Extension Migration Guide#

JupyterLab 3.x to 4.x#


With JupyterLab 4.x, the npm package version policy changed to not bump major version with the Python package unless required to ease extension compatibility.

API breaking changes#

Here is a list of JupyterLab npm packages that encountered API changes and therefore have bumped their major version (following semver convention). We want to point out particularly @jupyterlab/documentsearch and @jupyterlab/toc API that have been fully reworked.

  • @jupyterlab/application from 3.x to 4.x

    Major version bump to allow alternate ServiceManager implementations in JupyterFrontEnd. Specifically this allows the use of a mock manager. This also makes the JupyterLab.IOptions more permissive to not require a shell when options are given and allow a shell that meets the ILabShell interface. As a consequence, all other @jupyterlab/ packages have their major version bumped too. See jupyterlab/jupyterlab#11537 for more details.

  • @jupyterlab/apputils from 3.x to 4.x

    Rename IToolbarWidgetRegistry.registerFactory to IToolbarWidgetRegistry.addFactory

  • @jupyterlab/buildutils from 3.x to 4.x
    • The create-theme script has been removed. If you want to create a new theme extension, you should use the Theme Cookiecutter instead.

    • The add-sibling script has been removed. Check out Development workflow for source extensions instead.

    • The exitOnUuncaughtException util function has been renamed to exitOnUncaughtException (typo fix).

  • @jupyterlab/cells from 3.x to 4.x

    MarkdownCell.toggleCollapsedSignal renamed MarkdownCell.headingCollapsedChanged To support notebook windowing, cell widget children (e.g. the editor or the output area) are not instantiated when the cell is attached to the notebook. You can test for isPlaceholder() to see if the cell has been fully instantiated or wait for the promise ready to be resolved. Additionally an attribute inViewport and a signal inViewportChanged are available to test if the cell is attached to the DOM. If you instantiate standalone cells outside of a notebook, you will probably need to set the constructor option placeholder to false to ensure direct rendering of the cell.

  • @jupyterlab/completer from 3.x to 4.x

    Major version was bumped following major refactor aimed at performance improvements and enabling easier third-party integration.

    • Adding custom completion suggestions (items):
      • In 3.x and earlier adding custom completion items required re-registering the completer connector for each file/cell using register method of old manager provided by ICompletionManager token; in 4.x this token and associated ICompletableAttributes interface was removed and a proper method of registering a custom source of completions (a provider of completions) was added. To create a completer provider for JupyterLab, users need to implement the ICompletionProvider interface and then register this provider with ICompletionProviderManager token.

      • In 3.x merging completions from different sources had to be performed by creating a connector internally merging results from other connectors. in 4.x IProviderReconciliator is used to merge completions from multiple providers, and can be customised in constructor for custom completion handlers (CompletionHandler); customizing reconciliator in JupyterLab-managed completers is not yet possible.

    • Rendering with Completer.IRenderer:
      • In 3.x it was not possible to easily swap the renderer of JupyterLab-managed completers. In 4.x the renderer from the completion provider with highest rank is now used for all JupyterLab-managed completers. This behaviour is subject to revision in the future (please leave feedback).

      • Completer box is now using delayed rendering for off-screen content to improve time to first paint for top suggestions. To position the completer without rendering all items we search for the widest item using heuristic which can be adjusted in custom renderers (itemWidthHeuristic).

      • The documentation panel now implements a loading indicator (a progress bar) customizable via optional createLoadingDocsIndicator renderer method.

      • createItemNode was removed in favour of createCompletionItemNode which is now required.

      • createCompletionItemNode is no longer responsible for sanitization of labels which is now a responsibility of the model (see below).

    • Model:
      • In 3.x it was not possible to easily swap the model of JupyterLab-managed completers. In 4.x the model factory from the completion provider with highest rank is now used for JupyterLab-managed completers. This behaviour is subject to revision in the future (please leave feedback).

      • Old methods for updating and accessing the completion items: setOptions, options, and items were removed in favour of completionItems and setCompletionItems which are now required members of Completer.IModel.

      • New signal queryChanged was added and has to be emitted by models.

      • Model is now responsible for sanitization of labels and preserving original label on insertText attribute (if not already defined); this change was required to properly handle escaping of HTML tags.

