Jazz up the build system

[bennypowers]

This issue proposes to:

1. update typescript to latest (4.2 or 4.3 depending on when impl happens)
2. replace mocha-chrome-headless with @web/test-runner 2.1. use esbuildPlugin in wtr to run tests buildless and concurrently from ts sources 2.2. add "test" npm script to run wtr
3. add @web/dev-server to run the examples dir (maybe with npm start)
4. replace make with rollup
5. replace travis with github actions
6. implement semantic-release to automate releases on merge to master
7. master -> main

[matthewp]

All sound good to me!

[joryphillips]

Hi @bennypowers are you working on 2) in your list above -- new test library? Or is someone else?

Looking at fixing up some of the TypeScript nuances, including the component() HTMLElement issue , I think updating test files to TS would be a good thing to do first. I'm happy to work on that, or pick up anything you have in progress.

[bennypowers]

Go for it. ping me here or on "Lit & Friends" slack if you need help

[joryphillips]

@bennypowers (and @matthewp -- would love your input too if you have time!)

How does this initial direction for TypeScript tests look? As mentioned to Benny on Slack, trying for a light touch initially. (Although I did add a test for attributes being undefined when not present to highlight the issue -- it was unexpected)

• attributes test file
• test infra package.json

[bennypowers]

Looks really good, and it was so considerate of you to prepare your comment with those easy-to-understand links, thank you!

[matthewp]

Looks great to me