feat: Add AI tool building capabilities (#7336)

Github issue / Community forum post (link here to close automatically):
https://community.n8n.io/t/langchain-memory-chat/23733

---------

Signed-off-by: Oleg Ivaniv <me@olegivaniv.com>
Co-authored-by: Oleg Ivaniv <me@olegivaniv.com>
Co-authored-by: Val <68596159+valya@users.noreply.github.com>
Co-authored-by: Alex Grozav <alex@grozav.com>
Co-authored-by: कारतोफ्फेलस्क्रिप्ट™ <aditya@netroy.in>
Co-authored-by: Deborah <deborah@starfallprojects.co.uk>
Co-authored-by: Jesper Bylund <mail@jesperbylund.com>
Co-authored-by: Jon <jonathan.bennetts@gmail.com>
Co-authored-by: Michael Kret <88898367+michael-radency@users.noreply.github.com>
Co-authored-by: Giulio Andreini <andreini@netseven.it>
Co-authored-by: Mason Geloso <Mason.geloso@gmail.com>
Co-authored-by: Mason Geloso <hone@Masons-Mac-mini.local>
Co-authored-by: Mutasem Aldmour <mutasem@n8n.io>

packages/@n8n/nodes-langchain/nodes/output_parser/OutputParserItemList/ItemListOutputParser.ts

@@ -0,0 +1,51 @@
+import { BaseOutputParser, OutputParserException } from 'langchain/schema/output_parser';
+
+export class ItemListOutputParser extends BaseOutputParser<string[]> {
+	lc_namespace = ['n8n-nodes-langchain', 'output_parsers', 'list_items'];
+
+	private numberOfItems: number | undefined;
+
+	private separator: string;
+
+	constructor(options: { numberOfItems?: number; separator?: string }) {
+		super();
+		if (options.numberOfItems && options.numberOfItems > 0) {
+			this.numberOfItems = options.numberOfItems;
+		}
+		this.separator = options.separator ?? '\\n';
+		if (this.separator === '\\n') {
+			this.separator = '\n';
+		}
+	}
+
+	async parse(text: string): Promise<string[]> {
+		const response = text
+			.split(this.separator)
+			.map((item) => item.trim())
+			.filter((item) => item);
+
+		if (this.numberOfItems && response.length < this.numberOfItems) {
+			// Only error if to few items got returned, if there are to many we can autofix it
+			throw new OutputParserException(
+				`Wrong number of items returned. Expected ${this.numberOfItems} items but got ${response.length} items instead.`,
+			);
+		}
+
+		return response.slice(0, this.numberOfItems);
+	}
+
+	getFormatInstructions(): string {
+		const instructions = `Your response should be a list of ${
+			this.numberOfItems ? this.numberOfItems + ' ' : ''
+		}items separated by`;
+
+		const numberOfExamples = this.numberOfItems ?? 3;
+
+		const examples: string[] = [];
+		for (let i = 1; i <= numberOfExamples; i++) {
+			examples.push(`item${i}`);
+		}
+
+		return `${instructions} "${this.separator}" (for example: "${examples.join(this.separator)}")`;
+	}
+}

packages/@n8n/nodes-langchain/nodes/output_parser/OutputParserItemList/OutputParserItemList.node.ts

@@ -0,0 +1,95 @@
+/* eslint-disable n8n-nodes-base/node-dirname-against-convention */
+import {
+	NodeConnectionType,
+	type IExecuteFunctions,
+	type INodeType,
+	type INodeTypeDescription,
+	type SupplyData,
+} from 'n8n-workflow';
+import { logWrapper } from '../../../utils/logWrapper';
+import { getConnectionHintNoticeField } from '../../../utils/sharedFields';
+import { ItemListOutputParser } from './ItemListOutputParser';
+
+export class OutputParserItemList implements INodeType {
+	description: INodeTypeDescription = {
+		displayName: 'Item List Output Parser',
+		name: 'outputParserItemList',
+		icon: 'fa:bars',
+		group: ['transform'],
+		version: 1,
+		description: 'Return the results as separate items',
+		defaults: {
+			name: 'Item List Output Parser',
+		},
+
+		codex: {
+			categories: ['AI'],
+			subcategories: {
+				AI: ['Output Parsers'],
+			},
+			resources: {
+				primaryDocumentation: [
+					{
+						url: 'https://docs.n8n.io/integrations/builtin/cluster-nodes/sub-nodes/n8n-nodes-langchain.outputparseritemlist/',
+					},
+				],
+			},
+		},
+		// eslint-disable-next-line n8n-nodes-base/node-class-description-inputs-wrong-regular-node
+		inputs: [],
+		// eslint-disable-next-line n8n-nodes-base/node-class-description-outputs-wrong
+		outputs: [NodeConnectionType.AiOutputParser],
+		outputNames: ['Output Parser'],
+		properties: [
+			getConnectionHintNoticeField([NodeConnectionType.AiChain, NodeConnectionType.AiAgent]),
+			{
+				displayName: 'Options',
+				name: 'options',
+				type: 'collection',
+				placeholder: 'Add Option',
+				default: {},
+				options: [
+					{
+						displayName: 'Number Of Items',
+						name: 'numberOfItems',
+						type: 'number',
+						default: -1,
+						description:
+							'Defines many many items should be returned maximally. If set to -1, there is no limit.',
+					},
+					// For that to be easily possible the metadata would have to be returned and be able to be read.
+					// Would also be possible with a wrapper but that would be even more hacky and the output types
+					// would not be correct anymore.
+					// {
+					// 	displayName: 'Parse Output',
+					// 	name: 'parseOutput',
+					// 	type: 'boolean',
+					// 	default: true,
+					// 	description: 'Whether the output should be automatically be parsed or left RAW',
+					// },
+					{
+						displayName: 'Separator',
+						name: 'separator',
+						type: 'string',
+						default: '\\n',
+						description:
+							'Defines the separator that should be used to split the results into separate items. Defaults to a new line but can be changed depending on the data that should be returned.',
+					},
+				],
+			},
+		],
+	};
+
+	async supplyData(this: IExecuteFunctions, itemIndex: number): Promise<SupplyData> {
+		const options = this.getNodeParameter('options', itemIndex, {}) as {
+			numberOfItems?: number;
+			separator?: string;
+		};
+
+		const parser = new ItemListOutputParser(options);
+
+		return {
+			response: logWrapper(parser, this),
+		};
+	}
+}