Fixes #875. Prevent infinite nested recipes.

migrations/0108.sql

@@ -7,4 +7,46 @@ CREATE TRIGGER remove_items_from_deleted_shopping_list
     ON shopping_lists
 BEGIN
     DELETE FROM shopping_list WHERE shopping_list_id = OLD.id;
-END;
+END;
+
+DROP TRIGGER IF EXISTS prevent_infinite_nested_recipes_INS;
+
+CREATE TRIGGER prevent_infinite_nested_recipes_INS BEFORE INSERT ON recipes_nestings
+BEGIN
+    SELECT CASE WHEN((
+        SELECT 1
+        FROM recipes_nestings_resolved rnr
+        WHERE NEW.recipe_id = rnr.includes_recipe_id
+          AND NEW.includes_recipe_id = rnr.recipe_id
+    )
+        NOTNULL) THEN RAISE(ABORT, "Recursive nested recipe detected") END;
+END;
+
+DROP TRIGGER IF EXISTS prevent_infinite_nested_recipes_UPD;
+CREATE TRIGGER prevent_infinite_nested_recipes_UPD BEFORE UPDATE ON recipes_nestings
+BEGIN
+    SELECT CASE WHEN((
+        SELECT 1
+        FROM recipes_nestings_resolved rnr
+        WHERE NEW.recipe_id = rnr.includes_recipe_id
+          AND NEW.includes_recipe_id = rnr.recipe_id
+    )
+        NOTNULL) THEN RAISE(ABORT, "Recursive nested recipe detected") END;
+END;
+
+DROP VIEW recipes_nestings_resolved;
+CREATE VIEW recipes_nestings_resolved
+AS
+WITH RECURSIVE r1(recipe_id, includes_recipe_id, includes_servings)
+                   AS (
+        SELECT id, id, 1
+        FROM recipes
+
+        UNION ALL
+
+        SELECT rn.recipe_id, r1.includes_recipe_id, rn.servings
+        FROM recipes_nestings rn, r1 r1
+        WHERE rn.includes_recipe_id = r1.recipe_id
+    )
+SELECT recipe_id AS id, recipe_id, includes_recipe_id, includes_servings
+FROM r1;