Initialisation

Added the packages and files for the backend server

node_modules/graphql/validation/rules/PossibleFragmentSpreadsRule.mjs

@@ -0,0 +1,73 @@
+import { inspect } from '../../jsutils/inspect.mjs';
+import { GraphQLError } from '../../error/GraphQLError.mjs';
+import { isCompositeType } from '../../type/definition.mjs';
+import { doTypesOverlap } from '../../utilities/typeComparators.mjs';
+import { typeFromAST } from '../../utilities/typeFromAST.mjs';
+
+/**
+ * Possible fragment spread
+ *
+ * A fragment spread is only valid if the type condition could ever possibly
+ * be true: if there is a non-empty intersection of the possible parent types,
+ * and possible types which pass the type condition.
+ */
+export function PossibleFragmentSpreadsRule(context) {
+  return {
+    InlineFragment(node) {
+      const fragType = context.getType();
+      const parentType = context.getParentType();
+
+      if (
+        isCompositeType(fragType) &&
+        isCompositeType(parentType) &&
+        !doTypesOverlap(context.getSchema(), fragType, parentType)
+      ) {
+        const parentTypeStr = inspect(parentType);
+        const fragTypeStr = inspect(fragType);
+        context.reportError(
+          new GraphQLError(
+            `Fragment cannot be spread here as objects of type "${parentTypeStr}" can never be of type "${fragTypeStr}".`,
+            {
+              nodes: node,
+            },
+          ),
+        );
+      }
+    },
+
+    FragmentSpread(node) {
+      const fragName = node.name.value;
+      const fragType = getFragmentType(context, fragName);
+      const parentType = context.getParentType();
+
+      if (
+        fragType &&
+        parentType &&
+        !doTypesOverlap(context.getSchema(), fragType, parentType)
+      ) {
+        const parentTypeStr = inspect(parentType);
+        const fragTypeStr = inspect(fragType);
+        context.reportError(
+          new GraphQLError(
+            `Fragment "${fragName}" cannot be spread here as objects of type "${parentTypeStr}" can never be of type "${fragTypeStr}".`,
+            {
+              nodes: node,
+            },
+          ),
+        );
+      }
+    },
+  };
+}
+
+function getFragmentType(context, name) {
+  const frag = context.getFragment(name);
+
+  if (frag) {
+    const type = typeFromAST(context.getSchema(), frag.typeCondition);
+
+    if (isCompositeType(type)) {
+      return type;
+    }
+  }
+}