feat(delegate): deduplicate upstream documents

.changeset/blue-camels-camp.md

@@ -0,0 +1,5 @@
+---
+"@graphql-tools/delegate": patch
+---
+
+Deduplicate fields, inline fragment spreads and fragment spreads before sending the operation document to the subschema

packages/batch-execute/src/mergeRequests.ts

@@ -14,7 +14,11 @@ import {
   VariableNode,
   visit,
 } from 'graphql';
-import { ExecutionRequest, getOperationASTFromRequest } from '@graphql-tools/utils';
+import {
+  ExecutionRequest,
+  getOperationASTFromRequest,
+  SelectionSetBuilder,
+} from '@graphql-tools/utils';
 import { createPrefix } from './prefix.js';
 
 /**
@@ -60,7 +64,7 @@ export function mergeRequests(
 ): ExecutionRequest {
   const mergedVariables: Record<string, any> = Object.create(null);
   const mergedVariableDefinitions: Array<VariableDefinitionNode> = [];
-  const mergedSelections: Array<SelectionNode> = [];
+  const mergedSelections = new SelectionSetBuilder();
   const mergedFragmentDefinitions: Array<FragmentDefinitionNode> = [];
   let mergedExtensions: Record<string, any> = Object.create(null);
 
@@ -70,7 +74,9 @@ export function mergeRequests(
 
     for (const def of prefixedRequests.document.definitions) {
       if (isOperationDefinition(def)) {
-        mergedSelections.push(...def.selectionSet.selections);
+        for (const selection of def.selectionSet.selections) {
+          mergedSelections.addSelection(selection);
+        }
         if (def.variableDefinitions) {
           mergedVariableDefinitions.push(...def.variableDefinitions);
         }
@@ -90,10 +96,7 @@ export function mergeRequests(
     kind: Kind.OPERATION_DEFINITION,
     operation: operationType,
     variableDefinitions: mergedVariableDefinitions,
-    selectionSet: {
-      kind: Kind.SELECTION_SET,
-      selections: mergedSelections,
-    },
+    selectionSet: mergedSelections.getSelectionSet(),
   };
   const operationName = firstRequest.operationName ?? firstRequest.info?.operation?.name?.value;
   if (operationName) {

packages/batch-execute/tests/batchExecute.test.ts

@@ -126,8 +126,7 @@ describe('batch execution', () => {
     ])) as ExecutionResult[];
 
     const squishedDoc = executorDocument?.replace(/\s+/g, ' ');
-    expect(squishedDoc).toMatch('... on Query { _0_field1: field1 }');
-    expect(squishedDoc).toMatch('... on Query { _1_field2: field2 }');
+    expect(squishedDoc).toMatch('... on Query { _0_field1: field1 _1_field2: field2 }');
     expect(first?.data).toEqual({ field1: '1' });
     expect(second?.data).toEqual({ field2: '2' });
     expect(executorCalls).toEqual(1);

packages/delegate/src/createRequest.ts

@@ -11,14 +11,14 @@ import {
   NameNode,
   OperationDefinitionNode,
   OperationTypeNode,
-  SelectionNode,
   SelectionSetNode,
   typeFromAST,
   VariableDefinitionNode,
 } from 'graphql';
 import {
   createVariableNameGenerator,
   ExecutionRequest,
+  SelectionSetBuilder,
   serializeInputValue,
   updateArgument,
 } from '@graphql-tools/utils';
@@ -59,21 +59,16 @@ export function createRequest({
   if (selectionSet != null) {
     newSelectionSet = selectionSet;
   } else {
-    const selections: Array<SelectionNode> = [];
+    const selections = new SelectionSetBuilder();
     for (const fieldNode of fieldNodes || []) {
       if (fieldNode.selectionSet) {
         for (const selection of fieldNode.selectionSet.selections) {
-          selections.push(selection);
+          selections.addSelection(selection);
         }
       }
     }
 
-    newSelectionSet = selections.length
-      ? {
-          kind: Kind.SELECTION_SET,
-          selections,
-        }
-      : undefined;
+    newSelectionSet = selections.getSize() ? selections.getSelectionSet() : undefined;
 
     const args = fieldNodes?.[0]?.arguments;
     if (args) {

packages/delegate/src/finalizeGatewayRequest.ts

@@ -28,6 +28,7 @@ import {
   getDefinedRootType,
   implementsAbstractType,
   inspect,
+  SelectionSetBuilder,
   serializeInputValue,
   updateArgument,
 } from '@graphql-tools/utils';
@@ -179,7 +180,7 @@ function addVariablesToRootFields(
 
     const type = getDefinedRootType(targetSchema, operation.operation);
 
-    const newSelections: Array<SelectionNode> = [];
+    const selectionSetBuilder = new SelectionSetBuilder();
 
     for (const selection of operation.selectionSet.selections) {
       if (selection.kind === Kind.FIELD) {
@@ -198,25 +199,19 @@ function addVariablesToRootFields(
         if (targetField != null) {
           updateArguments(targetField, argumentNodeMap, variableDefinitionMap, newVariables, args);
         }
-
-        newSelections.push({
+        selectionSetBuilder.addSelection({
           ...selection,
           arguments: Object.values(argumentNodeMap),
         });
       } else {
-        newSelections.push(selection);
+        selectionSetBuilder.addSelection(selection);
       }
     }
 
