chore(sdk-py): type errors nicely (#6173)

This PR types errors in a nicer way

libs/sdk-py/tests/test_errors.py

@@ -0,0 +1,108 @@
+from __future__ import annotations
+
+from typing import cast
+
+import httpx
+import orjson
+import pytest
+
+from langgraph_sdk.errors import (
+    APIStatusError,
+    AuthenticationError,
+    BadRequestError,
+    ConflictError,
+    InternalServerError,
+    NotFoundError,
+    PermissionDeniedError,
+    RateLimitError,
+    UnprocessableEntityError,
+    _raise_for_status_typed,
+)
+
+
+def make_response(
+    status: int,
+    *,
+    json_body: dict | None = None,
+    text_body: str | None = None,
+    headers: dict[str, str] | None = None,
+) -> httpx.Response:
+    request = httpx.Request("GET", "https://example.com/test")
+    content: bytes | None
+    if json_body is not None:
+        content = orjson.dumps(json_body)
+    elif text_body is not None:
+        content = text_body.encode()
+    else:
+        content = b""
+    return httpx.Response(
+        status, headers=headers or {}, content=content, request=request
+    )
+
+
+@pytest.mark.parametrize(
+    "status,exc_type",
+    [
+        (400, BadRequestError),
+        (401, AuthenticationError),
+        (403, PermissionDeniedError),
+        (404, NotFoundError),
+        (409, ConflictError),
+        (422, UnprocessableEntityError),
+        (429, RateLimitError),
+        (500, InternalServerError),
+        (503, InternalServerError),  # any 5xx
+        (418, APIStatusError),  # unmapped 4xx falls back to base type
+    ],
+)
+def test_raise_for_status_typed_maps_exceptions_and_sets_status_code(
+    status: int, exc_type: type[APIStatusError]
+) -> None:
+    r = make_response(
+        status, json_body={"message": "boom", "code": "abc", "param": "p", "type": "t"}
+    )
+
+    with pytest.raises(exc_type) as ei:
+        _raise_for_status_typed(r)
+
+    err = cast(APIStatusError, ei.value)
+    assert err.status_code == status
+    # response attribute should be present and match
+    assert err.response.status_code == status
+
+
+def test_request_id_is_extracted_when_present() -> None:
+    r = make_response(
+        404, json_body={"detail": "missing"}, headers={"x-request-id": "req-123"}
+    )
+    with pytest.raises(NotFoundError) as ei:
+        _raise_for_status_typed(r)
+    err = cast(APIStatusError, ei.value)
+    # request_id only exists on APIStatusError subclasses
+    assert err.request_id == "req-123"
+
+
+def test_non_json_body_does_not_break_mapping() -> None:
+    r = make_response(429, text_body="Too many requests")
+    with pytest.raises(RateLimitError) as ei:
+        _raise_for_status_typed(r)
+    err = cast(APIStatusError, ei.value)
+    assert err.status_code == 429
+
+
+def test_field_extraction_from_json_body() -> None:
+    r = make_response(
+        400,
+        json_body={
+            "message": "Invalid parameter",
+            "code": "invalid_param",
+            "param": "limit",
+            "type": "invalid_request_error",
+        },
+    )
+    with pytest.raises(BadRequestError) as ei:
+        _raise_for_status_typed(r)
+    err = cast(APIStatusError, ei.value)
+    assert err.code == "invalid_param"
+    assert err.param == "limit"
+    assert err.type == "invalid_request_error"