Validator fails ES2019 public field declaration

[erosman]

ref: 75.0a1 (2020-02-27) (64-bit)

Validator fails ES2019 public field declaration even though Firefox works fine with.

Example:

class MyClass {

  a = 1;
  b = 2;
  c = 3;

}

PS. If support was added to Firefox, which version is it from?

[Rob--W]

This is not a "variable outside the constructor". It is a (public) field declaration, supported in Firefox as of version 75 (and Chrome 74+), with the relevant bug being https://bugzilla.mozilla.org/show_bug.cgi?id=1499448 . The documentation is at https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes/Class_fields#Public_fields (scroll a bit below to "Public instance fields" for your specific case).

[erosman]

Thank you Rob. Title updated.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes/Class_fields#Public_fields states support from Firefox 69 !!

[Rob--W]

I stand corrected; Public instance fields (what you're using here) have already been supported since 69 (https://bugzilla.mozilla.org/show_bug.cgi?id=1555464).

I had public static fields in mind (syntax is class {static name = value}), which differs from what you've reported here, and is supported in Firefox 75+ (https://bugzilla.mozilla.org/show_bug.cgi?id=1535804).

[lfilho]

Arrived here for the same reason.
Tried running the web-ext lint --ignore-files "**/.*js" in an attempt to let the addons-linter only lint the manifes.json file and leave all the .js files to my local eslint setup, but that --ignore-files argument is actually applied to web-ext and not only to the lint subcommand, failing the lint command completely with: "content script defined in the manifest could not be found at "content_script.js"".

Right now I'm just stopping to use web-ext lint anymore :-/

Ideally addons-linter would be able to identify an eslint already installed in the user's package.json and use that one instead?

Or maybe a even better idea is instead of having a customer linter here, you would create an eslint plugin/preset for WebExtensions instead?

Anyway, thanks!

[lfilho]

Another great workaround would be if we could just say: web-ext lint file-to-lint-1 file-to-lint-2. This way i could just point it to manifes.json while keeping the rest of of my .js files being linted by the eslint in my project.

[willdurand]

see also: #2758

[devsecdan]

I stand corrected; Public instance fields (what you're using here) have already been supported since 69 (https://bugzilla.mozilla.org/show_bug.cgi?id=1555464).

I had public static fields in mind (syntax is class {static name = value}), which differs from what you've reported here, and is supported in Firefox 75+ (https://bugzilla.mozilla.org/show_bug.cgi?id=1535804).

Ran into this issue today. Unable to publish my extension because it makes use of static fields.

[rpl]

Unfortunately this issue is still blocked on an upstream change: eslint officially supporting the class fields tc39 proposal.

It looks that the class fields tc39 proposal is still at stage 3 (see https://github.com/tc39/proposal-class-fields) and I'm pretty sure that eslint does not usually introduce support for new javascript syntaxes until their tc39 proposal does reach stage 4.

[regseb]

You can use @babel/eslint-parser and @babel/plugin-proposal-class-properties in ESLint configuration to support class field.

{
    parser: "@babel/eslint-parser",
    parserOptions: {
        requireConfigFile: false,
        babelOptions: {
            plugins: [
                "@babel/plugin-proposal-class-properties"
            ]
        }
    }
}

[muzuiget]

Please fix this issue.

Currently "Class Fields" feature is on stage 4, and Webpack 5 already supports it a few days ago webpack/webpack#10216

[Rob--W]

Depends on eslint/eslint#14343

[lydell]

ESLint v8.0.0-beta.0 (and ESLint v8.0.0-beta.1) have been released – with support for class fields – so if anyone would like to begin work on this, I guess it’s possible now!

[ioanarusiczki]

@willdurand
I verified this locally and with AMO dev using the example above and from docs

This was before:

publicfield.zip
publicfield2.zip