91 lines
3.1 KiB
JavaScript
91 lines
3.1 KiB
JavaScript
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import { OutputParserException } from "@langchain/core/output_parsers";
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import { AgentActionOutputParser } from "../types.js";
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import { FORMAT_INSTRUCTIONS } from "./prompt.js";
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export const FINAL_ANSWER_ACTION = "Final Answer:";
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/**
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* A class that extends the AgentActionOutputParser to parse the output of
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* the ChatAgent in LangChain. It checks if the output text contains the
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* final answer action or a JSON response, and parses it accordingly.
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* @example
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* ```typescript
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* const prompt = ChatPromptTemplate.fromMessages([
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* [
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* "ai",
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* `{PREFIX}
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* {FORMAT_INSTRUCTIONS}
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* {SUFFIX}`,
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* ],
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* ["human", "Question: {input}"],
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* ]);
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* const runnableAgent = RunnableSequence.from([
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* {
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* input: (i: { input: string; steps: AgentStep[] }) => i.input,
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* agent_scratchpad: (i: { input: string; steps: AgentStep[] }) =>
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* formatLogToString(i.steps),
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* },
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* prompt,
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* new OpenAI({ temperature: 0 }),
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* new ChatAgentOutputParser(),
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* ]);
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*
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* const executor = AgentExecutor.fromAgentAndTools({
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* agent: runnableAgent,
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* tools: [new SerpAPI(), new Calculator()],
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* });
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*
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* const result = await executor.invoke({
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* input:
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* "Who is Olivia Wilde's boyfriend? What is his current age raised to the 0.23 power?",
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* });
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* ```
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*/
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export class ChatAgentOutputParser extends AgentActionOutputParser {
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constructor() {
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super(...arguments);
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Object.defineProperty(this, "lc_namespace", {
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enumerable: true,
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configurable: true,
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writable: true,
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value: ["langchain", "agents", "chat"]
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});
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}
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/**
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* Parses the output text from the MRKL chain into an agent action or
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* agent finish. If the text contains the final answer action or does not
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* contain an action, it returns an AgentFinish with the output and log.
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* If the text contains a JSON response, it returns the tool, toolInput,
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* and log.
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* @param text The output text from the MRKL chain.
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* @returns An object that satisfies the AgentFinish interface or an object with the tool, toolInput, and log.
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*/
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async parse(text) {
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if (text.includes(FINAL_ANSWER_ACTION) || !text.includes(`"action":`)) {
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const parts = text.split(FINAL_ANSWER_ACTION);
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const output = parts[parts.length - 1].trim();
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return { returnValues: { output }, log: text };
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}
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const action = text.includes("```")
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? text.trim().split(/```(?:json)?/)[1]
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: text.trim();
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try {
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const response = JSON.parse(action.trim());
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return {
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tool: response.action,
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toolInput: response.action_input,
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log: text,
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};
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}
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catch {
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throw new OutputParserException(`Unable to parse JSON response from chat agent.\n\n${text}`);
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}
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}
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/**
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* Returns the format instructions used in the output parser for the
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* ChatAgent class.
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* @returns The format instructions as a string.
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*/
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getFormatInstructions() {
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return FORMAT_INSTRUCTIONS;
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}
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}
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