Request Links Example (Phase 7)

Output fields bound to the current request: FromHeader("X-Request-Id") and FromCookie("session_id"). Responses echo headers and cookies when present.

Code

from typing import Annotated
from pydantic import BaseModel
from semblance import FromCookie, FromHeader, FromInput, SemblanceAPI

class UserQuery(BaseModel):
    name: str = "alice"

class UserResponse(BaseModel):
    name: Annotated[str, FromInput("name")]
    request_id: Annotated[str, FromHeader("X-Request-Id")]
    session: Annotated[str, FromCookie("session_id")]

api = SemblanceAPI(seed=42)


@api.get(
    "/user",
    input=UserQuery,
    output=UserResponse,
    summary="Get user (echoes header and cookie)",
)
def get_user():
    """request_id comes from X-Request-Id header; session from session_id cookie."""
    pass


app = api.as_fastapi()

Run

semblance run examples.request_links.app:api --port 8000

Try

# With header and cookie
curl -i "http://127.0.0.1:8000/user?name=alice" \
  -H "X-Request-Id: req-abc-123" \
  -H "Cookie: session_id=sess-xyz"

# Response includes "request_id": "req-abc-123", "session": "sess-xyz"
# If header/cookie missing, those fields get generated values.

Example response with -H "X-Request-Id: id-1" -H "Cookie: session_id=sess-1" and ?name=alice (seed=42):

{"name": "alice", "request_id": "id-1", "session": "sess-1"}

Concepts

• Phase 7 — Built-in request links: FromHeader(name) and FromCookie(name).
• Resolved at response build time from the current request; works with test_client and live servers.
• See Request Links for details.