@guardian/prosemirror-elements

This Prosemirror plugin adds the ability to add custom 'elements' to a document.

Why does this exist?

Modelling non-text content in Prosemirror can be tricky. prosemirror-elements provides an abstraction that makes it easy to write custom elements that:

• contain user-defined fields that model many different kinds of content, including rich text fields and arbitrary data
• are first class citizens of the Prosemirror schema (for example, nested rich text fields play nicely with collaborative editing)
• are renderer-agnostic (we use React as a default)

Setup

yarn installs and sets up the project dependencies.

Run

1. Ensure nginx is running.
2. yarn start builds the project locally, spins up a webserver on http://localhost:7890, and watches for file changes.

Testing

• Run the unit tests via Jest with yarn test:unit.
• Run the integration tests via Cypress with yarn test:integration.
  • You'll need to be running the application via yarn start simultaneously for the tests to work – make sure the server is responding on http://localhost:7890 before running the tests.
  • For reasons we're not yet able to determine, Cypress won't run your tests immediately when you select them in the GUI. Hit the 'refresh' button and they should run normally.

Releasing

This repository uses semantic-release to publish new versions of this package when PRs are merged to main, and prelease versions when code is pushed to beta.

Version numbers are determined by the commit history of main, and so to trigger a release you'll need to use the commitizen format when naming pull requests. Then, when the PR is merged via a merge commit, the name of that commit (which corresponds to the name of the PR) will trigger a release.

For example, merging a PR named:

• fix: this one weird bug to main will trigger a release with a patch version bump
• feat: an exciting new thing to beta will trigger a release with a beta suffix and a minor version bump

Testing locally in applications using prosemirror-elements

We've found yalc useful in testing local changes to prosemirror-elements in applications that use it.

Setup:

1. Install yalc globally with npm i yalc -g or yarn global add yalc.
2. Run yarn yalc in your local project from your current branch, to build the project and push changes to yalc.
3. Run yalc add @guardian/prosemirror-elements within the project consuming prosemirror-elements locally.

Note: any changes you make to your local prosemirror-elements branch must be republished (step 3). Don't forget to run yarn yalc again!

Adding a new element using ProseMirror Elements:

Quick-Start Guide

Troubleshooting when developing this library

Problems with yarn link

ProseMirror and its dependencies sometimes use object identity checks (e.g. instanceof). When using yarn link, it's possible for the consuming code to bundle different versions of dependencies simultaneously. This can be difficult to work around. It will not happen during a normal install.

We recommend using yalc to avoid this issue, but it's also possible to work around it.

One known instance of this occurs when appending the NodeSpec generated by the library to the parent editor schema. This would normally be accomplished by appending it to a parent schema, like so:

const mySchema = new Schema({
  nodes: OrderedMap.from(schema.spec.nodes).append(nodeSpec),
  marks
});

This may fail if your bundler has included the ordered-map dependency twice in your project. Because ordered-map uses instanceof to determine if an incoming object is an OrderedMap, the incoming object will fail this check, despite it being the correct shape.

As a workaround, try reconstructing the map as an object:

const objectNodeSpec: Record<string, NodeSpec> = {}
nodeSpec.forEach((key, value) => objectNodeSpec[key] = value as NodeSpec);

const mySchema = new Schema({
  nodes: OrderedMap.from(schema.spec.nodes).append(objectNodeSpec),
  marks
});

Element-specific docs – for Guardian users only

It's useful to write fixture tests to ensure that the element you're creating doesn't disrupt existing data – see the fixture tests in src/elements/helpers/__tests__/transformFixtures.spec.ts for more details.

There's a script available at ./fixtures/parse-element.js to facilitate transforming element data from the Guardian CMS into a redacted form suitable for fixtures.