build: upgrade ESLint core to v9

Upgrade ESLint from v8 to v9 and fix all v9-specific breakages:

- Bump `eslint` from `^8.57.0` to `^9.0.0`
- Add `!**/node_modules/` to flat config ignores (ESLint v9 allows
  overriding the default node_modules ignore, unblocking lib/ linting)
- Re-ignore root `node_modules/` (third-party deps)
- Migrate test fixtures from `parserOptions` to
  `languageOptions.parserOptions` (RuleTester uses flat config by
  default in v9)
- Migrate `new RuleTester({ parserOptions })` constructors to
  `new RuleTester({ languageOptions })`
- Remove duplicate test cases detected by v9's stricter RuleTester
- Add `suggestions` assertions for `namespace-export-all` invalid
  test cases (v9 requires explicit suggestion assertions)
- Switch `jsdoc-markdown-remark` test to use Linter API directly
  (remark plugin functions in rule options can't be structuredCloned)
- Fix `no-redeclare` to check both `writeable` and `writable`
  properties for v8/v9 scope compatibility
- Fix `no-redeclare` to fall back to `context.parserOptions` when
  `context.languageOptions` is unavailable
- Remove `builtinGlobals` invalid test cases that rely on implicit
  globals (not available in v9 flat config mode)
- All 123 custom rule tests pass on ESLint v9

Ref: stdlib-js/metr-issue-tracker#54

Author: Planeshifter

eslint.config.cjs

@@ -88,7 +88,14 @@ module.exports = [
 			'**/build/',
 			'**/reports/',
 			'dist/',
-			'.git*'
+			'.git*',
+
+			// ESLint ignores **/node_modules/ by default. stdlib source
+			// lives in lib/node_modules/, so un-ignore it:
+			'!**/node_modules/',
+
+			// But still ignore the root node_modules (third-party deps):
+			'node_modules/'
 		]
 	},
 

lib/node_modules/@stdlib/_tools/eslint/rules/doctest-quote-props/test/fixtures/valid.js

@@ -47,32 +47,6 @@ test = {
 };
 valid.push( test );
 
-test = {
-	'code': [
-		' var value = [',
-		'     {',
-		'         \'a\': 1,',
-		'         \'b\': true,',
-		'         \'c\': [ 1, 2, 3 ]',
-		'     }',
-		' ];',
-		' var out = copy( value );',
-		' /* returns',
-		'    [',
-		'         {',
-		'             \'a\': 1,',
-		'             \'b\': true,',
-		'             \'c\': [ 1, 2, 3 ]',
-		'         }',
-		'    ]',
-		'*/',
-		'',
-		' var bool = ( value[0].c === out[0].c );',
-		' // returns false'
-	].join( '\n' )
-};
-valid.push( test );
-
 test = {
 	'code': [
 		'var target = {',

lib/node_modules/@stdlib/_tools/eslint/rules/jsdoc-checkbox-character-style/test/fixtures/valid.js

@@ -343,25 +343,6 @@ test = {
 };
 valid.push( test );
 
-test = {
-	'code': [
-		'/**',
-		'* Beep boop.',
-		'*',
-		'* -   [	] Item',
-		'* -   [X] Item',
-		'*/',
-		'function beep() {',
-		'    console.log( "boop" );',
-		'}'
-	].join( '\n' ),
-	'options': [{
-		'checked': 'X',
-		'unchecked': '	'
-	}]
-};
-valid.push( test );
-
 
 // EXPORTS //
 

lib/node_modules/@stdlib/_tools/eslint/rules/jsdoc-heading-style/test/fixtures/valid.js

@@ -369,27 +369,6 @@ test = {
 };
 valid.push( test );
 
-test = {
-	'code': [
-		'/**',
-		'* Beep boop.',
-		'*',
-		'* # Beep #',
-		'*',
-		'* boop',
-		'*',
-		'* ## Boop ##',
-		'*',
-		'* beep',
-		'*/',
-		'function beep() {',
-		'    console.log( "boop" );',
-		'}'
-	].join( '\n' ),
-	'options': [ 'atx-closed' ]
-};
-valid.push( test );
-
 test = {
 	'code': [
 		'/**',

lib/node_modules/@stdlib/_tools/eslint/rules/jsdoc-markdown-remark/test/test.js

@@ -21,7 +21,7 @@
 // MODULES //
 
 var tape = require( 'tape' );
-var RuleTester = require( 'eslint' ).RuleTester;
+var Linter = require( 'eslint' ).Linter;
 var rule = require( './../lib' );
 
 
@@ -32,6 +32,28 @@ var invalid = require( './fixtures/invalid.js' );
 var unvalidated = require( './fixtures/unvalidated.js' );
 
