Allow users to ignore mutants based on heuristics

[nicojs]

Is your feature request related to a problem? Please describe.

We have had a couple of requests in the past to allow to ignore specific mutants:

#2966 #1174 #1470 #1464

Some of these issues have been solved by allowing users to ignore using a comment, however, this isn't always practical.

For large codebases where you want to ignore the same pattern every time. For example: console.log().

Or you want to ignore mutants based on some other data, for example using the result of a git command, like the git checker seems to be doing.

Describe the solution you'd like

I would like to be able to ignore specific mutants based on heuristics (for lack of a better word). It would be run inside the instrumenter on each AST node visitation. It could then decide to ignore the current node with a reason.

The API could look like this

interface Ignorer {
  shouldIgnore(path: NodePath): string | void;  
}

We should document some examples for common use cases, like ignoring console.log statements. Issue #3230 needs to be solved to allow for locally defined plugins.

Describe alternatives you've considered

There are a number of issues linked where users thought of different approaches. However, I think this abstraction makes the most sense. It allows for the most freedom.

Additional context

All current plugin APIs are located inside the @stryker-mutator/api package. I want this to be no exception. However, the NodePath interface comes from @babel/core. I don't want that to be part of the dependencies of the API package. So we might want to mark it as a dev dependency 🤷‍♀️

[nicojs]

Note: we currently already have some arbitrary ignore rules configured in the babel-transformer. A good approach might be to abstract those away in Ignore plugins as well. It's a good test for the versatility of this plugin kind.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[nicojs]

Ignore-plugins are released in StrykerJS 7.3 🎉

https://twitter.com/stryker_mutator/status/1713557660832792870

https://stryker-mutator.io/docs/stryker-js/disable-mutants/#using-an-ignore-plugin