feat(Structured Output Parser Node): Refactor Output Parsers and Improve Error Handling (#11148)

packages/@n8n/nodes-langchain/utils/output_parsers/N8nStructuredOutputParser.ts

@@ -0,0 +1,116 @@
+import type { Callbacks } from '@langchain/core/callbacks/manager';
+import { StructuredOutputParser } from 'langchain/output_parsers';
+import get from 'lodash/get';
+import type { IExecuteFunctions } from 'n8n-workflow';
+import { NodeConnectionType, NodeOperationError } from 'n8n-workflow';
+import { z } from 'zod';
+
+import { logAiEvent } from '../helpers';
+
+const STRUCTURED_OUTPUT_KEY = '__structured__output';
+const STRUCTURED_OUTPUT_OBJECT_KEY = '__structured__output__object';
+const STRUCTURED_OUTPUT_ARRAY_KEY = '__structured__output__array';
+
+export class N8nStructuredOutputParser extends StructuredOutputParser<
+	z.ZodType<object, z.ZodTypeDef, object>
+> {
+	context: IExecuteFunctions;
+
+	constructor(context: IExecuteFunctions, zodSchema: z.ZodSchema<object>) {
+		super(zodSchema);
+		this.context = context;
+	}
+
+	lc_namespace = ['langchain', 'output_parsers', 'structured'];
+
+	async parse(
+		text: string,
+		_callbacks?: Callbacks,
+		errorMapper?: (error: Error) => Error,
+	): Promise<object> {
+		const { index } = this.context.addInputData(NodeConnectionType.AiOutputParser, [
+			[{ json: { action: 'parse', text } }],
+		]);
+		try {
+			const parsed = await super.parse(text);
+
+			const result = (get(parsed, [STRUCTURED_OUTPUT_KEY, STRUCTURED_OUTPUT_OBJECT_KEY]) ??
+				get(parsed, [STRUCTURED_OUTPUT_KEY, STRUCTURED_OUTPUT_ARRAY_KEY]) ??
+				get(parsed, STRUCTURED_OUTPUT_KEY) ??
+				parsed) as Record<string, unknown>;
+
+			void logAiEvent(this.context, 'ai-output-parsed', { text, response: result });
+
+			this.context.addOutputData(NodeConnectionType.AiOutputParser, index, [
+				[{ json: { action: 'parse', response: result } }],
+			]);
+
+			return result;
+		} catch (e) {
+			const nodeError = new NodeOperationError(
+				this.context.getNode(),
+				"Model output doesn't fit required format",
+				{
+					description:
+						"To continue the execution when this happens, change the 'On Error' parameter in the root node's settings",
+				},
+			);
+
+			void logAiEvent(this.context, 'ai-output-parsed', {
+				text,
+				response: e.message ?? e,
+			});
+
+			this.context.addOutputData(NodeConnectionType.AiOutputParser, index, nodeError);
+			if (errorMapper) {
+				throw errorMapper(e);
+			}
+
+			throw nodeError;
+		}
+	}
+
+	static async fromZodJsonSchema(
+		zodSchema: z.ZodSchema<object>,
+		nodeVersion: number,
+		context: IExecuteFunctions,
+	): Promise<N8nStructuredOutputParser> {
+		let returnSchema: z.ZodType<object, z.ZodTypeDef, object>;
+		if (nodeVersion === 1) {
+			returnSchema = z.object({
+				[STRUCTURED_OUTPUT_KEY]: z
+					.object({
+						[STRUCTURED_OUTPUT_OBJECT_KEY]: zodSchema.optional(),
+						[STRUCTURED_OUTPUT_ARRAY_KEY]: z.array(zodSchema).optional(),
+					})
+					.describe(
+						`Wrapper around the output data. It can only contain ${STRUCTURED_OUTPUT_OBJECT_KEY} or ${STRUCTURED_OUTPUT_ARRAY_KEY} but never both.`,
+					)
+					.refine(
+						(data) => {
+							// Validate that one and only one of the properties exists
+							return (
+								Boolean(data[STRUCTURED_OUTPUT_OBJECT_KEY]) !==
+								Boolean(data[STRUCTURED_OUTPUT_ARRAY_KEY])
+							);
+						},
+						{
+							message:
+								'One and only one of __structured__output__object and __structured__output__array should be present.',
+							path: [STRUCTURED_OUTPUT_KEY],
+						},
+					),
+			});
+		} else {
+			returnSchema = z.object({
+				output: zodSchema.optional(),
+			});
+		}
+
+		return new N8nStructuredOutputParser(context, returnSchema);
+	}
+
+	getSchema() {
+		return this.schema;
+	}
+}