.. _xkcd_extension_tutorial: Let's Make an xkcd JupyterLab Extension --------------------------------------- .. warning:: The extension developer API is not stable and will evolve in JupyterLab releases in the near future. JupyterLab extensions add features to the user experience. This page describes how to create one type of extension, an *application plugin*, that: - Adds a "Random `xkcd `__ comic" command to the *command palette* sidebar - Fetches the comic image and metadata when activated - Shows the image and metadata in a tab panel By working through this tutorial, you'll learn: - How to setup an extension development environment from scratch on a Linux or OSX machine. - Windows users: You'll need to modify the commands slightly. - How to start an extension project from `jupyterlab/extension-cookiecutter-ts `__ - How to iteratively code, build, and load your extension in JupyterLab - How to version control your work with git - How to release your extension for others to enjoy |Completed xkcd extension screenshot| Sound like fun? Excellent. Here we go! Setup a development environment ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Install conda using miniconda ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Start by opening your web browser and downloading the latest Python 3.x `Miniconda installer `__ to your home directory. When the download completes, open a terminal and create a root conda environment by running this command. .. code:: bash bash Miniconda3*.sh -b -p ~/miniconda Now activate the conda environment you just created so that you can run the ``conda`` package manager. .. code:: bash source ~/miniconda/bin/activate .. _install-nodejs-jupyterlab-etc-in-a-conda-environment: Install NodeJS, JupyterLab, etc. in a conda environment ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Next create a conda environment that includes: 1. the latest release of JupyterLab 2. `cookiecutter `__, the tool you'll use to bootstrap your extension project structure 3. `NodeJS `__, the JavaScript runtime you'll use to compile the web assets (e.g., TypeScript, CSS) for your extension 4. `git `__, a version control system you'll use to take snapshots of your work as you progress through this tutorial It's best practice to leave the root conda environment, the one created by the miniconda installer, untouched and install your project specific dependencies in a named conda environment. Run this command to create a new environment named ``jupyterlab-ext``. .. code:: bash conda create -n jupyterlab-ext nodejs jupyterlab cookiecutter git -c conda-forge Now activate the new environment so that all further commands you run work out of that environment. .. code:: bash source ~/miniconda/bin/activate jupyterlab-ext Note: You'll need to run the command above in each new terminal you open before you can work with the tools you installed in the ``jupyterlab-ext`` environment. Create a repository ~~~~~~~~~~~~~~~~~~~ Create a new repository for your extension. For example, on `GitHub `__. This is an optional step but highly recommended if you want to share your extension. Create an extension project ~~~~~~~~~~~~~~~~~~~~~~~~~~~ Initialize the project from a cookiecutter ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Next use cookiecutter to create a new project for your extension. .. code:: bash cookiecutter https://github.com/jupyterlab/extension-cookiecutter-ts When prompted, enter values like the following for all of the cookiecutter prompts. :: author_name []: Your Name extension_name [jupyterlab_myextension]: jupyterlab_xkcd project_short_description [A JupyterLab extension.]: Show a random xkcd.com comic in a JupyterLab panel repository [https://github.com/my_name/jupyterlab_myextension]: Your repository url Note: if not using a repository, leave the field blank. You can come back and edit the repository links in the ``package.json`` file later. Change to the directory the cookiecutter created and list the files. .. code:: bash cd jupyterlab_xkcd ls You should see a list like the following. :: README.md package.json src style tsconfig.json Build and install the extension for development ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Your new extension project has enough code in it to see it working in your JupyterLab. Run the following commands to install the initial project dependencies and install it in the JupyterLab environment. We defer building since it will be built in the next step. .. code:: bash npm install npm run build jupyter labextension install . --no-build After the install