Ignore more types in no-fn-reference-in-iterator and no-reduce rule

rules/no-fn-reference-in-iterator.js

@@ -2,6 +2,7 @@
 const {isParenthesized} = require('eslint-utils');
 const getDocumentationUrl = require('./utils/get-documentation-url');
 const methodSelector = require('./utils/method-selector');
+const {notFunctionSelector} = require('./utils/not-function');
 
 const ERROR_WITH_NAME_MESSAGE_ID = 'error-with-name';
 const ERROR_WITHOUT_NAME_MESSAGE_ID = 'error-without-name';
@@ -127,14 +128,11 @@ function check(context, node, method, options) {
 	context.report(problem);
 }
 
-const ignoredFirstArgumentSelector = `:not(${
-	[
-		'[arguments.0.type="FunctionExpression"]',
-		'[arguments.0.type="ArrowFunctionExpression"]',
-		'[arguments.0.type="Literal"]',
-		'[arguments.0.type="Identifier"][arguments.0.name="undefined"]'
-	].join(',')
-})`;
+const ignoredFirstArgumentSelector = [
+	notFunctionSelector('arguments.0'),
+	'[arguments.0.type!="FunctionExpression"]',
+	'[arguments.0.type!="ArrowFunctionExpression"]'
+].join('');
 
 const create = context => {
 	const sourceCode = context.getSourceCode();

rules/no-reduce.js

@@ -1,20 +1,13 @@
 'use strict';
 const methodSelector = require('./utils/method-selector');
 const getDocumentationUrl = require('./utils/get-documentation-url');
+const {notFunctionSelector} = require('./utils/not-function');
 
 const MESSAGE_ID_REDUCE = 'reduce';
 const MESSAGE_ID_REDUCE_RIGHT = 'reduceRight';
 
-const ignoredFirstArgumentSelector = `:not(${
-	[
-		'[arguments.0.type="Literal"]',
-		'[arguments.0.type="Identifier"][arguments.0.name="undefined"]'
-	].join(',')
-})`;
-
-const PROTOTYPE_SELECTOR = [
-	methodSelector({names: ['call', 'apply']}),
-	ignoredFirstArgumentSelector,
+const prototypeSelector = method => [
+	methodSelector({name: method}),
 	'[callee.object.type="MemberExpression"]',
 	'[callee.object.computed=false]',
 	`:matches(${
@@ -45,9 +38,16 @@ const PROTOTYPE_SELECTOR = [
 	})`
 ].join('');
 
+const PROTOTYPE_CALL_SELECTOR = [
+	prototypeSelector('call'),
+	notFunctionSelector('arguments.1')
+].join('');
+
+const PROTOTYPE_APPLY_SELECTOR = prototypeSelector('apply');
+
 const METHOD_SELECTOR = [
 	methodSelector({names: ['reduce', 'reduceRight'], min: 1, max: 2}),
-	ignoredFirstArgumentSelector
+	notFunctionSelector('arguments.0')
 ].join('');
 
 const create = context => {
@@ -56,9 +56,13 @@ const create = context => {
 			// For arr.reduce()
 			context.report({node: node.callee.property, messageId: node.callee.property.name});
 		},
-		[PROTOTYPE_SELECTOR](node) {
+		[PROTOTYPE_CALL_SELECTOR](node) {
 			// For cases [].reduce.call() and Array.prototype.reduce.call()
 			context.report({node: node.callee.object.property, messageId: node.callee.object.property.name});
+		},
+		[PROTOTYPE_APPLY_SELECTOR](node) {
+			// For cases [].reduce.apply() and Array.prototype.reduce.apply()
+			context.report({node: node.callee.object.property, messageId: node.callee.object.property.name});
 		}
 	};
 };

rules/utils/not-function.js

@@ -0,0 +1,35 @@
+'use strict';
+
+// AST Types:
+// https://github.com/eslint/espree/blob/master/lib/ast-node-types.js#L18
+// Only types possible to be `argument` are listed
+const impossibleNodeTypes = [
+	'ArrayExpression',
+	'BinaryExpression',
+	'ClassExpression',
+	'Literal',
+	'ObjectExpression',
+	'TemplateLiteral',
+	'UnaryExpression',
+	'UpdateExpression'
+];
+
+// Technically these nodes could be a function, but most likely not
+const mostLikelyNotNodeTypes = [
+	'AssignmentExpression',
+	'AwaitExpression',
+	'CallExpression',
+	'LogicalExpression',
+	'NewExpression',
+	'TaggedTemplateExpression',
+	'ThisExpression'
+];
+
+const notFunctionSelector = node => [
+	...[...impossibleNodeTypes, ...mostLikelyNotNodeTypes].map(type => `[${node}.type!="${type}"]`),
+	`:not([${node}.type="Identifier"][${node}.name="undefined"])`
+].join('');
+
+module.exports = {
+	notFunctionSelector
+};

test/no-fn-reference-in-iterator.js

@@ -2,6 +2,7 @@ import test from 'ava';
 import avaRuleTester from 'eslint-ava-rule-tester';
 import {outdent} from 'outdent';
 import rule from '../rules/no-fn-reference-in-iterator';
+import notFunctionTypes from './utils/not-function-types';
 
 const ERROR_WITH_NAME_MESSAGE_ID = 'error-with-name';
 const ERROR_WITHOUT_NAME_MESSAGE_ID = 'error-without-name';
@@ -22,8 +23,8 @@ const reduceLikeMethods = [
 ];
 
 const ruleTester = avaRuleTester(test, {
-	env: {
-		es6: true
+	parserOptions: {
+		ecmaVersion: 2020
 	}
 });
 
