[FeatureRequest] Allow jest to be ran without watch mode.

[ricokahler]

It seems like the only way to get jest to run in without watch mode is to run it with --coverage or set the environment variable to CI=true. Running npm test -- --watch=false (and similar) does not work.

My use case for this feature is debugging within VS Code through react scripts.

The following launch configuration was given in the create-react-app docs

{
  "version": "0.2.0",
  "configurations": [
    {
      "name": "Debug CRA Tests",
      "type": "node",
      "request": "launch",
      "runtimeExecutable": "${workspaceRoot}/node_modules/.bin/react-scripts",
      "args": [
        "test",
        "--runInBand",
        "--no-cache"
      ],
      "cwd": "${workspaceRoot}",
      "protocol": "inspector",
      "console": "integratedTerminal",
      "internalConsoleOptions": "neverOpen"
    }
  ]
}

This somewhat works but it does not break at breakpoints because (I think) react-scripts is runs jest in watch mode. Adding "env": { "CI": "true" }, allows breakpoints to work again because it disables watch mode.

{
  // Use IntelliSense to learn about possible attributes.
  // Hover to view descriptions of existing attributes.
  // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
  "version": "0.2.0",
  "configurations": [
    {
      "name": "Create react app debugging",
      "type": "node",
      "request": "launch",
      "env": { "CI": "true" }, // this makes breakpoints work 
      "runtimeExecutable": "${workspaceRoot}/node_modules/.bin/react-scripts",
      "args": ["test", "--runInBand", "--no-cache"],
      "cwd": "${workspaceRoot}",
      "protocol": "inspector",
      "console": "integratedTerminal",
      "internalConsoleOptions": "neverOpen"
    }
  ]
}

I'm fine with this workaround but I'd happier with a --watch=false, --no-watch, --single, or similar flag.

Thanks for the amazing tool and I apologize if I missed anything!

Somewhat related issues:

#784
#1137

[rally25rs]

+1 for this feature, especially considering #2393 (when in watch mode on linux, it fails with too many file watchers)

The fix for this is in jest@24, but as of now, react-scripts is locked to jest@23.6.0 but if you could run jest not in watch mode, then it would be a way to workaround the above issue.

[mrmckeb]

I think we need to address this, as it is raised often. I'd be open to a PR adding --no-watch.

@rally25rs, I'm not sure what feature you're referring to - can you provide a link?

I use it with watch-mode on Linux (Ubuntu) and it works well locally.

[ricokahler]

@mrmckeb I put up this one-line PR for --watch=false #6285 if you didn't see. Not sure if it solves the problem the correct way but the simple change seemed to do the job.

[rally25rs]

@mrmckeb #2393 and jestjs/jest#3254 are the issues I'm trying to resolve. In a very simple new react app (crate-react-app plus react-router and react-bootstrap; and the project has 2 views in it so far just to test out react-router):

vagrant@vagrant-ubuntu-trusty-64:~/projects/business_continuity/management_ui$ yarn test
yarn run v1.13.0
$ react-scripts test
internal/fs/watchers.js:173
    throw error;
    ^

Error: ENOSPC: System limit for number of file watchers reached, watch '/home/vagrant/projects/business_continuity/management_ui/node_modules/eslint-plugin-react/node_modules/resolve/test/module_dir/ymodules'
    at FSWatcher.start (internal/fs/watchers.js:165:26)
    at Object.watch (fs.js:1254:11)
    at NodeWatcher.watchdir (/home/vagrant/projects/business_continuity/management_ui/node_modules/sane/src/node_watcher.js:175:20)
    at Walker.<anonymous> (/home/vagrant/projects/business_continuity/management_ui/node_modules/sane/src/common.js:116:12)
    at Walker.emit (events.js:182:13)
    at /home/vagrant/projects/business_continuity/management_ui/node_modules/walker/lib/walker.js:69:16
    at go$readdir$cb (/home/vagrant/projects/business_continuity/management_ui/node_modules/graceful-fs/graceful-fs.js:162:14)
    at FSReqWrap.oncomplete (fs.js:141:20)
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

the issue seems to be that react-scripts forces jest --watch and jest then tries to watch every file in node_modules (i base this on the comments of these linked issues. it seems to make sense anyway, as my actual project not including node_modules only has a couple dozen files)

In the linked issue there is a comment that this is fixed in jest@24 but react-scripts errors if you use any version but 23.6.0. It also prevents you from setting the jest config option watchPathIgnorePatterns which you could use to tell jest to no longer watch files in node_modules. There is also no way to run jest without --watch and avoid this altogether.

react@16.7.0
react-scripts@2.1.3
jest@23.6.0

[mrmckeb]

We need to bump to jest@24, agreed @rally25rs. For now though, a no-watch flag would help a lot of people.