nodemon support

[guybedford]

This adds nodemon support for the SIGUSR2 handler, as described in #253 (comment).

[codecov-io]

Codecov Report

Merging #258 into master will increase coverage by 0.11%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #258      +/-   ##
==========================================
+ Coverage   74.26%   74.37%   +0.11%     
==========================================
  Files          17       17              
  Lines         882      886       +4     
==========================================
+ Hits          655      659       +4     
  Misses        227      227

Impacted Files	Coverage Δ
src/cli.js	60.5% <100%> (+1.03%)	⬆️

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[rauchg]

I'm ok with supporting this if we document in README? Unless it's a standard that I don't know about. cc @adamelliotfields

[guybedford]

So as far as I'm aware Node.js has no "generic" signal handling - all signals need to be handled individually by name, which does seem quite restrictive unfortunately.

In theory, we could support all signals as exit indicators (http://man7.org/linux/man-pages/man7/signal.7.html and I seriously considered this), but a good approach I think can be to expand this list based on user scenarios like this one. Unless anyone has other suggestions for how best to handle these signal responses generically.

[guybedford]

Another altenative here might be just to remove this error case scenario entirely and always just act as if ncc run -f were the default.

[adamelliotfields]

I'm with @guybedford for expanding the list based on user requests. Honestly, the only time I've encountered SIGUSR2 was with nodemon.

As for the docs, it would certainly be worthwhile to include instructions to users on how to gracefully handle signals. I'm using terminus which uses stoppable internally; but the way you handle it in serve is quite nice as well.

https://github.com/zeit/serve/blob/b7d9de3f647c78c581d8e9a6d33d4b63ab9cdbfb/bin/serve.js#L142-L155

Ideally, I'd like ncc to replace nodemon and ts-node so I can use the same tool in development and production 😄

[rauchg]

I hear you. I'm still really on the fence about watch mode. I'm not convinced ncc is as fast as it can be yet when re-running it "cold".

[guybedford]

I've posted #265 which can supersede this.