fix(16.x.x.): avoid stack size limit in overlapping field rules as well as execute

src/execution/__tests__/executor-test.ts

@@ -72,6 +72,47 @@ describe('Execute: Handles basic execution tasks', () => {
     );
   });
 
+  it('works with deeply nested fragments', async () => {
+    const DataType: GraphQLObjectType = new GraphQLObjectType({
+      name: 'Query',
+      fields: () => ({
+        a: { type: GraphQLString, resolve: () => 'Apple' },
+      }),
+    });
+
+    const n = 10000;
+    const fragments = Array.from(Array(n).keys()).reduce(
+      (acc, next) =>
+        acc.concat(`\n
+        fragment X${next + 1} on Query {
+          ...X${next}
+        }
+      `),
+      '',
+    );
+
+    const document = parse(`
+      query {
+        ...X${n}
+      }
+      ${fragments}
+      fragment X0 on Query {
+        a
+      }
+    `);
+
+    const result = await execute({
+      schema: new GraphQLSchema({ query: DataType }),
+      document,
+    });
+
+    expect(result).to.deep.equal({
+      data: {
+        a: 'Apple',
+      },
+    });
+  });
+
   it('executes arbitrary code', async () => {
     const data = {
       a: () => 'Apple',

src/execution/collectFields.ts

@@ -21,6 +21,11 @@ import { typeFromAST } from '../utilities/typeFromAST';
 
 import { getDirectiveValues } from './values';
 
+interface FragmentEntry {
+  fragment: FragmentDefinitionNode;
+  runtimeType: GraphQLObjectType;
+}
+
 /**
  * Given a selectionSet, collects all of the fields and returns them.
  *
@@ -37,16 +42,34 @@ export function collectFields(
   runtimeType: GraphQLObjectType,
   selectionSet: SelectionSetNode,
 ): Map<string, ReadonlyArray<FieldNode>> {
+  const foundFragments: Array<FragmentEntry> = [];
   const fields = new Map();
+  const visited = new Set<string>();
   collectFieldsImpl(
     schema,
     fragments,
     variableValues,
     runtimeType,
     selectionSet,
     fields,
-    new Set(),
+    visited,
+    foundFragments,
   );
+
+  let entry;
+  while ((entry = foundFragments.pop()) !== undefined) {
+    collectFieldsImpl(
+      schema,
+      fragments,
+      variableValues,
+      entry.runtimeType,
+      entry.fragment.selectionSet,
+      fields,
+      visited,
+      foundFragments,
+    );
+  }
+
   return fields;
 }
 
@@ -68,6 +91,7 @@ export function collectSubfields(
   fieldNodes: ReadonlyArray<FieldNode>,
 ): Map<string, ReadonlyArray<FieldNode>> {
   const subFieldNodes = new Map();
+  const foundFragments: Array<FragmentEntry> = [];
   const visitedFragmentNames = new Set<string>();
   for (const node of fieldNodes) {
     if (node.selectionSet) {
@@ -79,9 +103,25 @@ export function collectSubfields(
         node.selectionSet,
         subFieldNodes,
         visitedFragmentNames,
+        foundFragments,
       );
     }
   }
+
+  let entry;
+  while ((entry = foundFragments.pop()) !== undefined) {
+    collectFieldsImpl(
+      schema,
+      fragments,
+      variableValues,
+      entry.runtimeType,
+      entry.fragment.selectionSet,
+      subFieldNodes,
+      visitedFragmentNames,
+      foundFragments,
+    );
+  }
+
   return subFieldNodes;
 }
 
@@ -93,6 +133,7 @@ function collectFieldsImpl(
   selectionSet: SelectionSetNode,
   fields: Map<string, Array<FieldNode>>,
   visitedFragmentNames: Set<string>,
+  foundFragments: Array<FragmentEntry>,
 ): void {
   for (const selection of selectionSet.selections) {
     switch (selection.kind) {
@@ -124,6 +165,7 @@ function collectFieldsImpl(
           selection.selectionSet,
           fields,
           visitedFragmentNames,
+          foundFragments,
         );
         break;
       }
@@ -143,15 +185,8 @@ function collectFieldsImpl(
         ) {
           continue;
         }
-        collectFieldsImpl(
-          schema,
-          fragments,
-          variableValues,
-          runtimeType,
-          fragment.selectionSet,
-          fields,
-          visitedFragmentNames,
-        );
+
+        foundFragments.push({ runtimeType, fragment });
         break;
       }
     }

src/validation/__tests__/OverlappingFieldsCanBeMergedRule-test.ts

@@ -1138,4 +1138,70 @@ describe('Validate: Overlapping fields can be merged', () => {
       },
     ]);
   });
+
+  it('does not hit stack size limits', () => {
+    const n = 10000;
+    const fragments = Array.from(Array(n).keys()).reduce(
+      (acc, next) =>
+        acc.concat(`\n
+        fragment X${next + 1} on Query {
+          ...X${next}
+        }
+      `),
+      '',
+    );
+
+    const query = `
+      query Test {
+        ...X${n}
+      }
+      ${fragments}
+      fragment X0 on Query {
+        __typename
+      }
+    `;
+
+    expectErrors(query).toDeepEqual([]);
+  });
+
+  it('finds conflicts in nested fragments', () => {
+    const n = 10000;
+    const fragments = Array.from(Array(n).keys()).reduce(
+      (acc, next) =>
+        acc.concat(`\n
+        fragment X${next + 1} on Query {
+          ...X${next}
+        }
+      `),
+      '',
+    );
+
+    const query = `
+      query Test {
+        type: conflict
+        ...X${n}
+      }
+      ${fragments}
+      fragment X0 on Query {
+        type: conflict2
+        __typename
+      }
+    `;
+    expectErrors(query).toDeepEqual([
+      {
+        locations: [
+          {
+            column: 9,
+            line: 3,
+          },
+          {
+            column: 9,
+            line: 50008,
+          },
+        ],
+        message:
+          'Fields "type" conflict because "conflict" and "conflict2" are different fields. Use different aliases on the fields to fetch both if this was intentional.',
+      },
+    ]);
+  });
 });