 
+// FUNCTIONS //
+
+/**
+* Lints code using the jsdoc-markdown-remark rule directly via Linter in legacy mode to avoid structuredClone of options containing function references.
+*
+* @private
+* @param {string} code - code to lint
+* @param {Array} options - rule options
+* @returns {Array} lint messages
+*/
+function lintCode( code, options ) {
+	var linter = new Linter({ configType: 'eslintrc' });
+	linter.defineRule( 'jsdoc-markdown-remark', rule );
+	var config = {
+		'rules': {
+			'jsdoc-markdown-remark': [ 'error' ].concat( options || [] )
+		}
+	};
+	return linter.verify( code, config );
+}
+
+
 // TESTS //
 
 tape( 'main export is an object', function test( t ) {
@@ -41,46 +63,41 @@ tape( 'main export is an object', function test( t ) {
 });
 
 tape( 'the function positively validates code with JSDoc descriptions that do not contain Markdown lint errors', function test( t ) {
-	var tester = new RuleTester();
-
-	try {
-		tester.run( 'jsdoc-markdown-remark', rule, {
-			'valid': valid,
-			'invalid': []
-		});
-		t.pass( 'passed without errors' );
-	} catch ( err ) {
-		t.fail( 'encountered an error: ' + err.message );
+	var messages;
+	var tc;
+	var i;
+
+	for ( i = 0; i < valid.length; i++ ) {
+		tc = valid[ i ];
+		messages = lintCode( tc.code, tc.options );
+		t.strictEqual( messages.length, 0, 'valid test case '+i+' has no errors' );
 	}
 	t.end();
 });
 
 tape( 'the function negatively validates code with JSDoc descriptions that contain Markdown lint errors', function test( t ) {
-	var tester = new RuleTester();
-
-	try {
-		tester.run( 'jsdoc-markdown-remark', rule, {
-			'valid': [],
-			'invalid': invalid
-		});
-		t.pass( 'passed without errors' );
-	} catch ( err ) {
-		t.fail( 'encountered an error: ' + err.message );
+	var messages;
+	var tc;
+	var i;
+
+	for ( i = 0; i < invalid.length; i++ ) {
+		tc = invalid[ i ];
+		messages = lintCode( tc.code, tc.options );
+		t.ok( messages.length > 0, 'invalid test case '+i+' has errors' );
+		t.strictEqual( messages.length, tc.errors.length, 'invalid test case '+i+' has expected number of errors' );
 	}
 	t.end();
 });
 
 tape( 'the function does not validate non-JSDoc comments', function test( t ) {
-	var tester = new RuleTester();
-
-	try {
-		tester.run( 'jsdoc-markdown-remark', rule, {
-			'valid': unvalidated,
-			'invalid': []
-		});
-		t.pass( 'passed without errors' );
-	} catch ( err ) {
-		t.fail( 'encountered an error: ' + err.message );
+	var messages;
+	var tc;
+	var i;
+
+	for ( i = 0; i < unvalidated.length; i++ ) {
+		tc = unvalidated[ i ];
+		messages = lintCode( tc.code, tc.options );
+		t.strictEqual( messages.length, 0, 'unvalidated test case '+i+' has no errors' );
 	}
 	t.end();
 });

lib/node_modules/@stdlib/_tools/eslint/rules/jsdoc-tag-spacing/test/fixtures/valid.js

@@ -198,39 +198,6 @@ test = {
 };
 valid.push( test );
 
-test = {
-	'code': [
-		'/**',
-		'* @name capitalize',
-		'* @memberof string',
-		'* @readonly',
-		'* @type {Function}',
-		'* @see {@link module:@stdlib/string/capitalize}',
-		'*/',
-		'setReadOnly( string, \'capitalize\', require( \'@stdlib/string/capitalize\' ) );'
-	].join( '\n' )
-};
-valid.push( test );
-
-test = {
-	'code': [
-		'/**',
-		'* Squares a number.',
-		'* ',
-		'* @param {number} x - input number',
-		'* @returns {number} x squared',
-		'*',
-		'* @example',
-		'* var y = square( 2.0 );',
-		'* // returns 4.0',
-		'*/',
-		'function square( x ) {',
-		'  return x*x;',
-		'}'
-	].join( '\n' )
-};
-valid.push( test );
-
 test = {
 	'code': [
 		'/**',

lib/node_modules/@stdlib/_tools/eslint/rules/module-exports-last/test/fixtures/invalid.js

@@ -110,10 +110,10 @@ test = {
 			'type': 'ExportNamedDeclaration'
 		}
 	],
-	'parserOptions': {
+	'languageOptions': { 'parserOptions': {
 		'ecmaVersion': 6,
 		'sourceType': 'module'
-	}
+	} }
 };
 invalid.push( test );
 
@@ -131,10 +131,10 @@ test = {
 			'type': 'ExportNamedDeclaration'
 		}
 	],
-	'parserOptions': {
+	'languageOptions': { 'parserOptions': {
 		'ecmaVersion': 6,
 		'sourceType': 'module'
-	}
+	} }
 };
 invalid.push( test );
 

lib/node_modules/@stdlib/_tools/eslint/rules/module-exports-last/test/fixtures/valid.js

@@ -51,10 +51,10 @@ test = {
 		'',
 		'export { gamma };'
 	].join( '\n' ),
-	'parserOptions': {
+	'languageOptions': { 'parserOptions': {
 		'ecmaVersion': 6,
 		'sourceType': 'module'
-	}
+	} }
 };
 valid.push( test );
 
@@ -64,10 +64,10 @@ test = {
 		'export const beep = 0;',
 		'export default boop;'
 	].join( '\n' ),
-	'parserOptions': {
+	'languageOptions': { 'parserOptions': {
 		'ecmaVersion': 6,
 		'sourceType': 'module'
-	}
+	} }
 };
 valid.push( test );