Today, I encountered a bug that I believe should have been caught by the type system. Let me illustrate with an example:
function getModel(): Model { /* ... */ }
function processModelName(name: string) {
return name.replace('x', 'y') // recently added code
}
const model = getModel();
processModelName(model?.name);
The code above does not produce any TypeScript errors.
However, even though it is not declared, getModel could potentially return undefined. The function getModel is an external dependency, so changing its return type to undefined|Model is not possible. Even when hovering over the model variable, it appears to be of type Model.
Why is this type information getting lost? I expected that using optional chaining with processModelName would raise an error, as the function only accepts strings and we are dealing with a potential nullish case here.
How can this be configured in tsconfig.json?