ci: Introduce no-plain-errors lint rule for BE packages (no-changelog) (#7961)

## Summary
Require `ApplicationError` or its child classes instead of plain `Error`
in BE packages. This ensures the error will be normalized when reported
to Sentry, if applicable.

Follow-up to:
https://github.com/n8n-io/n8n/pulls?q=is%3Apr+is%3Aclosed+applicationerror

...

#### How to test the change:
1. ...


## Issues fixed
Include links to Github issue or Community forum post or **Linear
ticket**:
> Important in order to close automatically and provide context to
reviewers

...


## Review / Merge checklist
- [ ] PR title and summary are descriptive. **Remember, the title
automatically goes into the changelog. Use `(no-changelog)` otherwise.**
([conventions](https://github.com/n8n-io/n8n/blob/master/.github/pull_request_title_conventions.md))
- [ ] [Docs updated](https://github.com/n8n-io/n8n-docs) or follow-up
ticket created.
- [ ] Tests included.
> A bug is not considered fixed, unless a test is added to prevent it
from happening again. A feature is not complete without tests.
  >
> *(internal)* You can use Slack commands to trigger [e2e
tests](https://www.notion.so/n8n/How-to-use-Test-Instances-d65f49dfc51f441ea44367fb6f67eb0a?pvs=4#a39f9e5ba64a48b58a71d81c837e8227)
or [deploy test
instance](https://www.notion.so/n8n/How-to-use-Test-Instances-d65f49dfc51f441ea44367fb6f67eb0a?pvs=4#f6a177d32bde4b57ae2da0b8e454bfce)
or [deploy early access version on
Cloud](https://www.notion.so/n8n/Cloudbot-3dbe779836004972b7057bc989526998?pvs=4#fef2d36ab02247e1a0f65a74f6fb534e).

packages/@n8n/client-oauth2/.eslintrc.js

@@ -10,5 +10,6 @@ module.exports = {
 
 	rules: {
 		'@typescript-eslint/consistent-type-imports': 'error',
+		'n8n-local-rules/no-plain-errors': 'off',
 	},
 };

packages/@n8n/nodes-langchain/nodes/chains/ChainLLM/ChainLlm.node.ts

@@ -1,4 +1,4 @@
-import { NodeConnectionType, NodeOperationError } from 'n8n-workflow';
+import { ApplicationError, NodeConnectionType, NodeOperationError } from 'n8n-workflow';
 import type {
 	IBinaryData,
 	IDataObject,
@@ -105,7 +105,9 @@ async function getChainPromptTemplate(
 
 				if (!messageClass) {
 					// eslint-disable-next-line n8n-nodes-base/node-execute-block-wrong-error-thrown
-					throw new Error(`Invalid message type "${message.type}"`);
+					throw new ApplicationError('Invalid message type', {
+						extra: { messageType: message.type },
+					});
 				}
 
 				if (messageClass === HumanMessagePromptTemplate && message.messageType !== 'text') {

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

@@ -330,7 +330,7 @@ const config = (module.exports = {
 			{
 				selector: 'import',
 				format: ['camelCase', 'PascalCase'],
-			}
+			},
 		],
 
 		// ----------------------------------
@@ -360,6 +360,7 @@ const config = (module.exports = {
 		// ----------------------------------
 		//   eslint-plugin-n8n-local-rules
 		// ----------------------------------
+
 		'n8n-local-rules/no-uncaught-json-parse': 'error',
 
 		'n8n-local-rules/no-json-parse-json-stringify': 'error',
@@ -370,6 +371,8 @@ const config = (module.exports = {
 
 		'n8n-local-rules/no-unused-param-in-catch-clause': 'error',
 
+		'n8n-local-rules/no-plain-errors': 'error',
+
 		// ******************************************************************
 		//                    overrides to base ruleset
 		// ******************************************************************
@@ -469,6 +472,7 @@ const config = (module.exports = {
 		{
 			files: ['test/**/*.ts', 'src/__tests__/*.ts'],
 			rules: {
+				'n8n-local-rules/no-plain-errors': 'off',
 				'n8n-local-rules/no-skipped-tests':
 					process.env.NODE_ENV === 'development' ? 'warn' : 'error',
 

