Unable to open playground page when using add_routes() with FastAPI's APIRouter

[StreetLamb]

I'm using APIRouter to separate my routes like so:

# app/main.py
app.include_router(api_router, prefix='/api/v1')

# app/api/main.py
from app.api.routes import chat

api_router = APIRouter()
api_router.include_router(chat.router, prefix="/chat", tags=["chats"])

# app/api/routes/chat.py
router = APIRouter()
add_routes(
    router,
    ChatOpenAI(),
)

I am able to access http://localhost /api/v1/chat/invoke properly. However http://localhost/api/v1/chat/playground brings me to a blank page. I get the error: Failed to load module script: Expected a JavaScript module script but the server responded with a MIME type of "text/html". Strict MIME type checking is enforced for module scripts per HTML spec.

On inspecting network, issue seems to be that the page is incorrectly fetching the playground assets from the base URL http://localhost/playground/assets/index-dbc96538.js instead of http://localhost/api/v1/chat/playground/assets/index-dbc96538.js.

My workaround for now is to move all the prefixes into add_routes instead:

# app/main.py
app.include_router(api_router)

# app/api/main.py
from app.api.routes import chat

api_router = APIRouter()
api_router.include_router(chat.router, tags=["chats"])

# app/api/routes/chat.py
router = APIRouter()
add_routes(
    router,
    ChatOpenAI(),
    path="/api/v1/chat"
)

Ideally, it should be able to infer the correct path when working with prefixes.

[eyurtsev]

Thanks! Will take a look on Monday. Which version of langserve are you on?

[StreetLamb]

Thanks for looking into it! I'm using 0.0.51

[eyurtsev]

@StreetLamb I am unable to reproduce, would you be kind enough to help me create an MRE with the unit tests?

https://github.com/langchain-ai/langserve/pull/579/files#diff-0796d94e9487fc7c014344ad4a1150ba02c980991a7433ad811f3fef23d843dfR63

[StreetLamb]

Hi @eyurtsev, raised a PR to update the playground unit tests as requested.

[SwenRanj]

Hi, I am having the same issue on langserve version 0.1.1. I noticed that the playground works when you supply a path to the add_routes function, but not when you use the prefix in include_router (like the sample that @StreetLamb provided.

Any news on this issue?