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feat: add destructuredArrayIgnorePattern option in no-unused-vars (#15649)
* feat: add `destructuredArrayIgnorePattern` option in `no-unused-vars` Fixes #15611 * docs: add `destructuredArrayIgnorePattern` option in `no-unused-vars` * fix: remove false positives and false negatives * docs: update * test: add more cases * docs: update * fix: remove false positives * docs: update Co-authored-by: Milos Djermanovic <milos.djermanovic@gmail.com> * feat: improve error message * feat: cover more cases * docs: add more example * refactor: code * fix: check for all references * docs: add more examples * chore: apply suggestions from code review Co-authored-by: Milos Djermanovic <milos.djermanovic@gmail.com> Co-authored-by: Milos Djermanovic <milos.djermanovic@gmail.com>
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‎docs/rules/no-unused-vars.md

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@@ -238,6 +238,43 @@ function foo(x, _y) {
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foo();
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```
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### destructuredArrayIgnorePattern
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The `destructuredArrayIgnorePattern` option specifies exceptions not to check for usage: elements of array destructuring patterns whose names match a regexp pattern. For example, variables whose names begin with an underscore.
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Examples of **correct** code for the `{ "destructuredArrayIgnorePattern": "^_" }` option:
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```js
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/*eslint no-unused-vars: ["error", { "destructuredArrayIgnorePattern": "^_" }]*/
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const [a, _b, c] = ["a", "b", "c"];
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console.log(a+c);
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const { x: [_a, foo] } = bar;
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console.log(foo);
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function baz([_c, x]) {
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x;
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}
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baz();
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function test({p: [_q, r]}) {
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r;
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}
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test();
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let _m, n;
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foo.forEach(item => {
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[_m, n] = item;
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console.log(n);
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});
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let _o, p;
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_o = 1;
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[_o, p] = foo;
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p;
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```
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### caughtErrors
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The `caughtErrors` option is used for `catch` block arguments validation.

‎lib/rules/no-unused-vars.js

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@@ -67,6 +67,9 @@ module.exports = {
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},
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caughtErrorsIgnorePattern: {
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type: "string"
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},
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destructuredArrayIgnorePattern: {
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type: "string"
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}
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},
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additionalProperties: false
@@ -114,6 +117,10 @@ module.exports = {
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if (firstOption.caughtErrorsIgnorePattern) {
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config.caughtErrorsIgnorePattern = new RegExp(firstOption.caughtErrorsIgnorePattern, "u");
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}
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if (firstOption.destructuredArrayIgnorePattern) {
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config.destructuredArrayIgnorePattern = new RegExp(firstOption.destructuredArrayIgnorePattern, "u");
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}
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}
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}
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@@ -155,7 +162,14 @@ module.exports = {
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* @returns {UnusedVarMessageData} The message data to be used with this unused variable.
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*/
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function getAssignedMessageData(unusedVar) {
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const additional = config.varsIgnorePattern ? `. Allowed unused vars must match ${config.varsIgnorePattern.toString()}` : "";
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const def = unusedVar.defs[0];
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let additional = "";
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if (config.destructuredArrayIgnorePattern && def && def.name.parent.type === "ArrayPattern") {
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additional = `. Allowed unused elements of array destructuring patterns must match ${config.destructuredArrayIgnorePattern.toString()}`;
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} else if (config.varsIgnorePattern) {
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additional = `. Allowed unused vars must match ${config.varsIgnorePattern.toString()}`;
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}
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return {
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varName: unusedVar.name,
@@ -584,6 +598,19 @@ module.exports = {
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if (def) {
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const type = def.type;
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const refUsedInArrayPatterns = variable.references.some(ref => ref.identifier.parent.type === "ArrayPattern");
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// skip elements of array destructuring patterns
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if (
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(
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def.name.parent.type === "ArrayPattern" ||
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refUsedInArrayPatterns
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) &&
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config.destructuredArrayIgnorePattern &&
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config.destructuredArrayIgnorePattern.test(def.name.name)
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) {
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continue;
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}
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// skip catch variables
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if (type === "CatchClause") {

