR5cGVvZiB2YWx1ZSAhPSAnc3RyaW5nJykgZm9yKHZhciBrZXkgaW4gdmFsdWUpIF9fd2VicGFja19yZXF1aXJlX18uZChucywga2V5LCBmdW5jdGlvbihrZXkpIHsgcmV0dXJuIHZhbHVlW2tleV07IH0uYmluZChudWxsLCBrZXkpKTtcbiBcdFx0cmV0dXJuIG5zO1xuIFx0fTtcblxuIFx0Ly8gZ2V0RGVmYXVsdEV4cG9ydCBmdW5jdGlvbiBmb3IgY29tcGF0aWJpbGl0eSB3aXRoIG5vbi1oYXJtb255IG1vZHVsZXNcbiBcdF9fd2VicGFja19yZXF1aXJlX18ubiA9IGZ1bmN0aW9uKG1vZHVsZSkge1xuIFx0XHR2YXIgZ2V0dGVyID0gbW9kdWxlICYmIG1vZHVsZS5fX2VzTW9kdWxlID9cbiBcdFx0XHRmdW5jdGlvbiBnZXREZWZhdWx0KCkgeyByZXR1cm4gbW9kdWxlWydkZWZhdWx0J107IH0gOlxuIFx0XHRcdGZ1bmN0aW9uIGdldE1vZHVsZUV4cG9ydHMoKSB7IHJldHVybiBtb2R1bGU7IH07XG4gXHRcdF9fd2VicGFja19yZXF1aXJlX18uZChnZXR0ZXIsICdhJywgZ2V0dGVyKTtcbiBcdFx0cmV0dXJuIGdldHRlcjtcbiBcdH07XG5cbiBcdC8vIE9iamVjdC5wcm90b3R5cGUuaGFzT3duUHJvcGVydHkuY2FsbFxuIFx0X193ZWJwYWNrX3JlcXVpcmVfXy5vID0gZnVuY3Rpb24ob2JqZWN0LCBwcm9wZXJ0eSkgeyByZXR1cm4gT2JqZWN0LnByb3RvdHlwZS5oYXNPd25Qcm9wZXJ0eS5jYWxsKG9iamVjdCwgcHJvcGVydHkpOyB9O1xuXG4gXHQvLyBfX3dlYnBhY2tfcHVibGljX3BhdGhfX1xuIFx0X193ZWJwYWNrX3JlcXVpcmVfXy5wID0gXCJcIjtcblxuXG4gXHQvLyBMb2FkIGVudHJ5IG1vZHVsZSBhbmQgcmV0dXJuIGV4cG9ydHNcbiBcdHJldHVybiBfX3dlYnBhY2tfcmVxdWlyZV9fKF9fd2VicGFja19yZXF1aXJlX18ucyA9IFwiLi9zcmMvbWFpbi50c1wiKTtcbiIsImNvbnNvbGUubG9nKCdJdCB3b3JrcycpO1xuIl0sInNvdXJjZVJvb3QiOiIifQ==

Answer 1

Phew, I managed to make it work. Here's what needs to be done:

1. In webpack config:

   • Set target to 'node'

     config.target = 'node';
     

   • Set output library target to commonjs2

     config.output.libraryTarget = 'commonjs2';
     

   • Set your regular devtool

     config.devtool = 'source-map';
     

     Inline source-maps won't work in Screeps.

   • Set externals

     config.externals = {
       'main.js.map': 'main.js.map',
     };
     

   This is so that we can write require('main.js.map') in our code to load source map file in Screeps runtime and so that Webpack leave it alone.

2. In tsconfig.json set up config.compilerOptions.sourceMap to true.

3. Upload your code to Screeps server:

   • Upload your main.js bundle file as usual.
   • Upload your source map file. Name it main.js.map.js. The last .js is important - Screeps game will cut it off leaving desired main.js.map.

4. Parse your source map by yourself in runtime!

   • yarn add source-map/npm -i source-map --save.
   • Leave it at version ^0.6.1. ^0.7 (latest at the moment) is async only. Async code doesn't work in Screeps.
   • Use it to build your stacktrace message error by hand. Then print it using console.log().
   • Yes, this cost in-game CPU. Cache your error messages, so that when you encounter new error you only parse it once instead of in every tick.
   • Also, source map won't work in the simulation mode (I wish I knew that faster).

5. Wrap your code around error mapper:

   export const loop = () => {
     errorMapper(tick)();
   };
   
   const tick = () => { /* your regular code for current tick */};
   

6. Happy debugging in sane way!

---

Actually, this is my error-mapper.ts:

import { escape } from 'lodash';
import { MappedPosition, SourceMapConsumer } from 'source-map'; // leave it at version ^0.6.1. ^0.7 is async only.

export default function errorMapper(tick: () => void): () => void {
    return () => {
        try {
            tick();
        } catch (error) {
            if (error instanceof Error) {
                const isSimulation: boolean = ('sim' in Game.rooms);
                if (isSimulation) {
                    printOriginalError(error);
                } else {
                    printStackTrace(error);
                }
            } else {
                throw error;
            }
        }
    };
}

// tslint:disable-next-line: no-var-requires
const consumer: SourceMapConsumer = new SourceMapConsumer(require('main.js.map')); // High CPU usage!
const cache: { [key: string]: string } = {};

function getSourceMapStackTrace(error: Error | string): string {
    const originalStackTrace: string = error instanceof Error ? error.stack as string : error;
    if (cache[originalStackTrace]) {
        return cache[originalStackTrace];
    }

    const re = /^\s+at\s+(.+?\s+)?\(?([0-z._\-\\\/]+):(\d+):(\d+)\)?$/gm;
    let match: RegExpExecArray | null;
    let outputStackTrace: string = error.toString();

    // tslint:disable-next-line:no-conditional-assignment
    while ((match = re.exec(originalStackTrace)) !== null) {
        const nameFromOriginalStackTrace: string = match[1];
        const isStackTraceLineControlledByMe: boolean = match[2] === 'main';
        const lineFromOriginalStackTrace: number = parseInt(match[3], 10);
        const columnFromOriginalStackTrace: number = parseInt(match[4], 10);

        if (!isStackTraceLineControlledByMe) {
            break;
        }

        const { name, source, line, column }: MappedPosition = consumer.originalPositionFor({
            column: columnFromOriginalStackTrace,
            line: lineFromOriginalStackTrace,
        });

        if (!line) {
            break;
        }

        const finalName = (name) ? name : (nameFromOriginalStackTrace) ? nameFromOriginalStackTrace : '';

        outputStackTrace += stripWebpackFromStackTrace(
            `\n    at ${finalName}(${source}:${line}:${column})`,
        );
    }

    cache[originalStackTrace] = outputStackTrace;
    return outputStackTrace;
}

function printOriginalError(error: Error) {
    const message = `Source maps don't work in the Simulation mode.`;
    console.log(`<span style="color: tomato">${message}\n${escape(error.stack)}</span>`);
}

function printStackTrace(error: Error) {
    const errorMessage = escape(getSourceMapStackTrace(error));
    console.log(`<span style="color: tomato">${errorMessage}</span>`);
    Game.notify(errorMessage);
}

function stripWebpackFromStackTrace(text: string): string {
    return text.replace('webpack:///', '');
}

---

Also, thanks to screeps-typescript-starter, because it helped me a lot to understand source-map library usage in Screeps use case. I probably wouldn't have to spent too much on this problem, if I didn't want to write and understand all of my Screeps code and stick to Webpack. :)