Add ability to conditionally apply patches per platform (Linux, Mac, Windows)

Change-type: patch

package.json

@@ -45,7 +45,7 @@
     ]
   },
   "scripts": {
-    "postinstall": "patch-package --patch-dir patches0 && patch-package",
+    "postinstall": "node patches/apply-patches.js",
     "prebuild": "rimraf build/ build-bin/",
     "build": "npm run build:src && npm run catch-uncommitted",
     "build:src": "npm run lint && npm run build:fast && npm run build:test && npm run build:doc",

patches/apply-patches.js

@@ -0,0 +1,80 @@
+/**
+ * @license
+ * Copyright 2020 Balena Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+const { execFile } = require('child_process');
+const fs = require('fs');
+const path = require('path');
+
+const { promisify } = require('util');
+
+const execFileAsync = promisify(execFile);
+const patchesDir = 'patches';
+
+/** Run the patch-package tool in a child process and wait for it to finish */
+async function patchPackage(patchDir) {
+	// Equivalent to: `npx patch-package --patch-dir $patchDir`
+	const result = await execFileAsync('node', [
+		path.join('node_modules', 'patch-package', 'index.js'),
+		'--patch-dir',
+		patchDir,
+	]);
+	for (const out of [result.stdout, result.stderr]) {
+		if (out) {
+			if (out.includes('ERROR') || out.includes('Failed to apply')) {
+				throw new Error(out);
+			} else {
+				console.error(out);
+			}
+		}
+	}
+}
+
+/**
+ * Apply patch files found in the following directories, if they exist:
+ *   * patches/before-all - applied before all other patches
+ *   * patches/all        - patch files common to all platforms
+ *   * patches/unix       - patch files for Linux and macOS
+ *   * patches/darwin     - patch files for macOS only
+ *   * patches/linux      - patch files for Linux only
+ *   * patches/win32      - patch files for Windows only
+ */
+async function applyPatches() {
+	const isUnix = ['linux', 'darwin'].includes(process.platform);
+	const patchDirs = [
+		path.join(patchesDir, 'before-all'),
+		path.join(patchesDir, 'all'),
+		...(isUnix ? [path.join(patchesDir, 'unix')] : []),
+		path.join(patchesDir, process.platform),
+	];
+	for (const patchDir of patchDirs) {
+		if (fs.existsSync(patchDir)) {
+			console.error(`Applying patches from "${patchDir}"...`);
+			await patchPackage(patchDir);
+		}
+	}
+}
+
+async function run() {
+	try {
+		await applyPatches();
+	} catch (err) {
+		console.error(`Failed to apply some patches:\n${err}`);
+		process.exitCode = 1;
+	}
+}
+
+run();

tsconfig.dev.json

@@ -3,6 +3,7 @@
 	"include": [
 		"./automation/**/*",
 		"./lib/**/*",
+		"./patches/*",
 		"./tests/**/*",
 		"./typings/**/*",
 		"gulpfile.js"