fat arrow + implicit return, no-return-assign bug

array.filter(a => a.test = value) does not trigger an error with no-return-assign activated.

eslint version : v1.10.3

.eslintrc.js

module.exports = {
    "ecmaFeatures": {
        "modules": true,
        "experimentalObjectRestSpread": true,
        "jsx": true
    },
    "env": {
        "browser": true,
        "es6": true,
        "node": true
    },
    "plugins": [
        "react"
    ],
    "rules": {
        "accessor-pairs": 2,
        "arrow-spacing": [2, { "before": true, "after": true }],
        "block-spacing": [2, "always"],
        "brace-style": [2, "1tbs", { "allowSingleLine": true }],
        "comma-dangle": [2, "never"],
        "comma-spacing": [2, { "before": false, "after": true }],
        "comma-style": [2, "last"],
        "constructor-super": 2,
        "curly": [2, "multi-line"],
        "dot-location": [2, "property"],
        "eol-last": 2,
        "eqeqeq": [1, "allow-null"],
        "generator-star-spacing": [2, { "before": true, "after": true }],
        "handle-callback-err": [2, "^(err|error)$" ],
        "indent": 2,
        "key-spacing": [2, { "beforeColon": false, "afterColon": true }],
        "new-cap": [2, { "newIsCap": true, "capIsNew": false }],
        "new-parens": 2,
        "no-array-constructor": 2,
        "no-caller": 2,
        "no-class-assign": 2,
        "no-cond-assign": 2,
        "no-const-assign": 2,
        "no-control-regex": 0,
        "no-debugger": 2,
        "no-delete-var": 2,
        "no-dupe-args": 2,
        "no-dupe-class-members": 2,
        "no-dupe-keys": 2,
        "no-duplicate-case": 2,
        "no-empty-character-class": 2,
        "no-empty-label": 2,
        "no-eval": 2,
        "no-ex-assign": 2,
        "no-extend-native": 2,
        "no-extra-bind": 2,
        "no-extra-boolean-cast": 2,
        "no-extra-parens": [2, "functions"],
        "no-fallthrough": 2,
        "no-floating-decimal": 2,
        "no-func-assign": 2,
        "no-implied-eval": 2,
        "no-inner-declarations": [2, "functions"],
        "no-invalid-regexp": 2,
        "no-irregular-whitespace": 2,
        "no-iterator": 2,
        "no-label-var": 2,
        "no-labels": 2,
        "no-lone-blocks": 2,
        "no-mixed-spaces-and-tabs": [2, "smart-tabs"],
        "no-multi-spaces": 2,
        "no-multi-str": 2,
        "no-multiple-empty-lines": [2, { "max": 1 }],
        "no-native-reassign": 2,
        "no-negated-in-lhs": 2,
        "no-new": 2,
        "no-new-func": 2,
        "no-new-object": 2,
        "no-new-require": 2,
        "no-new-wrappers": 2,
        "no-obj-calls": 2,
        "no-octal": 2,
        "no-octal-escape": 2,
        "no-proto": 2,
        "no-redeclare": 2,
        "no-regex-spaces": 2,
        "no-return-assign": 2,
        "no-self-compare": 2,
        "no-sequences": 2,
        "no-shadow-restricted-names": 2,
        "no-spaced-func": 2,
        "no-sparse-arrays": 2,
        "no-this-before-super": 2,
        "no-throw-literal": 2,
        "no-trailing-spaces": 2,
        "no-undef": 2,
        "no-undef-init": 2,
        "no-unexpected-multiline": 2,
        "no-unneeded-ternary": [2, { "defaultAssignment": false }],
        "no-unreachable": 2,
        "no-unused-vars": [2, { "vars": "all", "args": "none" }],
        "no-useless-call": 2,
        "no-with": 2,
        "one-var": [2, { "initialized": "never" }],
        "operator-linebreak": [2, "after", { "overrides": { "?": "before", ":": "before" } }],
        "padded-blocks": [2, "never"],
        "quotes": [2, "double", "avoid-escape"],
        "radix": 2,
        "semi": [2, "never"],
        "semi-spacing": [2, { "before": false, "after": true }],
        "space-after-keywords": [2, "always"],
        "space-before-blocks": [2, "always"],
        "space-before-function-paren": [2, "always"],
        "space-before-keywords": [2, "always"],
        "space-in-parens": 0,
        "space-infix-ops": 2,
        "space-return-throw-case": 2,
        "space-unary-ops": [2, { "words": true, "nonwords": false }],
        "spaced-comment": [2, "always", { "markers": ["global", "globals", "eslint", "eslint-disable", "*package", "!", ","] }],
        "use-isnan": 2,
        "valid-typeof": 2,
        "wrap-iife": [2, "any"],
        "yoda": [2, "never"],
        "react/display-name": 0,
        "react/forbid-prop-types": [1, {"forbid": ["any", "array"]}],
        "react/jsx-boolean-value": 0,
        "react/jsx-closing-bracket-location": 2,
        "react/jsx-curly-spacing": [2, "never"],
        "react/jsx-handler-names": 1,
        "react/jsx-indent-props": [2, 4],
        "react/jsx-key": 0,
        "react/jsx-max-props-per-line": 0,
        "react/jsx-no-bind": 1,
        "react/jsx-no-duplicate-props": 1,
        "react/jsx-no-literals": 0,
        "react/jsx-no-undef": 1,
        "react/jsx-pascal-case": 1,
        "react/jsx-quotes": 1,
        "react/jsx-sort-prop-types": 0,
        "react/jsx-sort-props": 0,
        "react/jsx-uses-react": 2,
        "react/jsx-uses-vars": 1,
        "react/no-danger": 0,
        "react/no-did-mount-set-state": 1,
        "react/no-did-update-set-state": 1,
        "react/no-direct-mutation-state": 1,
        "react/no-multi-comp": 0,
        "react/no-set-state": 0,
        "react/no-unknown-property": 1,
        "react/prefer-es6-class": 0,
        "react/prop-types": 1,
        "react/react-in-jsx-scope": 1,
        "react/require-extension": 1,
        "react/self-closing-comp": 1,
        "react/sort-comp": 1,
        "react/wrap-multilines": 1
    }
}

[pvdz]

Food for thought?

arr.forEach(obj => obj.foo = i);

now must be

arr.forEach(obj => (obj.foo = i));

to satisfy this rule with the paren exception, or

arr.forEach(obj => { obj.foo = i; });

with the strict rule in place. Unless you disable the rule altogether, of course.

The counter case is:

arr.filter(obj => obj.foo = i);

but the distinction between a forEach and filter (etc) is only checkable under certain assumptions, with hard edge cases.

Still, the initial case had me scratching my head and led me here.

[nzakas]

Now it is