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feat!: enable JSX reference tracking (#20152)
* feat!: enable JSX reference tracking * apply suggestions and update migration guide * update Reference.identifier type to include JSXIdentifier * apply suggestions * apply suggestions * add tests for no-unused-vars rule * add guidance to remove workaround rules * simplify selector * apply suggestion
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‎docs/src/extend/scope-manager-interface.md‎

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@@ -274,7 +274,7 @@ Those members are defined but not used in ESLint.
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#### identifier
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- **Type:** `ASTNode`
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- **Description:** The `Identifier` node of this reference.
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- **Description:** The `Identifier` or `JSXIdentifier` node of this reference.
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#### from
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‎docs/src/use/migrate-to-10.0.0.md‎

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@@ -19,6 +19,7 @@ The lists below are ordered roughly by the number of users each change is expect
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- [`eslint:recommended` has been updated](#eslint-recommended)
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- [New configuration file lookup algorithm](#config-lookup-from-file)
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- [Old config format no longer supported](#remove-eslintrc)
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- [JSX references are now tracked](#jsx-reference-tracking)
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- [`eslint-env` comments are reported as errors](#eslint-env-comments)
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- [Jiti < v2.2.0 are no longer supported](#drop-old-jiti)
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- [POSIX character classes in glob patterns](#posix-character-classes)
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- [Node.js < v20.19, v21, v23 are no longer supported](#drop-old-node)
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- [Old config format no longer supported](#remove-eslintrc)
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- [JSX references are now tracked](#jsx-reference-tracking)
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- [Removal of `type` property in errors of invalid `RuleTester` cases](#ruletester-type-removed)
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- [`Program` AST node range spans entire source text](#program-node-range)
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- [Fixer methods now require string `text` arguments](#fixer-text-must-be-string)
@@ -103,6 +105,31 @@ Starting with ESLint v10.0.0, the old configuration format is no longer supporte
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**Related issue(s):** [#13481](https://github.com/eslint/eslint/issues/13481)
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## <a name="jsx-reference-tracking"></a> JSX references are now tracked
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ESLint v10.0.0 now tracks JSX references, enabling correct scope analysis of JSX elements.
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Previously, ESLint did not track references created by JSX identifiers, which could lead to incorrect results from rules that rely on scope information. For example:
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```jsx
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import { Card } from "./card.jsx";
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export function createCard(name) {
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return <Card name={name} />;
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}
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```
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Prior to v10.0.0, ESLint did not recognize that `<Card>` is a reference to the imported `Card`, which could result in false positives such as reporting `Card` as "defined but never used" ([`no-unused-vars`](../rules/no-unused-vars)) or false negatives such as failing to report `Card` as undefined ([`no-undef`](../rules/no-undef)) if the import is removed. Starting with v10.0.0, `<Card>` is treated as a normal reference to the variable in scope. This brings JSX handling in line with developer expectations and improves the linting experience for modern JavaScript applications using JSX.
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**To address:**
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- For users:
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- New linting reports may appear in files with JSX. Update your code accordingly or adjust rule configurations if needed.
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- Rules previously used to work around ESLint’s lack of JSX reference tracking (for example, [`@eslint-react/jsx-uses-vars`](https://www.eslint-react.xyz/docs/rules/jsx-uses-vars)) are no longer needed. Remove or disable them in your configuration.
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- For plugin developers: Custom rules relying on scope analysis may now encounter `JSXIdentifier` references. Update rules to handle these correctly.
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**Related issue(s):** [#19495](https://github.com/eslint/eslint/issues/19495)
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## <a name="eslint-env-comments"></a> `eslint-env` comments are reported as errors
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In the now obsolete ESLint v8 configuration system, `/* eslint-env */` comments could be used to define globals for a file. The current configuration system does not support such comments, and starting with ESLint v10.0.0, they are reported as errors during linting.

‎lib/languages/js/index.js‎

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@@ -55,6 +55,7 @@ function analyzeScope(ast, languageOptions, visitorKeys) {
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sourceType: languageOptions.sourceType || "script",
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childVisitorKeys: visitorKeys || evk.KEYS,
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fallback: evk.getKeys,
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jsx: ecmaFeatures.jsx,
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});
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}
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‎lib/linter/linter.js‎

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@@ -473,6 +473,7 @@ function analyzeScope(ast, languageOptions, visitorKeys) {
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sourceType: languageOptions.sourceType || "script",
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childVisitorKeys: visitorKeys || evk.KEYS,
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fallback: Traverser.getKeys,
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jsx: ecmaFeatures.jsx,
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});
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}
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‎lib/rules/no-useless-assignment.js‎

