perf: don't use middleware if has build

[mrloop]

This PR depends on a PR for ember-cli being merged first, see ember-cli/ember-cli#9205 merged

ember serve and ember test has a path flag to specify
an existing ember build to use, without rebuilding. ember-cli-typescript
will add typechecking middleware regardless of ember using an existing
build, the typechecking middleware is not required. This can slow
down the initial request to express server significantly.

For instance one project spends 49 secs for initial typecheck on first
request.

$ DEBUG=*:* ember s --path dist
...
– Serving on http://localhost:4200/admin/
...
ember-cli-typescript:typecheck-worker Typecheck complete (0 diagnostics) +49s
...

[jamescdavis]

I think this could be a nice perf improvement. I've experienced the same and agree that it doesn't make sense to run the type-checking middleware when you're just using an existing build.

[rwjblue]

FWIW, the ember-cli PR should land into the ember-cli@3.19.0-beta cycle today/tomorrow.

[mrloop]

Thanks @rwjblue I'll update this PR, add a test and remove the prettier update and not use optional chaining, this can be added in another PR.

[mrloop]

I've updated the PR ready for review, removing the prettier update and optional chaining causing prettier linting to fail. I've added tests to check that type checking worker is running or not running for both ember serve and ember test depending on the --path flag.

One of the required checks are failing CI / Test (linux, floating dependencies) (pull_request), this looks unrelated to PR and not sure how to fix it.

[chriskrycho]

Thank you! One of us will try to get to this in the next couple days!

[mrloop]

Rebased on master

[mrloop]

@chriskrycho is there anything I can do to help get this over line and merged? Is the testing approach good or is there a better way of doing it?

[jamescdavis]

Released in 4.0.0-rc.1