Fix race condition in mod asset extraction

Author: rubensworks

lib/modloader/ModLoader.ts

@@ -1,9 +1,8 @@
 import type { ChildProcess } from 'node:child_process';
 import { exec } from 'node:child_process';
-import { createWriteStream } from 'node:fs';
 import * as fs from 'node:fs';
 import * as Path from 'node:path';
-import { dirname, join, sep } from 'node:path';
+import { dirname, join } from 'node:path';
 import { promisify } from 'node:util';
 import { ncp } from 'ncp';
 import fetch from 'node-fetch';
@@ -333,42 +332,66 @@ export class ModLoader {
       openZip(modFile, { lazyEntries: true, autoClose: true }, (e, f) => {
         if (e) {
           reject(e);
+        } else {
+          resolve(f);
         }
-        resolve(f);
       });
     });
 
-    zipFile.readEntry();
-    zipFile.on('error', e => process.stdout.write(String(e)));
-    zipFile.on('entry', (entry: Entry) => {
-      if (entry.fileName.endsWith('/')) {
-        // Directory
-        zipFile.readEntry();
-      } else if (entry.fileName.startsWith('assets/') || entry.fileName.startsWith('data/')) {
-        // File
-        const prefix = entry.fileName.startsWith('assets/') ? 7 : 5;
-        const targetFile = join(
-          this.path,
-          'mod_assets',
-          entry.fileName.slice(prefix, entry.fileName.length),
-        );
-        const targetDir = dirname(targetFile);
-        void this.ensureDirExists(targetDir).then(() => {
-          zipFile.openReadStream(entry, (e, readStream) => {
-            if (e) {
-              throw e;
-            }
-            readStream.pipe(createWriteStream(targetFile));
-            readStream.on('end', () => zipFile.readEntry());
-          });
-        }).catch((e: unknown) => {
-          throw e;
-        });
-      } else {
-        zipFile.readEntry();
-      }
+    await new Promise<void>((resolve, reject) => {
+      let settled = false;
+      const settle = (err?: Error): void => {
+        console.log(`Settling with error: ${err}`);
+        if (settled) {
+          return;
+        }
+        settled = true;
+        if (err) {
+          zipFile.close();
+          reject(err);
+        } else {
+          resolve();
+        }
+      };
+
+      zipFile.on('error', (err: Error) => settle(err));
+      zipFile.on('end', () => settle());
+      zipFile.on('entry', (entry: Entry) => {
+        console.log(`Processing entry: ${entry.fileName}`);
+        if (entry.fileName.endsWith('/')) {
+          // Directory
+          zipFile.readEntry();
+        } else if (entry.fileName.startsWith('assets/') || entry.fileName.startsWith('data/')) {
+          // File
+          const prefix = entry.fileName.startsWith('assets/') ? 7 : 5;
+          const targetFile = join(
+            this.path,
+            'mod_assets',
+            entry.fileName.slice(prefix, entry.fileName.length),
+          );
+          const targetDir = dirname(targetFile);
+          fs.promises.mkdir(targetDir, { recursive: true }).then(() => {
+            zipFile.openReadStream(entry, (e, readStream) => {
+              if (e) {
+                settle(e);
+                return;
+              }
+              const chunks: Buffer[] = [];
+              readStream.on('data', (chunk: Buffer) => chunks.push(chunk));
+              readStream.on('error', (err: Error) => settle(err));
+              readStream.on('end', () => {
+                fs.promises.writeFile(targetFile, Buffer.concat(chunks))
+                  .then(() => zipFile.readEntry())
+                  .catch((err: Error) => settle(err));
+              });
+            });
+          }).catch((err: Error) => settle(err));
+        } else {
+          zipFile.readEntry();
+        }
+      });
+      zipFile.readEntry();
     });
-    await new Promise(resolve => zipFile.on('end', resolve));
   }
 
   /**
@@ -393,18 +416,6 @@ export class ModLoader {
   public async removeMods(): Promise<void> {
     await promisify(rimraf)(join(this.path, 'mods'));
   }
-
-  protected async ensureDirExists(path: string): Promise<void> {
-    const segments = path.slice(this.path.length, this.path.length + path.length).split(sep);
-    for (let i = 1; i <= segments.length; i++) {
-      const subPath = join(this.path, segments.slice(0, i).join(sep));
-      try {
-        await fs.promises.stat(subPath);
-      } catch {
-        await fs.promises.mkdir(subPath);
-      }
-    }
-  }
 }
 
 export interface IModLoaderArgs {