Drop or change hard-coded ecmaVersion

[brettz9]

I ran into some issues with the Cypress plugin hard-coding ES2019 to my files, not letting me use BigInt literals, for example.

I don't see any reason why Cypress has to have a particular ecmaVersion setting. The new default with ESLint is to use ecmaVersion: 'next'. If the purpose is to be more careful than the default, ensuring projects will err if they try to use too advanced of a feature for their browsers, one can use https://github.com/keithamus/eslint-plugin-escompat which, while it sets ecmaVersion to a recent version (now ES2023), detects the project's browser targets and provides linting errors if too recent of ES features are used.

[MikeMcC399]

@brettz9

Are you suggesting to drop ecmaVersion: 2019 setting for both legacy and flat configs?

eslint-plugin-cypress/legacy.js

Lines 27 to 30 in 0e835e9

	parserOptions: {
	ecmaVersion: 2019,
	sourceType: 'module',
	},

eslint-plugin-cypress/lib/flat.js

Lines 29 to 32 in 0e835e9

	const commonLanguageOptions = {
	ecmaVersion: 2019,
	sourceType: 'module'
	}

You say you had some issues. Were you able to override the settings in your local ESlint config?

I would definitely be in favor of dropping some backwards-compatible settings and configurations at an appropriate time moving forward.

v3.0.0 was a breaking change due to dropping support for ESLint v3, v4, v5 & v6. Apart from that, backwards-compatibility has been maintained. Currently there are still far more downloads of the v2.x plugin compared to the v3.x plugin, so uptake is slow-moving!

[brettz9]

@brettz9

Are you suggesting to drop ecmaVersion: 2019 setting for both legacy and flat configs?

Yes.

eslint-plugin-cypress/legacy.js

Lines 27 to 30 in 0e835e9

	parserOptions: {
	ecmaVersion: 2019,
	sourceType: 'module',
	},

eslint-plugin-cypress/lib/flat.js

Lines 29 to 32 in 0e835e9

	const commonLanguageOptions = {
	ecmaVersion: 2019,
	sourceType: 'module'
	}

You say you had some issues. Were you able to override the settings in your local ESlint config?

Yes.

I would definitely be in favor of dropping some backwards-compatible settings and configurations at an appropriate time moving forward.

v3.0.0 was a breaking change due to dropping support for ESLint v3, v4, v5 & v6. Apart from that, backwards-compatibility has been maintained. Currently there are still far more downloads of the v2.x plugin compared to the v3.x plugin, so uptake is slow-moving!

Yeah, removing it would probably not be backward-compatible, because for some it could be a higher ecmaVersion than their default. But setting it higher, e.g., to 2025 may work, but that would depend on their ESLint version supporting that as a value (and would require your periodically updating).

[MikeMcC399]

I would prefer to drop support for legacy configs completely and to move to the default ecmaVersion at some convenient stage so that the plugin is fully aligned with ESLint itself.

[MikeMcC399]

I'm going to suggest removing the commonLanguageOptions in the flat config of the next major release of the plugin. ESLint v8 reaches end-of-life on Oct 5, 2024 and that could be a trigger to provide a new release very soon.

I prefer not touching the legacy config though to avoid breaking existing setups, since there is no default for legacy. Users who need a higher version will probably already have an override in their configuration. Users who don't, might get surprised if this is updated. You could however argue either way - to keep or to update.

[Jikodis]

Adding cypressPlugin.configs.recommended to my existing flat config started throwing linting errors in my code since I use optional chaining. I agree with the decision to remove ecmaVersion in the flat config.

[MikeMcC399]

• PR feat: minimum version eslint v9 #234 is now submitted to remove the ecmaVersion from the flat config.

[MikeMcC399]

This issue is now resolved in [email protected] as far as flat configurations are concerned.

As described in the Flat Usage examples:

This version no longer specifies languageOptions for ecmaVersion and sourceType - see ESLint JavaScript languageOptions

Note that since ESLint v8 has reached end-of-life, it is no longer supported by eslint-plugin-cypress.

Deprecated legacy configuration

No change has been made to the deprecated legacy configuration parserOptions for backwards compatibility reasons, and this configuration is considered frozen. When a legacy configuration is used with ESLint 9.1 and above (ESLINT_USE_FLAT_CONFIG=false), ESLint outputs a warning similar to the following:

(node:25528) ESLintRCWarning: You are using an eslintrc configuration file, which is deprecated and support will be removed in v10.0.0. Please migrate to an eslint.config.js file. See https://eslint.org/docs/latest/use/configure/migration-guide for details.
(Use node --trace-warnings ... to show where the warning was created)