diff --git a/src/utilities/isValidLiteralValue.js b/src/utilities/isValidLiteralValue.js
index 6109218f11..719a2c24aa 100644
--- a/src/utilities/isValidLiteralValue.js
+++ b/src/utilities/isValidLiteralValue.js
@@ -15,7 +15,7 @@ import { visit, visitWithTypeInfo } from '../language/visitor';
 import type { GraphQLInputType } from '../type/definition';
 import { GraphQLSchema } from '../type/schema';
 import { ValuesOfCorrectType } from '../validation/rules/ValuesOfCorrectType';
-import { ValidationContext } from '../validation/validate';
+import ValidationContext from '../validation/ValidationContext';
 
 /**
  * Utility which determines if a value literal node is valid for an input type.
diff --git a/src/validation/ValidationContext.js b/src/validation/ValidationContext.js
new file mode 100644
index 0000000000..98f2e21cc4
--- /dev/null
+++ b/src/validation/ValidationContext.js
@@ -0,0 +1,221 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict
+ */
+
+import type { ObjMap } from '../jsutils/ObjMap';
+import { GraphQLError } from '../error';
+import { visit, visitWithTypeInfo } from '../language/visitor';
+import { Kind } from '../language/kinds';
+import type {
+  DocumentNode,
+  OperationDefinitionNode,
+  VariableNode,
+  SelectionSetNode,
+  FragmentSpreadNode,
+  FragmentDefinitionNode,
+} from '../language/ast';
+import { GraphQLSchema } from '../type/schema';
+import type {
+  GraphQLInputType,
+  GraphQLOutputType,
+  GraphQLCompositeType,
+  GraphQLField,
+  GraphQLArgument,
+} from '../type/definition';
+import type { GraphQLDirective } from '../type/directives';
+import { TypeInfo } from '../utilities/TypeInfo';
+
+type NodeWithSelectionSet = OperationDefinitionNode | FragmentDefinitionNode;
+type VariableUsage = { node: VariableNode, type: ?GraphQLInputType };
+
+/**
+ * An instance of this class is passed as the "this" context to all validators,
+ * allowing access to commonly useful contextual information from within a
+ * validation rule.
+ */
+export default class ValidationContext {
+  _schema: GraphQLSchema;
+  _ast: DocumentNode;
+  _typeInfo: TypeInfo;
+  _errors: Array<GraphQLError>;
+  _fragments: ObjMap<FragmentDefinitionNode>;
+  _fragmentSpreads: Map<SelectionSetNode, $ReadOnlyArray<FragmentSpreadNode>>;
+  _recursivelyReferencedFragments: Map<
+    OperationDefinitionNode,
+    $ReadOnlyArray<FragmentDefinitionNode>,
+  >;
+  _variableUsages: Map<NodeWithSelectionSet, $ReadOnlyArray<VariableUsage>>;
+  _recursiveVariableUsages: Map<
+    OperationDefinitionNode,
+    $ReadOnlyArray<VariableUsage>,
+  >;
+
+  constructor(
+    schema: GraphQLSchema,
+    ast: DocumentNode,
+    typeInfo: TypeInfo,
+  ): void {
+    this._schema = schema;
+    this._ast = ast;
+    this._typeInfo = typeInfo;
+    this._errors = [];
+    this._fragmentSpreads = new Map();
+    this._recursivelyReferencedFragments = new Map();
+    this._variableUsages = new Map();
+    this._recursiveVariableUsages = new Map();
+  }
+
+  reportError(error: GraphQLError): void {
+    this._errors.push(error);
+  }
+
+  getErrors(): $ReadOnlyArray<GraphQLError> {
+    return this._errors;
+  }
+
+  getSchema(): GraphQLSchema {
+    return this._schema;
+  }
+
+  getDocument(): DocumentNode {
+    return this._ast;
+  }
+
+  getFragment(name: string): ?FragmentDefinitionNode {
+    let fragments = this._fragments;
+    if (!fragments) {
+      this._fragments = fragments = this.getDocument().definitions.reduce(
+        (frags, statement) => {
+          if (statement.kind === Kind.FRAGMENT_DEFINITION) {
+            frags[statement.name.value] = statement;
+          }
+          return frags;
+        },
+        Object.create(null),
+      );
+    }
+    return fragments[name];
+  }
+
+  getFragmentSpreads(
+    node: SelectionSetNode,