  • @jupyterlab/codeeditor from 3.x to 4.x
    • Remove ISelectionStyle (and therefore defaultSelectionStyle and IEditor.selectionStyle). This was envisaged for real-time collaboration. But this is not used in the final implementation.

  • @jupyterlab/console from 3.x to 4.x

    The type of IConsoleHistory.sessionContext has been updated to ISessionContext | null instead of ISessionContext. This might break the compilation of plugins accessing the sessionContext from a ConsoleHistory, in particular those with the strict null checks enabled.

  • @jupyterlab/coreutils from 3.x to 4.x

    The Time namespace does not use the moment library anymore for managing dates. Instead it switched to using the Intl API now available in modern web browsers. The Time.format function is still available but does not accept the timeFormat argument anymore.

  • @jupyterlab/debugger from 3.x to 4.x
    • The command debugger:pause command ID has been renamed debugger:pause-on-exceptions to avoid ambiguity with pausing the current running thread.

  • @jupyterlab/docmanager from 3.x to 4.x
    • The renameDialog now receives the DocumentRegistry.Context instead of a path.

    • The interface DocumentManager.IWidgetOpener is now IDocumentWidgetOpener and is provided by a new plugin @jupyterlab/docmanager-extension:opener. The IDocumentWidgetOpener interface also now defines an `opened` signal that is emitted when a widget is opened.

    • Removed the property docProviderFactory from the interface DocumentManager.IOptions.

  • @jupyterlab/docprovider from 3.x to 4.x
    • WebSocketProviderWithLocks has been renamed to WebSocketProvider. acquireLock, releaseLock, requestInitialContent and putInitializedState have been removed from IDocumentProvider. renameAck is not optional anymore in IDocumentProvider.

    • Removed the token and type IDocumentProviderFactory.

    • Removed the property collaborative from the interface WebSocketProvider.IOptions. It doesn’t extend from IDocumentProviderFactory.IOptions. And the ymodel attribute has been renamed model.

  • @jupyterlab/documentsearch from 3.x to 4.x
    • @jupyterlab/documentsearch:plugin has been renamed to @jupyterlab/documentsearch-extension:plugin

    • @jupyterlab/documentsearch:labShellWidgetListener has been renamed to @jupyterlab/documentsearch-extension:labShellWidgetListener

    This may impact application configuration (for instance if the plugin was disabled). The search provider API has been fully reworked. But the logic is similar, for new type of documents you will need to register a ISearchProviderFactory to the ISearchProviderRegistry. The factory will build a ISearchProvider for the document widget.

  • @jupyterlab/extensionmanager from 3.x to 4.x

    The frontend API has been drastically reduced to fetch all information from the backend. It is now advised that you implement a custom ExtensionManager class for your needs rather than overriding the frontend plugins. See jupyterlab/extensions/pypi.py for an example using PyPI.org and pip. You can then register your manager by defining an entry point in the Python package; see pyproject.toml::project.entry-points."jupyterlab.extension_manager_v1".

  • @jupyterlab/fileeditor from 3.x to 4.x

    Remove the class FileEditorCodeWrapper, instead, you can use CodeEditorWrapper from @jupyterlab/codeeditor.

  • @jupyterlab/filebrowser from 3.x to 4.x

    Remove the property defaultBrowser from the interface IFileBrowserFactory. The default browser is now provided by it own plugin by requiring the token IDefaultFileBrowser.

  • @jupyterlab/filebrowser-extension from 3.x to 4.x

    Remove command filebrowser:create-main-launcher. You can replace by launcher:create (same behavior) All launcher creation actions are moved to @jupyterlab/launcher-extension.

  • @jupyterlab/galata from 4.x to 5.x
    • ContentsHelper and galata.newContentsHelper have new constructor arguments to use Playwright API request object: new ContentsHelper(baseURL, page?, request?) -> new ContentsHelper(request?, page?) galata.newContentsHelper(baseURL, page?, request?) -> galata.newContentsHelper(request?, page?) you need to provide request or page; they both are fixtures provided by Playwright.

    • galata.Mock.clearRunners(baseURL, runners, type) -> galata.Mock.clearRunners(request, runners, type)

  • @jupyterlab/docregistry from 3.x to 4.x
    • Removed the property docProviderFactory from the interface Context.IOptions.

    • The constructor of the class DocumentModel receives a parameter DocumentModel.IOptions.

    • The method IModelFactory.createNew receives a parameter DocumentRegistry.IModelOptions.

