feat(Email Trigger (IMAP) Node): Migrate from imap-simple to `@n8n/…

…imap` (#8899)

Co-authored-by: Jonathan Bennetts <jonathan.bennetts@gmail.com>

package.json

@@ -26,8 +26,8 @@
     "start:tunnel": "./packages/cli/bin/n8n start --tunnel",
     "start:windows": "cd packages/cli/bin && n8n",
     "test": "turbo run test",
-    "test:backend": "pnpm --filter=!@n8n/chat --filter=!n8n-design-system --filter=!n8n-editor-ui  --filter=!n8n-nodes-base test",
-    "test:nodes": "pnpm --filter=n8n-nodes-base test",
+    "test:backend": "pnpm --filter=!@n8n/chat --filter=!n8n-design-system --filter=!n8n-editor-ui --filter=!n8n-nodes-base --filter=!@n8n/n8n-nodes-langchain test",
+    "test:nodes": "pnpm --filter=n8n-nodes-base --filter=@n8n/n8n-nodes-langchain test",
     "test:frontend": "pnpm --filter=@n8n/chat --filter=n8n-design-system --filter=n8n-editor-ui test",
     "watch": "turbo run watch --parallel",
     "webhook": "./packages/cli/bin/n8n webhook",

packages/@n8n/imap/.eslintrc.js

@@ -0,0 +1,15 @@
+const sharedOptions = require('@n8n_io/eslint-config/shared');
+
+/**
+ * @type {import('@types/eslint').ESLint.ConfigData}
+ */
+module.exports = {
+	extends: ['@n8n_io/eslint-config/base'],
+
+	...sharedOptions(__dirname),
+
+	rules: {
+		'@typescript-eslint/consistent-type-imports': 'error',
+		'n8n-local-rules/no-plain-errors': 'off',
+	},
+};

packages/@n8n/imap/jest.config.js

@@ -0,0 +1,2 @@
+/** @type {import('jest').Config} */
+module.exports = require('../../../jest.config');

packages/@n8n/imap/package.json

@@ -0,0 +1,34 @@
+{
+  "name": "@n8n/imap",
+  "version": "0.1.0",
+  "scripts": {
+    "clean": "rimraf dist .turbo",
+    "dev": "pnpm watch",
+    "typecheck": "tsc",
+    "build": "tsc -p tsconfig.build.json",
+    "format": "prettier --write . --ignore-path ../../../.prettierignore",
+    "lint": "eslint . --quiet",
+    "lintfix": "eslint . --fix",
+    "watch": "tsc -p tsconfig.build.json --watch",
+    "test": "echo \"Error: no test created yet\""
+  },
+  "main": "dist/index.js",
+  "module": "src/index.ts",
+  "types": "dist/index.d.ts",
+  "files": [
+    "dist/**/*"
+  ],
+  "dependencies": {
+    "iconv-lite": "0.6.3",
+    "imap": "0.8.19",
+    "quoted-printable": "1.0.1",
+    "utf8": "3.0.0",
+    "uuencode": "0.0.4"
+  },
+  "devDependencies": {
+    "@types/imap": "^0.8.40",
+    "@types/quoted-printable": "^1.0.2",
+    "@types/utf8": "^3.0.3",
+    "@types/uuencode": "^0.0.3"
+  }
+}

