ts_devserver: ibazel livereloading if concatjs bundle is not used

[devversion]

🐞 bug report

Affected Rule

ts_devserver (@bazel/typescript)

Is this a regression?

No

Description

In some scenarios the concatjs bundle is not desired/used. e.g. for lazy loading.

One could say that in that case the concatjs bundle can be just empty.. but that doesn't work because the deps attribute will be used to add the lazy input files to the servable runfiles (that's a different issue though).

🔥 Exception or Error

The livereloading script from ibazel is currently served at a non-static URL. Meaning that we can't just add a script import to the livereload script in the index.html.

If the ts_devserver uses the concatjs bundle it works because the devserver go implementation currently reads the IBAZEL_LIVERELOAD_URL environment variable and adds the script to the concatjs bundle.

Anything else relevant?

One easy solution would be to provide a proxy URL in the devserver that always redirects to the URL specified in the IBAZEL_LIVERELOAD_URL environment variable.

I will have a look into this.

[alexeagle]

If not using concatjs, what's the advantage of using the ts_devserver at all? Why not something that gives you more control? I suppose the alternative devserver would need to know about the ibazel protocol for reloading the page when the bazel outputs are updated

[devversion]

Well, another reason to use ts_devserver besides the ibazel integration is the runfile resolution that makes it the only devserver implementation that also works on windows.

Surely we could implement our own devserver but ts_devserver works great for most cases right now and only lacks live-reloading for some targets right now (due to this issue). Happy to work on our own implementation of the ts_devserver if needed, but I feel like it restricts use-cases a lot if ts_devserver is only intended to be used with ConcatJS.

Additionally the use of concatjs is not ideal for lazy-loading. Otherwise we'd have used that.

[alexeagle]

we do have some experimental code in ts_devserver to support lazy-loading but it's not in the open-source version. It depends on a manifest file format that describes which sources go into which chunks. @evmar worked on that - I could imagine this might make some progress as we work on our dynamic bundling solution for production which relies on concatjs too.

thanks for explaining the runfiles bit too. We should really make other devserver packages from npm work on Windows without being so disruptive in how they locate files.

[alexeagle]

As stated, we aren't going to do this. ts_devserver should be better named concatjs_devserver.

I think a better FR is probably "show how to make my devserver do ibazel livereload and handle runfiles"