linter.verify does not validate rule configs

[not-an-aardvark]

Tell us about your environment

• ESLint Version: master
• Node Version: 7.7.4
• npm Version: 4.1.2

What did you do? Please include the actual source code causing the issue.

require("eslint").linter.verify("foo", {
    rules: {
        "no-restricted-properties": ["error", "foo"]
    }
});

What did you expect to happen?

I expected core to throw a config validation error. Note that ["foo"] is not a valid config for the no-restricted-properties rule, which accepts a list of objects.

What actually happened? Please include the actual, raw output from ESLint.

ESLint returns an empty array (i.e. reports no problems). The no-restricted-properties rule gets run with a string option, violating its schema invariant. (no-restricted-properties happens to handle this gracefully and report no errors, but some other rules crash when this happens.)

I'm pretty sure this is a bug -- although linter doesn't get configs from the filesystem, it seems like it should still preserve invariants for rules by throwing an error rather than having undefined behavior when a config is invalid.

[ilyavolodin]

I'm not sure it would be a good idea to validate config in linter. Doing that would validate config for every single file that you lint, vs. validating actual config. I think this could affect performance in a significant way.

[platinumazure]

In addition to @ilyavolodin's comments, I also feel that config validation would violate single responsibility principle for the linter object and so it wouldn't make sense architecturally.

[not-an-aardvark]

It seems like this is working as intended, so I'll close it. I had opened it because I thought it was unintended behavior (seems like we shouldn't expose an API that allows rules to be passed an invalid schema).