no-unnecessary-mapfilter

Please describe what the rule should do: reports on unnecessary use of .filter and .map on arrays. could be split into 2 rules, one for unnecessary use of .filter and one for unnecessary use of .map

What category of rule is this? (place an “X” next to just one item)

[x] Warns about a potential error (problem) [ ] Suggests an alternate way of doing something (suggestion) [ ] Enforces code style (layout) [ ] Other (please specify:)

Provide 2-3 code examples that this rule will warn about:

const myArr = [1,2,3];
myArr.filter(x => true) // filter isn't filtering any items

const myArr = [];
myArr.filter(x => 1)  // filter isn't filtering any items

const myArr = [];
myArr.map(x => x) // map isn't mapping to something new, unless a shallow copy is the goal which in case one should go for .slice(0)

Why should this rule be included in ESLint (instead of a plugin)? it’s simple enough to be a part of eslint, maybe too simple to be a part of eslint? ❓

Are you willing to submit a pull request to implement this rule? yes

[silverwind]

Proposal at https://github.com/eslint/eslint/issues/12980.

[silverwind]

Yes. I will after checking if there if there are any more methods that could benefit, not strictly limited to Array.