Initial Save

node_modules/graphql/validation/rules/PossibleFragmentSpreads.js.flow

@@ -0,0 +1,93 @@
+// @flow strict
+
+import inspect from '../../jsutils/inspect';
+
+import { GraphQLError } from '../../error/GraphQLError';
+
+import { type ASTVisitor } from '../../language/visitor';
+
+import { isCompositeType } from '../../type/definition';
+
+import { typeFromAST } from '../../utilities/typeFromAST';
+import { doTypesOverlap } from '../../utilities/typeComparators';
+
+import { type ValidationContext } from '../ValidationContext';
+
+export function typeIncompatibleSpreadMessage(
+  fragName: string,
+  parentType: string,
+  fragType: string,
+): string {
+  return `Fragment "${fragName}" cannot be spread here as objects of type "${parentType}" can never be of type "${fragType}".`;
+}
+
+export function typeIncompatibleAnonSpreadMessage(
+  parentType: string,
+  fragType: string,
+): string {
+  return `Fragment cannot be spread here as objects of type "${parentType}" can never be of type "${fragType}".`;
+}
+
+/**
+ * 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 PossibleFragmentSpreads(
+  context: ValidationContext,
+): ASTVisitor {
+  return {
+    InlineFragment(node) {
+      const fragType = context.getType();
+      const parentType = context.getParentType();
+      if (
+        isCompositeType(fragType) &&
+        isCompositeType(parentType) &&
+        !doTypesOverlap(context.getSchema(), fragType, parentType)
+      ) {
+        context.reportError(
+          new GraphQLError(
+            typeIncompatibleAnonSpreadMessage(
+              inspect(parentType),
+              inspect(fragType),
+            ),
+            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)
+      ) {
+        context.reportError(
+          new GraphQLError(
+            typeIncompatibleSpreadMessage(
+              fragName,
+              inspect(parentType),
+              inspect(fragType),
+            ),
+            node,
+          ),
+        );
+      }
+    },
+  };
+}
+
+function getFragmentType(context, name) {
+  const frag = context.getFragment(name);
+  if (frag) {
+    const type = typeFromAST(context.getSchema(), frag.typeCondition);
+    if (isCompositeType(type)) {
+      return type;
+    }
+  }
+}