Pipeline rendering does not work properly

[anakin87]

Describe the bug
New versions of Mermaid and mermaid.ink have been released.
This broke our Pipeline rendering. Also, we cannot pin an older version of Mermaid, since we are using an external service.

My impression is that the Mermaid code we are producing is not compatible with the new version (see code below).

To Reproduce

from haystack import Pipeline
from haystack.document_stores.in_memory import InMemoryDocumentStore
from haystack.components.retrievers.in_memory import InMemoryBM25Retriever
from haystack.components.generators import OpenAIGenerator
from haystack.components.builders.prompt_builder import PromptBuilder

prompt_template = """
Given these documents, answer the question.
Documents:
{% for doc in documents %}
    {{ doc.content }}
{% endfor %}
Question: {{question}}
Answer:
"""

retriever = InMemoryBM25Retriever(document_store=InMemoryDocumentStore())
prompt_builder = PromptBuilder(template=prompt_template)
llm = OpenAIGenerator()

rag_pipeline = Pipeline()
rag_pipeline.add_component("retriever", retriever)
rag_pipeline.add_component("prompt_builder", prompt_builder)
rag_pipeline.add_component("llm", llm)
rag_pipeline.connect("retriever", "prompt_builder.documents")
rag_pipeline.connect("prompt_builder", "llm")

rag_pipeline.draw("pipeline.png")

Rendering

Mermaid code

%%{ init: {'theme': 'neutral' } }%%

graph TD;

retriever["<b>retriever</b><br><small><i>InMemoryBM25Retriever<br><br>Optional inputs:<ul style='text-align:left;'><li>filters (Optional[Dict[str, Any]])</li><li>top_k (Optional[int])</li><li>scale_score (Optional[bool])</li></ul></i></small>"]:::component -. "documents -> documents (opt.)<br><small><i>List[Document]</i></small>" .-> prompt_builder["<b>prompt_builder</b><br><small><i>PromptBuilder<br><br>Optional inputs:<ul style='text-align:left;'><li>template (Optional[str])</li><li>template_variables (Optional[Dict[str, Any]])</li><li>question (Any)</li></ul></i></small>"]:::component
prompt_builder["<b>prompt_builder</b><br><small><i>PromptBuilder<br><br>Optional inputs:<ul style='text-align:left;'><li>template (Optional[str])</li><li>template_variables (Optional[Dict[str, Any]])</li><li>question (Any)</li></ul></i></small>"]:::component -- "prompt -> prompt<br><small><i>str</i></small>" --> llm["<b>llm</b><br><small><i>OpenAIGenerator<br><br>Optional inputs:<ul style='text-align:left;'><li>streaming_callback (Optional[Callable[]])</li><li>generation_kwargs (Optional[Dict[str, Any]])</li></ul></i></small>"]:::component
i{*} -- "query<br><small><i>str</i></small>" --> retriever["<b>retriever</b><br><small><i>InMemoryBM25Retriever<br><br>Optional inputs:<ul style='text-align:left;'><li>filters (Optional[Dict[str, Any]])</li><li>top_k (Optional[int])</li><li>scale_score (Optional[bool])</li></ul></i></small>"]:::component
llm["<b>llm</b><br><small><i>OpenAIGenerator<br><br>Optional inputs:<ul style='text-align:left;'><li>streaming_callback (Optional[Callable[]])</li><li>generation_kwargs (Optional[Dict[str, Any]])</li></ul></i></small>"]:::component -- "replies<br><small><i>List[str]</i></small>"--> o{*}
llm["<b>llm</b><br><small><i>OpenAIGenerator<br><br>Optional inputs:<ul style='text-align:left;'><li>streaming_callback (Optional[Callable[]])</li><li>generation_kwargs (Optional[Dict[str, Any]])</li></ul></i></small>"]:::component -- "meta<br><small><i>List[Dict[str, Any]]</i></small>"--> o{*}

classDef component text-align:center;

[anakin87]

I discovered that the issue is simply related to the asterisk (*) character, which is unsupported in Mermaid markdown.

[TuanaCelik]

Thabks @anakin87 i also just noticed this today.

Unfortunately this bug will persist in older versions of Haystack including the DLAI course I think correct?

[anakin87]

@TuanaCelik you are right.
If this is a problem, we can see if it makes sense/it is safe to update DLAI to 2.5.1 or otherwise release a 2.2.5 version with this fix and update DLAI to that.
Or otherwise do nothing.