build: add JSON and YAML linting via ESLint

eslint.config.cjs

@@ -30,9 +30,15 @@ var pluginCspell = require( '@cspell/eslint-plugin' );
 var pluginJsdoc = require( 'eslint-plugin-jsdoc' );
 var pluginImport = require( 'eslint-plugin-import' );
 var pluginExpectType = require( 'eslint-plugin-expect-type' );
+var pluginJsonc = require( 'eslint-plugin-jsonc' );
+var jsoncParser = require( 'jsonc-eslint-parser' );
+var pluginYml = require( 'eslint-plugin-yml' );
+var yamlParser = require( 'yaml-eslint-parser' );
 var stdlibPlugin = require( './lib/node_modules/@stdlib/_tools/eslint/rules/scripts/plugin.js' );
 var allRules = require( './etc/eslint/rules' );
 var tsRules = require( './etc/eslint/rules/typescript.js' );
+var jsonRules = require( './etc/eslint/rules/json.js' );
+var yamlRules = require( './etc/eslint/rules/yaml.js' );
 
 
 // VARIABLES //
@@ -101,6 +107,8 @@ module.exports = [
 			'**/reports/',
 			'dist/',
 			'.git*',
+			'!.github/',
+			'!.codecov.yml',
 
 			// ESLint ignores **/node_modules/ by default. stdlib source
 			// lives in lib/node_modules/, so un-ignore it:
@@ -217,5 +225,101 @@ module.exports = [
 		'rules': {
 			'jsdoc/require-jsdoc': 'off'
 		}
+	},
+
+	// Base JSON:
+	{
+		'files': [ '**/*.json' ],
+		'languageOptions': {
+			'parser': jsoncParser
+		},
+		'plugins': {
+			'jsonc': pluginJsonc
+		},
+		'rules': jsonRules
+	},
+
+	// cli_opts.json override (tab-indented per .editorconfig):
+	{
+		'files': [ '**/cli_opts.json' ],
+		'rules': {
+			'jsonc/indent': [ 'error', 'tab' ]
+		}
+	},
+
+	// package.json key ordering:
+	{
+		'files': [ '**/package.json' ],
+		'rules': {
+			'jsonc/sort-keys': [ 'error', {
+				'pathPattern': '^$',
+				'order': [
+					'name',
+					'private',
+					'version',
+					'description',
+					'license',
+					'licenses',
+					'author',
+					'maintainers',
+					'contributors',
+					'funding',
+					'bin',
+					'main',
+					'exports',
+					'browser',
+					'unpkg',
+					'gypfile',
+					'directories',
+					'types',
+					'scripts',
+					'homepage',
+					'repository',
+					'repositories',
+					'bugs',
+					'dependencies',
+					'optionalDependencies',
+					'devDependencies',
+					'engines',
+					'os',
+					'keywords',
+					'__stdlib__'
+				]
+			}]
+		}
+	},
+
+	// Base YAML:
+	{
+		'files': [ '**/*.yml' ],
+		'languageOptions': {
+			'parser': yamlParser
+		},
+		'plugins': {
+			'yml': pluginYml,
+			'stdlib': stdlibPlugin
+		},
+		'rules': {
+			...yamlRules,
+			'stdlib/yaml-license-header': 'error'
+		}
+	},
+
+	// GitHub Actions workflow key ordering:
+	{
+		'files': [ '.github/workflows/*.yml' ],
+		'rules': {
+			'yml/sort-keys': [ 'error', {
+				'pathPattern': '^$',
+				'order': [
+					'name',
+					'on',
+					'concurrency',
+					'permissions',
+					'env',
+					'jobs'
+				]
+			}]
+		}
 	}
 ];

