Add pre-serve build step to check if node_modules are up-to-date

.gitignore

@@ -1,4 +1,5 @@
 dist
+.tmp
 
 .vscode
 .idea

build/check-npm.js

@@ -0,0 +1,39 @@
+/* eslint-disable no-bitwise */
+
+const fs = require("fs");
+const path = require("path");
+const proc = require("child_process");
+
+function getHash(string) {
+  let hash = 0;
+  for (let i = 0; i < string.length; i++) {
+    const char = string.charCodeAt(i);
+    hash = ((hash << 5) - hash) + char;
+    // Convert to 32bit integer
+    hash &= hash;
+  }
+  return hash.toString();
+}
+
+const hashPath = path.resolve(__dirname, "../.tmp/package-lock.json.hash");
+let currentHash = undefined;
+if (fs.existsSync(hashPath)) {
+  currentHash = fs.readFileSync(hashPath, { encoding: "utf-8" });
+}
+
+const packageLockPath = path.resolve(__dirname, "../package-lock.json");
+const packageLockContents = fs.readFileSync(packageLockPath, { encoding: "utf-8" });
+const newHash = getHash(packageLockContents);
+
+if (newHash !== currentHash) {
+  const tmpPath = path.resolve(__dirname, "../.tmp");
+  if (!fs.existsSync(tmpPath)) {
+    fs.mkdirSync(tmpPath);
+  }
+
+  // eslint-disable-next-line no-console
+  console.log("package-lock.json changes were detected");
+  console.log("Running 'npm ci' (this might take a while)...");
+  proc.execSync("npm ci");
+  fs.writeFileSync(hashPath, newHash, {});
+}

package.json

@@ -1,7 +1,7 @@
 {
   "private": true,
   "scripts": {
-    "serve": "vue-cli-service serve",
+    "serve": "node build/check-npm.js && vue-cli-service serve",
     "build": "vue-cli-service build && node build/post-build.js",
     "lint": "vue-cli-service lint"
   },