-    const newSelectionSet: SelectionSetNode = {
-      kind: Kind.SELECTION_SET,
-      selections: newSelections,
-    };
-
     return {
       ...operation,
       variableDefinitions: Object.values(variableDefinitionMap),
-      selectionSet: newSelectionSet,
+      selectionSet: selectionSetBuilder.getSelectionSet(),
     };
   });
 

packages/delegate/src/prepareGatewayDocument.ts

@@ -11,7 +11,6 @@ import {
   isInterfaceType,
   isLeafType,
   Kind,
-  SelectionNode,
   SelectionSetNode,
   TypeInfo,
   visit,
@@ -22,6 +21,7 @@ import {
   getRootTypeNames,
   implementsAbstractType,
   memoize2,
+  SelectionSetBuilder,
 } from '@graphql-tools/utils';
 import { getDocumentMetadata } from './getDocumentMetadata.js';
 import { StitchingInfo } from './types.js';
@@ -116,7 +116,7 @@ function visitSelectionSet(
     Record<string, Array<(node: FieldNode) => SelectionSetNode>>
   >,
 ): SelectionSetNode {
-  const newSelections = new Set<SelectionNode>();
+  const selectionSetBuilder = new SelectionSetBuilder();
   const maybeType = typeInfo.getParentType();
 
   if (maybeType != null) {
@@ -126,20 +126,20 @@ function visitSelectionSet(
     const fieldNodes = fieldNodesByType[parentTypeName];
     if (fieldNodes) {
       for (const fieldNode of fieldNodes) {
-        newSelections.add(fieldNode);
+        selectionSetBuilder.addSelection(fieldNode);
       }
     }
 
     const interfaceExtensions = interfaceExtensionsMap[parentType.name];
-    const interfaceExtensionFields: Array<SelectionNode> = [];
+    const interfaceExtensionFieldsBuilder = new SelectionSetBuilder();
 
     for (const selection of node.selections) {
       if (selection.kind === Kind.INLINE_FRAGMENT) {
         if (selection.typeCondition != null) {
           const possibleTypes = possibleTypesMap[selection.typeCondition.name.value];
 
           if (possibleTypes == null) {
-            newSelections.add(selection);
+            selectionSetBuilder.addSelection(selection);
             continue;
           }
 
@@ -149,15 +149,17 @@ function visitSelectionSet(
               maybePossibleType != null &&
               implementsAbstractType(schema, parentType, maybePossibleType)
             ) {
-              newSelections.add(generateInlineFragment(possibleTypeName, selection.selectionSet));
+              selectionSetBuilder.addSelection(
+                generateInlineFragment(possibleTypeName, selection.selectionSet),
+              );
             }
           }
         }
       } else if (selection.kind === Kind.FRAGMENT_SPREAD) {
         const fragmentName = selection.name.value;
 
         if (!fragmentReplacements[fragmentName]) {
-          newSelections.add(selection);
+          selectionSetBuilder.addSelection(selection);
           continue;
         }
 
@@ -169,7 +171,7 @@ function visitSelectionSet(
             maybeReplacementType != null &&
             implementsAbstractType(schema, parentType, maybeType)
           ) {
-            newSelections.add({
+            selectionSetBuilder.addSelection({
               kind: Kind.FRAGMENT_SPREAD,
               name: {
                 kind: Kind.NAME,
@@ -184,7 +186,7 @@ function visitSelectionSet(
         const fieldNodes = fieldNodesByField[parentTypeName]?.[fieldName];
         if (fieldNodes != null) {
           for (const fieldNode of fieldNodes) {
-            newSelections.add(fieldNode);
+            selectionSetBuilder.addSelection(fieldNode);
           }
         }
 
@@ -194,22 +196,22 @@ function visitSelectionSet(
             const selectionSet = selectionSetFn(selection);
             if (selectionSet != null) {
               for (const selection of selectionSet.selections) {
-                newSelections.add(selection);
+                selectionSetBuilder.addSelection(selection);
               }
             }
           }
         }
 
         if (interfaceExtensions?.[fieldName]) {
-          interfaceExtensionFields.push(selection);
+          interfaceExtensionFieldsBuilder.addSelection(selection);
         } else {
-          newSelections.add(selection);
+          selectionSetBuilder.addSelection(selection);
         }
       }
     }
 
     if (reversePossibleTypesMap[parentType.name]) {
-      newSelections.add({
+      selectionSetBuilder.addSelection({
         kind: Kind.FIELD,
         name: {
           kind: Kind.NAME,
@@ -218,23 +220,21 @@ function visitSelectionSet(
       });
     }
 
-    if (interfaceExtensionFields.length) {
+    if (interfaceExtensionFieldsBuilder.getSize()) {
       const possibleTypes = possibleTypesMap[parentType.name];
       if (possibleTypes != null) {
         for (const possibleType of possibleTypes) {
-          newSelections.add(
-            generateInlineFragment(possibleType, {
-              kind: Kind.SELECTION_SET,
-              selections: interfaceExtensionFields,
-            }),
+          const interfaceExtensionFields = interfaceExtensionFieldsBuilder.getSelectionSet();
+          selectionSetBuilder.addSelection(
+            generateInlineFragment(possibleType, interfaceExtensionFields),
           );
         }
       }
     }
 
     return {
       ...node,
-      selections: Array.from(newSelections),
+      ...selectionSetBuilder.getSelectionSet(),
     };
   }