feat: check assignment patterns in no-underscore-dangle (#16693)

Author: mdjermanovic

docs/src/rules/no-underscore-dangle.md

@@ -28,7 +28,6 @@ Examples of **incorrect** code for this rule:
 var foo_;
 var __proto__ = {};
 foo._bar();
-const [_foo, ..._bar] = list;
 ```
 
 :::

lib/rules/no-underscore-dangle.js

@@ -205,60 +205,6 @@ module.exports = {
  checkForDanglingUnderscoreInFunctionParameters(node);
  }
 
- /**
- * Check if node has dangling underscore or if node is type of ArrayPattern check its elements recursively
- * @param {ASTNode} node node to evaluate
- * @param {string} parentNodeType the ASTNode['type'] of the node parent
- * @returns {void}
- * @private
- */
- function deepCheckDestructured(node, parentNodeType) {
- let identifier;
-
- if (!node || !node.type) {
- return;
- }
-
- switch (node.type) {
- case "ArrayPattern":
- node.elements.forEach(element => deepCheckDestructured(element, "ArrayPattern"));
- break;
- case "ObjectPattern":
- node.properties.forEach(property => deepCheckDestructured(property, "ObjectPattern"));
- break;
- case "RestElement":
- deepCheckDestructured(node.argument, parentNodeType);
- break;
- case "Property":
- deepCheckDestructured(node.value, "ObjectPattern");
- break;
- case "Identifier":
- identifier = node.name;
- break;
- default:
- break;
- }
-
- const isFromDestructuredObject = parentNodeType === "ObjectPattern" && !allowInObjectDestructuring;
- const isFromDestructuredArray = parentNodeType === "ArrayPattern" && !allowInArrayDestructuring;
- const hasDisallowedDestructuring = isFromDestructuredObject || isFromDestructuredArray;
-
- if (
- identifier &&
- hasDisallowedDestructuring &&
- hasDanglingUnderscore(identifier) &&
- !isSpecialCaseIdentifierInVariableExpression(identifier) &&
- !isAllowed(identifier)
- ) {
- context.report({
- node,
- messageId: "unexpectedUnderscore",
- data: {
- identifier
- }
- });
- }
- }
 
  /**
  * Check if variable expression has a dangling underscore
@@ -267,30 +213,32 @@ module.exports = {
  * @private
  */
  function checkForDanglingUnderscoreInVariableExpression(node) {
- if (node.id.type === "ArrayPattern") {
- node.id.elements.forEach(element => {
- deepCheckDestructured(element, node.id.type);
- });
- }
-
- if (node.id.type === "ObjectPattern") {
- node.id.properties.forEach(element => {
- deepCheckDestructured(element, node.id.type);
- });
- }
-
- const identifier = node.id.name;
+ context.getDeclaredVariables(node).forEach(variable => {
+ const definition = variable.defs.find(def => def.node === node);
+ const identifierNode = definition.name;
+ const identifier = identifierNode.name;
+ let parent = identifierNode.parent;
+
+ while (!["VariableDeclarator", "ArrayPattern", "ObjectPattern"].includes(parent.type)) {
+ parent = parent.parent;
+ }
 
- if (typeof identifier !== "undefined" && hasDanglingUnderscore(identifier) &&
- !isSpecialCaseIdentifierInVariableExpression(identifier) && !isAllowed(identifier)) {
- context.report({
- node,
- messageId: "unexpectedUnderscore",
- data: {
- identifier
- }
- });
- }
+ if (
+ hasDanglingUnderscore(identifier) &&
+ !isSpecialCaseIdentifierInVariableExpression(identifier) &&
+ !isAllowed(identifier) &&
+ !(allowInArrayDestructuring && parent.type === "ArrayPattern") &&
