Fix issues around multiple downloads (#13)

.npmignore

@@ -0,0 +1,7 @@
+tools
+biome.json
+jest.config.js
+test
+config
+__mocks__
+.github

CHANGELOG.md

@@ -1,3 +1,8 @@
+# 3.2.0 (2024-08-04)
+
+- Fix issues around starting multiple downloads at the same time.
+- No longer need to use `await` before a download call when multiple downloads are started at the same time.
+
 # 3.1.1 (2024-07-31)
 
 - Added more debug logging

README.md

@@ -25,8 +25,6 @@ import { ElectronDownloadManager } from 'electron-dl-manager';
 const manager = new ElectronDownloadManager();
 
 // Start a download
-// You *must* call manager.download() with await or 
-// you may get unexpected behavior
 const id = await manager.download({
   window: browserWindowInstance,
   url: 'https://example.com/file.zip',
@@ -188,8 +186,6 @@ interface DownloadManagerConstructorParams {
 
 Starts a file download. Returns the `id` of the download.
 
-**You must call `download()` with `await` or you may get unexpected behavior.**
-
 ```typescript
 download(params: DownloadParams): Promise<string>
 ```

package.json

@@ -1,6 +1,6 @@
 {
   "name": "electron-dl-manager",
-  "version": "3.1.1",
+  "version": "3.2.0",
   "description": "A library for implementing file downloads in Electron with 'save as' dialog and id support.",
   "main": "dist/cjs/index.js",
   "module": "dist/esm/index.js",

src/ElectronDownloadManager.ts

@@ -9,12 +9,34 @@ import type {
 } from "./types";
 import { truncateUrl } from "./utils";
 
+/**
+ * This is used to solve an issue where multiple downloads are started at the same time.
+ * For example, Promise.all([download1, download2, ...]) will start both downloads at the same
+ * time. This is problematic because the will-download event is not guaranteed to fire in the
+ * order that the downloads were started.
+ *
+ * So we use this to make sure that will-download fires in the order that the downloads were
+ * started by executing the downloads in a sequential fashion.
+ *
+ * For more information see:
+ * https://github.com/theogravity/electron-dl-manager/issues/11
+ */
+class DownloadQueue {
+  private promise = Promise.resolve() as unknown as Promise<string>;
+
+  add(task: () => Promise<string>): Promise<string> {
+    this.promise = this.promise.then(() => task());
+    return this.promise;
+  }
+}
+
 /**
  * Enables handling downloads in Electron.
  */
 export class ElectronDownloadManager implements IElectronDownloadManager {
   protected downloadData: Record<string, DownloadData>;
   protected logger: DebugLoggerFn;
+  private downloadQueue = new DownloadQueue();
 
   constructor(params: DownloadManagerConstructorParams = {}) {
     this.downloadData = {};
@@ -88,30 +110,33 @@ export class ElectronDownloadManager implements IElectronDownloadManager {
    * Returns the id of the download.
    */
   async download(params: DownloadConfig): Promise<string> {
-    return new Promise((resolve, reject) => {
-      try {
-        if (params.saveAsFilename && params.saveDialogOptions) {
-          return reject(Error("You cannot define both saveAsFilename and saveDialogOptions to start a download"));
-        }
-
-        const downloadInitiator = new DownloadInitiator({
-          debugLogger: this.logger,
-          onCleanup: (data) => {
-            this.cleanup(data);
-          },
-          onDownloadInit: (data) => {
-            this.downloadData[data.id] = data;
-            resolve(data.id);
-          },
-        });
-
-        this.log(`[${downloadInitiator.getDownloadId()}] Registering download for url: ${truncateUrl(params.url)}`);
-        params.window.webContents.session.once("will-download", downloadInitiator.generateOnWillDownload(params));
-        params.window.webContents.downloadURL(params.url, params.downloadURLOptions);
-      } catch (e) {
-        reject(e);
-      }
-    });
+    return this.downloadQueue.add(
+      () =>
+        new Promise<string>((resolve, reject) => {
+          try {
+            if (params.saveAsFilename && params.saveDialogOptions) {
+              return reject(Error("You cannot define both saveAsFilename and saveDialogOptions to start a download"));
+            }
+
+            const downloadInitiator = new DownloadInitiator({
+              debugLogger: this.logger,
+              onCleanup: (data) => {
+                this.cleanup(data);
+              },
+              onDownloadInit: (data) => {
+                this.downloadData[data.id] = data;
+                resolve(data.id);
+              },
+            });
+
+            this.log(`[${downloadInitiator.getDownloadId()}] Registering download for url: ${truncateUrl(params.url)}`);
+            params.window.webContents.session.once("will-download", downloadInitiator.generateOnWillDownload(params));
+            params.window.webContents.downloadURL(params.url, params.downloadURLOptions);
+          } catch (e) {
+            reject(e);
+          }
+        }),
+    );
   }
 
   protected cleanup(data: DownloadData) {
@@ -161,3 +186,16 @@ export class ElectronDownloadManager implements IElectronDownloadManager {
     dbg.detach();
   }
 }
+
+function waitTicks(n: number): Promise<void> {
+  return new Promise((resolve) => {
+    function tick(count: number) {
+      if (count <= 0) {
+        resolve();
+      } else {
+        process.nextTick(() => tick(count - 1));
+      }
+    }
+    tick(n);
+  });
+}