Rules fail with ESLint 9.0.0 - context.getScope is not a function

[tillig]

It appears there have been quite a few breaking changes with ESLint 9.0.0, and with that it looks like context.getScope() is no longer an available shortcut.

• It was there in v8.57.0 of ESLint
• It's gone in v9.0.0 of ESLint

It looks like a PR got merged that has the fix for this back on Feb 16, but it appears that hasn't been released yet - it's not in v10.4.1, which is the current latest.

Is there a plan to release that in the near future?

[MikeMcC399]

This issue relates to the blog Preparing your custom rules for ESLint v9.0.0 published on Sep 26, 2023

Good to see that there is already a merged PR for this as Eslint v9 was announced released on Apr 5, 2024.

[lo1tuma]

Thanks for reporting. I will take a look into it and try to make a patch release ASAP.

[lo1tuma]

I’ve cherry-picked the changes from #347 and made a patch release v10.4.2. Unfortunately I forgot to make a release after merging #347 to main and now main contains a few breaking changes which are planned for v11.

Please let me know if v10.4.2 fixes the issues with ESLint v9.

[MikeMcC399]

@lo1tuma

Please let me know if v10.4.2 fixes the issues with ESLint v9.

I tested with eslint@9.0.0 and my errors were gone. I also checked for backwards compatibility with eslint@8.57.0 and I saw no issue.

Many thanks!

[lo1tuma]

@MikeMcC399 thanks for confirming... in this case I will close this issue.

[tillig]

Yup, also verified. Thanks!

[mcat95]

Hello,

I believe the 10.4.2 patch broke compatibility with eslint versions prior to 8 (We get the error on 7.32.0):
TypeError: Cannot read properties of undefined (reading 'getScope')

[MikeMcC399]

@mcat95

I believe the 10.4.2 patch broke compatibility with eslint versions prior to 8 (We get the error on 7.32.0): TypeError: Cannot read properties of undefined (reading 'getScope')

Ouch!

It sounds like this needs to be a new issue leading to a new fix release.

The example in https://eslint.org/blog/2023/09/preparing-custom-rules-eslint-v9/#context.getscope() shows supporting both the deprecated API and the new API. If only the new API has been implemented, then it would break compatibility with anything below ESLint v8.37.0 🤭

module.exports = {
    create(context) {

        const { sourceCode } = context;

        return {
            Program(node) {
                const scope = sourceCode.getScope
                    ? sourceCode.getScope(node)
                    : context.getScope();

                // do something with scope
            }
        }
    }
};

[MikeMcC399]

@mcat95

• It's good that you spotted this issue and reported it! I've submitted it as a new open issue Regression: eslint-plugin-mocha@10.4.2 fails with eslint@8.39.0 and lower #354.

[MikeMcC399]

@mcat95

This was fixed in 10.4.3.