    • The method TextModelFactory.createNew receives a parameter DocumentModel.IOptions.

  • @jupyterlab/notebook from 3.x to 4.x
    • The NotebookPanel._onSave method is now private.

    • NotebookActions.collapseAll method renamed to NotebookActions.collapseAllHeadings.

    • Command Collapsible_Headings:Toggle_Collapse renamed to notebook:toggle-heading-collapse.

    • Command Collapsible_Headings:Collapse_All renamed to notebook:collapse-all-headings.

    • Command Collapsible_Headings:Expand_All renamed to notebook:expand-all-headings.

    • To support windowing, a new method scrollToItem(index, behavior) is available to scroll to any cell that may or may not be in the DOM. And new cellInViewportChanged signal is available to listen for cells entering or leaving the viewport (in windowing mode). And scrollToCell(cell) is now returning a Promise<void> calling internally scrollToItem.

    • fullyRendered, placeholderCellRendered and remainingCellToRenderCount have been removed. The defer rendering mode still exists. It will render some cells during spare CPU Idle time.

    • Settings numberCellsToRenderDirectly, remainingTimeBeforeRescheduling, renderCellOnIdle, observedTopMargin and observedBottomMargin have been removed. Instead a windowingMode with value of defer, full or none and overscanCount have been added to manage the rendering mode.

    • Added the property sharedModel to the interface NotebookModel.IOptions.

    • The method NotebookModelFactory.createNew receives a parameter NotebookModelFactory.IModelOptions.

  • @jupyterlab/rendermime from 3.x to 4.x The markdown parser has been extracted to its own plugin @jupyterlab/markedparser-extension:plugin that provides a new token IMarkdownParser (defined in @jupyterlab/rendermime). Consequently the IRendererFactory.createRenderer has a new option markdownParser.

  • @jupyterlab/rendermime-interfaces from 3.x to 4.x Remove IRenderMime.IRenderer.translator? attribute; the translator object is still passed to the constructor if needed by the renderer factory.

  • @jupyterlab/services from 6.x to 7.x
    • Remove Contents.IDrive.modelDBFactory and Contents.IManager.getModelDBFactory.

    • Added Contents.IDrive.sharedModelFactory and Contents.IManager.getsharedModelFactory.

  • @jupyterlab/shared-models from 3.x to 4.x

    The createCellFromType function has been renamed to createCellModelFromSharedType

  • @jupyterlab/statusbar from 3.x to 4.x Setting @jupyterlab/statusbar-extension:plugin . startMode moved to @jupyterlab/application-extension:shell . startMode Plugin @jupyterlab/statusbar-extension:mode-switch renamed to @jupyterlab/application-extension:mode-switch Plugin @jupyterlab/statusbar-extension:kernel-status renamed to @jupyterlab/apputils-extension:kernel-status Plugin @jupyterlab/statusbar-extension:running-sessions-status renamed to @jupyterlab/apputils-extension:running-sessions-status Plugin @jupyterlab/statusbar-extension:line-col-status renamed to @jupyterlab/codemirror-extension:line-col-status HoverBox component moved from @jupyterlab/apputils to @jupyterlab/ui-components.

  • @jupyterlab/terminal from 3.x to 4.x Xterm.js upgraded from 4.x to 5.x IThemeObject.selection renamed to selectionBackground

  • @jupyterlab/toc from 3.x to 4.x

    @jupyterlab/toc:plugin renamed @jupyterlab/toc-extension:registry This may impact application configuration (for instance if the plugin was disabled). The namespace TableOfContentsRegistry has been renamed TableOfContents. The API has been fully reworked. The new table of content providers must implement a factory TableOfContents.IFactory that will create a model TableOfContents.IModel<TableOfContents.IHeading> for supported widget. The model provides a list of headings described by a text and a level and optionally a prefix, a collapsed state and a dataset (data DOM attributes dictionary).

  • @jupyterlab/ui-components from 3.x to 4.x
    • Major version bumped following removal of Blueprint JS dependency. Extensions using proxied components like Checkbox, Select or Intent will need to import them explicitly from Blueprint JS library. Extensions using Button, Collapse or InputGroup may need to switch to the Blueprint components as the interfaces of those components in JupyterLab do not match those of Blueprint JS.

    • Remove Collapse React component.

