scribbles: attempt to add eslint

[sandersn]

This PR collects the notes about switching to ESLint.

So far:

1. Add dependencies in package.json
2. Hack lint.ts to call eslint instead of tslint.
3. Collect a list of tslint overrides that will need to be ported.

I've also got an in-progress .eslintrc.js[on] in my clone of DT which I will add here in a comment. I used tslint-to-eslint-config to produce the initial version, which didn't seem to be super accurate.

I haven't started porting any of our custom rules.

[sandersn]

.eslintrc.js:

/*
👋 Hi! This file was autogenerated by tslint-to-eslint-config.
https://github.com/typescript-eslint/tslint-to-eslint-config

It represents the closest reasonable ESLint configuration to this
project's original TSLint configuration.

We recommend eventually switching this configuration to extend from
the recommended rulesets in typescript-eslint. 
https://github.com/typescript-eslint/tslint-to-eslint-config/blob/master/docs/FAQs.md

Happy linting! 💖
*/
module.exports = {
    "env": {
        "browser": true,
        "es6": true
    },
    "parser": "@typescript-eslint/parser",
    "parserOptions": {
        "project": "../DefinitelyTyped/types/aframe/tsconfig.json",
        "sourceType": "module"
    },
    "plugins": [
        "eslint-plugin-prefer-arrow",
        "eslint-plugin-import",
        "eslint-plugin-no-null",
        "eslint-plugin-unicorn",
        "eslint-plugin-jsdoc",
        "@typescript-eslint",
        "@typescript-eslint/tslint"
    ],
    "rules": {
        "@typescript-eslint/adjacent-overload-signatures": "error",
        "@typescript-eslint/array-type": [
            "error",
            {
                "default": "array-simple"
            }
        ],
        "@typescript-eslint/await-thenable": "error",
        "@typescript-eslint/ban-ts-comment": "error",
        "@typescript-eslint/ban-types": [
            "error",
            {
                "types": {
                    "object": false,
                    "{}": false,
                    "Object": {
                        "message": "Avoid using the `Object` type. Did you mean `object`?"
                    },
                    "Function": {
                        "message": "Avoid using the `Function` type. Prefer a specific function type, like `() => void`."
                    },
                    "Boolean": {
                        "message": "Avoid using the `Boolean` type. Did you mean `boolean`?"
                    },
                    "Number": {
                        "message": "Avoid using the `Number` type. Did you mean `number`?"
                    },
                    "String": {
                        "message": "Avoid using the `String` type. Did you mean `string`?"
                    },
                    "Symbol": {
                        "message": "Avoid using the `Symbol` type. Did you mean `symbol`?"
                    }
                }
            }
        ],
        "@typescript-eslint/consistent-type-assertions": "error",
        "@typescript-eslint/consistent-type-definitions": "error",
        "@typescript-eslint/dot-notation": "off",
        "@typescript-eslint/explicit-member-accessibility": [
            "error",
            {
                "accessibility": "no-public"
            }
        ],
        "@typescript-eslint/indent": "off",
        "@typescript-eslint/member-delimiter-style": [
            "error",
            {
                "multiline": {
                    "delimiter": "semi",
                    "requireLast": true
                },
                "singleline": {
                    "delimiter": "semi",
                    "requireLast": false
                }
            }
        ],
        "@typescript-eslint/member-ordering": "off",
        "@typescript-eslint/naming-convention": "off",
        "@typescript-eslint/no-empty-function": "off",
        "@typescript-eslint/no-empty-interface": "error",
        "@typescript-eslint/no-explicit-any": "off",
        "@typescript-eslint/no-extraneous-class": "error",
        "@typescript-eslint/no-floating-promises": "off",
        "@typescript-eslint/no-for-in-array": "error",
        "@typescript-eslint/no-inferrable-types": [
            "error",
            {
                "ignoreParameters": true
            }
        ],
        "@typescript-eslint/no-misused-new": "error",
        "@typescript-eslint/no-namespace": "error",
        "@typescript-eslint/no-non-null-assertion": "off",
        "@typescript-eslint/no-param-reassign": "off",
        "@typescript-eslint/no-parameter-properties": "off",
        "@typescript-eslint/no-require-imports": "off",
        "@typescript-eslint/no-shadow": [
            "off",
            {
                "hoist": "all"
            }
        ],
        "@typescript-eslint/no-this-alias": "off",
        "@typescript-eslint/no-unnecessary-boolean-literal-compare": "error",
        "@typescript-eslint/no-unnecessary-qualifier": "error",
        "@typescript-eslint/no-unnecessary-type-arguments": "error",
        "@typescript-eslint/no-unnecessary-type-assertion": "error",
        "@typescript-eslint/no-unused-expressions": "off",
        "@typescript-eslint/no-unused-vars": "off",
        "@typescript-eslint/no-use-before-define": "off",
        "@typescript-eslint/no-var-requires": "error",
        "@typescript-eslint/prefer-for-of": "error",
        "@typescript-eslint/prefer-function-type": "off",
        "@typescript-eslint/prefer-namespace-keyword": "error",
        "@typescript-eslint/prefer-readonly": "error",
        "@typescript-eslint/promise-function-async": "off",
        "@typescript-eslint/quotes": "off",
        "@typescript-eslint/require-await": "error",
        "@typescript-eslint/restrict-plus-operands": "off",
        "@typescript-eslint/semi": [
            "error",
            "always"
        ],
        "@typescript-eslint/strict-boolean-expressions": "off",
        "@typescript-eslint/triple-slash-reference": [
            "off",
            {
                "path": "always",
                "types": "prefer-import",
                "lib": "always"
            }
        ],
        "@typescript-eslint/type-annotation-spacing": "error",
        "@typescript-eslint/unbound-method": "off",
        "@typescript-eslint/unified-signatures": "error",
