How to use more than 1 set of rules in extends in eslint yaml file? - node.js

Question

If I have
env:
commonjs: true
es6: true
node: true
extends:
- plugin:mocha/recommended
...
I get no error, i.e. linting passes with
eslint .
but if I try and add in eslint:recommended in addition to the mocha one, i.e.
env:
commonjs: true
es6: true
node: true
extends:
- eslint:recommended
- plugin:mocha/recommended
...
I get loads of errors as the mocha one isn't applied
71:3 error 'it' is not defined no-undef <-- from the mocha tests
How can I have both recommendations in a yaml file?

Answer 1

This is nothing to do with using a YAML file, and the Mocha plugin is being applied in both cases. The first linting passes because, without eslint:recommended, the rule no-undef is not enabled. For example, given the following basic setup:
temp/
node_modules/
.eslintrc.yml
package.json
package-lock.json
test.js
Where test.js contains:
describe("something",function () {
it("should pass linting", function () {});
});
and .eslintrc.yml contains:
extends:
- plugin:mocha/recommended
then linting passes. But if I just add that one rule:
extends:
- plugin:mocha/recommended
rules:
no-undef: error
then linting fails with:
path/to/temp/test.js
1:1 error 'describe' is not defined no-undef
2:3 error 'it' is not defined no-undef
✖ 2 problems (2 errors, 0 warnings)
Per the configuration docs, you need to set the environment for the globals to be defined; for example, the following configuration is back to passing:
env:
mocha: true
extends:
- plugin:mocha/recommended
rules:
no-undef: error
Now you can enable the full suite of recommended rules and still pass linting:
env:
mocha: true
extends:
- eslint:recommended
- plugin:mocha/recommended