completes, open a second terminal. Run these commands to activate the ``jupyterlab-ext`` environment and to start a JupyterLab instance in watch mode so that it will keep up with our changes as we make them. .. code:: bash source ~/miniconda/bin/activate jupyterlab-ext jupyter lab --watch See the initial extension in action ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ JupyterLab should appear momentarily in your default web browser. If all goes well, the last bunch of messages you should see in your terminal should look something like the following: :: Webpack is watching the files… Hash: 1c15fc765a97c45c075c Version: webpack 2.7.0 Time: 6423ms Asset Size Chunks Chunk Names 674f50d287a8c48dc19ba404d20fe713.eot 166 kB [emitted] af7ae505a9eed503f8b8e6982036873e.woff2 77.2 kB [emitted] fee66e712a8a08eef5805a46892932ad.woff 98 kB [emitted] b06871f281fee6b241d60582ae9369b9.ttf 166 kB [emitted] 912ec66d7572ff821749319396470bde.svg 444 kB [emitted] [big] 0.bundle.js 890 kB 0 [emitted] [big] main.bundle.js 6.82 MB 1 [emitted] [big] main 0.bundle.js.map 1.08 MB 0 [emitted] main.bundle.js.map 8.19 MB 1 [emitted] main [27] ./~/@jupyterlab/application/lib/index.js 5.66 kB {1} [built] [427] ./~/@jupyterlab/application-extension/lib/index.js 6.14 kB {1} [optional] [built] [443] ./~/@jupyterlab/pdf-extension/lib/index.js 4.98 kB {1} [optional] [built] [445] ./~/@jupyterlab/settingeditor-extension/lib/index.js 2.67 kB {1} [optional] [built] [446] ./~/@jupyterlab/shortcuts-extension/lib/index.js 3.75 kB {1} [optional] [built] [447] ./~/@jupyterlab/tabmanager-extension/lib/index.js 1.8 kB {1} [optional] [built] [448] ./~/@jupyterlab/terminal-extension/lib/index.js 7.33 kB {1} [optional] [built] [449] ./~/@jupyterlab/theme-dark-extension/lib/index.js 800 bytes {1} [optional] [built] [450] ./~/@jupyterlab/theme-light-extension/lib/index.js 804 bytes {1} [optional] [built] [451] ./~/@jupyterlab/tooltip-extension/lib/index.js 5.61 kB {1} [optional] [built] [453] ./~/es6-promise/auto.js 179 bytes {1} [built] [454] /Users/foo/workspace/xkcd/lib/index.js 353 bytes {1} [optional] [built] [455] ./~/font-awesome/css/font-awesome.min.css 892 bytes {1} [built] [860] ./build/index.out.js 35.2 kB {1} [built] + 1114 hidden modules Return to the browser. Open the JavaScript console in the JupyterLab tab by following the instructions for your browser: - `Accessing the DevTools in Google Chrome `__ - `Opening the Web Console in Firefox `__ You should see a message that says ``JupyterLab extension jupyterlab_xkcd is activated!`` in the console. If you do, congrats, you're ready to start modifying the the extension! If not, go back, make sure you didn't miss a step, and `reach out `__ if you're stuck. Note: Leave the terminal running the ``jupyter lab --watch`` command open. Commit what you have to git ^^^^^^^^^^^^^^^^^^^^^^^^^^^ Run the following commands in your ``jupyterlab_xkcd`` folder to initialize it as a git repository and commit the current code. .. code:: bash git init git add . git commit -m 'Seed xkcd project from cookiecutter' Note: This step is not technically necessary, but it is good practice to track changes in version control system in case you need to rollback to an earlier version or want to collaborate with others. For example, you can compare your work throughout this tutorial with the commits in a reference version of ``jupyterlab_xkcd`` on GitHub at https://github.com/jupyterlab/jupyterlab_xkcd. Add an xkcd widget ~~~~~~~~~~~~~~~~~~ Show an empty panel ^^^^^^^^^^^^^^^^^^^ The *command palette* is the primary view of all commands available to you in JupyterLab. For your first addition, you're going to add a *Random xkcd comic* command to the palette and get it to show an *xkcd* tab panel when invoked. Fire up your favorite text editor and open the ``src/index.ts`` file in your extension project. Add the following import at the top of the file to get a reference to the command palette interface. .. code:: typescript import { ICommandPalette } from '@jupyterlab/apputils'; You will also need to install this dependency. Run the following command in the repository root folder install the dependency and save it to your `package.json`: .. code:: bash npm install --save @jupyterlab/apputils Locate the ``extension`` object of type ``JupyterLabPlugin``. Change the definition so that it reads like so: .. code:: typescript /** * Initialization data for the jupyterlab_xkcd extension. */ const extension: JupyterLabPlugin = { id: 'jupyterlab_xkcd', autoStart: true, requires: [ICommandPalette], activate: (app: JupyterLab, palette: ICommandPalette) => { console.log('JupyterLab extension jupyterlab_xkcd is activated!'); console.log('ICommandPalette:', palette); } }; The ``requires`` attribute states that your plugin needs an object that implements the ``ICommandPalette`` interface when it starts. JupyterLab will pass an instance of ``ICommandPalette`` as the second parameter of ``activate`` in order to satisfy this requirement. Defining ``palette: ICommandPalette`` makes this instance available to your code in that function. The second ``console.log`` line exists only so that you can immediately check that your changes work. Run the following to rebuild your extension. .. code:: bash npm run build When the build completes, return to the browser tab that opened when you started JupyterLab. Refresh it and look in the console. You should see the same activation message as before, plus the new message about the ICommandPalette instance you just added. If you don't, check the output of the build command for errors and correct your code. :: JupyterLab extension jupyterlab_xkcd is activated! ICommandPalette: Palette {_palette: CommandPalette} Note that we had to run ``npm run build`` in order for the bundle to update, because it is using the compiled JavaScript files in ``/lib``. If you wish to avoid running ``npm run build`` after each change, you can open a third terminal, and run the ``npm run watch`` command from your extension directory, which will automatically compile the TypeScript files as they change. Now return to your editor. Add the following additional import to the top of the file. .. code:: typescript import { Widget } from '@phosphor/widgets'; Install this dependency as well: .. code:: bash npm install --save @phosphor/widgets Then modify the ``activate`` function again so that it has the following code: .. code-block:: typescript activate: (app: JupyterLab, palette: ICommandPalette) => { console.log('JupyterLab extension jupyterlab_xkcd is activated!'); // Create a single widget let widget: Widget = new Widget(); widget.id = 'xkcd-jupyterlab'; widget.title.label = 'xkcd.com'; widget.title.closable = true; // Add an application command const command: string = 'xkcd:open'; app.commands.addCommand(command, { label: 'Random xkcd comic', execute: () => { if (!widget.isAttached) { // Attach the widget to the main work area if it's not there app.shell.addToMainArea(widget); } // Activate the widget app.shell.activateById(widget.id); } }); // Add the command to the palette. palette.addItem({command, category: 'Tutorial'}); } The first new block of code creates a ``Widget`` instance, assigns it a unique ID, gives it a label that will appear as its tab title, and makes the tab closable by the user. The second block of code add a new command labeled *Random xkcd comic* to JupyterLab. When the command executes, it attaches the widget to the main display area if it is not already present and then makes it the active tab. The last new line of code adds the command to the command palette in a section called *Tutorial*. Build your extension again using ``npm run build`` (unless you are using ``npm run watch`` already) and refresh the browser tab. Open the command palette on the left side and type *xkcd*. Your *Random xkcd comic* command should appear. Click it or select it with the keyboard and press *Enter*. You should see a new, blank panel appear with the tab title *xkcd.com*. Click the *x* on the tab to close it and activate the command again. The tab should reappear. Finally, click one of the launcher tabs so that the *xkcd.com* panel is still open but no longer active. Now run the *Random xkcd comic* command one more time. The single *xkcd.com* tab should come to the foreground. |Empty xkcd extension panel| If your widget is not behaving, compare your code with the reference project state at the `01-show-a-panel tag `__. Once you've got everything working properly, git commit your changes and carry on. .. code-block:: bash git add . git commit -m 'Show xkcd command on panel' Show a comic in the panel ^^^^^^^^^^^^^^^^^^^^^^^^^ You've got an empty panel. It's time to add a comic to it. Go back to your code editor. Add the following code below the lines that create a ``Widget`` instance and above the lines that define the command. .. code-block:: typescript // Add an image element to the panel let img = document.createElement('img'); widget.node.appendChild(img); // Fetch info about a random comic fetch('https:////egszlpbmle.execute-api.us-east-1.amazonaws.com/prod').then(response => { return response.json(); }).then(data => { img.src = data.img; img.alt = data.title; img.title = data.alt; }); The first two lines create a new HTML ```` element and add it to the widget DOM node. The next lines make a request using the HTML `fetch `__ API that returns information about a random xkcd comic, and set the image source, alternate text, and title attributes based on the response. Rebuild your extension if necessary (``npm run build``), refresh your browser tab, and run the *Random xkcd comic* command again. You should now see a comic in the xkcd.com panel when it opens. |Single xkcd extension panel| Note that the comic is not centered in the panel nor does the panel scroll if the comic is larger than the panel area. Also note that the comic does not update no matter how many times you close and reopen the panel. You'll address both of these problems in the upcoming sections. If you don't see a comic at all, compare your code with the `02-show-a-comic tag `__ in the reference project. When it's working, make another git commit. .. code:: bash git add . git commit -m 'Show a comic in the panel' Improve the widget behavior ~~~~~~~~~~~~~~~~~~~~~~~~~~~ Center the comic and add attribution ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Open ``style/index.css`` in our extension project directory for editing. Add the following lines to it. .. code-block:: css .jp-xkcdWidget { display: flex; flex-direction: column; overflow: auto; } .jp-xkcdCartoon { margin: auto; } .jp-xkcdAttribution { margin: 20px auto; } The first rule stacks content vertically within the widget panel and lets the panel scroll when the content overflows. The other rules center the cartoon and attribution badge horizontally and space them out vertically. Return to the ``index.ts`` file. Note that there is already an import of the CSS file in the ``index.ts`` file. Modify the the ``activate`` function to apply the CSS classes and add the attribution badge markup. The beginning of the function should read like the following: .. code-block:: typescript :emphasize-lines: 9,13,16-22 activate: (app: JupyterLab, palette: ICommandPalette) => { console.log('JupyterLab extension jupyterlab_xkcd is activated!'); // Create a single widget let widget: Widget = new Widget(); widget.id = 'xkcd-jupyterlab'; widget.title.label = 'xkcd.com'; widget.title.closable = true; widget.addClass('jp-xkcdWidget'); // new line // Add an image element to the panel let img = document.createElement('img'); img.className = 'jp-xkcdCartoon'; // new line widget.node.appendChild(img); // New: add an attribution badge img.insertAdjacentHTML('afterend', `` ); // Keep all the remaining fetch and command lines the same // as before from here down ... Build your extension if necessary (``npm run build``) and refresh your JupyterLab browser tab. Invoke the *Random xkcd comic* command and confirm the comic is centered with an attribution badge below it. Resize the browser window or the panel so that the comic is larger than the available area. Make sure you can scroll the panel over the entire area of the comic. |Styled xkcd panel with attribution| If anything is misbehaving, compare your code with the reference project `03-style-and-attribute tag `__. When everything is working as expected, make another commit. .. code:: bash git add . git commit -m 'Add styling, attribution' Show a new comic on demand ^^^^^^^^^^^^^^^^^^^^^^^^^^ The ``activate`` function has grown quite long, and there's still more functionality to add. You should refactor the code into two separate parts: 1. An ``XkcdWidget`` that encapsulates the xkcd panel elements, configuration, and soon-to-be-added update behavior 2. An ``activate`` function that adds the widget instance to the UI and decide when the comic should refresh Start by refactoring the widget code into the new ``XkcdWidget`` class. Add the following additional import to the top of the file. .. code-block:: typescript import { Message } from '@phosphor/messaging'; Install this dependency: .. code:: bash npm install --save @phosphor/messaging Then add the class just below the import statements in the ``index.ts`` file. .. code-block:: typescript /** * An xckd comic viewer. */ class XkcdWidget extends Widget { /** * Construct a new xkcd widget. */ constructor() { super(); this.id = 'xkcd-jupyterlab'; this.title.label = 'xkcd.com'; this.title.closable = true; this.addClass('jp-xkcdWidget'); this.img = document.createElement('img'); this.img.className = 'jp-xkcdCartoon'; this.node.appendChild(this.img); this.img.insertAdjacentHTML('afterend', `` ); } /** * The image element associated