flow like the river

BACK_BACK/node_modules/graphql/validation/rules/KnownDirectivesRule.js.flow

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+// @flow strict
+import inspect from '../../jsutils/inspect';
+import invariant from '../../jsutils/invariant';
+
+import { GraphQLError } from '../../error/GraphQLError';
+
+import type { ASTVisitor } from '../../language/visitor';
+import type { ASTNode, OperationTypeNode } from '../../language/ast';
+import type { DirectiveLocationEnum } from '../../language/directiveLocation';
+import { Kind } from '../../language/kinds';
+import { DirectiveLocation } from '../../language/directiveLocation';
+
+import { specifiedDirectives } from '../../type/directives';
+
+import type {
+  ValidationContext,
+  SDLValidationContext,
+} from '../ValidationContext';
+
+/**
+ * Known directives
+ *
+ * A GraphQL document is only valid if all `@directives` are known by the
+ * schema and legally positioned.
+ */
+export function KnownDirectivesRule(
+  context: ValidationContext | SDLValidationContext,
+): ASTVisitor {
+  const locationsMap = Object.create(null);
+
+  const schema = context.getSchema();
+  const definedDirectives = schema
+    ? schema.getDirectives()
+    : specifiedDirectives;
+  for (const directive of definedDirectives) {
+    locationsMap[directive.name] = directive.locations;
+  }
+
+  const astDefinitions = context.getDocument().definitions;
+  for (const def of astDefinitions) {
+    if (def.kind === Kind.DIRECTIVE_DEFINITION) {
+      locationsMap[def.name.value] = def.locations.map((name) => name.value);
+    }
+  }
+
+  return {
+    Directive(node, _key, _parent, _path, ancestors) {
+      const name = node.name.value;
+      const locations = locationsMap[name];
+
+      if (!locations) {
+        context.reportError(
+          new GraphQLError(`Unknown directive "@${name}".`, node),
+        );
+        return;
+      }
+
+      const candidateLocation = getDirectiveLocationForASTPath(ancestors);
+      if (candidateLocation && locations.indexOf(candidateLocation) === -1) {
+        context.reportError(
+          new GraphQLError(
+            `Directive "@${name}" may not be used on ${candidateLocation}.`,
+            node,
+          ),
+        );
+      }
+    },
+  };
+}
+
+function getDirectiveLocationForASTPath(
+  ancestors: $ReadOnlyArray<ASTNode | $ReadOnlyArray<ASTNode>>,
+): DirectiveLocationEnum | void {
+  const appliedTo = ancestors[ancestors.length - 1];
+  invariant(!Array.isArray(appliedTo));
+
+  switch (appliedTo.kind) {
+    case Kind.OPERATION_DEFINITION:
+      return getDirectiveLocationForOperation(appliedTo.operation);
+    case Kind.FIELD:
+      return DirectiveLocation.FIELD;
+    case Kind.FRAGMENT_SPREAD:
+      return DirectiveLocation.FRAGMENT_SPREAD;
+    case Kind.INLINE_FRAGMENT:
+      return DirectiveLocation.INLINE_FRAGMENT;
+    case Kind.FRAGMENT_DEFINITION:
+      return DirectiveLocation.FRAGMENT_DEFINITION;
+    case Kind.VARIABLE_DEFINITION:
+      return DirectiveLocation.VARIABLE_DEFINITION;
+    case Kind.SCHEMA_DEFINITION:
+    case Kind.SCHEMA_EXTENSION:
+      return DirectiveLocation.SCHEMA;
+    case Kind.SCALAR_TYPE_DEFINITION:
+    case Kind.SCALAR_TYPE_EXTENSION:
+      return DirectiveLocation.SCALAR;
+    case Kind.OBJECT_TYPE_DEFINITION:
+    case Kind.OBJECT_TYPE_EXTENSION:
+      return DirectiveLocation.OBJECT;
+    case Kind.FIELD_DEFINITION:
+      return DirectiveLocation.FIELD_DEFINITION;
+    case Kind.INTERFACE_TYPE_DEFINITION:
+    case Kind.INTERFACE_TYPE_EXTENSION:
+      return DirectiveLocation.INTERFACE;
+    case Kind.UNION_TYPE_DEFINITION:
+    case Kind.UNION_TYPE_EXTENSION:
+      return DirectiveLocation.UNION;
+    case Kind.ENUM_TYPE_DEFINITION:
+    case Kind.ENUM_TYPE_EXTENSION:
+      return DirectiveLocation.ENUM;
+    case Kind.ENUM_VALUE_DEFINITION:
+      return DirectiveLocation.ENUM_VALUE;
+    case Kind.INPUT_OBJECT_TYPE_DEFINITION:
+    case Kind.INPUT_OBJECT_TYPE_EXTENSION:
+      return DirectiveLocation.INPUT_OBJECT;
+    case Kind.INPUT_VALUE_DEFINITION: {
+      const parentNode = ancestors[ancestors.length - 3];
+      return parentNode.kind === Kind.INPUT_OBJECT_TYPE_DEFINITION
+        ? DirectiveLocation.INPUT_FIELD_DEFINITION
+        : DirectiveLocation.ARGUMENT_DEFINITION;
+    }
+  }
+}
+
+function getDirectiveLocationForOperation(
+  operation: OperationTypeNode,
+): DirectiveLocationEnum {
+  switch (operation) {
+    case 'query':
+      return DirectiveLocation.QUERY;
+    case 'mutation':
+      return DirectiveLocation.MUTATION;
+    case 'subscription':
+      return DirectiveLocation.SUBSCRIPTION;
+  }
+
+  // istanbul ignore next (Not reachable. All possible types have been considered)
+  invariant(false, 'Unexpected operation: ' + inspect((operation: empty)));
+}