Repository: eslint/eslint
File: tests/lib/rules/array-callback-return.js (JavaScript)

Code before:
        { code: "foo.forEach(x => x)", options: allowImplicitCheckForEach, parserOptions: { ecmaVersion: 6 }, errors: [{ messageId: "expectedNoReturnValue", data: { name: "arrow function", arrayMethodName: "Array.prototype.forEach" } }] },
        { code: "foo.forEach(function(x) { if (a == b) {return x;}})", options: allowImplicitCheckForEach, errors: [{ messageId: "expectedNoReturnValue", data: { name: "function", arrayMethodName: "Array.prototype.forEach" } }] },
        { code: "foo.forEach(function bar(x) { return x;})", options: allowImplicitCheckForEach, errors: [{ messageId: "expectedNoReturnValue", data: { name: "function 'bar'", arrayMethodName: "Array.prototype.forEach" } }] },

        // // options: { checkForEach: true }
        { code: "foo.forEach(x => x)", options: checkForEachOptions, parserOptions: { ecmaVersion: 6 }, errors: [{ messageId: "expectedNoReturnValue", data: { name: "arrow function", arrayMethodName: "Array.prototype.forEach" } }] },
        { code: "foo.forEach(val => y += val)", options: checkForEachOptions, parserOptions: { ecmaVersion: 6 }, errors: [{ messageId: "expectedNoReturnValue", data: { name: "arrow function", arrayMethodName: "Array.prototype.forEach" } }] },
        { code: "[\"foo\",\"bar\"].forEach(x => ++x)", options: checkForEachOptions, parserOptions: { ecmaVersion: 6 }, errors: [{ messageId: "expectedNoReturnValue", data: { name: "arrow function", arrayMethodName: "Array.prototype.forEach" } }] },
        { code: "foo.bar().forEach(x => x === y)", options: checkForEachOptions, parserOptions: { ecmaVersion: 6 }, errors: [{ messageId: "expectedNoReturnValue", data: { name: "arrow function", arrayMethodName: "Array.prototype.forEach" } }] },
        { code: "foo.forEach(function() {return function() { if (a == b) { return a; }}}())", options: checkForEachOptions, errors: [{ messageId: "expectedNoReturnValue", data: { name: "function", arrayMethodName: "Array.prototype.forEach" } }] },
        { code: "foo.forEach(function(x) { if (a == b) {return x;}})", options: checkForEachOptions, errors: [{ messageId: "expectedNoReturnValue", data: { name: "function", arrayMethodName: "Array.prototype.forEach" } }] },
        { code: "foo.forEach(function(x) { if (a == b) {return undefined;}})", options: checkForEachOptions, errors: [{ messageId: "expectedNoReturnValue", data: { name: "function", arrayMethodName: "Array.prototype.forEach" } }] },
        { code: "foo.forEach(function bar(x) { return x;})", options: checkForEachOptions, errors: [{ messageId: "expectedNoReturnValue", data: { name: "function 'bar'", arrayMethodName: "Array.prototype.forEach" } }] },
        { code: "foo.forEach(function bar(x) { return x;})", options: checkForEachOptions, errors: ["Array.prototype.forEach() expects no useless return value from function 'bar'."] },
        { code: "foo.bar().forEach(function bar(x) { return x;})", options: checkForEachOptions, errors: [{ messageId: "expectedNoReturnValue", data: { name: "function 'bar'", arrayMethodName: "Array.prototype.forEach" } }] },
        { code: "[\"foo\",\"bar\"].forEach(function bar(x) { return x;})", options: checkForEachOptions, errors: [{ messageId: "expectedNoReturnValue", data: { name: "function 'bar'", arrayMethodName: "Array.prototype.forEach" } }] },
        { code: "foo.forEach((x) => { return x;})", options: checkForEachOptions, parserOptions: { ecmaVersion: 6 }, errors: [{ messageId: "expectedNoReturnValue", data: { name: "arrow function", arrayMethodName: "Array.prototype.forEach" } }] },
        { code: "Array.from(x, function() {})", options: checkForEachOptions, errors: [{ messageId: "expectedInside", data: { name: "function", arrayMethodName: "Array.from" } }] },
        { code: "foo.every(function() {})", options: checkForEachOptions, errors: [{ messageId: "expectedInside", data: { name: "function", arrayMethodName: "Array.prototype.every" } }] },
        { code: "foo.filter(function foo() {})", options: checkForEachOptions, errors: [{ messageId: "expectedInside", data: { name: "function 'foo'", arrayMethodName: "Array.prototype.filter" } }] },
        { code: "foo.filter(function foo() { return; })", options: checkForEachOptions, errors: [{ messageId: "expectedReturnValue", data: { name: "function 'foo'", arrayMethodName: "Array.prototype.filter" } }] },
        { code: "foo.every(cb || function() {})", options: checkForEachOptions, errors: ["Array.prototype.every() expects a return value from function."] },
        { code: "foo.forEach((x) => void x)", options: checkForEachOptions, parserOptions: { ecmaVersion: 6 }, errors: [{ messageId: "expectedNoReturnValue" }] },
        { code: "foo.forEach((x) => void bar(x))", options: checkForEachOptions, parserOptions: { ecmaVersion: 6 }, errors: [{ messageId: "expectedNoReturnValue" }] },
        { code: "foo.forEach((x) => { return void bar(x); })", options: checkForEachOptions, parserOptions: { ecmaVersion: 6 }, errors: [{ messageId: "expectedNoReturnValue" }] },
        { code: "foo.forEach((x) => { if (a === b) { return void a; } bar(x) })", options: checkForEachOptions, parserOptions: { ecmaVersion: 6 }, errors: [{ messageId: "expectedNoReturnValue" }] },