with the widget. */ readonly img: HTMLImageElement; /** * Handle update requests for the widget. */ onUpdateRequest(msg: Message): void { fetch('https://egszlpbmle.execute-api.us-east-1.amazonaws.com/prod').then(response => { return response.json(); }).then(data => { this.img.src = data.img; this.img.alt = data.title; this.img.title = data.alt; }); } }; You've written all of the code before. All you've done is restructure it to use instance variables and move the comic request to its own function. Next move the remaining logic in ``activate`` to a new, top-level function just below the ``XkcdWidget`` class definition. Modify the code to create a widget when one does not exist in the main JupyterLab area or to refresh the comic in the exist widget when the command runs again. The code for the ``activate`` function should read as follows after these changes: .. code-block:: typescript /** * Activate the xckd widget extension. */ function activate(app: JupyterLab, palette: ICommandPalette) { console.log('JupyterLab extension jupyterlab_xkcd is activated!'); // Create a single widget let widget: XkcdWidget = new XkcdWidget(); // Add an application command const command: string = 'xkcd:open'; app.commands.addCommand(command, { label: 'Random xkcd comic', execute: () => { if (!widget.isAttached) { // Attach the widget to the main work area if it's not there app.shell.addToMainArea(widget); } // Refresh the comic in the widget widget.update(); // Activate the widget app.shell.activateById(widget.id); } }); // Add the command to the palette. palette.addItem({ command, category: 'Tutorial' }); }; Remove the ``activate`` function definition from the ``JupyterLabPlugin`` object and refer instead to the top-level function like so: .. code-block:: typescript const extension: JupyterLabPlugin = { id: 'jupyterlab_xkcd', autoStart: true, requires: [ICommandPalette], activate: activate }; Make sure you retain the ``export default extension;`` line in the file. Now build the extension again and refresh the JupyterLab browser tab. Run the *Random xkcd comic* command more than once without closing the panel. The comic should update each time you execute the command. Close the panel, run the command, and it should both reappear and show a new comic. If anything is amiss, compare your code with the `04-refactor-and-refresh tag `__ to debug. Once it's working properly, commit it. .. code:: bash git add . git commit -m 'Refactor, refresh comic' Restore panel state when the browser refreshes ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ You may notice that every time you refresh your browser tab, the xkcd panel disappears, even if it was open before you refreshed. Other open panels, like notebooks, terminals, and text editors, all reappear and return to where you left them in the panel layout. You can make your extension behave this way too. Update the imports at the top of your ``index.ts`` file so that the entire list of import statements looks like the following: .. code-block:: typescript :emphasize-lines: 2,6,9-11 import { JupyterLab, JupyterLabPlugin, ILayoutRestorer // new } from '@jupyterlab/application'; import { ICommandPalette, InstanceTracker // new } from '@jupyterlab/apputils'; import { JSONExt // new } from '@phosphor/coreutils'; import { Message } from '@phosphor/messaging'; import { Widget } from '@phosphor/widgets'; import '../style/index.css'; Install this dependency: .. code:: bash npm install --save @phosphor/coreutils Then, add the ``ILayoutRestorer`` interface to the ``JupyterLabPlugin`` definition. This addition passes the global ``LayoutRestorer`` to the third parameter of the ``activate``. .. code:: typescript const extension: JupyterLabPlugin = { id: 'jupyterlab_xkcd', autoStart: true, requires: [ICommandPalette, ILayoutRestorer], activate: activate }; Finally, rewrite the ``activate`` function so that it: 1. Declares a widget variable, but does not create an instance immediately 2. Constructs an ``InstanceTracker`` and tells the ``ILayoutRestorer`` to use it to save/restore panel state 3. Creates, tracks, shows, and refreshes the widget panel appropriately .. code-block:: typescript function activate(app: JupyterLab, palette: ICommandPalette, restorer: ILayoutRestorer) { console.log('JupyterLab extension jupyterlab_xkcd is activated!'); // Declare a widget variable let widget: XkcdWidget; // Add an application command const command: string = 'xkcd:open'; app.commands.addCommand(command, { label: 'Random xkcd comic', execute: () => { if (!widget) { // Create a new widget if one does not exist