app.routes contains _IncludedRouter with no .path since 0.137

[FBosler]

Since 0.137, app.routes can contain _IncludedRouter objects that have no .path attribute. Code that iterates app.routes and reads route.path worked on earlier versions and now raises AttributeError.

from fastapi import FastAPI, APIRouter

sub = APIRouter()

@sub.get("/items")
def items():
    return {}

app = FastAPI()
app.include_router(sub, prefix="/v1")

[route.path for route in app.routes]
# AttributeError: '_IncludedRouter' object has no attribute 'path'

Before 0.137, include_router copied each child route into app.routes, so every entry exposed .path. Now it appends a single _IncludedRouter that matches lazily and has no .path. On a CORS preflight (path matches, method doesn't) it returns a partial match, and a consumer that reads .path on the matched route raises.

This has hit a few tools that read .path off app.routes:

• opentelemetry-instrumentation-fastapi reads route.path on a partial match; this took down our preflights in production (every browser OPTIONS to the API 500'd with no CORS header)
• AttributeError: '_IncludedRouter' object has no attribute 'path' with FastAPI 0.137.0 trallnag/prometheus-fastapi-instrumentator#370
• [Bug]: fastapi error '_IncludedRouter' object has no attribute 'path' vllm-project/vllm#45597

Would you want _IncludedRouter to expose .path (the include prefix), matching Route/Mount/Host, or handle it another way? Happy to send a PR.

[YuriiMotov]

Please, see #15782 and PR #15785