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

@@ -52,5 +52,6 @@ module.exports = {
 		'vue/no-side-effects-in-computed-properties': 'warn',
 		'vue/no-v-text-v-html-on-component': 'warn',
 		'vue/return-in-computed-property': 'warn',
+		'n8n-local-rules/no-plain-errors': 'off',
 	},
 };

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

@@ -353,6 +353,49 @@ module.exports = {
 			};
 		},
 	},
+
+	'no-plain-errors': {
+		meta: {
+			type: 'problem',
+			docs: {
+				description:
+					'Only `ApplicationError` (from the `workflow` package) or its child classes must be thrown. This ensures the error will be normalized when reported to Sentry, if applicable.',
+				recommended: 'error',
+			},
+			messages: {
+				useApplicationError:
+					'Throw an `ApplicationError` (from the `workflow` package) or its child classes.',
+			},
+			fixable: 'code',
+		},
+		create(context) {
+			return {
+				ThrowStatement(node) {
+					if (!node.argument) return;
+
+					const isNewError =
+						node.argument.type === 'NewExpression' && node.argument.callee.name === 'Error';
+
+					const isNewlessError =
+						node.argument.type === 'CallExpression' && node.argument.callee.name === 'Error';
+
+					if (isNewError || isNewlessError) {
+						return context.report({
+							messageId: 'useApplicationError',
+							node,
+							fix: (fixer) =>
+								fixer.replaceText(
+									node,
+									`throw new ApplicationError(${node.argument.arguments
+										.map((arg) => arg.raw)
+										.join(', ')})`,
+								),
+						});
+					}
+				},
+			};
+		},
+	},
 };
 
 const isJsonParseCall = (node) =>

packages/cli/src/environments/sourceControl/sourceControl.service.ee.ts

@@ -117,7 +117,7 @@ export class SourceControlService {
 			this.gitService.resetService();
 			return this.sourceControlPreferencesService.sourceControlPreferences;
 		} catch (error) {
-			throw Error(`Failed to disconnect from source control: ${(error as Error).message}`);
+			throw new ApplicationError('Failed to disconnect from source control', { cause: error });
 		}
 	}
 

packages/cli/src/environments/sourceControl/sourceControlExport.service.ee.ts

@@ -6,7 +6,7 @@ import {
 	SOURCE_CONTROL_TAGS_EXPORT_FILE,
 	SOURCE_CONTROL_WORKFLOW_EXPORT_FOLDER,
 } from './constants';
-import type { ICredentialDataDecryptedObject } from 'n8n-workflow';
+import { ApplicationError, type ICredentialDataDecryptedObject } from 'n8n-workflow';
 import { writeFile as fsWriteFile, rm as fsRm } from 'fs/promises';
 import { rmSync } from 'fs';
 import { Credentials, InstanceSettings } from 'n8n-core';
@@ -138,7 +138,7 @@ export class SourceControlExportService {
 				})),
 			};
 		} catch (error) {
-			throw Error(`Failed to export workflows to work folder: ${(error as Error).message}`);
+			throw new ApplicationError('Failed to export workflows to work folder', { cause: error });
 		}
 	}
 
@@ -168,7 +168,9 @@ export class SourceControlExportService {
 				],
 			};
 		} catch (error) {
-			throw Error(`Failed to export variables to work folder: ${(error as Error).message}`);
+			throw new ApplicationError('Failed to export variables to work folder', {
+				cause: error,
+			});
 		}
 	}
 
@@ -208,7 +210,7 @@ export class SourceControlExportService {
 				],
 			};
 		} catch (error) {
-			throw Error(`Failed to export variables to work folder: ${(error as Error).message}`);
+			throw new ApplicationError('Failed to export variables to work folder', { cause: error });
 		}
 	}
 
@@ -280,7 +282,7 @@ export class SourceControlExportService {
 				missingIds,
 			};
 		} catch (error) {
-			throw Error(`Failed to export credentials to work folder: ${(error as Error).message}`);
+			throw new ApplicationError('Failed to export credentials to work folder', { cause: error });
 		}
 	}
 }

packages/cli/src/environments/sourceControl/sourceControlPreferences.service.ee.ts