        "arrow-body-style": "error",
        "arrow-parens": [
            "off",
            "always"
        ],
        "brace-style": [
            "error",
            "1tbs"
        ],
        "class-methods-use-this": "off",
        "comma-dangle": "off",
        "complexity": "off",
        "constructor-super": "error",
        "curly": "off",
        "default-case": "off",
        "eol-last": "error",
        "eqeqeq": [
            "error",
            "smart"
        ],
        "guard-for-in": "off",
        "id-blacklist": "off",
        "id-match": "off",
        "import/no-default-export": "off",
        "import/no-deprecated": "off",
        "import/no-extraneous-dependencies": "off",
        "import/no-internal-modules": "off",
        "import/no-unassigned-import": "off",
        "import/order": "off",
        "jsdoc/check-alignment": "error",
        "jsdoc/check-indentation": "error",
        "jsdoc/newline-after-description": "error",
        "jsdoc/no-types": "off",
        "linebreak-style": "off",
        "max-classes-per-file": "off",
        "max-len": [
            "error",
            {
                "code": 200
            }
        ],
        "max-lines": "off",
        "new-parens": "error",
        "newline-per-chained-call": "off",
        "no-bitwise": "off",
        "no-caller": "error",
        "no-cond-assign": "error",
        "no-console": "off",
        "no-debugger": "error",
        "no-duplicate-case": "error",
        "no-duplicate-imports": "error",
        "no-empty": "off",
        "no-eval": "error",
        "no-extra-bind": "error",
        "no-irregular-whitespace": "error",
        "no-magic-numbers": "off",
        "no-multiple-empty-lines": "error",
        "no-new-func": "error",
        "no-new-wrappers": "error",
        "no-null/no-null": "off",
        "no-plusplus": [
            "off",
            {
                "allowForLoopAfterthoughts": true
            }
        ],
        "no-redeclare": "off",
        "no-return-await": "error",
        "no-sequences": "error",
        "no-sparse-arrays": "error",
        "no-template-curly-in-string": "error",
        "no-throw-literal": "error",
        "no-trailing-spaces": "error",
        "no-undef-init": "error",
        "no-underscore-dangle": "off",
        "no-unsafe-finally": "error",
        "no-unused-labels": "error",
        "no-useless-constructor": "off",
        "no-var": "error",
        "no-void": "error",
        "object-shorthand": "error",
        "one-var": [
            "error",
            "never"
        ],
        "padding-line-between-statements": [
            "off",
            {
                "blankLine": "always",
                "prev": "*",
                "next": "return"
            }
        ],
        "prefer-arrow/prefer-arrow-functions": "error",
        "prefer-const": "error",
        "prefer-object-spread": "error",
        "prefer-template": "error",
        "quote-props": [
            "error",
            "as-needed"
        ],
        "radix": "error",
        "space-before-function-paren": [
            "error",
            {
                "anonymous": "never",
                "asyncArrow": "always",
                "named": "never"
            }
        ],
        "space-in-parens": [
            "error",
            "never"
        ],
        "spaced-comment": [
            "error",
            "always",
            {
                "markers": [
                    "/"
                ]
            }
        ],
        "unicorn/filename-case": "off",
        "use-isnan": "error",
        "yoda": "off",
        "@typescript-eslint/tslint/config": [
            "error",
            {
                "rules": {
                    "comment-type": [
                        true,
                        "singleline",
                        "multiline",
                        "doc",
                        "directive"
                    ],
                    "dt-header": true,
                    "encoding": true,
                    "expect": true,
                    "export-just-namespace": true,
                    "import-spacing": true,
                    "no-any-union": true,
                    "no-bad-reference": true,
                    "no-const-enum": true,
                    "no-dead-reference": true,
                    "no-declare-current-package": true,
                    "no-dynamic-delete": true,
                    "no-import-default-of-export-equals": true,
                    "no-mergeable-namespace": true,
                    "no-null-undefined-union": true,
                    "no-outside-dependencies": true,
                    "no-padding": true,
                    "no-redundant-jsdoc-2": true,
                    "no-redundant-undefined": true,
                    "no-relative-import-in-test": true,
                    "no-self-import": true,
                    "no-single-declare-module": true,
                    "no-unnecessary-callback-wrapper": true,
                    "no-unnecessary-generics": true,
                    "no-useless-files": true,
                    "npm-naming": [
                        true,
                        {
                            "mode": "code",
                            "errors": [
                                [
                                    "NeedsExportEquals",
                                    false
                                ]
                            ]
                        }
                    ],
                    "prefer-conditional-expression": true,
                    "prefer-declare-function": true,
                    "prefer-switch": true,
                    "prefer-while": true,
                    "static-this": true,
                    "strict-comparisons": true,
                    "strict-export-declare-modifiers": true,
                    "trim-file": true,
                    "void-return": true,
                    "whitespace": [
                        true,
                        "check-branch",
                        "check-decl",
                        "check-operator",
                        "check-module",
                        "check-separator",
                        "check-type",
                        "check-typecast"
                    ]
                }
            }
        ]
    }
};