        // full location tests
        {
            code: "foo.filter(bar => { baz(); } )",
            parserOptions: { ecmaVersion: 6 },
            errors: [{
                messageId: "expectedInside",
                data: { name: "arrow function", arrayMethodName: "Array.prototype.filter" },
                type: "ArrowFunctionExpression",
                line: 1,
                column: 16,
                endLine: 1,
                endColumn: 18
            }]
        },
        {
            code: "foo.filter(\n() => {} )",
            parserOptions: { ecmaVersion: 6 },
            errors: [{
                messageId: "expectedInside",
                data: { name: "arrow function", arrayMethodName: "Array.prototype.filter" },
                type: "ArrowFunctionExpression",
                line: 2,
                column: 4,
                endLine: 2,

Review comment (suggestion):
Can you add a few tests to check if `allowVoid: true` allows only `void` expressions? For example:

```suggestion
        { code: "foo.forEach((x) => { if (a === b) { return void a; } bar(x) })", options: checkForEachOptions, parserOptions: { ecmaVersion: 6 }, errors: [{ messageId: "expectedNoReturnValue" }] },
        { code: "foo.forEach((x) => x)", options: checkForEachAllowVoid, parserOptions: { ecmaVersion: 6 }, errors: [{ messageId: "expectedNoReturnValue" }] },
        { code: "foo.forEach((x) => !x)", options: checkForEachAllowVoid, parserOptions: { ecmaVersion: 6 }, errors: [{ messageId: "expectedNoReturnValue" }] },
        { code: "foo.forEach((x) => { return x; })", options: checkForEachAllowVoid, parserOptions: { ecmaVersion: 6 }, errors: [{ messageId: "expectedNoReturnValue" }] },
        { code: "foo.forEach((x) => { return !x; })", options: checkForEachAllowVoid, parserOptions: { ecmaVersion: 6 }, errors: [{ messageId: "expectedNoReturnValue" }] },
```

Code after:
        { code: "foo.forEach(x => x)", options: allowImplicitCheckForEach, parserOptions: { ecmaVersion: 6 }, errors: [{ messageId: "expectedNoReturnValue", data: { name: "arrow function", arrayMethodName: "Array.prototype.forEach" } }] },
        { code: "foo.forEach(function(x) { if (a == b) {return x;}})", options: allowImplicitCheckForEach, errors: [{ messageId: "expectedNoReturnValue", data: { name: "function", arrayMethodName: "Array.prototype.forEach" } }] },
        { code: "foo.forEach(function bar(x) { return x;})", options: allowImplicitCheckForEach, errors: [{ messageId: "expectedNoReturnValue", data: { name: "function 'bar'", arrayMethodName: "Array.prototype.forEach" } }] },

