It is not an anti-pattern to call setState in componentDidMount. In fact, ReactJS provides an example of this in their documentation:
You should populate data with AJAX calls in the componentDidMount lifecycle method. This is so you can use setState to update your component when the data is retrieved.
componentDidMount() {
fetch("https://api.example.com/items")
.then(res => res.json())
.then(
(result) => {
this.setState({
isLoaded: true,
items: result.items
});
},
// Note: it's important to handle errors here
// instead of a catch() block so that we don't swallow
// exceptions from actual bugs in components.
(error) => {
this.setState({
isLoaded: true,
error
});
}
)
}