[Bug]: Parsing Non-Existent Inline Images in External Uncontrolled Input Text

[ebotiab]

In the followings lines of code:

prompty/runtime/prompty/prompty/parsers.py

Lines 38 to 40 in b18a21e

	image_path = self.path / image_item
	with open(image_path, "rb") as f:
	base64_image = base64.b64encode(f.read()).decode("utf-8")

A text variable in prompty may contain references to image paths (e.g., during RAG). However, the parser does not account for cases where these image paths point to non-existent files. This could result in unexpected behavior when processing uncontrolled external input.

Proposed Fix:

• Add a validation step to check if the referenced image paths exist before attempting to parse them.
• Alternatively, introduce a configuration option that allows users to disable parsing of inline images if needed.

[beduncs]

I encountered this issue recently as well. We use prompty to render prompts from user input which can contain markdown. Attempting to parse and read arbitrary files based on user provided messages is unsafe. At minimum the suggestion of validating the path and not throwing a Runtime Error would be good.

How to replicate:
Pass input to prompty containing markdown formatted image link:

![](/file)This is an image link

Behavior:

raise RuntimeError(f"Failed to prepare prompt: {e}")
    | RuntimeError: Failed to prepare prompt: [Errno 2] No such file or directory: '/file'

Expected Behavior:
Allow this parsing to be disabled completely and passthrough the image link raw.

[beduncs]

PR #146 looks to attempt to address this