[Packager] Watchman fails silently if no root_files are found (ex. .git)

[jaredly]

I kept getting this error:

 ERROR  Watcher took too long to load
Try running `watchman version` from your terminal
https://facebook.github.io/watchman/docs/troubleshooting.html
Error: Watcher took too long to load
Try running `watchman version` from your terminal
https://facebook.github.io/watchman/docs/troubleshooting.html
    at [object Object]._onTimeout (/Users/jaredly/clone/meditrate/node_modules/react-native/packager/react-packager/src/FileWatcher/index.js:98:16)
    at Timer.listOnTimeout (timers.js:110:15)

See http://facebook.github.io/react-native/docs/troubleshooting.html
for common problems and solutions.

And reinstalled watchman a bunch of times, restarted my mac, etc...

Digging into the sane package, and adding this patch, I was able to discover that the actual watchman error (it was working just fine) was:

resolve_projpath: none of the files listed in global config root_files are present in path `{the project root}` or any of its parent directories

Which really meant: running git init solved everything. But I wasted a lot of time wondering why things were broken.

So I think the right thing to do here is turn off enforce_root_files.

[wez]

@jaredly FWIW, at FB, we require enforce_root_files to be set to avoid having folks unwittingly create overlapping watches. Because our source trees are so large this is a very real cause of performance and reliability issues with watching the filesystem, and is in fact the reason why this feature even exists :-)

@amasad is this a side effect of using watch-project exclusively now in sane? Do we know if the only people that are hitting this are at FB? I don't believe that folks outside FB will have the root files restrictions enabled, and certainly not by default. It would be great to double check what is happening there as watch-project is supposed to fall back to watching the directory of interest if we can't locate a root.

[jaredly]

Ok -- yeah I guess it's just because of the watchman config in /etc/watchman.json.
This is an error that we should be able to detect though (as soon as sane exposes error events), and report.

[linshu123]

I just spent half an hour on this problem. It should really be documented in the troubleshooting page.