feat(core): Add no-template-placeholders ESLint rule for community nodes (#29796)

packages/@n8n/eslint-plugin-community-nodes/README.md

@@ -61,6 +61,7 @@ export default [
 | [no-restricted-globals](docs/rules/no-restricted-globals.md)                             | Disallow usage of restricted global variables in community nodes.                                                                           | ✅    |      |    |    |    |
 | [no-restricted-imports](docs/rules/no-restricted-imports.md)                             | Disallow usage of restricted imports in community nodes.                                                                                    | ✅    |      |    |    |    |
 | [no-runtime-dependencies](docs/rules/no-runtime-dependencies.md)                         | Disallow non-empty "dependencies" in community node package.json                                                                            | ✅ ☑️ |      |    |    |    |
+| [no-template-placeholders](docs/rules/no-template-placeholders.md)                       | Disallow unresolved template placeholders in package.json                                                                                   | ✅ ☑️ |      |    |    |    |
 | [node-class-description-icon-missing](docs/rules/node-class-description-icon-missing.md) | Node class description must have an `icon` property defined. Deprecated: use `require-node-description-fields` instead.                     |      |      |    | 💡 | ❌  |
 | [node-connection-type-literal](docs/rules/node-connection-type-literal.md)               | Disallow string literals in node description `inputs`/`outputs` — use `NodeConnectionTypes` enum instead                                    | ✅ ☑️ |      | 🔧 |    |    |
 | [node-operation-error-itemindex](docs/rules/node-operation-error-itemindex.md)           | Require { itemIndex } in NodeOperationError / NodeApiError options inside item loops                                                        | ✅ ☑️ |      |    |    |    |

packages/@n8n/eslint-plugin-community-nodes/docs/rules/no-template-placeholders.md

@@ -0,0 +1,51 @@
+# Disallow unresolved template placeholders in package.json (`@n8n/community-nodes/no-template-placeholders`)
+
+💼 This rule is enabled in the following configs: ✅ `recommended`, ☑️ `recommendedWithoutN8nCloudSupport`.
+
+<!-- end auto-generated rule header -->
+
+## Rule Details
+
+Community node packages are typically scaffolded from a starter template that contains
+placeholder values such as `<PACKAGE_NAME>`, `<USERNAME>`, or `{{ authorName }}`. When
+these placeholders survive into a published `package.json`, the package metadata is
+broken — the name is invalid, the repository link is dead, etc.
+
+This rule scans every string value in `package.json` and reports any value containing
+an unresolved placeholder pattern. It catches:
+
+- Angle bracket placeholders: `<...>`
+- Mustache placeholders: `{{...}}`
+
+The rule applies to **all** string fields, including custom ones — not just the well-known
+fields like `name`, `description`, `homepage`, or `repository.url`.
+
+## Examples
+
+### Incorrect
+
+```json
+{
+  "name": "n8n-nodes-<PACKAGE_NAME>",
+  "description": "An n8n community node for {{service}}",
+  "homepage": "https://github.com/<USERNAME>/n8n-nodes-example#readme",
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/<USERNAME>/n8n-nodes-example.git"
+  }
+}
+```
+
+### Correct
+
+```json
+{
+  "name": "n8n-nodes-acme",
+  "description": "An n8n community node for the Acme API",
+  "homepage": "https://github.com/acme/n8n-nodes-acme#readme",
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/acme/n8n-nodes-acme.git"
+  }
+}
+```

packages/@n8n/eslint-plugin-community-nodes/src/plugin.ts

@@ -33,6 +33,7 @@ const configs = {
 			'@n8n/community-nodes/no-http-request-with-manual-auth': 'error',
 			'@n8n/community-nodes/no-overrides-field': 'error',
 			'@n8n/community-nodes/no-runtime-dependencies': 'error',
+			'@n8n/community-nodes/no-template-placeholders': 'error',
 			'@n8n/community-nodes/icon-validation': 'error',
 			'@n8n/community-nodes/options-sorted-alphabetically': 'warn',
 			'@n8n/community-nodes/resource-operation-pattern': 'warn',
@@ -67,6 +68,7 @@ const configs = {
 			'@n8n/community-nodes/no-http-request-with-manual-auth': 'error',
 			'@n8n/community-nodes/no-overrides-field': 'error',
 			'@n8n/community-nodes/no-runtime-dependencies': 'error',
+			'@n8n/community-nodes/no-template-placeholders': 'error',
 			'@n8n/community-nodes/icon-validation': 'error',
 			'@n8n/community-nodes/options-sorted-alphabetically': 'warn',
 			'@n8n/community-nodes/credential-documentation-url': 'error',