packages/@n8n/imap/src/ImapSimple.ts

@@ -0,0 +1,235 @@
+/* eslint-disable @typescript-eslint/no-use-before-define */
+import { EventEmitter } from 'events';
+import type Imap from 'imap';
+import { type ImapMessage } from 'imap';
+import * as qp from 'quoted-printable';
+import * as iconvlite from 'iconv-lite';
+import * as utf8 from 'utf8';
+import * as uuencode from 'uuencode';
+
+import { getMessage } from './helpers/getMessage';
+import type { Message, MessagePart } from './types';
+
+const IMAP_EVENTS = ['alert', 'mail', 'expunge', 'uidvalidity', 'update', 'close', 'end'] as const;
+
+export class ImapSimple extends EventEmitter {
+	/** flag to determine whether we should suppress ECONNRESET from bubbling up to listener */
+	private ending = false;
+
+	constructor(private readonly imap: Imap) {
+		super();
+
+		// pass most node-imap `Connection` events through 1:1
+		IMAP_EVENTS.forEach((event) => {
+			this.imap.on(event, this.emit.bind(this, event));
+		});
+
+		// special handling for `error` event
+		this.imap.on('error', (e: Error & { code?: string }) => {
+			// if .end() has been called and an 'ECONNRESET' error is received, don't bubble
+			if (e && this.ending && e.code?.toUpperCase() === 'ECONNRESET') {
+				return;
+			}
+			this.emit('error', e);
+		});
+	}
+
+	/** disconnect from the imap server */
+	end(): void {
+		// set state flag to suppress 'ECONNRESET' errors that are triggered when .end() is called.
+		// it is a known issue that has no known fix. This just temporarily ignores that error.
+		// https://github.com/mscdex/node-imap/issues/391
+		// https://github.com/mscdex/node-imap/issues/395
+		this.ending = true;
+
+		// using 'close' event to unbind ECONNRESET error handler, because the node-imap
+		// maintainer claims it is the more reliable event between 'end' and 'close'.
+		// https://github.com/mscdex/node-imap/issues/394
+		this.imap.once('close', () => {
+			this.ending = false;
+		});
+
+		this.imap.end();
+	}
+
+	/**
+	 * Search the currently open mailbox, and retrieve the results
+	 *
+	 * Results are in the form:
+	 *
+	 * [{
+	 *   attributes: object,
+	 *   parts: [ { which: string, size: number, body: string }, ... ]
+	 * }, ...]
+	 *
+	 * See node-imap's ImapMessage signature for information about `attributes`, `which`, `size`, and `body`.
+	 * For any message part that is a `HEADER`, the body is automatically parsed into an object.
+	 */
+	async search(
+		/** Criteria to use to search. Passed to node-imap's .search() 1:1 */
+		// eslint-disable-next-line @typescript-eslint/no-explicit-any
+		searchCriteria: any[],
+		/** Criteria to use to fetch the search results. Passed to node-imap's .fetch() 1:1 */
+		fetchOptions: Imap.FetchOptions,
+	) {
+		return await new Promise<Message[]>((resolve, reject) => {
+			this.imap.search(searchCriteria, (e, uids) => {
+				if (e) {
+					reject(e);
+					return;
+				}
+
+				if (uids.length === 0) {
+					resolve([]);
+					return;
+				}
+
+				const fetch = this.imap.fetch(uids, fetchOptions);
+				let messagesRetrieved = 0;
+				const messages: Message[] = [];
+
+				const fetchOnMessage = async (message: Imap.ImapMessage, seqNo: number) => {
+					const msg: Message = await getMessage(message);
+					msg.seqNo = seqNo;
+					messages[seqNo] = msg;
+
+					messagesRetrieved++;
+					if (messagesRetrieved === uids.length) {
+						resolve(messages.filter((m) => !!m));
+					}
+				};
+
+				const fetchOnError = (error: Error) => {
+					fetch.removeListener('message', fetchOnMessage);
+					fetch.removeListener('end', fetchOnEnd);
+					reject(error);
+				};
+
+				const fetchOnEnd = () => {
+					fetch.removeListener('message', fetchOnMessage);
+					fetch.removeListener('error', fetchOnError);
+				};
+
+				fetch.on('message', fetchOnMessage);
+				fetch.once('error', fetchOnError);
+				fetch.once('end', fetchOnEnd);
+			});
+		});
+	}
+
+	/** Download a "part" (either a portion of the message body, or an attachment) */
+	async getPartData(
+		/** The message returned from `search()` */
+		message: Message,
+		/** The message part to be downloaded, from the `message.attributes.struct` Array */
+		part: MessagePart,
+	) {
+		return await new Promise<string>((resolve, reject) => {
+			const fetch = this.imap.fetch(message.attributes.uid, {
+				bodies: [part.partID],
+				struct: true,
+			});
+
+			const fetchOnMessage = async (msg: ImapMessage) => {
+				const result = await getMessage(msg);
+				if (result.parts.length !== 1) {
+					reject(new Error('Got ' + result.parts.length + ' parts, should get 1'));
+					return;
+				}
+
+				const data = result.parts[0].body as string;
+
+				const encoding = part.encoding.toUpperCase();
+
+				if (encoding === 'BASE64') {
+					resolve(Buffer.from(data, 'base64').toString());
+					return;
+				}
+
+				if (encoding === 'QUOTED-PRINTABLE') {
+					if (part.params?.charset?.toUpperCase() === 'UTF-8') {
+						resolve(Buffer.from(utf8.decode(qp.decode(data))).toString());
+					} else {
+						resolve(Buffer.from(qp.decode(data)).toString());
+					}
+					return;
+				}
+
+				if (encoding === '7BIT') {
+					resolve(Buffer.from(data).toString('ascii'));
+					return;
+				}
+
+				if (encoding === '8BIT' || encoding === 'BINARY') {
+					const charset = part.params?.charset ?? 'utf-8';
+					resolve(iconvlite.decode(Buffer.from(data), charset));
+					return;
+				}
+
+				if (encoding === 'UUENCODE') {
+					const parts = data.toString().split('\n'); // remove newline characters
+					const merged = parts.splice(1, parts.length - 4).join(''); // remove excess lines and join lines with empty string
+					resolve(uuencode.decode(merged));
+					return;
+				}
+
+				// if it gets here, the encoding is not currently supported
+				reject(new Error('Unknown encoding ' + part.encoding));
+			};
+
+			const fetchOnError = (error: Error) => {
+				fetch.removeListener('message', fetchOnMessage);
+				fetch.removeListener('end', fetchOnEnd);
+				reject(error);
+			};
+
+			const fetchOnEnd = () => {
+				fetch.removeListener('message', fetchOnMessage);
+				fetch.removeListener('error', fetchOnError);
+			};
+
+			fetch.once('message', fetchOnMessage);
+			fetch.once('error', fetchOnError);
+			fetch.once('end', fetchOnEnd);
+		});
+	}
+
+	/** Adds the provided flag(s) to the specified message(s). */
+	async addFlags(
+		/** The messages uid */
+		uid: number[],
+		/** The flags to add to the message(s). */
+		flags: string | string[],
+	) {
+		return await new Promise<void>((resolve, reject) => {
+			this.imap.addFlags(uid, flags, (e) => (e ? reject(e) : resolve()));
+		});
+	}
+
+	/** Returns a list of mailboxes (folders). */
+	async getBoxes() {
+		return await new Promise<Imap.MailBoxes>((resolve, reject) => {
+			this.imap.getBoxes((e, boxes) => (e ? reject(e) : resolve(boxes)));
+		});
+	}
+
+	/** Open a mailbox */
+	async openBox(
+		/** The name of the box to open */
+		boxName: string,
+	): Promise<Imap.Box> {
+		return await new Promise((resolve, reject) => {
+			this.imap.openBox(boxName, (e, result) => (e ? reject(e) : resolve(result)));
+		});
+	}
+
+	/** Close a mailbox */
+	async closeBox(
+		/** If autoExpunge is true, any messages marked as Deleted in the currently open mailbox will be removed @default true */
+		autoExpunge = true,
+	) {
+		return await new Promise<void>((resolve, reject) => {
+			this.imap.closeBox(autoExpunge, (e) => (e ? reject(e) : resolve()));
+		});
+	}
+}

