The expression inside {{}} was not parsed during the workflow execution

[xhzkp]

Bug Description

I installed self-hosted n8n on a Windows 10 system via npm.
I used a chat trigger to upload a docx file and then wrote the file to the "abc" folder. However, the file name is incorrect as the variable inside {{}} was not parsed. This can be clearly seen in the video below.

BugDemo.mp4

workflow config:

{
  "nodes": [
    {
      "parameters": {},
      "id": "63d2bf70-2d86-4862-8020-702bfea5ce3f",
      "name": "Window Buffer Memory",
      "type": "@n8n/n8n-nodes-langchain.memoryBufferWindow",
      "typeVersion": 1.2,
      "position": [
        520,
        80
      ]
    },
    {
      "parameters": {
        "public": true,
        "initialMessages": "upload file",
        "options": {
          "allowFileUploads": true,
          "responseMode": "lastNode",
          "showWelcomeScreen": false
        }
      },
      "id": "37b26983-0f0c-4cfa-a7b7-511d7ba377a8",
      "name": "When chat message received",
      "type": "@n8n/n8n-nodes-langchain.chatTrigger",
      "typeVersion": 1.1,
      "position": [
        -20,
        -140
      ],
      "webhookId": "1c1f408c-25b5-4776-a3cf-da267611b299"
    },
    {
      "parameters": {
        "options": {
          "baseURL": "https://oneapi.6868ai.com/v1",
          "temperature": 0.3
        }
      },
      "id": "a267a5d5-ac9a-4fb2-88de-bfed809ca9d3",
      "name": "OpenAI",
      "type": "@n8n/n8n-nodes-langchain.lmChatOpenAi",
      "typeVersion": 1,
      "position": [
        380,
        80
      ],
      "notesInFlow": false,
      "credentials": {
        "openAiApi": {
          "id": "iuBjR0mRLNV8iloe",
          "name": "OpenAi account"
        }
      }
    },
    {
      "parameters": {
        "operation": "write",
        "fileName": "=C:\\\\Users\\\\Administrator\\\\Desktop\\\\abc\\\\{{ $json.files[0].fileName}}",
        "dataPropertyName": "=data0",
        "options": {}
      },
      "type": "n8n-nodes-base.readWriteFile",
      "typeVersion": 1,
      "position": [
        240,
        -140
      ],
      "id": "f8657482-a31d-4f4e-82f3-8f133b067615",
      "name": "Read/Write Files from Disk1"
    },
    {
      "parameters": {
        "promptType": "define",
        "text": "=uploadFile: {{ $json.fileName}}\nchatInput: {{ $json.chatInput }}\nsessionId: {{ $json.sessionId }}",
        "options": {}
      },
      "type": "@n8n/n8n-nodes-langchain.agent",
      "typeVersion": 1.7,
      "position": [
        460,
        -140
      ],
      "id": "72166ca4-d01a-41a5-a993-4647e178ed1c",
      "name": "AI Agent1"
    }
  ],
  "connections": {
    "Window Buffer Memory": {
      "ai_memory": [
        [
          {
            "node": "AI Agent1",
            "type": "ai_memory",
            "index": 0
          }
        ]
      ]
    },
    "When chat message received": {
      "main": [
        [
          {
            "node": "Read/Write Files from Disk1",
            "type": "main",
            "index": 0
          }
        ]
      ]
    },
    "OpenAI": {
      "ai_languageModel": [
        [
          {
            "node": "AI Agent1",
            "type": "ai_languageModel",
            "index": 0
          }
        ]
      ]
    },
    "Read/Write Files from Disk1": {
      "main": [
        [
          {
            "node": "AI Agent1",
            "type": "main",
            "index": 0
          }
        ]
      ]
    }
  },
  "pinData": {}
}

To Reproduce

1. copy config
2. run it

Expected behavior

The variable inside {{}} should be parsed correctly.

Operating System

self-hosted n8n on a Windows 10

n8n Version

1.70.1

Node.js Version

20.18.0

Database

SQLite (default)

Execution mode

main (default)

[Joffcom]

Hey @xhzkp,

We have created an internal ticket to look into this which we will be tracking as "GHC-543"

[MarcL]

Hey @xhzkp,

We've looked at this and found a bug in the way we parse our expressions.
We should have a fix in the next release once n8n-io/tournament#20 is merged.

[Joffcom]

We’re taking some time to review and tidy up our issue tracker. It looks like this issue hasn’t had any recent activity for the past 6 months. To keep our backlog focused on current priorities, we’re closing this issue for now.

That said, this doesn’t mean the issue is forgotten! If this is still relevant or you have more information to add, feel free to reopen it or create a new issue and we’d be happy to revisit it.

Thank you for understanding and for contributing to the project!