+ !(allowInObjectDestructuring && parent.type === "ObjectPattern")
+ ) {
+ context.report({
+ node,
+ messageId: "unexpectedUnderscore",
+ data: {
+ identifier
+ }
+ });
+ }
+ });
  }
 
  /**

tests/lib/rules/no-underscore-dangle.js

@@ -70,8 +70,14 @@ ruleTester.run("no-underscore-dangle", rule, {
  { code: "function foo( { _bar }) {}", options: [{ allowFunctionParams: false }], parserOptions: { ecmaVersion: 6 } },
  { code: "function foo( { _bar = 0 } = {}) {}", options: [{ allowFunctionParams: false }], parserOptions: { ecmaVersion: 6 } },
  { code: "function foo(...[_bar]) {}", options: [{ allowFunctionParams: false }], parserOptions: { ecmaVersion: 2016 } },
+ { code: "const [_foo] = arr", parserOptions: { ecmaVersion: 6 } },
+ { code: "const [_foo] = arr", options: [{}], parserOptions: { ecmaVersion: 6 } },
+ { code: "const [_foo] = arr", options: [{ allowInArrayDestructuring: true }], parserOptions: { ecmaVersion: 6 } },
  { code: "const [foo, ...rest] = [1, 2, 3]", options: [{ allowInArrayDestructuring: false }], parserOptions: { ecmaVersion: 2022 } },
  { code: "const [foo, _bar] = [1, 2, 3]", options: [{ allowInArrayDestructuring: false, allow: ["_bar"] }], parserOptions: { ecmaVersion: 2022 } },
+ { code: "const { _foo } = obj", parserOptions: { ecmaVersion: 6 } },
+ { code: "const { _foo } = obj", options: [{}], parserOptions: { ecmaVersion: 6 } },
+ { code: "const { _foo } = obj", options: [{ allowInObjectDestructuring: true }], parserOptions: { ecmaVersion: 6 } },
  { code: "const { foo, bar: _bar } = { foo: 1, bar: 2 }", options: [{ allowInObjectDestructuring: false, allow: ["_bar"] }], parserOptions: { ecmaVersion: 2022 } },
  { code: "const { foo, _bar } = { foo: 1, _bar: 2 }", options: [{ allowInObjectDestructuring: false, allow: ["_bar"] }], parserOptions: { ecmaVersion: 2022 } },
  { code: "const { foo, _bar: bar } = { foo: 1, _bar: 2 }", options: [{ allowInObjectDestructuring: false }], parserOptions: { ecmaVersion: 2022 } },
@@ -112,6 +118,11 @@ ruleTester.run("no-underscore-dangle", rule, {
  options: [{ allowInArrayDestructuring: false }],
  parserOptions: { ecmaVersion: 2022 },
  errors: [{ messageId: "unexpectedUnderscore", data: { identifier: "_bar" } }]
+ }, {
+ code: "const [_foo = 1] = arr",
+ options: [{ allowInArrayDestructuring: false }],
+ parserOptions: { ecmaVersion: 2022 },
+ errors: [{ messageId: "unexpectedUnderscore", data: { identifier: "_foo" } }]
  }, {
  code: "const [foo, ..._rest] = [1, 2, 3]",
  options: [{ allowInArrayDestructuring: false }],
@@ -127,6 +138,16 @@ ruleTester.run("no-underscore-dangle", rule, {
  options: [{ allowInObjectDestructuring: false }],
  parserOptions: { ecmaVersion: 2022 },
  errors: [{ messageId: "unexpectedUnderscore", data: { identifier: "_foo" } }]
+ }, {
+ code: "const { _foo = 1 } = obj",
+ options: [{ allowInObjectDestructuring: false }],
+ parserOptions: { ecmaVersion: 2022 },
+ errors: [{ messageId: "unexpectedUnderscore", data: { identifier: "_foo" } }]
+ }, {
+ code: "const { bar: _foo = 1 } = obj",
+ options: [{ allowInObjectDestructuring: false }],
+ parserOptions: { ecmaVersion: 2022 },
+ errors: [{ messageId: "unexpectedUnderscore", data: { identifier: "_foo" } }]
  }, {
  code: "const { foo: _foo, bar } = { foo: 1, bar: 2 }",
  options: [{ allowInObjectDestructuring: false }],