    • Form component registry changes:
      • Rename the plugin '@jupyterlab/ui-components-extension:form-component-registry' to '@jupyterlab/ui-components-extension:form-renderer-registry'

      • Rename the IFormComponentRegistry token to IFormRendererRegistry, from @jupyterlab/ui-components:ISettingEditorRegistry to @jupyterlab/ui-components:IFormRendererRegistry.

      • The FormRendererRegistry registers IFormRenderer instead of Field renderers. A IFormRenderer defines a fieldRenderer (this is the renderer to set for backward compatibility) or a widgetRenderer. The renderer id must follow the convention <ISettingRegistry.IPlugin.id>.<propertyName>. This is to ensure a custom renderer is not used for property with the same name but different schema.

  • @jupyterlab/translation from 3.x to 4.x

    Renamed the method locale into the property languageCode in the NullTranslator

  • jupyter.extensions.hub-extension from 3.x to 4.x
    • Renamed jupyter.extensions.hub-extension to @jupyterlab/hub-extension:plugin.

    • Renamed jupyter.extensions.hub-extension:plugin to @jupyterlab/hub-extension:menu.

  • TypeScript 4.7 update

    As a result of the update to TypeScript 4.7, a couple of interfaces have had their definitions changed. The anchor parameter of HoverBox.IOptions is now a DOMRect instead of ClientRect. The CodeEditor.ICoordinate interface now extends DOMRectReadOnly instead of JSONObject, ClientRect.

  • React 18.2.0 update The update to React 18.2.0 (from 17.0.1) should be propagated to extensions as well. Here is the documentation about the migration to react 18.

Testing with Jest#

Jest has been updated to 29.2.0 (and ts-jest to 29.0.0). And therefore the jest configuration provided by @jupyterlab/testutils is compatible for that version. In particular:

  • The unmaintained reporter jest-summary-reporter has been replaced by the new default github-actions reporter.

  • The helper flakyIt has been removed. You can use the new jest.retryTimes instead.

With JupyterLab 4, we fixed circular dependencies due to the testutils package. So it is now only a facade to export helpers from various core packages. The exported helpers are the same as before expect for:

  • NBTestUtils.DEFAULT_CONTENT: Removed - you could imported from @jupyterlab/notebook/lib/testutils but we strongly advice not to and to use your own test data.

  • NBTestUtils.DEFAULT_CONTENT_45: Removed

Extension Development Changes#

  • The externalExtensions field in the dev_mode/package.json file corresponding to the @jupyterlab/application-top private package has now been removed in 4.0. If you were using this field to develop source extensions against a development build of JupyterLab, you should instead switch to the federated extensions system (via the --extensions-in-dev-mode flag) or to using the --splice-source option. See Developing a prebuilt extension and Development workflow for source extensions for more information.

  • The webpack dependency in @jupyterlab/builder has been updated to 5.72 (or newer). Base rules have been updated to use the Asset Modules instead of the previous file-loader, raw-loader and url-loader. This might affect third-party extensions if they were relying on specific behaviors from these loaders.

  • In JupyterLab 3.x, the CSS for a _disabled_ prebuilt extensions would still be loaded on the page. This is no longer the case in JupyterLab 4.0.

  • window.jupyterlab is not exposed anymore when starting JupyterLab with the --expose-app-in-browser flag. Use window.jupyterapp instead.

JupyterLab 3.5 to 3.6#

Real-Time Collaboration#

In JupyterLab v3.6, it is necessary to install Jupyter Server v2.0 to use real-time collaboration. This requirement was introduced to take advantage of the new identity API in Jupyter Server v2.0.

On the other side, we also changed how JupyterLab loads documents (only in collaborative mode). Instead of using the content API, now the provider opens a WebSocket connection to the YDocWebSocketHandler, which is implemented in an external jupyter server extension.

In addition, the shared models’ package was moved to an external package called @jupyter/ydoc. All the extensions that depend on @jupyterlab/shared-models will need to update to depend in @jupyter/ydoc@~0.2.2; the API should be the same.

API Changes: To be able to fix RTC and make it stable. It was necessary to change the API and make a few breaking changes. These changes should not affect the vast majority of extensions. They will only affect a couple of extensions focused on RTC.

It was necessary to change the paradigm of how JupyterLab loads documents and replace the locking mechanism in the back-end. Instead of identifying the first client to open the document, it now centralizes the process by instantiating a YDoc client in the back-end. This client is the only one that loads the content of the document into memory and shares it with every other client connected.