[sandersn]

12 ESLint rules behave differently from their TSLint counterparts:

• @typescript-eslint/ban-ts-comment:
  • The typescript-eslint now bans @ts- comments from being used
• prefer-arrow/prefer-arrow-functions:
  • ESLint does not support allowing standalone function declarations.
  • ESLint does not support allowing named functions defined with the function keyword.
• no-redeclare:
  • ESLint does not support check-parameters.
• @typescript-eslint/no-unused-expressions:
  • The TSLint optional config "allow-new" is the default ESLint behavior and will no longer be ignored.
• no-void:
  • ESLint does not support ignoring arrow function shorthand.
• eqeqeq:
  • Option "smart" allows for comparing two literal values, evaluating the value of typeof and null comparisons.
• arrow-body-style:
  • ESLint will throw an error if the function body is multiline yet has a one-line return on it.
• no-plusplus:
  • ++ and -- operators will now only be allowed in for loops.
• prefer-template:
  • Single concatenations will no longer be ignored.
• space-before-function-paren:
  • Option "constructor" is not supported by ESLint.
  • Option "method" is not supported by ESLint.
• no-underscore-dangle:
  • Leading or trailing underscores (_) on identifiers will now be forbidden.
• @typescript-eslint/no-unused-vars:
  • Please read the following article as the rule behaviour may change on the short term: [meta] Problems with the rules that use scope analysis [no-unused-vars][no-undef][no-shadow][no-redeclare][no-use-before-define] typescript-eslint/typescript-eslint#1856

