Use coincident if crossOriginIsolated, comlink otherwise (#108)

* Add comlink dependency

* Use either coincident or comlink

* typos

* cleanup

* fixes

* ready

* fixes

* Fix mounting logic

* Fix communication with comlink worker

* Linting

* Back to a working coincident setup

* Add comment as per review

---------

Co-authored-by: martinRenou <martin.renou@gmail.com>

.gitignore

@@ -128,5 +128,6 @@ dmypy.json
 experiment.sh
 env.yml
 
-# Jupyterlite cache
+# JupyterLite
 .jupyterlite.doit.db
+_output

package.json

@@ -60,7 +60,8 @@
         "@jupyterlite/server": "^0.2.0 || ^0.3.0 || ^0.4.0",
         "@lumino/coreutils": "^2",
         "@lumino/signaling": "^2",
-        "coincident": "^1.2.3"
+        "coincident": "^1.2.3",
+        "comlink": "^4.4.1"
     },
     "devDependencies": {
         "@jupyterlab/builder": "^4.1.0",

src/coincident.worker.ts

@@ -0,0 +1,80 @@
+// Copyright (c) Thorsten Beier
+// Copyright (c) JupyterLite Contributors
+// Distributed under the terms of the Modified BSD License.
+
+import coincident from 'coincident';
+
+import {
+  ContentsAPI,
+  DriveFS,
+  TDriveRequest,
+  TDriveMethod,
+  TDriveResponse
+} from '@jupyterlite/contents';
+
+import { IXeusWorkerKernel } from './tokens';
+import { XeusRemoteKernel } from './worker';
+
+const workerAPI = coincident(self) as IXeusWorkerKernel;
+
+/**
+ * An Emscripten-compatible synchronous Contents API using shared array buffers.
+ */
+export class SharedBufferContentsAPI extends ContentsAPI {
+  request<T extends TDriveMethod>(data: TDriveRequest<T>): TDriveResponse<T> {
+    return workerAPI.processDriveRequest(data);
+  }
+}
+
+/**
+ * A custom drive implementation which uses shared array buffers (via coincident) if available
+ */
+class XeusDriveFS extends DriveFS {
+  createAPI(options: DriveFS.IOptions): ContentsAPI {
+    return new SharedBufferContentsAPI(
+      options.driveName,
+      options.mountpoint,
+      options.FS,
+      options.ERRNO_CODES
+    );
+  }
+}
+
+export class XeusCoincidentKernel extends XeusRemoteKernel {
+  /**
+   * Setup custom Emscripten FileSystem
+   */
+  async mount(
+    driveName: string,
+    mountpoint: string,
+    baseUrl: string
+  ): Promise<void> {
+    const { FS, PATH, ERRNO_CODES } = globalThis.Module;
+
+    if (!FS) {
+      return;
+    }
+
+    const drive = new XeusDriveFS({
+      FS,
+      PATH,
+      ERRNO_CODES,
+      baseUrl,
+      driveName,
+      mountpoint
+    });
+
+    FS.mkdir(mountpoint);
+    FS.mount(drive, {}, mountpoint);
+    FS.chdir(mountpoint);
+  }
+}
+
+const worker = new XeusCoincidentKernel();
+
+workerAPI.initialize = worker.initialize.bind(worker);
+workerAPI.mount = worker.mount.bind(worker);
+workerAPI.ready = worker.ready.bind(worker);
+workerAPI.cd = worker.cd.bind(worker);
+workerAPI.isDir = worker.isDir.bind(worker);
+workerAPI.processMessage = worker.processMessage.bind(worker);