@@ -90,15 +91,26 @@ ruleTester.run('no-fn-reference-in-iterator', rule, {
 		'React.children.forEach(children, fn)',
 		'Vue.filter(name, fn)',
 
+		// First argument is not a function
+		...notFunctionTypes.map(data => `foo.map(${data})`),
+
 		// Ignored
 		'foo.map(() => {})',
 		'foo.map(function() {})',
 		'foo.map(function bar() {})',
-		'foo.map("string")',
-		'foo.map(null)',
-		'foo.map(1)',
-		'foo.map(true)',
-		'foo.map(undefined)'
+
+		// #755
+		outdent`
+			const results = collection
+				.find({
+					$and: [cursorQuery, params.query]
+				}, {
+					projection: params.projection
+				})
+				.sort($sort)
+				.limit(params.limit + 1)
+				.toArray()
+		`
 	],
 	invalid: [
 		// Suggestions
@@ -201,15 +213,6 @@ ruleTester.run('no-fn-reference-in-iterator', rule, {
 				'foo.map((element, index, array) => (a ? b : c)(element, index, array))'
 			]
 		}),
-		invalidTestCase({
-			code: 'foo.map((() => _.map)())',
-			method: 'map',
-			suggestions: [
-				'foo.map((element) => (() => _.map)()(element))',
-				'foo.map((element, index) => (() => _.map)()(element, index))',
-				'foo.map((element, index, array) => (() => _.map)()(element, index, array))'
-			]
-		}),
 		// Note: `await` is not handled, not sure if this is needed
 		// invalidTestCase({
 		// 	code: `foo.map(await foo())`,

test/no-reduce.js

@@ -3,6 +3,7 @@ import avaRuleTester from 'eslint-ava-rule-tester';
 import {flatten} from 'lodash';
 import rule from '../rules/no-reduce';
 import {outdent} from 'outdent';
+import notFunctionTypes from './utils/not-function-types';
 
 const MESSAGE_ID_REDUCE = 'reduce';
 const MESSAGE_ID_REDUCE_RIGHT = 'reduceRight';
@@ -27,14 +28,7 @@ const tests = {
 		'[1, 2].reduce.call(() => {}, 34)',
 
 		// First argument is not a function
-		'a.reduce(123)',
-		'a.reduce(\'abc\')',
-		'a.reduce(null)',
-		'a.reduce(undefined)',
-		'a.reduce(123, initialValue)',
-		'a.reduce(\'abc\', initialValue)',
-		'a.reduce(null, initialValue)',
-		'a.reduce(undefined, initialValue)',
+		...notFunctionTypes.map(data => `foo.reduce(${data})`),
 
 		// Test `.reduce`
 		// Not `CallExpression`
@@ -104,7 +98,11 @@ const tests = {
 		'[].reducex.call(arr, foo)',
 		'[].xreduce.call(arr, foo)',
 		'Array.prototype.reducex.call(arr, foo)',
-		'Array.prototype.xreduce.call(arr, foo)'
+		'Array.prototype.xreduce.call(arr, foo)',
+
+		// Second argument is not a function
+		...notFunctionTypes.map(data => `Array.prototype.reduce.call(foo, ${data})`)
+
 	].map(code => [code, code.replace('reduce', 'reduceRight')])),
 	invalid: flatten([
 		'arr.reduce((total, item) => total + item)',

test/utils/not-function-types.js

@@ -0,0 +1,52 @@
+'use strict';
+
+module.exports = [
+	// ArrayExpression
+	'[]',
+	'[element]',
+	'[...elements]',
+	// BinaryExpression
+	'1 + fn',
+	'"length" in fn',
+	'fn instanceof Function',
+	// ClassExpression
+	'class ClassCantUseAsFunction {}',
+	// Literal
+	'0',
+	'1',
+	'0.1',
+	'""',
+	'"string"',
+	'/regex/',
+	'null',
+	'0n',
+	'1n',
+	'true',
+	'false',
+	// ObjectExpression
+	'{}',
+	// TemplateLiteral
+	'`templateLiteral`',
+	// Undefined
+	'undefined',
+	// UnaryExpression
+	'- fn',
+	'+ fn',
+	'~ fn',
+	'typeof fn',
+	'void fn',
+	'delete fn',
+	// UpdateExpression
+	'++ fn',
+	'-- fn',
+
+	// Following are not safe
+	'a = fn', // Could be a function
+	// 'await fn', // This requires async function to test, ignore for now
+	'fn()', // Could be a factory returns a function
+	'fn1 || fn2', // Could be a function
+	'new ClassReturnsFunction()', // `class` constructor could return a function
+	'new Function()', // `function`
+	'fn``', // Same as `CallExpression`
+	'this' // Could be a function
+];