        // // options: { checkForEach: true }
        { code: "foo.forEach(x => x)", options: checkForEachOptions, parserOptions: { ecmaVersion: 6 }, errors: [{ messageId: "expectedNoReturnValue", data: { name: "arrow function", arrayMethodName: "Array.prototype.forEach" } }] },
        { code: "foo.forEach(val => y += val)", options: checkForEachOptions, parserOptions: { ecmaVersion: 6 }, errors: [{ messageId: "expectedNoReturnValue", data: { name: "arrow function", arrayMethodName: "Array.prototype.forEach" } }] },
        { code: "[\"foo\",\"bar\"].forEach(x => ++x)", options: checkForEachOptions, parserOptions: { ecmaVersion: 6 }, errors: [{ messageId: "expectedNoReturnValue", data: { name: "arrow function", arrayMethodName: "Array.prototype.forEach" } }] },
        { code: "foo.bar().forEach(x => x === y)", options: checkForEachOptions, parserOptions: { ecmaVersion: 6 }, errors: [{ messageId: "expectedNoReturnValue", data: { name: "arrow function", arrayMethodName: "Array.prototype.forEach" } }] },
        { code: "foo.forEach(function() {return function() { if (a == b) { return a; }}}())", options: checkForEachOptions, errors: [{ messageId: "expectedNoReturnValue", data: { name: "function", arrayMethodName: "Array.prototype.forEach" } }] },
        { code: "foo.forEach(function(x) { if (a == b) {return x;}})", options: checkForEachOptions, errors: [{ messageId: "expectedNoReturnValue", data: { name: "function", arrayMethodName: "Array.prototype.forEach" } }] },
        { code: "foo.forEach(function(x) { if (a == b) {return undefined;}})", options: checkForEachOptions, errors: [{ messageId: "expectedNoReturnValue", data: { name: "function", arrayMethodName: "Array.prototype.forEach" } }] },
        { code: "foo.forEach(function bar(x) { return x;})", options: checkForEachOptions, errors: [{ messageId: "expectedNoReturnValue", data: { name: "function 'bar'", arrayMethodName: "Array.prototype.forEach" } }] },
        { code: "foo.forEach(function bar(x) { return x;})", options: checkForEachOptions, errors: ["Array.prototype.forEach() expects no useless return value from function 'bar'."] },
        { code: "foo.bar().forEach(function bar(x) { return x;})", options: checkForEachOptions, errors: [{ messageId: "expectedNoReturnValue", data: { name: "function 'bar'", arrayMethodName: "Array.prototype.forEach" } }] },
        { code: "[\"foo\",\"bar\"].forEach(function bar(x) { return x;})", options: checkForEachOptions, errors: [{ messageId: "expectedNoReturnValue", data: { name: "function 'bar'", arrayMethodName: "Array.prototype.forEach" } }] },
        { code: "foo.forEach((x) => { return x;})", options: checkForEachOptions, parserOptions: { ecmaVersion: 6 }, errors: [{ messageId: "expectedNoReturnValue", data: { name: "arrow function", arrayMethodName: "Array.prototype.forEach" } }] },
        { code: "Array.from(x, function() {})", options: checkForEachOptions, errors: [{ messageId: "expectedInside", data: { name: "function", arrayMethodName: "Array.from" } }] },
        { code: "foo.every(function() {})", options: checkForEachOptions, errors: [{ messageId: "expectedInside", data: { name: "function", arrayMethodName: "Array.prototype.every" } }] },
        { code: "foo.filter(function foo() {})", options: checkForEachOptions, errors: [{ messageId: "expectedInside", data: { name: "function 'foo'", arrayMethodName: "Array.prototype.filter" } }] },
        { code: "foo.filter(function foo() { return; })", options: checkForEachOptions, errors: [{ messageId: "expectedReturnValue", data: { name: "function 'foo'", arrayMethodName: "Array.prototype.filter" } }] },
        { code: "foo.every(cb || function() {})", options: checkForEachOptions, errors: ["Array.prototype.every() expects a return value from function."] },
        { code: "foo.forEach((x) => void x)", options: checkForEachOptions, parserOptions: { ecmaVersion: 6 }, errors: [{ messageId: "expectedNoReturnValue" }] },
        { code: "foo.forEach((x) => void bar(x))", options: checkForEachOptions, parserOptions: { ecmaVersion: 6 }, errors: [{ messageId: "expectedNoReturnValue" }] },
        { code: "foo.forEach((x) => { return void bar(x); })", options: checkForEachOptions, parserOptions: { ecmaVersion: 6 }, errors: [{ messageId: "expectedNoReturnValue" }] },
        { code: "foo.forEach((x) => { if (a === b) { return void a; } bar(x) })", options: checkForEachOptions, parserOptions: { ecmaVersion: 6 }, errors: [{ messageId: "expectedNoReturnValue" }] },

        // options: { checkForEach: true, allowVoid: true }
        { code: "foo.forEach((x) => x)", options: checkForEachAllowVoid, parserOptions: { ecmaVersion: 6 }, errors: [{ messageId: "expectedNoReturnValue" }] },
        { code: "foo.forEach((x) => !x)", options: checkForEachAllowVoid, parserOptions: { ecmaVersion: 6 }, errors: [{ messageId: "expectedNoReturnValue" }] },
        { code: "foo.forEach((x) => { return x; })", options: checkForEachAllowVoid, parserOptions: { ecmaVersion: 6 }, errors: [{ messageId: "expectedNoReturnValue" }] },
        { code: "foo.forEach((x) => { return !x; })", options: checkForEachAllowVoid, parserOptions: { ecmaVersion: 6 }, errors: [{ messageId: "expectedNoReturnValue" }] },
        { code: "foo.forEach((x) => { if (a === b) { return x; } })", options: checkForEachAllowVoid, parserOptions: { ecmaVersion: 6 }, errors: [{ messageId: "expectedNoReturnValue" }] },
        { code: "foo.forEach((x) => { if (a === b) { return !x } })", options: checkForEachAllowVoid, parserOptions: { ecmaVersion: 6 }, errors: [{ messageId: "expectedNoReturnValue" }] },

        // full location tests
        {
            code: "foo.filter(bar => { baz(); } )",
            parserOptions: { ecmaVersion: 6 },
            errors: [{
                messageId: "expectedInside",
                data: { name: "arrow function", arrayMethodName: "Array.prototype.filter" },
                type: "ArrowFunctionExpression",
                line: 1,
                column: 16,
                endLine: 1,
                endColumn: 18
            }]
        },
        {
            code: "foo.filter(\n() => {} )",