src/comlink.worker.ts

@@ -0,0 +1,65 @@
+// Copyright (c) Jupyter Development Team.
+// Distributed under the terms of the Modified BSD License.
+
+/**
+ * A WebWorker entrypoint that uses comlink to handle postMessage details
+ */
+
+import { expose } from 'comlink';
+
+import {
+  ContentsAPI,
+  DriveFS,
+  ServiceWorkerContentsAPI
+} from '@jupyterlite/contents';
+
+import { XeusRemoteKernel } from './worker';
+
+/**
+ * A custom drive implementation which uses the service worker
+ */
+class XeusDriveFS extends DriveFS {
+  createAPI(options: DriveFS.IOptions): ContentsAPI {
+    return new ServiceWorkerContentsAPI(
+      options.baseUrl,
+      options.driveName,
+      options.mountpoint,
+      options.FS,
+      options.ERRNO_CODES
+    );
+  }
+}
+
+export class XeusComlinkKernel extends XeusRemoteKernel {
+  /**
+   * Setup custom Emscripten FileSystem
+   */
+  async mount(
+    driveName: string,
+    mountpoint: string,
+    baseUrl: string
+  ): Promise<void> {
+    const { FS, PATH, ERRNO_CODES } = globalThis.Module;
+
+    if (!FS) {
+      return;
+    }
+
+    const drive = new XeusDriveFS({
+      FS,
+      PATH,
+      ERRNO_CODES,
+      baseUrl,
+      driveName,
+      mountpoint
+    });
+
+    FS.mkdir(mountpoint);
+    FS.mount(drive, {}, mountpoint);
+    FS.chdir(mountpoint);
+  }
+}
+
+const worker = new XeusComlinkKernel();
+
+expose(worker);

src/index.ts

@@ -76,7 +76,7 @@ const plugins = kernel_list.map((kernel): JupyterLiteServerPlugin<void> => {
             ...options,
             contentsManager,
             mountDrive,
-            kernelspec
+            kernelSpec: kernelspec
           });
         }
       });

src/tokens.ts

@@ -0,0 +1,89 @@
+// Copyright (c) Jupyter Development Team.
+// Distributed under the terms of the Modified BSD License.
+
+/**
+ * Definitions for the Xeus kernel.
+ */
+
+import {
+  TDriveMethod,
+  TDriveRequest,
+  TDriveResponse
+} from '@jupyterlite/contents';
+
+import { IWorkerKernel } from '@jupyterlite/kernel';
+
+/**
+ * An interface for Xeus workers.
+ */
+export interface IXeusWorkerKernel extends IWorkerKernel {
+  /**
+   * Handle any lazy initialization activities.
+   */
+  initialize(options: IXeusWorkerKernel.IOptions): Promise<void>;
+
+  /**
+   * Process drive request
+   * @param data
+   */
+  processDriveRequest<T extends TDriveMethod>(
+    data: TDriveRequest<T>
+  ): TDriveResponse<T>;
+
+  /**
+   * Process a message sent from the main thread to the worker.
+   * @param msg
+   */
+  processMessage(msg: any): void;
+
+  /**
+   * Process worker message
+   * @param msg
+   */
+  processWorkerMessage(msg: any): void;
+
+  /**
+   * Register a callback for handling messages from the worker.
+   */
+  registerCallback(callback: (msg: any) => void): void;
+
+  /**
+   * Whether the kernel is ready.
+   * @returns a promise that resolves when the kernel is ready.
+   */
+  ready(): Promise<void>;
+
+  /**
+   * Mount a drive
+   * @param driveName The name of the drive
+   * @param mountpoint The mountpoint of the drive
+   * @param baseUrl The base URL of the server
+   */
+  mount(driveName: string, mountpoint: string, baseUrl: string): Promise<void>;
+
+  /**
+   * Change the current working directory
+   * @param path The path to change to
+   */
+  cd(path: string): Promise<void>;
+
+  /**
+   * Check if a path is a directory
+   * @param path The path to check
+   */
+  isDir(path: string): Promise<boolean>;
+}
+
+/**
+ * An namespace for Xeus workers.
+ */
+export namespace IXeusWorkerKernel {
+  /**
+   * Initialization options for a worker.
+   */
+  export interface IOptions extends IWorkerKernel.IOptions {
+    baseUrl: string;
+    kernelSpec: any;
+    mountDrive: boolean;
+  }
+}