feat(Custom n8n Workflow Tool Node): Add support for tool input schema (#9470)

Signed-off-by: Oleg Ivaniv <me@olegivaniv.com>

packages/@n8n/nodes-langchain/utils/descriptions.ts

@@ -1,5 +1,70 @@
 import type { INodeProperties } from 'n8n-workflow';
 
+export const schemaTypeField: INodeProperties = {
+	displayName: 'Schema Type',
+	name: 'schemaType',
+	type: 'options',
+	noDataExpression: true,
+	options: [
+		{
+			name: 'Generate From JSON Example',
+			value: 'fromJson',
+			description: 'Generate a schema from an example JSON object',
+		},
+		{
+			name: 'Define Below',
+			value: 'manual',
+			description: 'Define the JSON schema manually',
+		},
+	],
+	default: 'fromJson',
+	description: 'How to specify the schema for the function',
+};
+
+export const jsonSchemaExampleField: INodeProperties = {
+	displayName: 'JSON Example',
+	name: 'jsonSchemaExample',
+	type: 'json',
+	default: `{
+	"some_input": "some_value"
+}`,
+	noDataExpression: true,
+	typeOptions: {
+		rows: 10,
+	},
+	displayOptions: {
+		show: {
+			schemaType: ['fromJson'],
+		},
+	},
+	description: 'Example JSON object to use to generate the schema',
+};
+
+export const inputSchemaField: INodeProperties = {
+	displayName: 'Input Schema',
+	name: 'inputSchema',
+	type: 'json',
+	default: `{
+"type": "object",
+"properties": {
+	"some_input": {
+		"type": "string",
+		"description": "Some input to the function"
+		}
+	}
+}`,
+	noDataExpression: true,
+	typeOptions: {
+		rows: 10,
+	},
+	displayOptions: {
+		show: {
+			schemaType: ['manual'],
+		},
+	},
+	description: 'Schema to use for the function',
+};
+
 export const promptTypeOptions: INodeProperties = {
 	displayName: 'Prompt',
 	name: 'promptType',

packages/@n8n/nodes-langchain/utils/schemaParsing.ts

@@ -0,0 +1,81 @@
+import { makeResolverFromLegacyOptions } from '@n8n/vm2';
+import { json as generateJsonSchema } from 'generate-schema';
+import type { SchemaObject } from 'generate-schema';
+import type { JSONSchema7 } from 'json-schema';
+import { JavaScriptSandbox } from 'n8n-nodes-base/dist/nodes/Code/JavaScriptSandbox';
+import { getSandboxContext } from 'n8n-nodes-base/dist/nodes/Code/Sandbox';
+import type { IExecuteFunctions } from 'n8n-workflow';
+import { NodeOperationError, jsonParse } from 'n8n-workflow';
+
+const vmResolver = makeResolverFromLegacyOptions({
+	external: {
+		modules: ['json-schema-to-zod', 'zod'],
+		transitive: false,
+	},
+	resolve(moduleName, parentDirname) {
+		if (moduleName === 'json-schema-to-zod') {
+			return require.resolve(
+				'@n8n/n8n-nodes-langchain/node_modules/json-schema-to-zod/dist/cjs/jsonSchemaToZod.js',
+				{
+					paths: [parentDirname],
+				},
+			);
+		}
+		if (moduleName === 'zod') {
+			return require.resolve('@n8n/n8n-nodes-langchain/node_modules/zod.cjs', {
+				paths: [parentDirname],
+			});
+		}
+		return;
+	},
+	builtin: [],
+});
+
+export function getSandboxWithZod(ctx: IExecuteFunctions, schema: JSONSchema7, itemIndex: number) {
+	const context = getSandboxContext.call(ctx, itemIndex);
+	let itemSchema: JSONSchema7 = schema;
+	try {
+		// If the root type is not defined, we assume it's an object
+		if (itemSchema.type === undefined) {
+			itemSchema = {
+				type: 'object',
+				properties: itemSchema.properties ?? (itemSchema as { [key: string]: JSONSchema7 }),
+			};
+		}
+	} catch (error) {
+		throw new NodeOperationError(ctx.getNode(), 'Error during parsing of JSON Schema.');
+	}
+
+	// Make sure to remove the description from root schema
+	const { description, ...restOfSchema } = itemSchema;
+	const sandboxedSchema = new JavaScriptSandbox(
+		context,
+		`
+			const { z } = require('zod');
+			const { parseSchema } = require('json-schema-to-zod');
+			const zodSchema = parseSchema(${JSON.stringify(restOfSchema)});
+			const itemSchema = new Function('z', 'return (' + zodSchema + ')')(z)
+			return itemSchema
+		`,
+		itemIndex,
+		ctx.helpers,
+		{ resolver: vmResolver },
+	);
+	return sandboxedSchema;
+}
+
+export function generateSchema(schemaString: string): JSONSchema7 {
+	const parsedSchema = jsonParse<SchemaObject>(schemaString);
+
+	return generateJsonSchema(parsedSchema) as JSONSchema7;
+}
+
+export function throwIfToolSchema(ctx: IExecuteFunctions, error: Error) {
+	if (error?.message?.includes('tool input did not match expected schema')) {
+		throw new NodeOperationError(
+			ctx.getNode(),
+			`${error.message}.
+			This is most likely because some of your tools are configured to require a specific schema. This is not supported by Conversational Agent. Remove the schema from the tool configuration or use Tools agent instead.`,
+		);
+	}
+}