The involved packages are:

  • @jupyterlab/docprovider:
    • The interface IDocumentProvider, now extends from IDisposable. Removed: acquireLock, releaseLock, setPath, destroy, requestInitialContent and putInitializedState. Added: ready and isDisposed.

    • IDocumentProviderFactory.IOptions is now templated with T extends ISharedDocument = ISharedDocument. And the ymodel attribute has been renamed model typed T (relaxing typing from YDocument to ISharedDocument).

    • WebSocketProviderWithLocks has been renamed to WebSocketProvider. It does not extend WebSocketProvider from y-websocket anymore.

    • WebSocketProvider.IOptions has a new optional attribute, user.

  • @jupyterlab/services:
    • The interface IManager has a new optional property, user that implement User.IManager.

    • The ServiceManager class implements the optional property user from the IManager.

JupyterLab 3.0 to 3.1#

New main and context menus customization#

JupyterLab 3.1 introduces a new way to hook commands into Main Menu and Context Menu. It allows the final user to customize those menus through settings as it is already possible for the shortcuts. Using the API is not recommended any longer except to create dynamic menus.

Jest configuration update#

If you are using jest to test your extension, some new ES6 packages dependencies are added to JupyterLab. They need to be ignore when transforming the code with Jest. You will need to update the transformIgnorePatterns to match:

const esModules = [

// ...

transformIgnorePatterns: [`/node_modules/(?!${esModules}).+`]

For more information, have a look at Testing your extension.


Here is an example of pull request to update to JupyterLab 3.1 in @jupyterlab/git extension: jupyterlab/jupyterlab-git#files

JupyterLab 2.x to 3.x#

Here are some helpful tips for migrating an extension from JupyterLab 2.x to JupyterLab 3.x.

Upgrading library versions manually#

To update the extensions so it is compatible with the 3.0 release, update the compatibility range of the @jupyterlab dependencies in the package.json. The diff should be similar to:

index 6f1562f..3fcdf37 100644
^^^ a/package.json
+++ b/package.json
   "dependencies": {
-    "@jupyterlab/application": "^2.0.0",
+    "@jupyterlab/application": "^3.0.0",

Upgrading library versions using the upgrade script#

JupyterLab 3.0 provides a script to upgrade an existing extension to use the new extension system and packaging.

First, make sure to update to JupyterLab 3.0 and install jupyter-packaging and cookiecutter. With pip:

pip install jupyterlab -U
pip install jupyter-packaging cookiecutter

Or with conda:

conda install -c conda-forge jupyterlab=3 jupyter-packaging cookiecutter

Then at the root folder of the extension, run:

python -m jupyterlab.upgrade_extension .

The upgrade script creates the necessary files for packaging the JupyterLab extension as a Python package, such as setup.py and pyproject.toml.

The upgrade script also updates the dependencies in package.json to the ^3.0.0 packages. Here is an example diff:

index 6f1562f..3fcdf37 100644
^^^ a/package.json
+++ b/package.json
@@ -29,9 +29,13 @@
   "scripts": {
-    "build": "tsc",
-    "build:labextension": "npm run clean:labextension && mkdirp myextension/labextension && cd myextension/labextension && npm pack ../..",
-    "clean": "rimraf lib tsconfig.tsbuildinfo",
+    "build": "jlpm run build:lib && jlpm run build:labextension:dev",
+    "build:prod": "jlpm run build:lib && jlpm run build:labextension",
+    "build:lib": "tsc",
+    "build:labextension": "jupyter labextension build .",
+    "build:labextension:dev": "jupyter labextension build --development True .",
+    "clean": "rimraf lib tsconfig.tsbuildinfo myextension/labextension",
+    "clean:all": "jlpm run clean:lib && jlpm run clean:labextension",
   "clean:labextension": "rimraf myextension/labextension",
   "eslint": "eslint . --ext .ts,.tsx --fix",
   "eslint:check": "eslint . --ext .ts,.tsx",
@@ -59,12 +63,12 @@
   "dependencies": {
-    "@jupyterlab/application": "^2.0.0",
-    "@jupyterlab/apputils": "^2.0.0",
-    "@jupyterlab/observables": "^3.0.0",
+    "@jupyterlab/builder": "^3.0.0",
+    "@jupyterlab/application": "^3.0.0",
+    "@jupyterlab/apputils": "^3.0.0",
+    "@jupyterlab/observables": "^3.0.0",
   "@lumino/algorithm": "^1.2.3",
   "@lumino/commands": "^1.10.1",
   "@lumino/disposable": "^1.3.5",
@@ -99,6 +103,13 @@
-    "typescript": "~3.8.3"
+    "typescript": "~4.0.1"
   "jupyterlab": {
-    "extension": "lib/plugin"
+    "extension": "lib/plugin",
+    "outputDir": "myextension/labextension/"

On the diff above, we see that additional development scripts are also added, as they are used by the new extension system workflow.

