npm/firmware: add version constant

This adds a string constant to get the firmware version of the files
included in the package.

Issue: pybricks/support#412

npm/firmware/.gitignore

@@ -0,0 +1 @@
+version.ts

npm/firmware/CHANGELOG.md

@@ -1,3 +1,7 @@
+## Unreleased
+### Added
+- Added firmware version constant.
+
 ## 4.13.0-alpha.3 - 2021-07-19
 ### Changed
 - Updated firmware to v3.1.0a3.

npm/firmware/index.test.ts

@@ -4,10 +4,14 @@
 import * as fs from 'fs';
 import * as path from 'path';
 import * as util from 'util';
-import { FirmwareReader, FirmwareReaderErrorCode } from '.';
+import { firmwareVersion, FirmwareReader, FirmwareReaderErrorCode } from '.';
 
 const readFile = util.promisify(fs.readFile);
 
+test('firmware version', () => {
+    expect(firmwareVersion).toMatch(/^\d+\.\d+\.\d+/);
+});
+
 test('bad zip data', async () => {
     try {
         await FirmwareReader.load(new Uint8Array(100));

npm/firmware/index.ts

@@ -1,7 +1,13 @@
 // SPDX-License-Identifier: MIT
-// Copyright (c) 2020 The Pybricks Authors
+// Copyright (c) 2020-2021 The Pybricks Authors
 
 import JSZip, { JSZipObject } from 'jszip';
+import {PACKAGE_VERSION} from './version';
+
+/**
+ * String containing the firmware version.
+ */
+export const firmwareVersion = PACKAGE_VERSION.substring(PACKAGE_VERSION.lastIndexOf('v') + 1);
 
 /**
  * LEGO Powered Up Hub IDs

npm/firmware/package.json

@@ -19,6 +19,7 @@
     "author": "The Pybricks Authors",
     "license": "MIT",
     "scripts": {
+        "prebuild": "node -p \"'export const PACKAGE_VERSION = ' + JSON.stringify(require('./package.json').version) + ';'\" > version.ts",
         "build": "./download-firmware.py && tsc",
         "test": "tsc && jest"
     },