Fix: Tool action_input containing markdown with JSON

langchain/src/agents/chat_convo/outputParser.ts

@@ -3,29 +3,67 @@ import { FORMAT_INSTRUCTIONS } from "./prompt.js";
 
 export class ChatConversationalAgentOutputParser extends AgentActionOutputParser {
   async parse(text: string) {
-    let jsonOutput = text.trim();
-    if (jsonOutput.includes("```json")) {
-      jsonOutput = jsonOutput.split("```json")[1].trimStart();
-    } else if (jsonOutput.includes("```")) {
-      const firstIndex = jsonOutput.indexOf("```");
-      jsonOutput = jsonOutput.slice(firstIndex + 3).trimStart();
-    }
-    const lastIndex = jsonOutput.lastIndexOf("```");
-    if (lastIndex !== -1) {
-      jsonOutput = jsonOutput.slice(0, lastIndex).trimEnd();
+    const trimmedText = text.trim();
+    let action: string | undefined;
+    let action_input: string | undefined;
+
+    try {
+      ({ action, action_input } = JSON.parse(trimmedText));
+    } catch (_error) {
+      ({ action, action_input } = this.findActionAndInput(trimmedText));
     }
 
-    const response = JSON.parse(jsonOutput);
+    if (!action) {
+      throw new Error(`\`action\` could not be found in: "${trimmedText}"`);
+    }
 
-    const { action, action_input } = response;
+    if (!action_input) {
+      throw new Error(
+        `\`action_input\` could not be found in: "${trimmedText}"`
+      );
+    }
 
     if (action === "Final Answer") {
       return { returnValues: { output: action_input }, log: text };
     }
+
     return { tool: action, toolInput: action_input, log: text };
   }
 
   getFormatInstructions(): string {
     return FORMAT_INSTRUCTIONS;
   }
+
+  private findActionAndInput(text: string): {
+    action: string | undefined;
+    action_input: string | undefined;
+  } {
+    const jsonOutput = this.findJson(text);
+
+    try {
+      const response = JSON.parse(jsonOutput);
+
+      return response;
+    } catch (error) {
+      return { action: undefined, action_input: undefined };
+    }
+  }
+
+  private findJson(text: string) {
+    let jsonOutput = text;
+
+    if (jsonOutput.includes("```json")) {
+      jsonOutput = jsonOutput.split("```json")[1].trimStart();
+    } else if (jsonOutput.includes("```")) {
+      const firstIndex = jsonOutput.indexOf("```");
+      jsonOutput = jsonOutput.slice(firstIndex + 3).trimStart();
+    }
+    const lastIndex = jsonOutput.lastIndexOf("```");
+
+    if (lastIndex !== -1) {
+      jsonOutput = jsonOutput.slice(0, lastIndex).trimEnd();
+    }
+
+    return jsonOutput;
+  }
 }

langchain/src/agents/tests/chat_output_parser.test.ts

@@ -42,6 +42,14 @@ test("Can parse JSON with text in front of it", async () => {
       toolInput:
         "```sql\nSELECT * FROM orders\nJOIN users ON users.id = orders.user_id\nWHERE users.email = 'bud'```",
     },
+    {
+      input:
+        '{"action":"ToolWithJson","action_input":"The tool input ```json\\n{\\"yes\\":true}\\n```"}',
+      output:
+        '{"action":"ToolWithJson","action_input":"The tool input ```json\\n{\\"yes\\":true}\\n```"}',
+      tool: "ToolWithJson",
+      toolInput: 'The tool input ```json\n{"yes":true}\n```',
+    },
   ];
 
   const p = new ChatConversationalAgentOutputParser();
@@ -62,3 +70,66 @@ test("Can parse JSON with text in front of it", async () => {
     }
   }
 });
+
+test("will throw exceptions if action or action_input are not found", async () => {
+  const parser = new ChatConversationalAgentOutputParser();
+
+  type MissingItem = "action" | "action_input";
+  type TestCase = { message: string; missing: MissingItem };
+
+  const testCases: TestCase[] = [
+    {
+      message: "",
+      missing: "action",
+    },
+    {
+      message: '{"action": "Final Answer"}',
+      missing: "action_input",
+    },
+    {
+      message: '{"action_input": "I have no action"}',
+      missing: "action",
+    },
+    {
+      message:
+        'I have a prefix ```json\n{"action_input": "I have no action"}```',
+      missing: "action",
+    },
+    {
+      message: 'I have a prefix ```{"action_input": "I have no action"}```',
+      missing: "action",
+    },
+    {
+      message:
+        'I have a prefix ```json\n{"action_input": "I have no action"}\n```',
+      missing: "action",
+    },
+    {
+      message: 'I have a prefix ```\n{"action_input": "I have no action"}\n```',
+      missing: "action",
+    },
+
+    {
+      message: 'I have a prefix ```json\n{"action": "ToolThing"}```',
+      missing: "action_input",
+    },
+    {
+      message: 'I have a prefix ```{"action": "ToolThing"}```',
+      missing: "action_input",
+    },
+    {
+      message: 'I have a prefix ```json\n{"action": "ToolThing"}\n```',
+      missing: "action_input",
+    },
+    {
+      message: 'I have a prefix ```\n{"action": "ToolThing"}\n```',
+      missing: "action_input",
+    },
+  ];
+
+  for (const { message, missing } of testCases) {
+    await expect(parser.parse(message)).rejects.toThrow(
+      `\`${missing}\` could not be found in: "${message}"`
+    );
+  }
+});