See https://blockprotocol.org/docs/blocks/develop
TL;DR: Run npx create-block-app@latest [your-block-name] --template=custom-element
Other templates are available. See npx create-block-app@latest --help
A key part of the Block Protocol is the use of types to describe the data your block will work with.
Your block should be associated with an “entity type” which will be used by embedding applications to understand what sorts of entities can be sent to it (e.g. what properties do they have?).
You can create an entity type on blockprotocol.org — see the docs for a full guide.
Once you have created the type representing the data your block needs, copy its URL for use in the next step.
-
Change into the folder:
cd path/to/your-block-name
-
Update the
blockprotocol
metadata object in package.json:
- set
blockEntityType
to the URL of the entity type you created in the previous step - change the default
tagName
underblockType
to the tag for your element - optionally update additional fields which will be used to identify and describe the block when published:
-
displayName
: a friendly display name -
examples
: an array of example data structures your block would accept and use -
image
: a preview image showing your block in action (in place ofpublic/block-preview.png
) -
icon
: an icon to be associated with your block (in place ofpublic/omega.svg
) -
name
: a slugified name for your block (which may differ to the packagename
in package.json)- this may either be in the format
slug
or@namespace/slug
wherenamespace
is your blockprotocol.org username
- this may either be in the format
-
- Run
yarn codegen
to automatically generate TypeScript types from your block's entity type (you can modify thecodegen
field to generate code for other types as well)
This template uses the Lit custom element framework. Please see the Lit docs for general help in defining an element using the framework.
-
Write your block starting in
app.ts
. To test it during development:-
edit
dev.tsx
to give your block starting properties -
run the dev server with
yarn dev
(ornpm run dev
)
-
-
When finished, run
yarn build
(ornpm run build
), which:- Bundles the component into a single source file
- Generates a
block-metadata.json
file which:- points to the
schema
andsource
files - brings in metadata from
package.json
, such as the block name and description - additional brings in anything in the
blockprotocol
object inpackage.json
, e.g.-
displayName
: a friendly display name -
examples
: an array of example data structures your block would accept and use -
image
: a preview image showing your block in action -
icon
: an icon to be associated with your block -
name
: a slugified name for your block (which may differ to the packagename
in package.json); it can be defined asblockname
or@namespace/blockname
, wherenamespace
must be your username on blockprotocol.org if you intend to publish it there
-
- lists the
externals
- libraries the block expects the host app to provide
- points to the
- Once uploaded to a remote folder, embedding applications can access
block-metadata.json
to load a block and its schema. This file is documented in full here.
Please see the Block Protocol docs for a fuller explanation of querying, creating and updating entity data from your block.
You can format your code using yarn format
(or npm run format
).
If you want to use environment variables in development, add a .env
file in this directory, and then you can access variables defined in it via process.env.VARIABLE_NAME
. This is useful for providing a blockProtocolApiKey
to MockBlockDock
in dev.tsx
.
e.g. your .env
file might look like this:
BLOCK_PROTOCOL_API_KEY=super-secret
and dev.tsx
like this:
return (
<MockBlockDock
blockProtocolApiKey={process.env.BLOCK_PROTOCOL_API_KEY}
Head over to blockprotocol.org to read instructions on publishing your block.
The component can be debugged locally by first starting yarn dev
.
Now (using VS Code), go to the Debug tab, select "Launch Chrome" and start the debugger (F5).
You should now be able to set breakpoints and step through the code.