wip(eslint-plugin): add new blank-line-declaration-usage rule and tests for it

Author: kresimir-coko

projects/eslint-plugin/configs/general.js

@@ -93,6 +93,7 @@ const config = {
 		'@liferay/aui/no-node': 'error',
 		'@liferay/aui/no-object': 'error',
 		'@liferay/aui/no-one': 'error',
+		'@liferay/blank-line-declaration-usage': 'error',
 		'@liferay/destructure-requires': 'error',
 		'@liferay/empty-line-between-elements': 'error',
 		'@liferay/expect-assert': 'error',

projects/eslint-plugin/rules/general/lib/rules/blank-line-declaration-usage.js

@@ -0,0 +1,69 @@
+/**
+ * SPDX-FileCopyrightText: © 2017 Liferay, Inc. <https://liferay.com>
+ * SPDX-License-Identifier: MIT
+ */
+
+module.exports = {
+	create(context) {
+		return {
+			VariableDeclaration(node) {
+				if (!node.declarations.length) {
+					return;
+				}
+
+				const variableName = node.declarations[0].id.name;
+
+				const variableDeclarationIndex = node.parent.body.indexOf(node);
+
+				const nodeToCheck =
+					node.parent.body[variableDeclarationIndex + 1];
+
+				if (!nodeToCheck) {
+					return;
+				}
+
+				const linesBetween =
+					nodeToCheck.loc.start.line - node.loc.end.line;
+
+				if (linesBetween > 1) {
+					return;
+				}
+
+				let nodeToCheckName;
+
+				if (nodeToCheck.type === 'ExpressionStatement') {
+					const matchingArgument = nodeToCheck.expression.arguments.find(
+						(argument) => argument.name === variableName
+					);
+
+					if (matchingArgument) {
+						nodeToCheckName = matchingArgument.name;
+					}
+				}
+				else {
+					nodeToCheckName =
+						nodeToCheck.declarations[0].init.object.name;
+				}
+
+				if (nodeToCheckName === variableName) {
+					context.report({
+						message: 'error msg',
+						node,
+					});
+				}
+			},
+		};
+	},
+
+	meta: {
+		docs: {
+			category: 'Best Practices',
+			description: 'error msg',
+			recommended: false,
+			url: 'https://github.com/liferay/eslint-config-liferay/issues/139',
+		},
+		fixable: 'code', // or "code" or "whitespace"
+		schema: [],
+		type: 'problem',
+	},
+};

projects/eslint-plugin/rules/general/tests/lib/rules/blank-line-declaration-usage.js

@@ -0,0 +1,68 @@
+/**
+ * SPDX-FileCopyrightText: © 2017 Liferay, Inc. <https://liferay.com>
+ * SPDX-License-Identifier: MIT
+ */
+
+const MultiTester = require('../../../../../scripts/MultiTester');
+const rule = require('../../../lib/rules/blank-line-declaration-usage');
+
+const parserOptions = {
+	parserOptions: {
+		ecmaVersion: 6,
+	},
+};
+
+const ruleTester = new MultiTester(parserOptions);
+
+ruleTester.run('blank-line-declaration-usage', rule, {
+	invalid: [
+		{
+			code: `
+				const test = 'test';
+				const testLength = test.length;
+			`,
+			errors: [
+				{
+					message: 'error msg',
+					type: 'VariableDeclaration',
+				},
+			],
+		},
+		{
+			code: `
+				const obj = {
+					foo: 'bar',
+					bar: 'foo',
+					hi: 'bryce',
+				}
+			  	Object.keys(obj)
+			`,
+			errors: [
+				{
+					message: 'error msg',
+					type: 'VariableDeclaration',
+				},
+			],
+		},
+	],
+	valid: [
+		{
+			code: `
+				const test = 'test';
+
+				const testLength = test.length;
+			`,
+		},
+		{
+			code: `
+				const obj = {
+					foo: 'bar',
+					bar: 'foo',
+					hi: 'bryce',
+				}
+				
+				Object.keys(obj)
+			`,
+		},
+	],
+});