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@@ -336,9 +336,12 @@ module.exports = {
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}
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if (
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targetAssignment.variable.references.some(
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ref => ref.identifier.type !== "Identifier",
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)
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targetAssignment.variable.references.some(ref => {
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const type = ref.identifier.type;
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return (
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type !== "Identifier" && type !== "JSXIdentifier"
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);
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})
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) {
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/**
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* Skip checking for a variable that has at least one non-identifier reference.
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TryStatement(node) {
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scopeStack.tryStatementBlocks.push(node.block);
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},
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Identifier(node) {
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"Identifier, JSXIdentifier"(node) {
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for (const segment of scopeStack.currentSegments) {
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const segmentInfo = scopeStack.segments[segment.id];
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segmentInfo.last = node;
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}
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},
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":matches(VariableDeclarator[init!=null], AssignmentExpression, UpdateExpression):exit"(
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"VariableDeclarator[init!=null], AssignmentExpression, UpdateExpression:exit"(
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node,
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) {
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if (scopeStack.currentSegments.size === 0) {

‎lib/types/index.d.ts‎

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@@ -125,6 +125,11 @@ export namespace AST {
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}
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}
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interface JSXIdentifier extends ESTree.BaseNode {
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type: "JSXIdentifier";
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name: string;
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}
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export namespace Scope {
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interface ScopeManager {
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scopes: Scope[];
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}
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interface Reference {
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identifier: ESTree.Identifier;
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identifier: ESTree.Identifier | JSXIdentifier;
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from: Scope;
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resolved: Variable | null;
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writeExpr: ESTree.Node | null;

‎tests/lib/rules/no-undef.js‎

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@@ -225,6 +225,42 @@ ruleTester.run("no-undef", rule, {
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code: "AsyncDisposableStack; DisposableStack; SuppressedError",
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languageOptions: { ecmaVersion: 2026 },
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},
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{
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code: "/*global App*/ <App />;",
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languageOptions: {
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ecmaVersion: 6,
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parserOptions: { ecmaFeatures: { jsx: true } },
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},
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},
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{
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code: "const App = () => <div/>; <App />;",
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languageOptions: {
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ecmaVersion: 6,
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parserOptions: { ecmaFeatures: { jsx: true } },
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},
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},
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{
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code: "let Foo, Bar; <Foo><Bar /></Foo>;",
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languageOptions: {
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ecmaVersion: 6,
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parserOptions: { ecmaFeatures: { jsx: true } },
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},
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},
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{
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code: "import App from './App.jsx'; <App />;",
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languageOptions: {
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ecmaVersion: 6,
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sourceType: "module",
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parserOptions: { ecmaFeatures: { jsx: true } },
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},
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},
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{
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code: "function App() { return <div/> } <App />;",
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languageOptions: {
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ecmaVersion: 6,
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parserOptions: { ecmaFeatures: { jsx: true } },
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},
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},
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],
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invalid: [
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{
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},
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errors: [{ messageId: "undef", data: { name: "a" }, column: 31 }],
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},
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{
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code: "<App />;",
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languageOptions: {
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ecmaVersion: 6,
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parserOptions: { ecmaFeatures: { jsx: true } },
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},
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errors: [
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{
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messageId: "undef",
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data: { name: "App" },
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line: 1,
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column: 2,
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endLine: 1,
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endColumn: 5,
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},
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],
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},
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{
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code: "let React; React.render(<App />);",
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languageOptions: {
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ecmaVersion: 6,
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parserOptions: { ecmaFeatures: { jsx: true } },
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},
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errors: [
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{
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messageId: "undef",
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data: { name: "App" },
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line: 1,
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column: 26,
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endLine: 1,
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endColumn: 29,
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},
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],
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},
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{
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code: "function f() { return <Button/> }",
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languageOptions: {
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ecmaVersion: 6,
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parserOptions: { ecmaFeatures: { jsx: true } },
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},
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errors: [
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{
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messageId: "undef",
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data: { name: "Button" },
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line: 1,
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column: 24,
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endLine: 1,
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endColumn: 30,
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},
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],
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},
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{
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code: "<Foo.Bar />",
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languageOptions: {
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ecmaVersion: 6,
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parserOptions: { ecmaFeatures: { jsx: true } },
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},
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errors: [
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{
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messageId: "undef",
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data: { name: "Foo" },
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line: 1,
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column: 2,
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endLine: 1,
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endColumn: 5,
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},
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],
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},
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],
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});

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