fix: fix AQL error when trying to update child entities when there currently were no child entities

When the dict-based child entity impelemntation was used, and an non-empty
update... for child entity was given, and this child entity list for the
updated root entity was currently empty, and AQL error was generated.

The problem was that we used a range generator that should have generated
an empty range, but the AQL ranges are never empty, they just are inverted
if the end position is lower than the start position. This resulted in an
invalid ZIP call, which yielded NULL.

Author: Yogu

spec/regression/logistics/tests/update-empty-child-entities-list-dict.context.json

@@ -0,0 +1,4 @@
+{
+  "childEntityUpdatesViaDictStrategyThreshold": 1,
+  "authRoles": ["allusers"]
+}

spec/regression/logistics/tests/update-empty-child-entities-list-dict.graphql

@@ -0,0 +1,59 @@
+# in the .context.json, childEntityUpdatesViaDictStrategyThreshold is set to 1
+# so we will always use the dict strategy to update child entities
+
+# this test makes sure that updating child entities works (even though it does nothing)
+# when the child entity list in the database is empty
+# this regression test exists because of two bugs we had in the initial dict-based implementation
+# - an AQL error when there were updates but the collection was empty
+# - updates that did not correspond to actual were persisted as new items (just without id etc.)
+
+mutation clearItems {
+    updateDelivery(
+        input: { id: "@{ids/Delivery/1}", removeItems: ["id_init_0000", "id_init_0001"] }
+    ) {
+        items {
+            id
+            itemNumber
+        }
+    }
+}
+
+# to verify it is cleared in the db
+query afterClear {
+    Delivery(id: "@{ids/Delivery/1}") {
+        items {
+            id
+            itemNumber
+        }
+    }
+}
+
+mutation updateMultiple {
+    updateDelivery(
+        input: {
+            id: "@{ids/Delivery/1}"
+            updateItems: [
+                { id: "id_test_0003", itemNumber: "updated03" }
+                { id: "id_test_0005", itemNumber: "updated05" }
+                { id: "id_test_0009", itemNumber: "updated09" }
+                { id: "id_test_0007", itemNumber: "updated07" }
+                { id: "id_test_0008", itemNumber: "updated08" }
+            ]
+        }
+    ) {
+        items {
+            id
+            itemNumber
+        }
+    }
+}
+
+# just sanity check - should do nothign
+query afterUpdateMultiple {
+    Delivery(id: "@{ids/Delivery/1}") {
+        items {
+            id
+            itemNumber
+        }
+    }
+}

spec/regression/logistics/tests/update-empty-child-entities-list-dict.result.json

@@ -0,0 +1,30 @@
+{
+  "clearItems": {
+    "data": {
+      "updateDelivery": {
+        "items": []
+      }
+    }
+  },
+  "afterClear": {
+    "data": {
+      "Delivery": {
+        "items": []
+      }
+    }
+  },
+  "updateMultiple": {
+    "data": {
+      "updateDelivery": {
+        "items": []
+      }
+    }
+  },
+  "afterUpdateMultiple": {
+    "data": {
+      "Delivery": {
+        "items": []
+      }
+    }
+  }
+}

spec/regression/logistics/tests/update-empty-child-entities-list.context.json

@@ -0,0 +1,4 @@
+{
+  "childEntityUpdatesViaDictStrategyThreshold": 100,
+  "authRoles": ["allusers"]
+}

spec/regression/logistics/tests/update-empty-child-entities-list.graphql

@@ -0,0 +1,56 @@
+# this test makes sure that updating child entities works (even though it does nothing)
+# when the child entity list in the database is empty
+# this regression test exists because of two bugs we had in the initial dict-based implementation
+# - an AQL error when there were updates but the collection was empty
+# - updates that did not correspond to actual were persisted as new items (just without id etc.)
+
+mutation clearItems {
+    updateDelivery(
+        input: { id: "@{ids/Delivery/1}", removeItems: ["id_init_0000", "id_init_0001"] }
+    ) {
+        items {
+            id
+            itemNumber
+        }
+    }
+}
+
+# to verify it is cleared in the db
+query afterClear {
+    Delivery(id: "@{ids/Delivery/1}") {
+        items {
+            id
+            itemNumber
+        }
+    }
+}
+
+mutation updateMultiple {
+    updateDelivery(
+        input: {
+            id: "@{ids/Delivery/1}"
+            updateItems: [
+                { id: "id_test_0003", itemNumber: "updated03" }
+                { id: "id_test_0005", itemNumber: "updated05" }
+                { id: "id_test_0009", itemNumber: "updated09" }
+                { id: "id_test_0007", itemNumber: "updated07" }
+                { id: "id_test_0008", itemNumber: "updated08" }
+            ]
+        }
+    ) {
+        items {
+            id
+            itemNumber
+        }
+    }
+}
+
+# just sanity check - should do nothign
+query afterUpdateMultiple {
+    Delivery(id: "@{ids/Delivery/1}") {
+        items {
+            id
+            itemNumber
+        }
+    }
+}

spec/regression/logistics/tests/update-empty-child-entities-list.result.json

@@ -0,0 +1,30 @@
+{
+  "clearItems": {
+    "data": {
+      "updateDelivery": {
+        "items": []
+      }
+    }
+  },
+  "afterClear": {
+    "data": {
+      "Delivery": {
+        "items": []
+      }
+    }
+  },
+  "updateMultiple": {
+    "data": {
+      "updateDelivery": {
+        "items": []
+      }
+    }
+  },
+  "afterUpdateMultiple": {
+    "data": {
+      "Delivery": {
+        "items": []
+      }
+    }
+  }
+}

src/database/arangodb/aql-generator.ts

@@ -829,7 +829,9 @@ register(UpdateChildEntitiesQueryNode, (node, context) => {
         // temporary property to store the index of the child entity in the list
         aql`LET ${itemsWithIndexVar} = ${aqlExt.parenthesizeList(
             aql`FOR ${indexVar}`,
-            aql`IN 0..(LENGTH(${itemsVar}) - 1)`,
+            // 0..-1 would evaluate to [0, -1], so the ZIP would complain because the right side
+            // has more entries (2) than the left (0). RANGE() behaves the same
+            aql`IN LENGTH(${itemsVar}) > 0 ? 0..(LENGTH(${itemsVar}) - 1) : []`,
             aql`RETURN MERGE(NTH(${itemsVar}, ${indexVar}), { __index: ${indexVar} })`,
         )}`,