+  ): $ReadOnlyArray<FragmentSpreadNode> {
+    let spreads = this._fragmentSpreads.get(node);
+    if (!spreads) {
+      spreads = [];
+      const setsToVisit: Array<SelectionSetNode> = [node];
+      while (setsToVisit.length !== 0) {
+        const set = setsToVisit.pop();
+        for (let i = 0; i < set.selections.length; i++) {
+          const selection = set.selections[i];
+          if (selection.kind === Kind.FRAGMENT_SPREAD) {
+            spreads.push(selection);
+          } else if (selection.selectionSet) {
+            setsToVisit.push(selection.selectionSet);
+          }
+        }
+      }
+      this._fragmentSpreads.set(node, spreads);
+    }
+    return spreads;
+  }
+
+  getRecursivelyReferencedFragments(
+    operation: OperationDefinitionNode,
+  ): $ReadOnlyArray<FragmentDefinitionNode> {
+    let fragments = this._recursivelyReferencedFragments.get(operation);
+    if (!fragments) {
+      fragments = [];
+      const collectedNames = Object.create(null);
+      const nodesToVisit: Array<SelectionSetNode> = [operation.selectionSet];
+      while (nodesToVisit.length !== 0) {
+        const node = nodesToVisit.pop();
+        const spreads = this.getFragmentSpreads(node);
+        for (let i = 0; i < spreads.length; i++) {
+          const fragName = spreads[i].name.value;
+          if (collectedNames[fragName] !== true) {
+            collectedNames[fragName] = true;
+            const fragment = this.getFragment(fragName);
+            if (fragment) {
+              fragments.push(fragment);
+              nodesToVisit.push(fragment.selectionSet);
+            }
+          }
+        }
+      }
+      this._recursivelyReferencedFragments.set(operation, fragments);
+    }
+    return fragments;
+  }
+
+  getVariableUsages(node: NodeWithSelectionSet): $ReadOnlyArray<VariableUsage> {
+    let usages = this._variableUsages.get(node);
+    if (!usages) {
+      const newUsages = [];
+      const typeInfo = new TypeInfo(this._schema);
+      visit(
+        node,
+        visitWithTypeInfo(typeInfo, {
+          VariableDefinition: () => false,
+          Variable(variable) {
+            newUsages.push({ node: variable, type: typeInfo.getInputType() });
+          },
+        }),
+      );
+      usages = newUsages;
+      this._variableUsages.set(node, usages);
+    }
+    return usages;
+  }
+
+  getRecursiveVariableUsages(
+    operation: OperationDefinitionNode,
+  ): $ReadOnlyArray<VariableUsage> {
+    let usages = this._recursiveVariableUsages.get(operation);
+    if (!usages) {
+      usages = this.getVariableUsages(operation);
+      const fragments = this.getRecursivelyReferencedFragments(operation);
+      for (let i = 0; i < fragments.length; i++) {
+        Array.prototype.push.apply(
+          usages,
+          this.getVariableUsages(fragments[i]),
+        );
+      }
+      this._recursiveVariableUsages.set(operation, usages);
+    }
+    return usages;
+  }
+
+  getType(): ?GraphQLOutputType {
+    return this._typeInfo.getType();
+  }
+
+  getParentType(): ?GraphQLCompositeType {
+    return this._typeInfo.getParentType();
+  }
+
+  getInputType(): ?GraphQLInputType {
+    return this._typeInfo.getInputType();
+  }
+
+  getParentInputType(): ?GraphQLInputType {
+    return this._typeInfo.getParentInputType();
+  }
+
+  getFieldDef(): ?GraphQLField<*, *> {
+    return this._typeInfo.getFieldDef();
+  }
+
+  getDirective(): ?GraphQLDirective {
+    return this._typeInfo.getDirective();
+  }
+
+  getArgument(): ?GraphQLArgument {
+    return this._typeInfo.getArgument();
+  }
+}
diff --git a/src/validation/index.js b/src/validation/index.js
index 01b7e47e2f..6d33dce405 100644
--- a/src/validation/index.js
+++ b/src/validation/index.js
@@ -7,7 +7,11 @@
  * @flow strict
  */
 
