deno watch for web development

[MarkTiedemann]

Would love to have a better web development experience with Deno out of the box.

• First, the server should restart whenever I make changes.
• Second, the website should reload whenever I make changes.

For the server, I'd like to propose a deno watch subcommand or deno run --watch flag that automatically restarts the server in a controlled way, e.g.

deno watch *.ts --run main.ts --allow-net
# or
deno run --watch *.ts --allow-net main.ts

If we also had a Deno.watch API for watching directories or files, we could then implement a simple client refresh via server-sent events (example) or web sockets.

EDIT: It would be nice if the watch subcommand/flag would be able to notify the running code that it will/should be restarted - maybe something via signals (e.g. SIGUSR1), command line flags, some API, or a similar mechanism - so that the server could notify the client that it will be restarted and that the client needs to be reloaded.

[kitsonk]

Duplicate of #1826

[MarkTiedemann]

Duplicate of #1826

I'd say it's related rather than a duplicate. #1826 is about the Deno.watch API, but does not mention a watch subcommand or --watch flag.

I also found #2251 which is related. It's about "automatically restarting the server". I think the solution to that would be the subcommand / flag.

[ry]

Once #1826 is done, I would consider this. Tho it would need to be carefully specified - and I'm not sure if it can be accomplished in general.

[Caesar2011]

Now, when #1826 is done, we can consider this again. Based on another issue #4830 I implemented a small typescript script.

https://github.com/Caesar2011/rhinoder

This could at least be used for Deno.watch().

[eliassjogreen]

I have made denon which serves the same purpose but with a bit more configurability.

[MarkTiedemann]

Don't think that this should be part of Deno core anymore, closing.

[rudyhuynh]

@MarkTiedemann I think this should be part of Deno core. We already have unit test, code format, bundler, .etc. Watch for development must be major piece of Deno core as well.

[Caesar2011]

Consider deno run --watch file.ts.

[MarkTiedemann]

First of all, I think Deno is fast enough that you don't really need a watcher. Just Ctrl+C, Up, Enter is probably fine for 90% of use cases. It has been working quite fine for me working with Deno on a daily basis for the past one and a half years. You should try it. :)

Then there's two arguments I made when originally opening this issue:

1. The server should restart whenever I make changes.
2. The website should reload whenever I make changes.

2, I think, is out of scope anyways. Deno should not have live-reload integration or some hacky server-sent events that trigger in-browser refresh, as I originally proposed. In retrospect, I think that is a dumb idea. If you really need something like that, write it yourself, put it on GitHub - but I don't think this should ever be in core.

1, I think, is doable and could potentially be in core some day. But then again, I don't think deno run --watch app.ts is any better than denon run app.ts, or using the usual general purpose filewatching tools that have long solved this problem (https://github.com/emcrisostomo/fswatch, https://github.com/facebook/watchman, etc.)

If someone wants to open another issue for this, feel free. This one I'd like to keep closed.

[jtwebman]

@MarkTiedemann Closing the whole issue because 2 isn't a good idea but 1 would be a big win. It is very common when working on an API application to restart deno. The sad part is right now I use Node.js nodemon to do it.

npx nodemon --exec "deno run --allow-net=0.0.0.0" server.js

But will gladly open another issue to be more clear with what is needed and the win for having it in the core. --watch in the run command will allow for you to only watch the files that are loaded with the command vs restarting if anything changes.

[notfilippo]

Also, there is denosaurs/denon

[rwieruch]

I was surprised seeing that there is no watch mode for development purposes in Deno (correct me if I am wrong). After going through Deno's philosophy, IMO it shouldn't be the case that I already have to fallback to nodemon or a third-party (?) like denon for this. This is a core developer experience issue for me.

[pedropaulosuzuki]

Just in case someone is wondering, #7382 got merged successfully 22 days ago

[tbsvttr]

deno bundle --unstable --watch ./src/app.ts ./build/app.bundle.ts works for me with deno 1.6.0.

[asbjornu]

Seems like --watch supports globbing and multiple paths separated by comma as well. This works for me, at least:

deno run --watch=./**/*.ts,./**/*.tsx server.ts

[bebraw]

@asbjornu Through research at jurassiscripts/velociraptor#80 we found out watch supports only a boolean flag right now. I opened #12197 with a small proposal.