The diff also shows the new @jupyterlab/builder as a devDependency. @jupyterlab/builder is a package required to build the extension as a federated (prebuilt) extension. It hides away internal dependencies such as webpack, and produces the assets that can then be distributed as part of a Python package.

Extension developers do not need to interact with @jupyterlab/builder directly, but instead can use the jupyter labextension build command. This command is run automatically as part of the build script (jlpm run build).

For more details about the new file structure and packaging of the extension, check out the extension tutorial: Extension Tutorial

Publishing the extension to PyPI and conda-forge#

Starting from JupyterLab 3.0, extensions can be distributed as a Python package.

The extension tutorial provides explanations to package the extension so it can be published on PyPI and conda forge: Publishing your extension.


While publishing to PyPI is the new recommended way for distributing extensions to users, it is still useful to continue publishing extensions to npm as well, so other developers can extend them in their own extensions.

JupyterLab 1.x to 2.x#

Here are some helpful tips for migrating an extension from JupyterLab 1.x to JupyterLab 2.x. We will look at two examples of extensions that cover most of the APIs that extension authors might be using:

Upgrading library versions#

The @phosphor/* libraries that JupyterLab 1.x uses have been renamed to @lumino/*. Updating your package.json is straightforward. The easiest way to do this is to look in the JupyterLab core packages code base and to simply adopt the versions of the relevant libraries that are used there.

Updating the debugger extension’s libraries in package.json#

Updating the shortcuts UI extension’s libraries in package.json#


In these examples, note that we are using the 2.0.0-beta.x version of many libraries. This was to test the extensions against the JupyterLab 2.0 beta release before the final version. For the final release, your package.json should depend on version ^2.0.0 of these packages.

Migrating from @phosphor to @lumino ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^-

The foundational packages used by JupyterLab are now all prefixed with the NPM namespace @lumino instead of @phosphor. The APIs for these packages have not changed. The @phosphor namespaced imports need to be updated to the new @lumino namespaced packages:

Update from @phosphor/... to @lumino/...#


































p- prefixed CSS classes, data-p- attributes and p- DOM events are deprecated. They will continue to work until the next major release of Lumino.

  • .p- CSS classes such as .p-Widget should be updated to .lm-, e.g. .lm-Widget

  • data-p- attributes such as data-p-dragscroll should be updated to data-lm-, e.g. data-lm-dragscroll

  • p- DOM events such as p-dragenter should be updated to lm-, e.g. lm-dragenter

Updating former @jupyterlab/coreutils imports ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^-

JupyterLab 2.0 introduces several new packages with classes and tokens that have been moved out of @jupyterlab/coreutils into their own packages. These exports have been moved.


It might be helpful to delete node_modules and yarn.lock when updating these libraries.











































Using Session and SessionContext to manage kernel sessions#


For full API documentation and examples of how to use @jupyterlab/services, consult the repository.

ConsolePanel and NotebookPanel now expose a sessionContext: ISessionContext attribute that allows for a uniform way to interact with kernel sessions.

Any widget that matches the interface IDocumentWidget has a context: DocumentRegistry.IContext attribute with a sessionContext: ISessionContext attribute.

For example, consider how the @jupyterlab/debugger extension’s DebuggerService updated its isAvailable() method.

From the PR migrating the debugger extension to JupyterLab 2.0#


await kernel.ready is no longer necessary before the kernel connection kernel can be used. Kernel messages will be buffered as needed while a kernel connection is coming online, so you should be able to use a kernel connection immediately. If you want to retrieve the kernel info (or if for some other reason you want to wait until at least one message has returned from a new kernel connection), you can do await kernel.info.

Using the new icon system and LabIcon#


For full API documentation and examples of how to use the new icon support based on LabIcon from @jupyterlab/ui-components, consult the repository.