-export { validate, ValidationContext } from './validate';
+export { validate } from './validate';
+
+// https://github.com/tc39/proposal-export-default-from
+import ValidationContext from './ValidationContext';
+export { ValidationContext };
 
 export { specifiedRules } from './specifiedRules';
 
diff --git a/src/validation/rules/ExecutableDefinitions.js b/src/validation/rules/ExecutableDefinitions.js
index 6f8c5ec6fa..b7b2d9a382 100644
--- a/src/validation/rules/ExecutableDefinitions.js
+++ b/src/validation/rules/ExecutableDefinitions.js
@@ -7,7 +7,7 @@
  * @flow strict
  */
 
-import type { ValidationContext } from '../index';
+import type ValidationContext from '../ValidationContext';
 import { GraphQLError } from '../../error';
 import { Kind } from '../../language/kinds';
 import type { ASTVisitor } from '../../language/visitor';
diff --git a/src/validation/rules/FieldsOnCorrectType.js b/src/validation/rules/FieldsOnCorrectType.js
index c779a4270e..168fc1bca7 100644
--- a/src/validation/rules/FieldsOnCorrectType.js
+++ b/src/validation/rules/FieldsOnCorrectType.js
@@ -7,7 +7,7 @@
  * @flow strict
  */
 
-import type { ValidationContext } from '../index';
+import type ValidationContext from '../ValidationContext';
 import { GraphQLError } from '../../error';
 import suggestionList from '../../jsutils/suggestionList';
 import quotedOrList from '../../jsutils/quotedOrList';
diff --git a/src/validation/rules/FragmentsOnCompositeTypes.js b/src/validation/rules/FragmentsOnCompositeTypes.js
index 83378629e4..ea03734d85 100644
--- a/src/validation/rules/FragmentsOnCompositeTypes.js
+++ b/src/validation/rules/FragmentsOnCompositeTypes.js
@@ -7,7 +7,7 @@
  * @flow strict
  */
 
-import type { ValidationContext } from '../index';
+import type ValidationContext from '../ValidationContext';
 import { GraphQLError } from '../../error';
 import { print } from '../../language/printer';
 import type { ASTVisitor } from '../../language/visitor';
diff --git a/src/validation/rules/KnownArgumentNames.js b/src/validation/rules/KnownArgumentNames.js
index b2b77f4834..a775880c21 100644
--- a/src/validation/rules/KnownArgumentNames.js
+++ b/src/validation/rules/KnownArgumentNames.js
@@ -7,7 +7,7 @@
  * @flow strict
  */
 
-import type { ValidationContext } from '../index';
+import type ValidationContext from '../ValidationContext';
 import { GraphQLError } from '../../error';
 import type { ASTVisitor } from '../../language/visitor';
 import suggestionList from '../../jsutils/suggestionList';
diff --git a/src/validation/rules/KnownDirectives.js b/src/validation/rules/KnownDirectives.js
index 61ce36e48a..9972ce8acf 100644
--- a/src/validation/rules/KnownDirectives.js
+++ b/src/validation/rules/KnownDirectives.js
@@ -7,7 +7,7 @@
  * @flow strict
  */
 
-import type { ValidationContext } from '../index';
+import type ValidationContext from '../ValidationContext';
 import { GraphQLError } from '../../error';
 import find from '../../jsutils/find';
 import { Kind } from '../../language/kinds';
diff --git a/src/validation/rules/KnownFragmentNames.js b/src/validation/rules/KnownFragmentNames.js
index 33db878324..c3893415f0 100644
--- a/src/validation/rules/KnownFragmentNames.js
+++ b/src/validation/rules/KnownFragmentNames.js
@@ -7,7 +7,7 @@
  * @flow strict
  */
 
-import type { ValidationContext } from '../index';
+import type ValidationContext from '../ValidationContext';
 import { GraphQLError } from '../../error';
 import type { ASTVisitor } from '../../language/visitor';
 
diff --git a/src/validation/rules/KnownTypeNames.js b/src/validation/rules/KnownTypeNames.js
index 6da7c2d0e7..8ad1b7775f 100644
--- a/src/validation/rules/KnownTypeNames.js
+++ b/src/validation/rules/KnownTypeNames.js
@@ -7,7 +7,7 @@
  * @flow strict
  */
 
