Console: ASCII control characters not correctly handled for chatlas responses in Python

[petetronic]

System details:

Positron and OS details:

Positron Version: 2025.01.0 (Universal) build 39
Code - OSS Version: 1.93.0
Commit: c7ef34f

Interpreter details:

Python 3.11.7

Describe the issue:

Our Console handling of line clearing ASCII control sequences is not quite right, leaving superfluous newlines / whitespace.

Steps to reproduce the issue:

1. Note: this scenario relies on an OpenAPI key to reproduce live, though with some logging information below you may not need to run this to devise a fix. Setup an env var for OPENAI_API_KEY. Ensure the key is permissioned for the model selected.

2. Run this Python in Positron's Console. It uses the chatlas package to chat with OpenAPI:

from chatlas import ChatOpenAI
import os

# Setup your Open API key in an env var
OPENAI_API_KEY = os.getenv("OPENAI_API_KEY")

def chat_with_chatlas(prompt: str):
    chatlas_client = ChatOpenAI(api_key=OPENAI_API_KEY, model="gpt-4o-mini")
    try:
        response = chatlas_client.chat(prompt)
        return response
    except Exception as e:
        return f"An error occurred: {e}"

prompt = "What is the capital of France?"
response = chat_with_chatlas(prompt)

3. Note the extra whitespace in the output in the console:

>>> %run "chatlastest.py"
                                                                                                      
                                                                                                      
                                                                                                      
                                                                                                      
                                                                                                      
                                                                                                      
                                                                                                      
The capital of France is Paris.                                                                       

>>>

Expected or desired behavior:

Here's what the same program run in an ipython Terminal looks like:

In [1]: %run chatlastest.py

The capital of France is Paris.                                                                                                                       

In [2]: 

Were there any error messages in the UI, Output panel, or Developer Tools console?

The chatlas package responds with partially complete lines as tokens are streamed from Open AI, replacing the output content using ASCII control chars. Here's the rough jupyter output message sequence, including escaped ASCII control chars in the JSON representation of messages:

2024-12-18 17:07:13.692 [debug] <<< RECV stream [iopub]: {"name":"stdout","text":"\u001b[?25l"}
2024-12-18 17:07:14.167 [debug] <<< RECV stream [iopub]: {"name":"stdout","text":"\r\u001b[2K\nThe                                                                                                                              "}
2024-12-18 17:07:14.170 [debug] <<< RECV stream [iopub]: {"name":"stdout","text":"\r\u001b[2K\u001b[1A\u001b[2K\nThe capital                                                                                                                      "}
2024-12-18 17:07:14.181 [debug] <<< RECV stream [iopub]: {"name":"stdout","text":"\r\u001b[2K\u001b[1A\u001b[2K\nThe capital of                                                                                                                   "}
2024-12-18 17:07:14.183 [debug] <<< RECV stream [iopub]: {"name":"stdout","text":"\r\u001b[2K\u001b[1A\u001b[2K\nThe capital of France                                                                                                            "}
2024-12-18 17:07:14.215 [debug] <<< RECV stream [iopub]: {"name":"stdout","text":"\r\u001b[2K\u001b[1A\u001b[2K\nThe capital of France is                                                                                                         "}
2024-12-18 17:07:14.217 [debug] <<< RECV stream [iopub]: {"name":"stdout","text":"\r\u001b[2K\u001b[1A\u001b[2K\nThe capital of France is Paris                                                                                                   "}
2024-12-18 17:07:14.223 [debug] <<< RECV stream [iopub]: {"name":"stdout","text":"\r\u001b[2K\u001b[1A\u001b[2K\nThe capital of France is Paris.                                                                                                  "}
2024-12-18 17:07:14.225 [debug] <<< RECV stream [iopub]: {"name":"stdout","text":"\r\u001b[2K\u001b[1A\u001b[2K\nThe capital of France is Paris.                                                                                                  \n\u001b[?25h"}

[petetronic]

For reference, he's an explanation of the chars involved:

1. \r:

• ASCII carriage return (CR, 0x0D).
• Moves the cursor to the beginning of the current line without advancing to the next line.

2. \u001b[2K:

• ANSI escape sequence to clear the current line.
• \u001b is the escape character (ESC, 0x1B).
• [2K specifies "Erase Line," where 2 clears the entire line (including the cursor position).

3. \u001b[1A:

• ANSI escape sequence to move the cursor up one line.
• [1A specifies "Cursor Up," where 1 is the number of lines to move.

4. \u001b[2K (repeated):

• Clears the entire line again. At this point, the cursor has already moved up one line due to the previous command.

5. \n:

• ASCII line feed (LF, 0x0A).
• Moves the cursor down to the beginning of the next line.

6. The capital of France is Paris.:

• Regular text output displayed in the terminal.

7. Whitespace Padding:

• The large number of spaces at the end of the text ensures that any previously displayed content on the same line is overwritten.

8. \n:

• Another line feed to move the cursor to a new line.

9. \u001b[?25h:

• ANSI escape sequence to show the cursor.
• \u001b[?25h is a terminal control code where:
  • ?25 refers to the cursor visibility setting.
  • h enables the setting (show the cursor).