etc/eslint/rules/json.js

@@ -0,0 +1,121 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2026 The Stdlib Authors.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+*    http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+'use strict';
+
+/**
+* ESLint rules for JSON files.
+*
+* @namespace rules
+*/
+var rules = {};
+
+/**
+* Enforce 2-space indentation per `.editorconfig`.
+*
+* @name jsonc/indent
+* @memberof rules
+* @type {Array}
+*/
+rules[ 'jsonc/indent' ] = [ 'error', 2 ];
+
+/**
+* Disallow comments in JSON files.
+*
+* @name jsonc/no-comments
+* @memberof rules
+* @type {string}
+*/
+rules[ 'jsonc/no-comments' ] = 'error';
+
+/**
+* Disallow trailing commas.
+*
+* @name jsonc/comma-dangle
+* @memberof rules
+* @type {Array}
+*/
+rules[ 'jsonc/comma-dangle' ] = [ 'error', 'never' ];
+
+/**
+* Disallow duplicate keys.
+*
+* @name jsonc/no-dupe-keys
+* @memberof rules
+* @type {string}
+*/
+rules[ 'jsonc/no-dupe-keys' ] = 'error';
+
+/**
+* Disallow floating decimals (e.g., `.5` or `1.`).
+*
+* @name jsonc/no-floating-decimal
+* @memberof rules
+* @type {string}
+*/
+rules[ 'jsonc/no-floating-decimal' ] = 'error';
+
+/**
+* Disallow irregular whitespace characters.
+*
+* @name jsonc/no-irregular-whitespace
+* @memberof rules
+* @type {string}
+*/
+rules[ 'jsonc/no-irregular-whitespace' ] = 'error';
+
+/**
+* Disallow multi-line strings.
+*
+* @name jsonc/no-multi-str
+* @memberof rules
+* @type {string}
+*/
+rules[ 'jsonc/no-multi-str' ] = 'error';
+
+/**
+* Disallow octal literals.
+*
+* @name jsonc/no-octal
+* @memberof rules
+* @type {string}
+*/
+rules[ 'jsonc/no-octal' ] = 'error';
+
+/**
+* Disallow useless escape characters.
+*
+* @name jsonc/no-useless-escape
+* @memberof rules
+* @type {string}
+*/
+rules[ 'jsonc/no-useless-escape' ] = 'error';
+
+/**
+* Enforce valid JSON number literals.
+*
+* @name jsonc/valid-json-number
+* @memberof rules
+* @type {string}
+*/
+rules[ 'jsonc/valid-json-number' ] = 'error';
+
+
+// EXPORTS //
+
+module.exports = rules;

etc/eslint/rules/yaml.js

@@ -0,0 +1,144 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2026 The Stdlib Authors.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+*    http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+'use strict';
+
+/**
+* ESLint rules for YAML files.
+*
+* @namespace rules
+*/
+var rules = {};
+
+/**
+* Enforce 2-space indentation per `.editorconfig`.
+*
+* @name yml/indent
+* @memberof rules
+* @type {Array}
+*/
+rules[ 'yml/indent' ] = [ 'error', 2 ];
+
+/**
+* Disallow empty YAML documents.
+*
+* @name yml/no-empty-document
+* @memberof rules
+* @type {string}
+*/
+rules[ 'yml/no-empty-document' ] = 'error';
+
+/**
+* Disallow empty keys.
+*
+* @name yml/no-empty-key
+* @memberof rules
+* @type {string}
+*/
+rules[ 'yml/no-empty-key' ] = 'error';
+
+/**
+* Disallow empty mapping values.
+*
+* @name yml/no-empty-mapping-value
+* @memberof rules
+* @type {string}
+*/
+rules[ 'yml/no-empty-mapping-value' ] = 'error';
+
+/**
+* Disallow empty sequence entries.
+*
+* @name yml/no-empty-sequence-entry
+* @memberof rules
+* @type {string}
+*/
+rules[ 'yml/no-empty-sequence-entry' ] = 'error';
+
+/**
+* Disallow irregular whitespace characters.
+*
+* @name yml/no-irregular-whitespace
+* @memberof rules
+* @type {string}
+*/
+rules[ 'yml/no-irregular-whitespace' ] = 'error';
+
+/**
+* Disallow tab indentation.
+*
+* @name yml/no-tab-indent
+* @memberof rules
+* @type {string}
+*/
+rules[ 'yml/no-tab-indent' ] = 'error';
+
+/**
+* Require string keys.
+*
+* @name yml/require-string-key
+* @memberof rules
+* @type {string}
+*/
+rules[ 'yml/require-string-key' ] = 'error';
+
+/**
+* Enforce block-style mappings.
+*
+* @name yml/block-mapping
+* @memberof rules
+* @type {string}
+*/
+rules[ 'yml/block-mapping' ] = 'error';
+
+/**
+* Enforce block-style sequences.
+*
+* @name yml/block-sequence
+* @memberof rules
+* @type {string}
+*/
+rules[ 'yml/block-sequence' ] = 'error';
+
+/**
+* Disallow multiple consecutive empty lines.
+*
+* @name yml/no-multiple-empty-lines
+* @memberof rules
+* @type {Array}
+*/
+rules[ 'yml/no-multiple-empty-lines' ] = [ 'error', {
+	'max': 1
+}];
+
+/**
+* Prefer single quotes (warn first to assess impact on `${{ }}` expressions).
+*
+* @name yml/quotes
+* @memberof rules
+* @type {Array}
+*/
+rules[ 'yml/quotes' ] = [ 'warn', {
+	'prefer': 'single',
+	'avoidEscape': true
+}];
+
+
+// EXPORTS //
+
+module.exports = rules;