NPM and Yarn may only warn about this, but it could be better to avoid altogether.
This rule aims to ensure the uniqueness of a package.
Examples of incorrect code for this rule:
{
"dependencies": {
"foo": "0.0.0"
},
"devDependencies": {
"foo": "0.0.0"
}
}
Examples of correct code for this rule:
{
"dependencies": {
"foo": "0.0.0"
}
}
{
"dependencies": {
"foo": "0.0.0"
},
"devDependencies": {
"bar": "0.0.0"
}
}
Since it doesn't hurt to have this problem, you could ignore it.