Description
(Note: I couldn’t find any issue template/info about feature requests, I hope this is ok! 🙏 )
Summary: Disallow .join() calls on Arrays that aren’t Array<string>.
Motivation:
I had a function like this:
function noCommonRoot(paths: Array<string>): string {
return `
I could not find a common ancestor for these paths:
${paths.join("\n")}
Files on different drives is not supported.
`.trim();
}I had trouble with using too much string types an mixing stuff up, so I introduced an AbsolutePath type to help me, and replaced string with AbsolutePath in many places.
type AbsolutePath = { tag: "AbsolutePath"; absolutePath: string };
function noCommonRoot(paths: Array<AbsolutePath>): string {
return `
I could not find a common ancestor for these paths:
${paths.join("\n")}
Files on different drives is not supported.
`.trim();
}When I had fixed all compile errors, I had accidentally introduced a bug! noCommonRoot now outputs:
I could not find a common ancestor for these paths:
[object Object]
[object Object]
[object Object]
Files on different drives is not supported.
Oops!
I searched for .join in the entire project and switched to using this function instead, to avoid this problem in the future:
function join(array: Array<string>, separator: string): string {
return array.join(separator);
}That way I could fix the noCommonRoot function:
function noCommonRoot(paths: Array<AbsolutePath>): string {
return `
I could not find a common ancestor for these paths:
${join(
paths.map((path) => path.absolutePath),
"\n"
)}
Files on different drives is not supported.
`.trim();
}Bonus: my join function requires the separator argument. That would be nice to lint too. The default "," is never what I want.