-import type { ValidationContext } from '../index';
+import type ValidationContext from '../ValidationContext';
 import { GraphQLError } from '../../error';
 import suggestionList from '../../jsutils/suggestionList';
 import quotedOrList from '../../jsutils/quotedOrList';
diff --git a/src/validation/rules/LoneAnonymousOperation.js b/src/validation/rules/LoneAnonymousOperation.js
index 9dbe41a8a4..745de201cb 100644
--- a/src/validation/rules/LoneAnonymousOperation.js
+++ b/src/validation/rules/LoneAnonymousOperation.js
@@ -7,7 +7,7 @@
  * @flow strict
  */
 
-import type { ValidationContext } from '../index';
+import type ValidationContext from '../ValidationContext';
 import { GraphQLError } from '../../error';
 import { Kind } from '../../language/kinds';
 import type { ASTVisitor } from '../../language/visitor';
diff --git a/src/validation/rules/NoFragmentCycles.js b/src/validation/rules/NoFragmentCycles.js
index 2c7891aa3a..0a51122759 100644
--- a/src/validation/rules/NoFragmentCycles.js
+++ b/src/validation/rules/NoFragmentCycles.js
@@ -7,7 +7,7 @@
  * @flow strict
  */
 
-import type { ValidationContext } from '../index';
+import type ValidationContext from '../ValidationContext';
 import { GraphQLError } from '../../error';
 import type { FragmentDefinitionNode } from '../../language/ast';
 import type { ASTVisitor } from '../../language/visitor';
diff --git a/src/validation/rules/NoUndefinedVariables.js b/src/validation/rules/NoUndefinedVariables.js
index 0fdcac4a01..d74a49265b 100644
--- a/src/validation/rules/NoUndefinedVariables.js
+++ b/src/validation/rules/NoUndefinedVariables.js
@@ -7,7 +7,7 @@
  * @flow strict
  */
 
-import type { ValidationContext } from '../index';
+import type ValidationContext from '../ValidationContext';
 import { GraphQLError } from '../../error';
 import type { ASTVisitor } from '../../language/visitor';
 
diff --git a/src/validation/rules/NoUnusedFragments.js b/src/validation/rules/NoUnusedFragments.js
index 5a0902e772..4e2b6e2b7f 100644
--- a/src/validation/rules/NoUnusedFragments.js
+++ b/src/validation/rules/NoUnusedFragments.js
@@ -7,7 +7,7 @@
  * @flow strict
  */
 
-import type { ValidationContext } from '../index';
+import type ValidationContext from '../ValidationContext';
 import { GraphQLError } from '../../error';
 import type { ASTVisitor } from '../../language/visitor';
 
diff --git a/src/validation/rules/NoUnusedVariables.js b/src/validation/rules/NoUnusedVariables.js
index 505abd04a6..c5637e22db 100644
--- a/src/validation/rules/NoUnusedVariables.js
+++ b/src/validation/rules/NoUnusedVariables.js
@@ -7,7 +7,7 @@
  * @flow strict
  */
 
-import type { ValidationContext } from '../index';
+import type ValidationContext from '../ValidationContext';
 import { GraphQLError } from '../../error';
 import type { ASTVisitor } from '../../language/visitor';
 
diff --git a/src/validation/rules/OverlappingFieldsCanBeMerged.js b/src/validation/rules/OverlappingFieldsCanBeMerged.js
index b37f2f4156..6dea9df741 100644
--- a/src/validation/rules/OverlappingFieldsCanBeMerged.js
+++ b/src/validation/rules/OverlappingFieldsCanBeMerged.js
@@ -7,7 +7,7 @@
  * @flow strict
  */
 
-import type { ValidationContext } from '../index';
+import type ValidationContext from '../ValidationContext';
 import { GraphQLError } from '../../error';
 import find from '../../jsutils/find';
 import type { ObjMap } from '../../jsutils/ObjMap';
diff --git a/src/validation/rules/PossibleFragmentSpreads.js b/src/validation/rules/PossibleFragmentSpreads.js
index 614b32c564..31bca238d8 100644
--- a/src/validation/rules/PossibleFragmentSpreads.js
+++ b/src/validation/rules/PossibleFragmentSpreads.js
@@ -7,7 +7,7 @@
  * @flow strict
  */
 
