N8n:create Community Node Lint Rule

Create Community Node Lint Rule

Guide for adding new ESLint rules to packages/@n8n/eslint-plugin-community-nodes/.

All paths below are relative to packages/@n8n/eslint-plugin-community-nodes/.

Step 1: Understand the Rule

Before writing code, clarify:

• What does the rule detect? (missing property, wrong pattern, bad value)
• Where does it apply? (.node.ts files, credential classes, both)
• Severity: error (must fix) or warn (should fix)?
• Fixable? Can it be auto-fixed safely, or only suggest?
• Scope: Both recommended configs, or exclude from recommendedWithoutN8nCloudSupport?

Step 2: Implement the Rule

Create src/rules/<rule-name>.ts:

import { AST_NODE_TYPES } from '@typescript-eslint/utils';

import {
  isNodeTypeClass,       // or isCredentialTypeClass
  findClassProperty,
  findObjectProperty,
  createRule,
} from '../utils/index.js';

export const YourRuleNameRule = createRule({
  name: 'rule-name',
  meta: {
    type: 'problem',  // or 'suggestion'
    docs: {
      description: 'One-line description of what the rule enforces',
    },
    messages: {
      messageId: 'Human-readable message. Use {{placeholder}} for dynamic data.',
    },
    fixable: 'code',     // omit if not auto-fixable
    hasSuggestions: true, // omit if no suggestions
    schema: [],           // add options schema if configurable
  },
  defaultOptions: [],
  create(context) {
    return {
      ClassDeclaration(node) {
        if (!isNodeTypeClass(node)) return;

        const descriptionProperty = findClassProperty(node, 'description');
        if (!descriptionProperty) return;

        const descriptionValue = descriptionProperty.value;
        if (descriptionValue?.type !== AST_NODE_TYPES.ObjectExpression) return;

        // Rule logic here — use findObjectProperty(), getLiteralValue(), etc.

        context.report({
          node: targetNode,
          messageId: 'messageId',
          data: { /* template vars */ },
          fix(fixer) {
            return fixer.replaceText(targetNode, 'replacement');
          },
        });
      },
    };
  },
});

Naming: Export as PascalCaseRule (e.g. MissingPairedItemRule). The name field is kebab-case.

Available AST helpers — see reference.md for the full catalog of ast-utils and file-utils exports.

Step 3: Write Tests

Create src/rules/<rule-name>.test.ts:

import { RuleTester } from '@typescript-eslint/rule-tester';

import { YourRuleNameRule } from './rule-name.js';

const ruleTester = new RuleTester();

// Helper to generate test code — keeps test cases readable
function createNodeCode(/* parameterize the varying parts */): string {
  return `
import type { INodeType, INodeTypeDescription } from 'n8n-workflow';

export class TestNode implements INodeType {
  description: INodeTypeDescription = {
    displayName: 'Test Node',
    name: 'testNode',
    group: ['input'],
    version: 1,
    description: 'A test node',
    defaults: { name: 'Test Node' },
    inputs: [],
    outputs: [],
    properties: [],
  };
}`;
}

ruleTester.run('rule-name', YourRuleNameRule, {
  valid: [
    { name: 'class that does not implement INodeType', code: '...' },
    { name: 'node with correct pattern', code: createNodeCode(/* correct */) },
  ],
  invalid: [
    {
      name: 'descriptive case name',
      code: createNodeCode(/* incorrect */),
      errors: [{ messageId: 'messageId', data: { /* expected template vars */ } }],
      output: createNodeCode(/* expected after fix */),  // or `output: null` if no fix
    },
  ],
});

Test guidelines:

• Always test that non-INodeType classes are skipped (valid case)
• Test both the error message and the fixed output for fixable rules
• For rules with options, test each option combination
• For rules using filesystem, mock with vi.mock('../utils/file-utils.js')
• For suggestion-only rules, use errors: [{ messageId, suggestions: [...] }]

Step 4: Register the Rule

4a. Add to src/rules/index.ts

import { YourRuleNameRule } from './rule-name.js';

// Add to the rules object:
export const rules = {
  // ... existing rules
  'rule-name': YourRuleNameRule,
} satisfies Record<string, AnyRuleModule>;

4b. Add to src/plugin.ts configs

Add to both config objects (unless the rule depends on n8n cloud features):

'@n8n/community-nodes/rule-name': 'error',  // or 'warn'

• Use error for rules that catch bugs or required patterns
• Use warn for style/convention rules (like options-sorted-alphabetically)
• If the rule uses no-restricted-globals or no-restricted-imports patterns, only add to recommended (not recommendedWithoutN8nCloudSupport)

Step 5: Write Documentation

Create docs/rules/<rule-name>.md:

# Description of what the rule does (`@n8n/community-nodes/rule-name`)

<!-- end auto-generated rule header -->

## Rule Details

Explain why this rule exists and what problem it prevents.

## Examples

### Incorrect

\`\`\`typescript
// code that triggers the rule
\`\`\`

### Correct

\`\`\`typescript
// code that passes the rule
\`\`\`

The header above <!-- end auto-generated rule header --> will be regenerated by pnpm build:docs. Write a reasonable first version — it gets overwritten.

Step 6: Verify

Run from packages/@n8n/eslint-plugin-community-nodes/:

pushd packages/@n8n/eslint-plugin-community-nodes
pnpm test <rule-name>.test.ts   # tests pass
pnpm typecheck                   # types are clean
pnpm build                       # compiles
pnpm build:docs                  # regenerates doc headers and README table
pnpm lint:docs                   # docs match schema
popd

Checklist

• Rule file: src/rules/<rule-name>.ts
• Test file: src/rules/<rule-name>.test.ts
• Registered in src/rules/index.ts
• Added to configs in src/plugin.ts
• Doc file: docs/rules/<rule-name>.md
• README table updated via pnpm build:docs
• All verification commands pass