feat: Introduce prompt type option for Agent, Basic LLM Chain, and QA Chain nodes (#8697)

Signed-off-by: Oleg Ivaniv <me@olegivaniv.com>
Co-authored-by: Michael Kret <michael.k@radency.com>

packages/@n8n/nodes-langchain/nodes/agents/Agent/Agent.node.ts

@@ -24,10 +24,12 @@ import { sqlAgentAgentExecute } from './agents/SqlAgent/execute';
 // display based on the agent type
 function getInputs(
 	agent: 'conversationalAgent' | 'openAiFunctionsAgent' | 'reActAgent' | 'sqlAgent',
+	hasOutputParser?: boolean,
 ): Array<ConnectionTypes | INodeInputConfiguration> {
 	interface SpecialInput {
 		type: ConnectionTypes;
 		filter?: INodeInputFilter;
+		required?: boolean;
 	}
 
 	const getInputData = (
@@ -40,7 +42,7 @@ function getInputs(
 			[NodeConnectionType.AiOutputParser]: 'Output Parser',
 		};
 
-		return inputs.map(({ type, filter }) => {
+		return inputs.map(({ type, filter, required }) => {
 			const input: INodeInputConfiguration = {
 				type,
 				displayName: type in displayNames ? displayNames[type] : undefined,
@@ -100,6 +102,7 @@ function getInputs(
 			},
 			{
 				type: NodeConnectionType.AiTool,
+				required: true,
 			},
 			{
 				type: NodeConnectionType.AiOutputParser,
@@ -137,6 +140,11 @@ function getInputs(
 		];
 	}
 
+	if (hasOutputParser === false) {
+		specialInputs = specialInputs.filter(
+			(input) => input.type !== NodeConnectionType.AiOutputParser,
+		);
+	}
 	return [NodeConnectionType.Main, ...getInputData(specialInputs)];
 }
 
@@ -146,7 +154,7 @@ export class Agent implements INodeType {
 		name: 'agent',
 		icon: 'fa:robot',
 		group: ['transform'],
-		version: [1, 1.1, 1.2],
+		version: [1, 1.1, 1.2, 1.3],
 		description: 'Generates an action plan and executes it. Can use external tools.',
 		subtitle:
 			"={{ {	conversationalAgent: 'Conversational Agent', openAiFunctionsAgent: 'OpenAI Functions Agent', reactAgent: 'ReAct Agent', sqlAgent: 'SQL Agent' }[$parameter.agent] }}",
@@ -168,7 +176,12 @@ export class Agent implements INodeType {
 				],
 			},
 		},
-		inputs: `={{ ((agent) => { ${getInputs.toString()}; return getInputs(agent) })($parameter.agent) }}`,
+		inputs: `={{
+			((agent, hasOutputParser) => {
+				${getInputs.toString()};
+				return getInputs(agent, hasOutputParser)
+			})($parameter.agent, $parameter.hasOutputParser === undefined || $parameter.hasOutputParser === true)
+		}}`,
 		outputs: [NodeConnectionType.Main],
 		credentials: [
 			{
@@ -240,6 +253,71 @@ export class Agent implements INodeType {
 				],
 				default: 'conversationalAgent',
 			},
+			{
+				displayName: 'Prompt',
+				name: 'promptType',
+				type: 'options',
+				options: [
+					{
+						// eslint-disable-next-line n8n-nodes-base/node-param-display-name-miscased
+						name: 'Take from previous node automatically',
+						value: 'auto',
+						description: 'Looks for an input field called chatInput',
+					},
+					{
+						// eslint-disable-next-line n8n-nodes-base/node-param-display-name-miscased
+						name: 'Define below',
+						value: 'define',
+						description:
+							'Use an expression to reference data in previous nodes or enter static text',
+					},
+				],
+				displayOptions: {
+					hide: {
+						'@version': [{ _cnd: { lte: 1.2 } }],
+					},
+				},
+				default: 'auto',
+			},
+			{
+				displayName: 'Text',
+				name: 'text',
+				type: 'string',
+				required: true,
+				default: '',
+				placeholder: 'e.g. Hello, how can you help me?',
+				typeOptions: {
+					rows: 2,
+				},
+				displayOptions: {
+					show: {
+						promptType: ['define'],
+					},
+				},
+			},
+			{
+				displayName: 'Require Specific Output Format',
+				name: 'hasOutputParser',
+				type: 'boolean',
+				default: false,
+				displayOptions: {
+					hide: {
+						'@version': [{ _cnd: { lte: 1.2 } }],
+						agent: ['sqlAgent'],
+					},
+				},
+			},
+			{
+				displayName: `Connect an <a data-action='openSelectiveNodeCreator' data-action-parameter-connectiontype='${NodeConnectionType.AiOutputParser}'>output parser</a> on the canvas to specify the output format you require`,
+				name: 'notice',
+				type: 'notice',
+				default: '',
+				displayOptions: {
+					show: {
+						hasOutputParser: [true],
+					},
+				},
+			},
 
 			...conversationalAgentProperties,
 			...openAiFunctionsAgentProperties,