packages/@n8n/eslint-plugin-community-nodes/src/rules/index.ts

@@ -15,6 +15,7 @@ import { NoOverridesFieldRule } from './no-overrides-field.js';
 import { NoRestrictedGlobalsRule } from './no-restricted-globals.js';
 import { NoRestrictedImportsRule } from './no-restricted-imports.js';
 import { NoRuntimeDependenciesRule } from './no-runtime-dependencies.js';
+import { NoTemplatePlaceholdersRule } from './no-template-placeholders.js';
 import { NodeClassDescriptionIconMissingRule } from './node-class-description-icon-missing.js';
 import { NodeConnectionTypeLiteralRule } from './node-connection-type-literal.js';
 import { NodeOperationErrorItemIndexRule } from './node-operation-error-itemindex.js';
@@ -45,6 +46,7 @@ export const rules = {
 	'no-http-request-with-manual-auth': NoHttpRequestWithManualAuthRule,
 	'no-overrides-field': NoOverridesFieldRule,
 	'no-runtime-dependencies': NoRuntimeDependenciesRule,
+	'no-template-placeholders': NoTemplatePlaceholdersRule,
 	'icon-validation': IconValidationRule,
 	'resource-operation-pattern': ResourceOperationPatternRule,
 	'credential-documentation-url': CredentialDocumentationUrlRule,

packages/@n8n/eslint-plugin-community-nodes/src/rules/no-template-placeholders.test.ts

@@ -0,0 +1,135 @@
+import { RuleTester } from '@typescript-eslint/rule-tester';
+
+import { NoTemplatePlaceholdersRule } from './no-template-placeholders.js';
+
+const ruleTester = new RuleTester();
+
+ruleTester.run('no-template-placeholders', NoTemplatePlaceholdersRule, {
+	valid: [
+		{
+			name: 'package.json with no placeholders',
+			filename: 'package.json',
+			code: `{
+				"name": "n8n-nodes-example",
+				"version": "1.0.0",
+				"description": "An example community node",
+				"homepage": "https://example.com",
+				"repository": { "type": "git", "url": "git+https://github.com/acme/n8n-nodes-example.git" }
+			}`,
+		},
+		{
+			name: 'angle brackets that do not look like placeholders are ignored',
+			filename: 'package.json',
+			code: '{ "description": "Compares a < b values" }',
+		},
+		{
+			name: 'single curly braces are ignored',
+			filename: 'package.json',
+			code: '{ "description": "Use { key: value } syntax" }',
+		},
+		{
+			name: 'non-package.json file is ignored even if it has placeholders',
+			filename: 'tsconfig.json',
+			code: '{ "name": "<PACKAGE_NAME>" }',
+		},
+		{
+			name: 'numeric and boolean values are not flagged',
+			filename: 'package.json',
+			code: '{ "name": "n8n-nodes-example", "private": false, "engines": { "node": ">=18" } }',
+		},
+	],
+	invalid: [
+		{
+			name: 'angle bracket placeholder in name',
+			filename: 'package.json',
+			code: '{ "name": "n8n-nodes-<PACKAGE_NAME>" }',
+			errors: [
+				{
+					messageId: 'unresolvedPlaceholder',
+					data: { pattern: '<PACKAGE_NAME>' },
+				},
+			],
+		},
+		{
+			name: 'angle bracket placeholder in description',
+			filename: 'package.json',
+			code: '{ "description": "An n8n community node for <SERVICE>" }',
+			errors: [
+				{
+					messageId: 'unresolvedPlaceholder',
+					data: { pattern: '<SERVICE>' },
+				},
+			],
+		},
+		{
+			name: 'angle bracket placeholder in repository url',
+			filename: 'package.json',
+			code: '{ "repository": { "type": "git", "url": "git+https://github.com/<USERNAME>/n8n-nodes-example.git" } }',
+			errors: [
+				{
+					messageId: 'unresolvedPlaceholder',
+					data: { pattern: '<USERNAME>' },
+				},
+			],
+		},
+		{
+			name: 'angle bracket placeholder in homepage',
+			filename: 'package.json',
+			code: '{ "homepage": "https://github.com/<USERNAME>/n8n-nodes-example#readme" }',
+			errors: [
+				{
+					messageId: 'unresolvedPlaceholder',
+					data: { pattern: '<USERNAME>' },
+				},
+			],
+		},
+		{
+			name: 'mustache placeholder in author',
+			filename: 'package.json',
+			code: '{ "author": "{{ authorName }}" }',
+			errors: [
+				{
+					messageId: 'unresolvedPlaceholder',
+					data: { pattern: '{{ authorName }}' },
+				},
+			],
+		},
+		{
+			name: 'mustache placeholder inside larger string',
+			filename: 'package.json',
+			code: '{ "description": "Node by {{author}} for service" }',
+			errors: [
+				{
+					messageId: 'unresolvedPlaceholder',
+					data: { pattern: '{{author}}' },
+				},
+			],
+		},
+		{
+			name: 'placeholder in custom field',
+			filename: 'package.json',
+			code: '{ "n8n": { "n8nNodesApiVersion": 1, "credentials": ["<CREDENTIAL>"] } }',
+			errors: [
+				{
+					messageId: 'unresolvedPlaceholder',
+					data: { pattern: '<CREDENTIAL>' },
+				},
+			],
+		},
+		{
+			name: 'multiple placeholders in different fields are all reported',
+			filename: 'package.json',
+			code: '{ "name": "<NAME>", "description": "{{description}}" }',
+			errors: [
+				{
+					messageId: 'unresolvedPlaceholder',
+					data: { pattern: '<NAME>' },
+				},
+				{
+					messageId: 'unresolvedPlaceholder',
+					data: { pattern: '{{description}}' },
+				},
+			],
+		},
+	],
+});

