fix(boootstrap): prevent to override existing node addon file

prelude/bootstrap.js

@@ -181,28 +181,71 @@ function copyInChunks(
 
 // TODO: replace this with fs.cpSync when we drop Node < 16
 function copyFolderRecursiveSync(source, target) {
- let files = [];
-
- // Check if folder needs to be created or integrated
+ // Build target folder
  const targetFolder = path.join(target, path.basename(source));
+
+ // Check if target folder needs to be created or integrated
  if (!fs.existsSync(targetFolder)) {
  fs.mkdirSync(targetFolder);
  }
 
  // Copy
  if (fs.lstatSync(source).isDirectory()) {
- files = fs.readdirSync(source);
- files.forEach((file) => {
+ const files = fs.readdirSync(source);
+
+ for (const file of files) {
+ // Build source name
  const curSource = path.join(source, file);
+
+ // Call this function recursively as long as source is a directory
  if (fs.lstatSync(curSource).isDirectory()) {
  copyFolderRecursiveSync(curSource, targetFolder);
  } else {
- fs.copyFileSync(
- curSource,
- path.join(targetFolder, path.basename(curSource))
- );
+ // Current source is a file, it must be available on the real filesystem
+ // instead of the virtual snapshot file system to load it by process.dlopen.
+ //
+ // Before we try to copy we do some checks.
+ // See https:/vercel/pkg/issues/1589 for more details.
+
+ // Build target file name
+ const curTarget = path.join(targetFolder, path.basename(curSource));
+
+ if (fs.existsSync(curTarget)) {
+ // Target file already exists, read source and target file...
+ const curSourceContent = fs.readFileSync(curSource, {
+ encoding: 'binary',
+ });
+ const curTargetContent = fs.readFileSync(curTarget, {
+ encoding: 'binary',
+ });
+
+ // ...and calculate checksum from source and target file
+ const curSourceHash = createHash('sha256')
+ .update(curSourceContent)
+ .digest('hex');
+ const curTargetHash = createHash('sha256')
+ .update(curTargetContent)
+ .digest('hex');
+
+ // If checksums are equal then there is nothing to do here
+ // ==> target already exists and is up-to-date
+ if (curSourceHash === curTargetHash) {
+ continue;
+ }
+ }
+
+ // Target must be copied because it either does not exist or is outdated.
+ // Due to the possibility that mutliple instances of this app start simultaneously,
+ // the copy action might fail. Only one starting instance gets write access.
+ //
+ // We don't catch any error here because it does not make sense to go ahead and to
+ // try to load the file while another instance has not yet finished the copy action.
+ // If the app start fails then the user should try to start the app later again.
+ // Unfortunately, we cannot implement delayed retries ourselves because process.dlopen
+ // is a synchronous function, promises are not supported.
+ fs.copyFileSync(curSource, curTarget);
  }
- });
+ }
  }
 }