‎tests/lib/rules/no-unused-vars.js

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@@ -162,6 +162,81 @@ ruleTester.run("no-unused-vars", rule, {
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{ code: "function foo(_a) { } foo();", options: [{ args: "all", argsIgnorePattern: "^_" }] },
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{ code: "function foo(a, _b) { return a; } foo();", options: [{ args: "after-used", argsIgnorePattern: "^_" }] },
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{ code: "var [ firstItemIgnored, secondItem ] = items;\nconsole.log(secondItem);", options: [{ vars: "all", varsIgnorePattern: "[iI]gnored" }], parserOptions: { ecmaVersion: 6 } },
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{
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code: "const [ a, _b, c ] = items;\nconsole.log(a+c);",
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options: [{ destructuredArrayIgnorePattern: "^_" }],
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parserOptions: { ecmaVersion: 6 }
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},
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{
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code: "const [ [a, _b, c] ] = items;\nconsole.log(a+c);",
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options: [{ destructuredArrayIgnorePattern: "^_" }],
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parserOptions: { ecmaVersion: 6 }
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},
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{
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code: "const { x: [_a, foo] } = bar;\nconsole.log(foo);",
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options: [{ destructuredArrayIgnorePattern: "^_" }],
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parserOptions: { ecmaVersion: 6 }
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},
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{
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code: "function baz([_b, foo]) { foo; };\nbaz()",
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options: [{ destructuredArrayIgnorePattern: "^_" }],
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parserOptions: { ecmaVersion: 6 }
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},
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{
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code: "function baz({x: [_b, foo]}) {foo};\nbaz()",
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options: [{ destructuredArrayIgnorePattern: "^_" }],
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parserOptions: { ecmaVersion: 6 }
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},
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{
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code: "function baz([{x: [_b, foo]}]) {foo};\nbaz()",
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options: [{ destructuredArrayIgnorePattern: "^_" }],
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parserOptions: { ecmaVersion: 6 }
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},
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{
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code: `
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let _a, b;
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foo.forEach(item => {
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[_a, b] = item;
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doSomething(b);
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});
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`,
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options: [{ destructuredArrayIgnorePattern: "^_" }],
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parserOptions: { ecmaVersion: 6 }
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},
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{
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code: `
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// doesn't report _x
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let _x, y;
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_x = 1;
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[_x, y] = foo;
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y;
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// doesn't report _a
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let _a, b;
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[_a, b] = foo;
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_a = 1;
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b;
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`,
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options: [{ destructuredArrayIgnorePattern: "^_" }],
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parserOptions: { ecmaVersion: 2018 }
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},
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{
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code: `
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// doesn't report _x
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let _x, y;
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_x = 1;
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[_x, y] = foo;
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y;
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// doesn't report _a
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let _a, b;
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_a = 1;
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({_a, ...b } = foo);
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b;
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`,
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options: [{ destructuredArrayIgnorePattern: "^_", ignoreRestSiblings: true }],
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parserOptions: { ecmaVersion: 2018 }
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},
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// for-in loops (see #2342)
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"(function(obj) { var name; for ( name in obj ) return; })({});",
@@ -463,6 +538,131 @@ ruleTester.run("no-unused-vars", rule, {
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}]
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},
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// https://github.com/eslint/eslint/issues/15611
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{
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code: `
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const array = ['a', 'b', 'c'];
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const [a, _b, c] = array;
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const newArray = [a, c];
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`,
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options: [{ destructuredArrayIgnorePattern: "^_" }],
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parserOptions: { ecmaVersion: 2020 },
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errors: [
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// should report only `newArray`
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{ ...assignedError("newArray"), line: 4, column: 19 }
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]
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},
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{
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code: `
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const array = ['a', 'b', 'c', 'd', 'e'];
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const [a, _b, c] = array;
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`,
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options: [{ destructuredArrayIgnorePattern: "^_" }],
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parserOptions: { ecmaVersion: 2020 },
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errors: [
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{
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...assignedError("a", ". Allowed unused elements of array destructuring patterns must match /^_/u"),
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line: 3,
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column: 20
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},
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{
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...assignedError("c", ". Allowed unused elements of array destructuring patterns must match /^_/u"),
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line: 3,
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column: 27
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}
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]
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},
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{
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code: `
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const array = ['a', 'b', 'c'];
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const [a, _b, c] = array;
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const fooArray = ['foo'];
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const barArray = ['bar'];
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const ignoreArray = ['ignore'];
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`,
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options: [{ destructuredArrayIgnorePattern: "^_", varsIgnorePattern: "ignore" }],
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parserOptions: { ecmaVersion: 2020 },
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errors: [
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{
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...assignedError("a", ". Allowed unused elements of array destructuring patterns must match /^_/u"),
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line: 3,
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column: 20
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},
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{
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...assignedError("c", ". Allowed unused elements of array destructuring patterns must match /^_/u"),
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line: 3,
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column: 27
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},
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{
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...assignedError("fooArray", ". Allowed unused vars must match /ignore/u"),
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line: 4,
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column: 19
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},
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{
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...assignedError("barArray", ". Allowed unused vars must match /ignore/u"),
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line: 5,
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column: 19
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}
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]
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},
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{
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code: `
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const array = [obj];
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const [{_a, foo}] = array;
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console.log(foo);
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`,
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options: [{ destructuredArrayIgnorePattern: "^_" }],
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parserOptions: { ecmaVersion: 2020 },
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errors: [
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{
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...assignedError("_a"),
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line: 3,
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column: 21
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}
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]
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},
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{
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code: `
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function foo([{_a, bar}]) {
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bar;
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}
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foo();
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`,
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options: [{ destructuredArrayIgnorePattern: "^_" }],
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parserOptions: { ecmaVersion: 2020 },
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errors: [
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{
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...definedError("_a"),
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line: 2,
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column: 28
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}
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]
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},
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{
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code: `
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let _a, b;
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foo.forEach(item => {
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[a, b] = item;
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});
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`,
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options: [{ destructuredArrayIgnorePattern: "^_" }],
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parserOptions: { ecmaVersion: 2020 },
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errors: [
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{
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...definedError("_a"),
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line: 2,
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column: 17
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},
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{
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...assignedError("b"),
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line: 2,
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column: 21
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}
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]
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},
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// for-in loops (see #2342)
467667
{
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code: "(function(obj) { var name; for ( name in obj ) { i(); return; } })({});",

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