feat(eslint-config): add custom eslint rule 'no-uncaught-json-parse' (#4087)

feat(eslint-config): add custom eslint rule 'no-uncaugh-json-parse'

Co-authored-by: Iván Ovejero <ivov.src@gmail.com>

packages/@n8n_io/eslint-config/base.js

@@ -40,6 +40,12 @@ module.exports = {
 		 * https://github.com/paleite/eslint-plugin-diff#plugindiffdiff-recommended
 		 */
 		'eslint-plugin-diff',
+
+		/*
+		 * Plugin to allow specifying local ESLint rules.
+		 * https://github.com/ivov/eslint-plugin-n8n-local-rules
+		 */
+		'eslint-plugin-n8n-local-rules',
 	],
 
 	extends: [
@@ -324,6 +330,13 @@ module.exports = {
 		 */
 		'import/order': 'error',
 
+		// ----------------------------------
+		//   eslint-plugin-n8n-local-rules
+		// ----------------------------------
+
+		// TODO: set to `error` and fix offenses
+		'n8n-local-rules/no-uncaught-json-parse': 'warn',
+
 		// ******************************************************************
 		//                    overrides to base ruleset
 		// ******************************************************************

packages/@n8n_io/eslint-config/local-rules.js

@@ -0,0 +1,86 @@
+'use strict';
+
+/**
+ * This file contains any locally defined ESLint rules. They are picked up by
+ * eslint-plugin-n8n-local-rules and exposed as 'n8n-local-rules/<rule-name>'.
+ */
+module.exports = {
+	/**
+	 * A rule to detect calls to JSON.parse() that are not wrapped inside try/catch blocks.
+	 *
+	 * Valid:
+	 * ```js
+	 * try { JSON.parse(foo) } catch(err) { baz() }
+	 * ```
+	 *
+	 * Invalid:
+	 * ```js
+	 * JSON.parse(foo)
+	 * ```
+	 *
+	 * The pattern where an object is cloned with JSON.parse(JSON.stringify()) is allowed
+	 * (abundant in the n8n codebase):
+	 *
+	 * Valid:
+	 * ```js
+	 * JSON.parse(JSON.stringify(foo))
+	 * ```
+	 */
+	'no-uncaught-json-parse': {
+		meta: {
+			type: 'problem',
+			docs: {
+				description: 'Calls to JSON.parse() must be surrounded with a try/catch block.',
+				recommended: 'error',
+			},
+			schema: [],
+			messages: {
+				noUncaughtJsonParse: 'Surround the JSON.parse() call with a try/catch block.',
+			},
+		},
+		defaultOptions: [],
+		create(context) {
+			return {
+				CallExpression(node) {
+					if (!isJsonParseCall(node)) {
+						return;
+					}
+
+					if (isDeepCloneOperation(node)) {
+						return;
+					}
+
+					if (context.getAncestors().find((node) => node.type === 'TryStatement') !== undefined) {
+						return;
+					}
+
+					// Found a JSON.parse() call not wrapped into a try/catch, so report it
+					context.report({
+						messageId: 'noUncaughtJsonParse',
+						node,
+					});
+				},
+			};
+		},
+	},
+};
+
+const isJsonParseCall = (node) =>
+	node.callee.type === 'MemberExpression' &&
+	node.callee.object.type === 'Identifier' &&
+	node.callee.object.name === 'JSON' &&
+	node.callee.property.type === 'Identifier' &&
+	node.callee.property.name === 'parse';
+
+const isDeepCloneOperation = (node) => {
+	const parseArg = node.arguments?.[0];
+	return (
+		parseArg !== undefined &&
+		parseArg.type === 'CallExpression' &&
+		parseArg.callee.type === 'MemberExpression' &&
+		parseArg.callee.object.type === 'Identifier' &&
+		parseArg.callee.object.name === 'JSON' &&
+		parseArg.callee.property.type === 'Identifier' &&
+		parseArg.callee.property.name === 'stringify'
+	);
+};

packages/@n8n_io/eslint-config/local-rules.test.js

@@ -0,0 +1,23 @@
+'use strict';
+
+const rules = require('./local-rules'),
+	RuleTester = require('eslint').RuleTester;
+
+const ruleTester = new RuleTester();
+
+ruleTester.run('no-uncaught-json-parse', rules['no-uncaught-json-parse'], {
+	valid: [
+		{
+			code: 'try { JSON.parse(foo) } catch (e) {}',
+		},
+		{
+			code: 'JSON.parse(JSON.stringify(foo))',
+		},
+	],
+	invalid: [
+		{
+			code: 'JSON.parse(foo)',
+			errors: [{ messageId: 'noUncaughtJsonParse' }],
+		},
+	],
+});

packages/@n8n_io/eslint-config/package.json

@@ -11,7 +11,12 @@
     "eslint-config-prettier": "^8.5.0",
     "eslint-plugin-diff": "^2.0.1",
     "eslint-plugin-import": "^2.26.0",
+    "eslint-plugin-n8n-local-rules": "^1.0.0",
     "eslint-plugin-prettier": "^4.2.1",
-    "eslint-plugin-vue": "^9.4.0"
+    "eslint-plugin-vue": "^9.4.0",
+    "jest": "^28.1.3"
+  },
+  "scripts": {
+    "test": "jest"
   }
 }