-import type { ValidationContext } from '../index';
+import type ValidationContext from '../ValidationContext';
 import { GraphQLError } from '../../error';
 import type { ASTVisitor } from '../../language/visitor';
 import { doTypesOverlap } from '../../utilities/typeComparators';
diff --git a/src/validation/rules/ProvidedNonNullArguments.js b/src/validation/rules/ProvidedNonNullArguments.js
index cbefff5d90..5eda68eb32 100644
--- a/src/validation/rules/ProvidedNonNullArguments.js
+++ b/src/validation/rules/ProvidedNonNullArguments.js
@@ -7,7 +7,7 @@
  * @flow strict
  */
 
-import type { ValidationContext } from '../index';
+import type ValidationContext from '../ValidationContext';
 import { GraphQLError } from '../../error';
 import keyMap from '../../jsutils/keyMap';
 import { isNonNullType } from '../../type/definition';
diff --git a/src/validation/rules/ScalarLeafs.js b/src/validation/rules/ScalarLeafs.js
index 22fa642a6a..8f2291c3c3 100644
--- a/src/validation/rules/ScalarLeafs.js
+++ b/src/validation/rules/ScalarLeafs.js
@@ -7,7 +7,7 @@
  * @flow strict
  */
 
-import type { ValidationContext } from '../index';
+import type ValidationContext from '../ValidationContext';
 import { GraphQLError } from '../../error';
 import type { FieldNode } from '../../language/ast';
 import { getNamedType, isLeafType } from '../../type/definition';
diff --git a/src/validation/rules/SingleFieldSubscriptions.js b/src/validation/rules/SingleFieldSubscriptions.js
index af0650baaf..622e6fc5f8 100644
--- a/src/validation/rules/SingleFieldSubscriptions.js
+++ b/src/validation/rules/SingleFieldSubscriptions.js
@@ -7,7 +7,7 @@
  * @flow strict
  */
 
-import type { ValidationContext } from '../index';
+import type ValidationContext from '../ValidationContext';
 import { GraphQLError } from '../../error';
 import type { OperationDefinitionNode } from '../../language/ast';
 import type { ASTVisitor } from '../../language/visitor';
diff --git a/src/validation/rules/UniqueArgumentNames.js b/src/validation/rules/UniqueArgumentNames.js
index 31c4af7099..0516401079 100644
--- a/src/validation/rules/UniqueArgumentNames.js
+++ b/src/validation/rules/UniqueArgumentNames.js
@@ -7,7 +7,7 @@
  * @flow strict
  */
 
-import type { ValidationContext } from '../index';
+import type ValidationContext from '../ValidationContext';
 import { GraphQLError } from '../../error';
 import type { ASTVisitor } from '../../language/visitor';
 
diff --git a/src/validation/rules/UniqueDirectivesPerLocation.js b/src/validation/rules/UniqueDirectivesPerLocation.js
index 3bc6fe18f4..fb143d2a15 100644
--- a/src/validation/rules/UniqueDirectivesPerLocation.js
+++ b/src/validation/rules/UniqueDirectivesPerLocation.js
@@ -7,7 +7,7 @@
  * @flow strict
  */
 
-import type { ValidationContext } from '../index';
+import type ValidationContext from '../ValidationContext';
 import { GraphQLError } from '../../error';
 import type { DirectiveNode } from '../../language/ast';
 import type { ASTVisitor } from '../../language/visitor';
diff --git a/src/validation/rules/UniqueFragmentNames.js b/src/validation/rules/UniqueFragmentNames.js
index eab401ffb6..1a55cd7967 100644
--- a/src/validation/rules/UniqueFragmentNames.js
+++ b/src/validation/rules/UniqueFragmentNames.js
@@ -7,7 +7,7 @@
  * @flow strict
  */
 
-import type { ValidationContext } from '../index';
+import type ValidationContext from '../ValidationContext';
 import { GraphQLError } from '../../error';
 import type { ASTVisitor } from '../../language/visitor';
 
diff --git a/src/validation/rules/UniqueInputFieldNames.js b/src/validation/rules/UniqueInputFieldNames.js
index 96e39bea87..9290b60305 100644
--- a/src/validation/rules/UniqueInputFieldNames.js
+++ b/src/validation/rules/UniqueInputFieldNames.js
@@ -7,7 +7,7 @@
  * @flow strict
  */
 
