Route discovery fails when include_router is called with an indirect router reference

[tpemeja]

Description

The FastAPI extension fails to discover routes when app.include_router() is called with a router reference that is not a direct import name.

In the example only the route defined directly in main.py (GET /) is visible in the path explorer. All routes from the included router items are missing.

✅ Working example

❌ Using indirect router reference

Extension logs

2026-04-22 15:00:03.012 [info] Discovering FastAPI apps in 1 workspace folder(s)...
2026-04-22 15:00:03.041 [info] Found 1 candidate FastAPI file(s) in fastapi-extension
2026-04-22 15:00:03.044 [info] Analyzed "file://.../main.py": 1 routes, 1 routers, 1 include_router calls
2026-04-22 15:00:03.044 [info] Resolving include_router: router (prefix: {prefix})
2026-04-22 15:00:03.044 [info] No import found for router reference: router
2026-04-22 15:00:03.044 [info] Found 1 FastAPI app(s) with 1 route(s) in fastapi-extension

Repository link (if open source)

No response

Project structure

fastapi-extension/
├── items.py
└── main.py

FastAPI app and router setup

from fastapi import APIRouter, FastAPI
from items import router as items_router

app = FastAPI()

# Case 1 : Working
# app.include_router(items_router, prefix="/items", tags=["items"])

# Case 2 : Not working
routers: list[tuple[APIRouter, str, str]] = [
    (items_router, "/items", "items"),
]
for router, prefix, tag in routers:
    app.include_router(router, prefix=prefix, tags=[tag])

# Case 3 : Not working
# routers: list[tuple[APIRouter, str, str]] = [
#     (items_router, "/items", "items"),
# ]
# app.include_router(routers[0][0], prefix=routers[0][1], tags=[routers[0][2]])


@app.get("/")
async def root():
    return {"message": "Hello World"}

VS Code version

1.116.0

FastAPI extension version

0.2.0

Python version

3.11.11

FastAPI version

0.115.12

Operating system

macOS 26.3.1 (a) (25D771280a)

[savannahostrowski]

Thanks for the report. The extension currently discovers routes through static analysis. It does not execute the app or evaluate Python control flow/data structures.

In these examples, the include_router() calls that don't work do not contain a direct router reference. Resolving router, prefix, and tag would require evaluating the routers list, the loop binding, or indexed expressions like routers[0][0]. That is outside the current analysis model and can quickly become inaccurate for real Python code.

For now, the supported pattern is a direct include such as:

app.include_router(items_router, prefix="/items", tags=["items"])

I'll leave this open for visibility, but this is a limitation of the current static analyzer and not a scenario we plan to handle broadly.