packages/@n8n/eslint-plugin-community-nodes/src/rules/no-template-placeholders.ts

@@ -0,0 +1,68 @@
+import type { TSESTree } from '@typescript-eslint/utils';
+import { AST_NODE_TYPES } from '@typescript-eslint/utils';
+
+import { createRule } from '../utils/index.js';
+
+const ANGLE_PLACEHOLDER = /<[^<>\n]+?>/;
+const MUSTACHE_PLACEHOLDER = /\{\{[^{}\n]+?\}\}/;
+
+function findPlaceholder(value: string): { pattern: string; type: 'angle' | 'mustache' } | null {
+	const angleMatch = ANGLE_PLACEHOLDER.exec(value);
+	if (angleMatch) {
+		return { pattern: angleMatch[0], type: 'angle' };
+	}
+	const mustacheMatch = MUSTACHE_PLACEHOLDER.exec(value);
+	if (mustacheMatch) {
+		return { pattern: mustacheMatch[0], type: 'mustache' };
+	}
+	return null;
+}
+
+export const NoTemplatePlaceholdersRule = createRule({
+	name: 'no-template-placeholders',
+	meta: {
+		type: 'problem',
+		docs: {
+			description: 'Disallow unresolved template placeholders in package.json',
+		},
+		messages: {
+			unresolvedPlaceholder:
+				'String value contains an unresolved template placeholder "{{ pattern }}". Replace it with a real value before publishing.',
+		},
+		schema: [],
+	},
+	defaultOptions: [],
+	create(context) {
+		if (!context.filename.endsWith('package.json')) {
+			return {};
+		}
+
+		return {
+			Literal(node: TSESTree.Literal) {
+				if (typeof node.value !== 'string') {
+					return;
+				}
+
+				// Skip property keys — only flag values.
+				if (
+					node.parent?.type === AST_NODE_TYPES.Property &&
+					node.parent.key === node &&
+					!node.parent.computed
+				) {
+					return;
+				}
+
+				const placeholder = findPlaceholder(node.value);
+				if (!placeholder) {
+					return;
+				}
+
+				context.report({
+					node,
+					messageId: 'unresolvedPlaceholder',
+					data: { pattern: placeholder.pattern },
+				});
+			},
+		};
+	},
+});