@@ -108,7 +108,7 @@ export class SourceControlPreferencesService {
 				});
 				await fsWriteFile(this.sshKeyName, keyPair.privateKey, { encoding: 'utf8', mode: 0o600 });
 			} catch (error) {
-				throw Error(`Failed to save key pair: ${(error as Error).message}`);
+				throw new ApplicationError('Failed to save key pair', { cause: error });
 			}
 		}
 		// update preferences only after generating key pair to prevent endless loop

packages/node-dev/.eslintrc.js

@@ -12,5 +12,6 @@ module.exports = {
 	rules: {
 		'import/order': 'off', // TODO: remove this
 		'@typescript-eslint/ban-ts-comment': ['warn', { 'ts-ignore': true }],
+		'n8n-local-rules/no-plain-errors': 'off',
 	},
 };

packages/nodes-base/nodes/CompareDatasets/GenericFunctions.ts

@@ -259,11 +259,8 @@ export function findMatches(
 
 	if (disableDotNotation && skipFields.some((field) => field.includes('.'))) {
 		const fieldToSkip = skipFields.find((field) => field.includes('.'));
-		throw new Error(
-			`Dot notation is disabled, but field to skip comparing '${
-				fieldToSkip as string
-			}' contains dot`,
-		);
+		const msg = `Dot notation is disabled, but field to skip comparing '${fieldToSkip}' contains dot`;
+		throw new ApplicationError(msg, { level: 'warning' });
 	}
 
 	const filteredData = {
@@ -403,16 +400,18 @@ export function findMatches(
 
 export function checkMatchFieldsInput(data: IDataObject[]) {
 	if (data.length === 1 && data[0].field1 === '' && data[0].field2 === '') {
-		throw new Error(
+		throw new ApplicationError(
 			'You need to define at least one pair of fields in "Fields to Match" to match on',
+			{ level: 'warning' },
 		);
 	}
 	for (const [index, pair] of data.entries()) {
 		if (pair.field1 === '' || pair.field2 === '') {
-			throw new Error(
+			throw new ApplicationError(
 				`You need to define both fields in "Fields to Match" for pair ${index + 1},
 				 field 1 = '${pair.field1}'
 				 field 2 = '${pair.field2}'`,
+				{ level: 'warning' },
 			);
 		}
 	}
@@ -447,7 +446,10 @@ export function checkInputAndThrowError(
 			return get(entry.json, field, undefined) !== undefined;
 		});
 		if (!isPresent) {
-			throw new Error(`Field '${field}' is not present in any of items in '${inputLabel}'`);
+			throw new ApplicationError(
+				`Field '${field}' is not present in any of items in '${inputLabel}'`,
+				{ level: 'warning' },
+			);
 		}
 	}
 	return input;

packages/nodes-base/nodes/Kafka/Kafka.node.ts

@@ -14,7 +14,7 @@ import type {
 	INodeType,
 	INodeTypeDescription,
 } from 'n8n-workflow';
-import { NodeOperationError } from 'n8n-workflow';
+import { ApplicationError, NodeOperationError } from 'n8n-workflow';
 import { generatePairedItemData } from '../../utils/utilities';
 
 export class Kafka implements INodeType {
@@ -229,7 +229,10 @@ export class Kafka implements INodeType {
 					};
 					if (credentials.authentication === true) {
 						if (!(credentials.username && credentials.password)) {
-							throw Error('Username and password are required for authentication');
+							// eslint-disable-next-line n8n-nodes-base/node-execute-block-wrong-error-thrown
+							throw new ApplicationError('Username and password are required for authentication', {
+								level: 'warning',
+							});
 						}
 						config.sasl = {
 							username: credentials.username as string,

packages/nodes-base/nodes/TheHive/GenericFunctions.ts

@@ -119,7 +119,7 @@ export async function prepareCustomFields(
 
 			return customFields;
 		} else if (customFieldsJson) {
-			throw Error('customFieldsJson value is invalid');
+			throw new ApplicationError('customFieldsJson value is invalid', { level: 'warning' });
 		}
 	} else if (additionalFields.customFieldsUi) {
 		// Get Custom Field Types from TheHive