36 rules are not known by tslint-to-eslint-config to have ESLint equivalents:

• tslint-to-eslint-config does not know the ESLint equivalent for TSLint's "comment-type".
• tslint-to-eslint-config does not know the ESLint equivalent for TSLint's "dt-header".
• tslint-to-eslint-config does not know the ESLint equivalent for TSLint's "encoding".
• tslint-to-eslint-config does not know the ESLint equivalent for TSLint's "expect".
• tslint-to-eslint-config does not know the ESLint equivalent for TSLint's "export-just-namespace".
• tslint-to-eslint-config does not know the ESLint equivalent for TSLint's "import-spacing".
• tslint-to-eslint-config does not know the ESLint equivalent for TSLint's "no-any-union".
• tslint-to-eslint-config does not know the ESLint equivalent for TSLint's "no-bad-reference".
• tslint-to-eslint-config does not know the ESLint equivalent for TSLint's "no-const-enum".
• tslint-to-eslint-config does not know the ESLint equivalent for TSLint's "no-dead-reference".
• tslint-to-eslint-config does not know the ESLint equivalent for TSLint's "no-declare-current-package".
• tslint-to-eslint-config does not know the ESLint equivalent for TSLint's "no-dynamic-delete".
• tslint-to-eslint-config does not know the ESLint equivalent for TSLint's "no-import-default-of-export-equals".
• tslint-to-eslint-config does not know the ESLint equivalent for TSLint's "no-mergeable-namespace".
• tslint-to-eslint-config does not know the ESLint equivalent for TSLint's "no-null-undefined-union".
• tslint-to-eslint-config does not know the ESLint equivalent for TSLint's "no-outside-dependencies".
• tslint-to-eslint-config does not know the ESLint equivalent for TSLint's "no-padding".
• tslint-to-eslint-config does not know the ESLint equivalent for TSLint's "no-redundant-jsdoc-2".
• tslint-to-eslint-config does not know the ESLint equivalent for TSLint's "no-redundant-undefined".
• tslint-to-eslint-config does not know the ESLint equivalent for TSLint's "no-relative-import-in-test".
• tslint-to-eslint-config does not know the ESLint equivalent for TSLint's "no-self-import".
• tslint-to-eslint-config does not know the ESLint equivalent for TSLint's "no-single-declare-module".
• tslint-to-eslint-config does not know the ESLint equivalent for TSLint's "no-unnecessary-callback-wrapper".
• tslint-to-eslint-config does not know the ESLint equivalent for TSLint's "no-unnecessary-generics".
• tslint-to-eslint-config does not know the ESLint equivalent for TSLint's "no-useless-files".
• tslint-to-eslint-config does not know the ESLint equivalent for TSLint's "npm-naming".
• tslint-to-eslint-config does not know the ESLint equivalent for TSLint's "prefer-conditional-expression".
• tslint-to-eslint-config does not know the ESLint equivalent for TSLint's "prefer-declare-function".
• tslint-to-eslint-config does not know the ESLint equivalent for TSLint's "prefer-switch".
• tslint-to-eslint-config does not know the ESLint equivalent for TSLint's "prefer-while".
• tslint-to-eslint-config does not know the ESLint equivalent for TSLint's "static-this".
• tslint-to-eslint-config does not know the ESLint equivalent for TSLint's "strict-comparisons".
• tslint-to-eslint-config does not know the ESLint equivalent for TSLint's "strict-export-declare-modifiers".
• tslint-to-eslint-config does not know the ESLint equivalent for TSLint's "trim-file".
• tslint-to-eslint-config does not know the ESLint equivalent for TSLint's "void-return".
• tslint-to-eslint-config does not know the ESLint equivalent for TSLint's "whitespace".

