feat: introduce Message, Serializer, Deserializer and Binding interfaces

[lance]

Proposed Changes

This PR introduces the Message, Serializer and Deserializer, and Binding interfaces used to convert a CloudEvent into a Message that can be sent across a transport protocol. The first protocol implemented for this is HTTP, and some of the functionality formerly in src/transport/http has been simplified, reduced and/or moved to /src/messages/http.

Test for V1 events are in place. Conformance tests have been modified to use these new interfaces vs. the HTTP Receiver class.

Example usage

In an express.js application, simply create a Message using the incoming request headers and body. Then call HTTP.toEvent(message).

app.post("/", (req, res) => {
  const message = {
    headers: req.headers,
    body: req.body
  };

  const event = HTTP.toEvent(message);
});

Of course, this can be inlined as: HTTP.toEvent({ headers: req.headers, body: req.body });.

Sending a Message should also be straightforward. Convert a CloudEvent to a message, and send it using Axios or any other HTTP transport library that allows setting headers and body.

const message = HTTP.binary(event);
axios.post({
  url: 'https://event.receiver.com',
  headers: message.headers,
  body: message.body
});

• Fixes: Adding More Transport Protocols - A Proposal #322
• Fixes: isCloudEvent Function #295
• Version: 3.2.0

[lance]

@cloudevents/sdk-javascript-maintainers this should be ready now with both v1 and v03 of the spec being tested. PTAL

[lholmquist]

Regarding the removed tests, shouldn't we keep them until 4.0.0 to make sure we didn't break anything for the current usage?

[lance]

@lholmquist I can revert those tests if you think they are needed. My problem with them is that they were not really integration tests, as they were testing implementation details and not the public facing API. Coverage doesn't actually go down when these are removed!

[lholmquist]

they were testing implementation details and not the public facing API.

Ok, then it is probably fine to remove them

[lance]

@lholmquist I think this is probably ready to land, but I'm not sure if your comments are an implicit approval or not.

[lholmquist]

oh sorry, i think i forgot to press the approve button