-import type { ValidationContext } from '../index';
+import type ValidationContext from '../ValidationContext';
 import { GraphQLError } from '../../error';
 import type { ASTVisitor } from '../../language/visitor';
 
diff --git a/src/validation/rules/UniqueOperationNames.js b/src/validation/rules/UniqueOperationNames.js
index 04fc7addc1..765b0b80f4 100644
--- a/src/validation/rules/UniqueOperationNames.js
+++ b/src/validation/rules/UniqueOperationNames.js
@@ -7,7 +7,7 @@
  * @flow strict
  */
 
-import type { ValidationContext } from '../index';
+import type ValidationContext from '../ValidationContext';
 import { GraphQLError } from '../../error';
 import type { ASTVisitor } from '../../language/visitor';
 
diff --git a/src/validation/rules/UniqueVariableNames.js b/src/validation/rules/UniqueVariableNames.js
index a6d2e7cea8..90f84483ec 100644
--- a/src/validation/rules/UniqueVariableNames.js
+++ b/src/validation/rules/UniqueVariableNames.js
@@ -7,7 +7,7 @@
  * @flow strict
  */
 
-import type { ValidationContext } from '../index';
+import type ValidationContext from '../ValidationContext';
 import type { VariableDefinitionNode } from '../../language/ast';
 import { GraphQLError } from '../../error';
 import type { ASTVisitor } from '../../language/visitor';
diff --git a/src/validation/rules/ValuesOfCorrectType.js b/src/validation/rules/ValuesOfCorrectType.js
index 532b670b8f..d440a4ec3e 100644
--- a/src/validation/rules/ValuesOfCorrectType.js
+++ b/src/validation/rules/ValuesOfCorrectType.js
@@ -7,7 +7,7 @@
  * @flow strict
  */
 
-import type { ValidationContext } from '../index';
+import type ValidationContext from '../ValidationContext';
 import { GraphQLError } from '../../error';
 import type { ValueNode } from '../../language/ast';
 import { print } from '../../language/printer';
diff --git a/src/validation/rules/VariablesAreInputTypes.js b/src/validation/rules/VariablesAreInputTypes.js
index 74bbf663d7..b152025c02 100644
--- a/src/validation/rules/VariablesAreInputTypes.js
+++ b/src/validation/rules/VariablesAreInputTypes.js
@@ -7,7 +7,7 @@
  * @flow strict
  */
 
-import type { ValidationContext } from '../index';
+import type ValidationContext from '../ValidationContext';
 import { GraphQLError } from '../../error';
 import type { VariableDefinitionNode } from '../../language/ast';
 import { print } from '../../language/printer';
diff --git a/src/validation/rules/VariablesDefaultValueAllowed.js b/src/validation/rules/VariablesDefaultValueAllowed.js
index 2b93963032..019b55e9fe 100644
--- a/src/validation/rules/VariablesDefaultValueAllowed.js
+++ b/src/validation/rules/VariablesDefaultValueAllowed.js
@@ -7,7 +7,7 @@
  * @flow strict
  */
 
-import type { ValidationContext } from '../index';
+import type ValidationContext from '../ValidationContext';
 import { GraphQLError } from '../../error';
 import type { ASTVisitor } from '../../language/visitor';
 import { isNonNullType } from '../../type/definition';
diff --git a/src/validation/rules/VariablesInAllowedPosition.js b/src/validation/rules/VariablesInAllowedPosition.js
index e7214ed44e..47073e5757 100644
--- a/src/validation/rules/VariablesInAllowedPosition.js
+++ b/src/validation/rules/VariablesInAllowedPosition.js
@@ -7,7 +7,7 @@
  * @flow strict
  */
 
-import type { ValidationContext } from '../index';
+import type ValidationContext from '../ValidationContext';
 import { GraphQLError } from '../../error';
 import type { ASTVisitor } from '../../language/visitor';
 import { isNonNullType } from '../../type/definition';
diff --git a/src/validation/specifiedRules.js b/src/validation/specifiedRules.js
index 48268e5dc6..b5e45f90cb 100644
--- a/src/validation/specifiedRules.js
+++ b/src/validation/specifiedRules.js
@@ -88,7 +88,7 @@ import { OverlappingFieldsCanBeMerged } from './rules/OverlappingFieldsCanBeMerg
 // Spec Section: "Input Object Field Uniqueness"
 import { UniqueInputFieldNames } from './rules/UniqueInputFieldNames';
 