widget = new XkcdWidget(); widget.update(); } if (!tracker.has(widget)) { // Track the state of the widget for later restoration tracker.add(widget); } if (!widget.isAttached) { // Attach the widget to the main work area if it's not there app.shell.addToMainArea(widget); } else { // Refresh the comic in the widget widget.update(); } // Activate the widget app.shell.activateById(widget.id); } }); // Add the command to the palette. palette.addItem({ command, category: 'Tutorial' }); // Track and restore the widget state let tracker = new InstanceTracker({ namespace: 'xkcd' }); restorer.restore(tracker, { command, args: () => JSONExt.emptyObject, name: () => 'xkcd' }); }; Rebuild your extension one last time and refresh your browser tab. Execute the *Random xkcd comic* command and validate that the panel appears with a comic in it. Refresh the browser tab again. You should see an xkcd panel appear immediately without running the command. Close the panel and refresh the browser tab. You should not see an xkcd tab after the refresh. Refer to the `05-restore-panel-state tag `__ if your extension is misbehaving. Make a commit when the state of your extension persists properly. .. code:: bash git add . git commit -m 'Restore panel state' Congrats! You've implemented all of the behaviors laid out at the start of this tutorial. Now how about sharing it with the world? .. _publish-your-extension-to-npmjsorg: Publish your extension to npmjs.org ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ npm is both a JavaScript package manager and the de facto registry for JavaScript software. You can `sign up for an account on the npmjs.com site `__ or create an account from the command line by running ``npm adduser`` and entering values when prompted. Create an account now if you do not already have one. If you already have an account, login by running ``npm login`` and answering the prompts. Next, open the project ``package.json`` file in your text editor. Prefix the ``name`` field value with ``@your-npm-username>/`` so that the entire field reads ``"name": "@your-npm-username/xkcd-extension"`` where you've replaced the string ``your-npm-username`` with your real username. Review the homepage, repository, license, and `other supported package.json `__ fields while you have the file open. Then open the ``README.md`` file and adjust the command in the *Installation* section so that it includes the full, username-prefixed package name you just included in the ``package.json`` file. For example: .. code:: bash jupyter labextension install @your-npm-username/xkcd-extension Return to your terminal window and make one more git commit: .. code:: bash git add . git commit -m 'Prepare to publish package' Now run the following command to publish your package: .. code:: bash npm publish --access=public Check that your package appears on the npm website. You can either search for it from the homepage or visit ``https://www.npmjs.com/package/@your-username/jupyterlab_xkcd`` directly. If it doesn't appear, make sure you've updated the package name properly in the ``package.json`` and run the npm command correctly. Compare your work with the state of the reference project at the `06-prepare-to-publish tag `__ for further debugging. |Extension page on npmjs.com| You can now try installing your extension as a user would. Open a new terminal and run the following commands, again substituting your npm username where appropriate: .. code:: bash conda create -n jupyterlab-xkcd jupyterlab nodejs source activate jupyterlab-xkcd jupyter labextension install @your-npm-username/xkcd-extension jupyter lab You should see a fresh JupyterLab browser tab appear. When it does, execute the *Random xkcd comic* command to prove that your extension works when installed from npm. Learn more ~~~~~~~~~~ You've completed the tutorial. Nicely done! If you want to keep learning, here are some suggestions about what to try next: - Assign a hotkey to the *Random xkcd comic* command. - Make the image a link to the comic on https://xkcd.com. - Push your extension git repository to GitHub. - Give users the ability to pin comics in separate, permanent panels. - Learn how to write `other kinds of extensions <./extension_dev.html>`__. .. |Completed xkcd extension screenshot| image:: xkcd_tutorial_complete.png .. |Empty xkcd extension panel| image:: xkcd_tutorial_empty.png .. |Single xkcd extension panel| image:: xkcd_tutorial_single.png .. |Styled xkcd panel with attribution| image:: xkcd_tutorial_complete.png .. |Extension page on npmjs.com| image:: xkcd_tutorial_npm.png