Initial public release

backend/tests/test_paged_acquisition_stops.py

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+"""The paged readers' loop protections, exercised rather than assumed.
+
+GRB and official vector both refuse a repeated page URL and bound the page
+count, and GRB deduplicates on feature identity. None of that had a test, so
+none of it was known to work — the same category as the redirect handler that
+turned out to be dead code while looking like protection.
+
+A provider that answers every page with a "next" link pointing back at itself
+is not hypothetical: it is what a misconfigured cursor or a caching proxy in
+front of an OGC endpoint produces.
+"""
+
+from __future__ import annotations
+
+import pytest
+from shapely.geometry import Polygon
+
+from app.core.config import Settings
+from app.core.errors import AppError
+from app.services.grb_acquisition_service import GrbAcquisitionService
+from tests.test_sprint239_bounded_grb_acquisition import JsonResponse, polygon_feature
+
+COLLECTION_ITEMS = "https://geo.api.vlaanderen.be/GRB/ogc/features/v1/collections/GBG/items"
+SCOPE = Polygon([(5.15, 51.18), (5.17, 51.18), (5.17, 51.20), (5.15, 51.20), (5.15, 51.18)])
+
+
+def _building(feature_id: str) -> dict:
+    return polygon_feature(
+        feature_id,
+        [(5.155, 51.185), (5.175, 51.185), (5.175, 51.195), (5.155, 51.195), (5.155, 51.185)],
+    )
+
+
+def _fetch(opener):
+    return GrbAcquisitionService._fetch_features(
+        GrbAcquisitionService._product("buildings"),
+        SCOPE,
+        SCOPE.bounds,
+        "bounded_selection",
+        Settings(_env_file=None),
+        opener,
+    )
+
+
+def test_a_next_link_pointing_at_itself_is_refused() -> None:
+    requests: list[str] = []
+
+    def opener(request, timeout):  # noqa: ARG001
+        requests.append(request.full_url)
+        return JsonResponse(
+            {
+                "type": "FeatureCollection",
+                "features": [_building("GBG.1")],
+                "links": [{"rel": "next", "href": f"{COLLECTION_ITEMS}?cursor=stuck"}],
+            }
+        )
+
+    with pytest.raises(AppError) as exc_info:
+        _fetch(opener)
+
+    assert exc_info.value.code == "GRB_PROVIDER_PAGINATION_LOOP"
+    # Refused on the second sighting, not after exhausting the page budget.
+    assert len(requests) == 2
+
+
+def test_an_endless_chain_of_fresh_pages_stops_at_the_page_limit() -> None:
+    """Distinct URLs defeat the loop check, so the page budget is the backstop."""
+
+    settings = Settings(_env_file=None)
+    requests: list[str] = []
+
+    def opener(request, timeout):  # noqa: ARG001
+        requests.append(request.full_url)
+        cursor = len(requests)
+        return JsonResponse(
+            {
+                "type": "FeatureCollection",
+                "features": [_building(f"GBG.{cursor}")],
+                "links": [{"rel": "next", "href": f"{COLLECTION_ITEMS}?cursor=p{cursor}"}],
+            }
+        )
+
+    with pytest.raises(AppError) as exc_info:
+        _fetch(opener)
+
+    assert exc_info.value.code == "GRB_SELECTION_TOO_LARGE"
+    assert exc_info.value.status_code == 422
+    assert len(requests) == settings.grb_max_pages
+
+
+def test_a_repeated_feature_across_pages_is_counted_once() -> None:
+    """Two pages, distinct URLs, overlapping content.
+
+    Unlike a repeated URL this is not necessarily provider misbehaviour — a
+    cursor over a changing table can hand back a record twice — so the reader
+    keeps it once rather than failing the acquisition.
+    """
+
+    def opener(request, timeout):  # noqa: ARG001
+        if "cursor=next" in request.full_url:
+            return JsonResponse(
+                {
+                    "type": "FeatureCollection",
+                    "features": [_building("GBG.1"), _building("GBG.2")],
+                    "links": [],
+                }
+            )
+        return JsonResponse(
+            {
+                "type": "FeatureCollection",
+                "features": [_building("GBG.1")],
+                "links": [{"rel": "next", "href": f"{COLLECTION_ITEMS}?cursor=next"}],
+            }
+        )
+
+    features, transfer = _fetch(opener)
+
+    assert {feature["id"] for feature in features} == {"GBG:GBG.1", "GBG:GBG.2"}
+    assert transfer["candidate_feature_count"] == 3
+    assert transfer["feature_count"] == 2