-import type { ValidationContext } from './index';
+import type ValidationContext from './ValidationContext';
 
 /**
  * This set includes all validation rules defined by the GraphQL spec.
diff --git a/src/validation/validate.js b/src/validation/validate.js
index 09a7494c8d..61213f8b86 100644
--- a/src/validation/validate.js
+++ b/src/validation/validate.js
@@ -8,31 +8,15 @@
  */
 
 import invariant from '../jsutils/invariant';
-import type { ObjMap } from '../jsutils/ObjMap';
 import { GraphQLError } from '../error';
 import { visit, visitInParallel, visitWithTypeInfo } from '../language/visitor';
-import { Kind } from '../language/kinds';
-import type {
-  DocumentNode,
-  OperationDefinitionNode,
-  VariableNode,
-  SelectionSetNode,
-  FragmentSpreadNode,
-  FragmentDefinitionNode,
-} from '../language/ast';
+import type { DocumentNode } from '../language/ast';
 import type { ASTVisitor } from '../language/visitor';
 import { GraphQLSchema } from '../type/schema';
-import type {
-  GraphQLInputType,
-  GraphQLOutputType,
-  GraphQLCompositeType,
-  GraphQLField,
-  GraphQLArgument,
-} from '../type/definition';
-import type { GraphQLDirective } from '../type/directives';
 import { assertValidSchema } from '../type/validate';
 import { TypeInfo } from '../utilities/TypeInfo';
 import { specifiedRules } from './specifiedRules';
+import ValidationContext from './ValidationContext';
 
