Error: Problem validating fields in app.json

Actual Behavior

I got the following message when starting up my first project:

Starting packager...
***ERROR STARTING PACKAGER***

Error: Problem validating fields in app.json. See https://docs.expo.io/versions/v25.0.0/guides/configuration.html.
 • Field: slug - 'slug' should match pattern "^[a-zA-Z0-9\-]+$".
Packager started!

Steps to Reproduce

I just updated my node to version 9.5.0 And wanted to try my hand at using create-react-native-app

1. Installed node 9.5.0 using homebrew
2. installed create-react-native-app using npm install -g create-react-native-app
3. created my app within a folder using create-react-native-app project_name
4. cd into the folder and used npm start

Expected Behavior

Is it necessary to use yarn? I’ve not used it before but notice lots of the help that was output was saying to use yarn start? Is this actually causing me an issue or is this error unimportant?

I apologize if I’m not posting in the right place in any way. I’m newer to online community as a whole as I’m beginning my professional exploration of programming. If I am in error please accept my apologies and if possible point me somewhere I should be! I landed here after searching for my issue and finding similar posts here, but none identical (that I could find).

[bnowak008]

I just ran into this problem. It’s because the project name has the underscore. Doesn’t comply with the fields pattern. • Field: slug - ‘slug’ should match pattern “^[a-zA-Z0-9-]+$”.

[iamclaytonray]

Hey @prodeniser - I’m not sure why that error is occurring. I’m newer to Expo. Can you add this to you app.json and see if your build works?

app.json:

{
  "expo": {
    "sdkVersion": "25.0.0",
    "slug": "project_name"
  }
}