Fix permission rule source attribution to use pluggy call order (#2978)

Pair each hook result with reversed(get_hookimpls()): pluggy runs implementations in reverse registration order and appends results in that order. Adds regression tests.

tests/test_permission_source_attribution.py

@@ -0,0 +1,70 @@
+"""Permission rules are attributed to the plugin that returned them (#2978).
+
+``gather_permission_sql_from_hooks()`` used to pair each hook result with a
+hook implementation by index into ``get_hookimpls()``, but pluggy calls
+implementations in reverse registration order — so every rule whose plugin
+did not set ``PermissionSQL.source`` explicitly was attributed to whichever
+plugin happened to sit at that index.
+"""
+
+import pytest
+
+from datasette import hookimpl
+from datasette.app import Datasette
+from datasette.permissions import PermissionSQL
+from datasette.utils.permissions import gather_permission_sql_from_hooks
+
+
+class AlphaPlugin:
+    @hookimpl
+    def permission_resources_sql(self, datasette, actor, action):
+        if action == "view-table":
+            return PermissionSQL(sql="select 'a' as parent, 'x' as child, 1 as allow, 'from-alpha' as reason")
+
+
+class BetaPlugin:
+    @hookimpl
+    def permission_resources_sql(self, datasette, actor, action):
+        if action == "view-table":
+            return PermissionSQL(sql="select 'b' as parent, 'y' as child, 1 as allow, 'from-beta' as reason")
+
+
+@pytest.mark.asyncio
+async def test_permission_sql_source_names_the_calling_plugin():
+    ds = Datasette(memory=True)
+    ds.pm.register(AlphaPlugin(), name="alpha")
+    ds.pm.register(BetaPlugin(), name="beta")
+    try:
+        await ds.invoke_startup()
+        sqls = await gather_permission_sql_from_hooks(datasette=ds, actor={"id": "alice"}, action="view-table")
+    finally:
+        ds.pm.unregister(name="beta")
+        ds.pm.unregister(name="alpha")
+        ds.close()
+    by_plugin = {}
+    for permission_sql in sqls:
+        if "'a' as parent" in (permission_sql.sql or ""):
+            by_plugin["alpha"] = permission_sql.source
+        elif "'b' as parent" in (permission_sql.sql or ""):
+            by_plugin["beta"] = permission_sql.source
+    assert by_plugin == {"alpha": "alpha", "beta": "beta"}
+
+
+@pytest.mark.asyncio
+async def test_explicit_permission_sql_source_is_preserved():
+    class ExplicitPlugin:
+        @hookimpl
+        def permission_resources_sql(self, datasette, actor, action):
+            if action == "view-table":
+                return PermissionSQL(sql="select 'e' as parent, 'z' as child, 1 as allow, 'explicit' as reason", source="my-source")
+
+    ds = Datasette(memory=True)
+    ds.pm.register(ExplicitPlugin(), name="explicit")
+    try:
+        await ds.invoke_startup()
+        sqls = await gather_permission_sql_from_hooks(datasette=ds, actor={"id": "alice"}, action="view-table")
+    finally:
+        ds.pm.unregister(name="explicit")
+        ds.close()
+    sources = [permission_sql.source for permission_sql in sqls if "'e' as parent" in (permission_sql.sql or "")]
+    assert sources == ["my-source"]