 /**
  * Implements the "Validation" section of the spec.
@@ -85,193 +69,3 @@ function visitUsingRules(
   visit(documentAST, visitWithTypeInfo(typeInfo, visitInParallel(visitors)));
   return context.getErrors();
 }
-
-type NodeWithSelectionSet = OperationDefinitionNode | FragmentDefinitionNode;
-type VariableUsage = { node: VariableNode, type: ?GraphQLInputType };
-
-/**
- * An instance of this class is passed as the "this" context to all validators,
- * allowing access to commonly useful contextual information from within a
- * validation rule.
- */
-export class ValidationContext {
-  _schema: GraphQLSchema;
-  _ast: DocumentNode;
-  _typeInfo: TypeInfo;
-  _errors: Array<GraphQLError>;
-  _fragments: ObjMap<FragmentDefinitionNode>;
-  _fragmentSpreads: Map<SelectionSetNode, $ReadOnlyArray<FragmentSpreadNode>>;
-  _recursivelyReferencedFragments: Map<
-    OperationDefinitionNode,
-    $ReadOnlyArray<FragmentDefinitionNode>,
-  >;
-  _variableUsages: Map<NodeWithSelectionSet, $ReadOnlyArray<VariableUsage>>;
-  _recursiveVariableUsages: Map<
-    OperationDefinitionNode,
-    $ReadOnlyArray<VariableUsage>,
-  >;
-
-  constructor(
-    schema: GraphQLSchema,
-    ast: DocumentNode,
-    typeInfo: TypeInfo,
-  ): void {
-    this._schema = schema;
-    this._ast = ast;
-    this._typeInfo = typeInfo;
-    this._errors = [];
-    this._fragmentSpreads = new Map();
-    this._recursivelyReferencedFragments = new Map();
-    this._variableUsages = new Map();
-    this._recursiveVariableUsages = new Map();
-  }
-
-  reportError(error: GraphQLError): void {
-    this._errors.push(error);
-  }
-
-  getErrors(): $ReadOnlyArray<GraphQLError> {
-    return this._errors;
-  }
-
-  getSchema(): GraphQLSchema {
-    return this._schema;
-  }
-
-  getDocument(): DocumentNode {
-    return this._ast;
-  }
-
-  getFragment(name: string): ?FragmentDefinitionNode {
-    let fragments = this._fragments;
-    if (!fragments) {
-      this._fragments = fragments = this.getDocument().definitions.reduce(
-        (frags, statement) => {
-          if (statement.kind === Kind.FRAGMENT_DEFINITION) {
-            frags[statement.name.value] = statement;
-          }
-          return frags;
-        },
-        Object.create(null),
-      );
-    }
-    return fragments[name];
-  }
-
-  getFragmentSpreads(
-    node: SelectionSetNode,
-  ): $ReadOnlyArray<FragmentSpreadNode> {
-    let spreads = this._fragmentSpreads.get(node);
-    if (!spreads) {
-      spreads = [];
-      const setsToVisit: Array<SelectionSetNode> = [node];
-      while (setsToVisit.length !== 0) {
-        const set = setsToVisit.pop();
-        for (let i = 0; i < set.selections.length; i++) {
-          const selection = set.selections[i];
-          if (selection.kind === Kind.FRAGMENT_SPREAD) {
-            spreads.push(selection);
-          } else if (selection.selectionSet) {
-            setsToVisit.push(selection.selectionSet);
-          }
-        }
-      }
-      this._fragmentSpreads.set(node, spreads);
-    }
-    return spreads;
-  }
-
-  getRecursivelyReferencedFragments(
-    operation: OperationDefinitionNode,
-  ): $ReadOnlyArray<FragmentDefinitionNode> {
-    let fragments = this._recursivelyReferencedFragments.get(operation);
-    if (!fragments) {
-      fragments = [];
-      const collectedNames = Object.create(null);
-      const nodesToVisit: Array<SelectionSetNode> = [operation.selectionSet];
-      while (nodesToVisit.length !== 0) {
-        const node = nodesToVisit.pop();
-        const spreads = this.getFragmentSpreads(node);
-        for (let i = 0; i < spreads.length; i++) {
-          const fragName = spreads[i].name.value;
-          if (collectedNames[fragName] !== true) {
-            collectedNames[fragName] = true;
-            const fragment = this.getFragment(fragName);
-            if (fragment) {
-              fragments.push(fragment);
-              nodesToVisit.push(fragment.selectionSet);
-            }
-          }
-        }
-      }
-      this._recursivelyReferencedFragments.set(operation, fragments);
-    }
-    return fragments;
-  }
-
-  getVariableUsages(node: NodeWithSelectionSet): $ReadOnlyArray<VariableUsage> {
-    let usages = this._variableUsages.get(node);
-    if (!usages) {
-      const newUsages = [];
-      const typeInfo = new TypeInfo(this._schema);
-      visit(
-        node,
-        visitWithTypeInfo(typeInfo, {
-          VariableDefinition: () => false,
-          Variable(variable) {
-            newUsages.push({ node: variable, type: typeInfo.getInputType() });
-          },
-        }),
-      );
-      usages = newUsages;
-      this._variableUsages.set(node, usages);
-    }
-    return usages;
-  }
-
-  getRecursiveVariableUsages(
-    operation: OperationDefinitionNode,
-  ): $ReadOnlyArray<VariableUsage> {
-    let usages = this._recursiveVariableUsages.get(operation);
-    if (!usages) {
-      usages = this.getVariableUsages(operation);
-      const fragments = this.getRecursivelyReferencedFragments(operation);
-      for (let i = 0; i < fragments.length; i++) {
-        Array.prototype.push.apply(
-          usages,
-          this.getVariableUsages(fragments[i]),
-        );
-      }
-      this._recursiveVariableUsages.set(operation, usages);
-    }
-    return usages;
-  }
-
-  getType(): ?GraphQLOutputType {
-    return this._typeInfo.getType();
-  }
-
-  getParentType(): ?GraphQLCompositeType {
-    return this._typeInfo.getParentType();
-  }
-
-  getInputType(): ?GraphQLInputType {
-    return this._typeInfo.getInputType();
-  }
-
-  getParentInputType(): ?GraphQLInputType {
-    return this._typeInfo.getParentInputType();
-  }
-
-  getFieldDef(): ?GraphQLField<*, *> {
-    return this._typeInfo.getFieldDef();
-  }
-
-  getDirective(): ?GraphQLDirective {
-    return this._typeInfo.getDirective();
-  }
-
-  getArgument(): ?GraphQLArgument {
-    return this._typeInfo.getArgument();
-  }
-}