on type safety in LangChain TS

snippet-7.ts

  async safePlanNextStep(previousSteps: AgentStep[]): Promise<AgentAction> {
    try {
      // This will return either an AgentAction or AgentFinish through outputParser.parse
      output = await this.agent.plan(steps, inputs);
    } catch (e) {
      if (e instanceof OutputParserException) {
        let observation;
        const text = e.message;
        if (this.handleParsingErrors === true) {
          observation = "Invalid or incomplete response";
        } else if (typeof this.handleParsingErrors === "string") {
          observation = this.handleParsingErrors;
        } else if (typeof this.handleParsingErrors === "function") {
          observation = this.handleParsingErrors(e);
        } else {
          throw e;
        }
        output = {
          tool: "_Exception",
          toolInput: observation,
          log: text,
        } as AgentAction;
      } else {
        throw e;
      }
    }
  }