feat: add no-property-in-node rule (#433)

* feat: add no-property-in-node rule

* Add ☑️ emoji for recommended-type-checked

* tests: valid before invalid

* Also check for whether the node has a 'type'

* Added docs and example to isAstNodeType

* Expanded rule details

* Add more valid test cases

* Fixed test path to fixtures

* Use parserOptions.project: true for eslint-remote-tester on TS files

* nit: avoid shadowing name for typePart

* <!-- omit from toc -->

* Downgraded to typescript-eslint@v5

* Also remove @typescript-eslint/utils

* Or rather, make @typescript-eslint/utils a -D

* Remove ts-api-utils too

* Removed recommended-type-checked

* Removed README.md section too

* Removed eslint-remote-tester.config.js parserOptions.project too

* Redid README.md presets table

* Added all-type-checked

* Removed file notice

Author: JoshuaKGoldberg

.eslint-doc-generatorrc.js

@@ -6,6 +6,7 @@ const prettier = require('prettier');
 module.exports = {
   ignoreConfig: [
     'all',
+    'all-type-checked',
     'rules',
     'rules-recommended',
     'tests',

README.md

@@ -0,0 +1,8 @@
+'use strict';
+
+const mod = require('../lib/index.js');
+
+module.exports = {
+  plugins: { 'eslint-plugin': mod },
+  rules: mod.configs['all-type-checked'].rules,
+};

configs/all-type-checked.js

@@ -0,0 +1,56 @@
+# Disallow using `in` to narrow node types instead of looking at properties (`eslint-plugin/no-property-in-node`)
+
+💭 This rule requires type information.
+
+<!-- end auto-generated rule header -->
+
+When working with a node of type `ESTree.Node` or `TSESTree.Node`, it can be tempting to use the `'in'` operator to narrow the node's type.
+`'in'` narrowing is susceptible to confusing behavior from quirks of ASTs, such as node properties sometimes being omitted from nodes and other times explicitly being set to `null` or `undefined`.
+
+Instead, checking a node's `type` property is generally considered preferable.
+
+## Rule Details
+
+Examples of **incorrect** code for this rule:
+
+```ts
+/* eslint eslint-plugin/no-property-in-node: error */
+
+/** @type {import('eslint').Rule.RuleModule} */
+module.exports = {
+  meta: {
+    /* ... */
+  },
+  create(context) {
+    return {
+      'ClassDeclaration, FunctionDeclaration'(node) {
+        if ('superClass' in node) {
+          console.log('This is a class declaration:', node);
+        }
+      },
+    };
+  },
+};
+```
+
+Examples of **correct** code for this rule:
+
+```ts
+/* eslint eslint-plugin/no-property-in-node: error */
+
+/** @type {import('eslint').Rule.RuleModule} */
+module.exports = {
+  meta: {
+    /* ... */
+  },
+  create(context) {
+    return {
+      'ClassDeclaration, FunctionDeclaration'(node) {
+        if (node.type === 'ClassDeclaration') {
+          console.log('This is a class declaration:', node);
+        }
+      },
+    };
+  },
+};
+```

docs/rules/no-property-in-node.md

@@ -15,7 +15,8 @@ const packageMetadata = require('../package');
 const PLUGIN_NAME = packageMetadata.name.replace(/^eslint-plugin-/, '');
 
 const configFilters = {
-  all: () => true,
+  all: (rule) => !rule.meta.docs.requiresTypeChecking,
+  'all-type-checked': () => true,
   recommended: (rule) => rule.meta.docs.recommended,
   rules: (rule) => rule.meta.docs.category === 'Rules',
   tests: (rule) => rule.meta.docs.category === 'Tests',