[sandersn]

@43081j you might be interested in this

[sandersn]

DT also added the following devDependencies:

        "@typescript-eslint/eslint-plugin-tslint": "^4.19.0",
        "@typescript-eslint/parser": "^4.19.0",
        "danger": "^10.1.1",
        "dtslint": "latest",
        "eslint": "^7.22.0",
        "eslint-plugin-import": "^2.22.1",
        "eslint-plugin-jsdoc": "^32.3.0",
        "eslint-plugin-no-null": "^1.0.2",
        "eslint-plugin-prefer-arrow": "^1.2.3",
        "eslint-plugin-unicorn": "^29.0.0",

and the following dependencies (which should likely be devDeps since there were none before):

    "dependencies": {
        "@typescript-eslint/eslint-plugin": "^4.19.0",
        "tslint": "5.18"
    }

I think this was just to support tslint-to-eslint-config, though

[43081j]

This is great, good to see it picked up again :D

For the eslint config, we could probably trim it down a huge amount by extending eslint and typescript-eslint:

{
  "extends": [
    "eslint:recommended",
    "plugin:@typescript-eslint/eslint-recommended",
    "plugin:@typescript-eslint/recommended"
  ]
}

which means your typescript-eslint rules would come down to these:

{
        "@typescript-eslint/array-type": [
            "error",
            {
                "default": "array-simple"
            }
        ],
        "@typescript-eslint/await-thenable": "error",
        "@typescript-eslint/consistent-type-assertions": "error",
        "@typescript-eslint/consistent-type-definitions": "error",
        "@typescript-eslint/explicit-member-accessibility": [
            "error",
            {
                "accessibility": "no-public"
            }
        ],
        "@typescript-eslint/indent": "off",
        "@typescript-eslint/member-delimiter-style": "error",
        "@typescript-eslint/no-empty-function": "off",
        "@typescript-eslint/no-explicit-any": "off",
        "@typescript-eslint/no-extraneous-class": "error",
        "@typescript-eslint/no-for-in-array": "error",
        "@typescript-eslint/no-inferrable-types": [
            "error",
            {
                "ignoreParameters": true
            }
        ],
        "@typescript-eslint/no-non-null-assertion": "off",
        "@typescript-eslint/no-shadow": "off",
        "@typescript-eslint/no-this-alias": "off",
        "@typescript-eslint/no-unnecessary-boolean-literal-compare": "error",
        "@typescript-eslint/no-unnecessary-qualifier": "error",
        "@typescript-eslint/no-unnecessary-type-arguments": "error",
        "@typescript-eslint/no-unnecessary-type-assertion": "error",
        "@typescript-eslint/no-unused-vars": "off",
        "@typescript-eslint/prefer-for-of": "error",
        "@typescript-eslint/prefer-readonly": "error",
        "@typescript-eslint/require-await": "error",
        "@typescript-eslint/triple-slash-reference": "off",
        "@typescript-eslint/type-annotation-spacing": "error",
        "@typescript-eslint/unified-signatures": "error"
}

i removed all the ones which are:

• missing in the inherited config (which means they are already off)
• the exact same default config than what we had

there will be a few you can remove due to being now inherited from eslint too, but i didn't have chance to diff those.

[43081j]

You can also drop the unnecessary "unicorn" plugin. It isn't used and will have been pulled in just to reference a disabled rule so can be removed entirely instead.

Is the plan to "all or nothing" it? Convert all the rules at once? Would be happy to help if needed

[sandersn]

Yeah, I was planning for all-or-nothing. But it might be easier to double-lint to start, and switch over slowly.

The biggest problem for me is funding, since it's hard for me to spend time on code that works stably and reliably, even though its dependency is not being maintained anymore.

@danvk @JoshuaKGoldberg @OliverJAsh were discussing this on twitter, so maybe they have plans to contribute something.

[43081j]

thats fair enough

@JoshuaKGoldberg @danvk @OliverJAsh this is being tracked by #300, would be useful if you could give input there if you're planning on opening an alternative PR.

hilariously in that issue, i'd previously sent you here! 😂 the ol' switcheroo