Bound connector source previews

tests/test_datasource_origins.py

@@ -81,6 +81,11 @@ class ConnectorDatasourceOriginTests(unittest.TestCase):
         self.assertEqual((self.source.ref,), tuple(item.ref for item in origins))
         self.assertEqual(("live", "cached"), origins[0].supported_modes)
         self.assertEqual(({"id": 1, "name": "Ada"},), result.rows)
+        self.assertEqual("cached", origins[0].source_mode)
+        self.assertTrue(origins[0].pushdown.projections)
+        self.assertEqual("healthy", origins[0].health.status)
+        self.assertGreater(result.returned_bytes, 2)
+        self.assertEqual(1_000_000, result.effective_byte_limit)
 
 
 if __name__ == "__main__":

tests/test_tabular_sources.py

@@ -12,6 +12,7 @@ from govoplan_core.core.tabular_sources import (
     TabularReadRequest,
     TabularSnapshotInput,
     TabularSourceAccessError,
+    TabularSourceUnavailableError,
     TabularSourceValidationError,
 )
 from govoplan_core.db.base import Base
@@ -91,6 +92,94 @@ class ConnectorsTabularSourceTests(unittest.TestCase):
         self.assertEqual(1, len(preview.rows))
         self.assertTrue(preview.truncated)
         self.assertEqual(created.fingerprint, preview.source.fingerprint)
+        self.assertEqual("cached", preview.source.source_mode)
+        self.assertTrue(preview.source.pushdown.projections)
+        self.assertTrue(preview.source.pushdown.pagination)
+        self.assertEqual("healthy", preview.source.health.status)
+        self.assertGreater(preview.returned_bytes, 2)
+        self.assertEqual(1, preview.effective_row_limit)
+        self.assertEqual("preview.row_limit_reached", preview.diagnostics[0].code)
+
+    def test_preview_enforces_byte_time_and_provider_ceiling_budgets(self) -> None:
+        created = self.provider.create_snapshot(
+            self.session,
+            principal(),
+            snapshot=TabularSnapshotInput(
+                name="Bounded",
+                source_name="bounded",
+                rows=(
+                    {"id": 1, "value": "first"},
+                    {"id": 2, "value": "second"},
+                ),
+            ),
+        )
+        self.session.commit()
+
+        bounded = self.provider.read_source(
+            self.session,
+            principal(),
+            request=TabularReadRequest(
+                source_ref=created.ref,
+                limit=500,
+                max_bytes=35,
+                timeout_ms=2_000,
+            ),
+        )
+        self.assertEqual(1, len(bounded.rows))
+        self.assertTrue(bounded.truncated)
+        self.assertEqual(
+            "preview.byte_limit_reached",
+            bounded.diagnostics[-1].code,
+        )
+        with self.assertRaisesRegex(
+            TabularSourceValidationError,
+            "single source row exceeds",
+        ):
+            self.provider.read_source(
+                self.session,
+                principal(),
+                request=TabularReadRequest(
+                    source_ref=created.ref,
+                    max_bytes=2,
+                ),
+            )
+
+        tightened = self.provider.read_source(
+            self.session,
+            principal(),
+            request=TabularReadRequest(
+                source_ref=created.ref,
+                limit=5_000,
+                max_bytes=5_000_000,
+                timeout_ms=10_000,
+            ),
+        )
+        self.assertEqual(500, tightened.effective_row_limit)
+        self.assertEqual(1_000_000, tightened.effective_byte_limit)
+        self.assertEqual(2_000, tightened.effective_timeout_ms)
+        self.assertEqual(
+            {
+                "preview.row_limit_tightened",
+                "preview.byte_limit_tightened",
+                "preview.timeout_tightened",
+            },
+            {item.code for item in tightened.diagnostics},
+        )
+
+        times = iter((0.0, 0.01))
+        timeout_provider = SqlTabularSourceProvider(clock=lambda: next(times))
+        with self.assertRaisesRegex(
+            TabularSourceUnavailableError,
+            "time budget",
+        ):
+            timeout_provider.read_source(
+                self.session,
+                principal(),
+                request=TabularReadRequest(
+                    source_ref=created.ref,
+                    timeout_ms=1,
+                ),
+            )
 
     def test_tenant_and_scope_isolation_are_enforced(self) -> None:
         created = self.provider.create_snapshot(