lib/index.js

@@ -0,0 +1,86 @@
+'use strict';
+
+const typedNodeSourceFileTesters = [
+  /@types[/\\]estree[/\\]index\.d\.ts/,
+  /@typescript-eslint[/\\]types[/\\]dist[/\\]generated[/\\]ast-spec\.d\.ts/,
+];
+
+/**
+ * Given a TypeScript type, determines whether the type appears to be for a known
+ * AST type from the typings of @typescript-eslint/types or estree.
+ * We check based on two rough conditions:
+ * - The type has a 'kind' property (as AST node types all do)
+ * - The type is declared in one of those package's .d.ts types
+ *
+ * @example
+ * ```
+ * module.exports = {
+ *  create(context) {
+ *    BinaryExpression(node) {
+ *      const type = services.getTypeAtLocation(node.right);
+ *      //    ^^^^
+ *      // This variable's type will be TSESTree.BinaryExpression
+ *    }
+ *  }
+ * }
+ * ```
+ *
+ * @param {import('typescript').Type} type
+ * @returns Whether the type seems to include a known ESTree or TSESTree AST node.
+ */
+function isAstNodeType(type) {
+  return (type.types || [type])
+    .filter((typePart) => typePart.getProperty('type'))
+    .flatMap(
+      (typePart) => (typePart.symbol && typePart.symbol.declarations) || []
+    )
+    .some((declaration) => {
+      const fileName = declaration.getSourceFile().fileName;
+      return (
+        fileName &&
+        typedNodeSourceFileTesters.some((tester) => tester.test(fileName))
+      );
+    });
+}
+
+/** @type {import('eslint').Rule.RuleModule} */
+module.exports = {
+  meta: {
+    type: 'suggestion',
+    docs: {
+      description:
+        'disallow using `in` to narrow node types instead of looking at properties',
+      category: 'Rules',
+      recommended: false,
+      requiresTypeChecking: true,
+      url: 'https://github.com/eslint-community/eslint-plugin-eslint-plugin/tree/HEAD/docs/rules/no-property-in-node.md',
+    },
+    schema: [],
+    messages: {
+      in: 'Prefer checking specific node properties instead of a broad `in`.',
+    },
+  },
+
+  create(context) {
+    return {
+      'BinaryExpression[operator=in]'(node) {
+        // TODO: Switch this to ESLintUtils.getParserServices with typescript-eslint@>=6
+        // https://github.com/eslint-community/eslint-plugin-eslint-plugin/issues/269
+        const services = (context.sourceCode || context).parserServices;
+        if (!services.program) {
+          throw new Error(
+            'You have used a rule which requires parserServices to be generated. You must therefore provide a value for the "parserOptions.project" property for @typescript-eslint/parser.'
+          );
+        }
+
+        const checker = services.program.getTypeChecker();
+        const tsNode = services.esTreeNodeToTSNodeMap.get(node.right);
+        const type = checker.getTypeAtLocation(tsNode);
+
+        if (isAstNodeType(type)) {
+          context.report({ messageId: 'in', node });
+        }
+      },
+    };
+  },
+};

lib/rules/no-property-in-node.js

@@ -55,7 +55,10 @@
     "@eslint/eslintrc": "^2.0.2",
     "@eslint/js": "^8.37.0",
     "@release-it/conventional-changelog": "^4.3.0",
-    "@typescript-eslint/parser": "^5.36.2",
+    "@types/eslint": "^8.56.2",
+    "@types/estree": "^1.0.5",
+    "@typescript-eslint/parser": "^5.62.0",
+    "@typescript-eslint/utils": "^5.62.0",
     "chai": "^4.3.6",
     "dirty-chai": "^2.0.1",
     "eslint": "^8.23.0",
@@ -81,7 +84,7 @@
     "nyc": "^15.1.0",
     "prettier": "^2.7.1",
     "release-it": "^14.14.3",
-    "typescript": "^5.0.4"
+    "typescript": "5.1.3"
   },
   "peerDependencies": {
     "eslint": ">=7.0.0"

package.json

@@ -0,0 +1,5 @@
+{
+  "compilerOptions": {
+    "moduleResolution": "NodeNext"
+  }
+}