packages/@n8n/imap/src/errors.ts

@@ -0,0 +1,27 @@
+export abstract class ImapError extends Error {}
+
+/** Error thrown when a connection attempt has timed out */
+export class ConnectionTimeoutError extends ImapError {
+	constructor(
+		/** timeout in milliseconds that the connection waited before timing out */
+		readonly timeout?: number,
+	) {
+		let message = 'connection timed out';
+		if (timeout) {
+			message += `. timeout = ${timeout} ms`;
+		}
+		super(message);
+	}
+}
+
+export class ConnectionClosedError extends ImapError {
+	constructor() {
+		super('Connection closed unexpectedly');
+	}
+}
+
+export class ConnectionEndedError extends ImapError {
+	constructor() {
+		super('Connection ended unexpectedly');
+	}
+}

packages/@n8n/imap/src/helpers/getMessage.ts

@@ -0,0 +1,53 @@
+import {
+	parseHeader,
+	type ImapMessage,
+	type ImapMessageBodyInfo,
+	type ImapMessageAttributes,
+} from 'imap';
+import type { Message, MessageBodyPart } from '../types';
+
+/**
+ * Given an 'ImapMessage' from the node-imap library, retrieves the `Message`
+ */
+export async function getMessage(
+	/** an ImapMessage from the node-imap library */
+	message: ImapMessage,
+): Promise<Message> {
+	return await new Promise((resolve) => {
+		let attributes: ImapMessageAttributes;
+		const parts: MessageBodyPart[] = [];
+
+		const messageOnBody = (stream: NodeJS.ReadableStream, info: ImapMessageBodyInfo) => {
+			let body: string = '';
+
+			const streamOnData = (chunk: Buffer) => {
+				body += chunk.toString('utf8');
+			};
+
+			stream.on('data', streamOnData);
+			stream.once('end', () => {
+				stream.removeListener('data', streamOnData);
+
+				parts.push({
+					which: info.which,
+					size: info.size,
+					body: /^HEADER/g.test(info.which) ? parseHeader(body) : body,
+				});
+			});
+		};
+
+		const messageOnAttributes = (attrs: ImapMessageAttributes) => {
+			attributes = attrs;
+		};
+
+		const messageOnEnd = () => {
+			message.removeListener('body', messageOnBody);
+			message.removeListener('attributes', messageOnAttributes);
+			resolve({ attributes, parts });
+		};
+
+		message.on('body', messageOnBody);
+		message.once('attributes', messageOnAttributes);
+		message.once('end', messageOnEnd);
+	});
+}