Check type name conflicts in SelectionSet

Apollo.xcodeproj/project.pbxproj

@@ -14,6 +14,7 @@
 		54DDB0921EA045870009DD99 /* InMemoryNormalizedCache.swift in Sources */ = {isa = PBXBuildFile; fileRef = 54DDB0911EA045870009DD99 /* InMemoryNormalizedCache.swift */; };
 		5AC6CA4322AAF7B200B7C94D /* GraphQLHTTPMethod.swift in Sources */ = {isa = PBXBuildFile; fileRef = 5AC6CA4222AAF7B200B7C94D /* GraphQLHTTPMethod.swift */; };
 		5BB2C0232380836100774170 /* VersionNumberTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 5BB2C0222380836100774170 /* VersionNumberTests.swift */; };
+		66321AE72A126C4400CC35CB /* IR+Formatting.swift in Sources */ = {isa = PBXBuildFile; fileRef = 66321AE62A126C4400CC35CB /* IR+Formatting.swift */; };
 		96F32D3B27CCD16B00F3383C /* animalkingdom-graphql in Resources */ = {isa = PBXBuildFile; fileRef = 96F32D3A27CCD16B00F3383C /* animalkingdom-graphql */; };
 		96F32D3C27CCD16D00F3383C /* animalkingdom-graphql in Resources */ = {isa = PBXBuildFile; fileRef = 96F32D3A27CCD16B00F3383C /* animalkingdom-graphql */; };
 		9B1CCDD92360F02C007C9032 /* Bundle+Helpers.swift in Sources */ = {isa = PBXBuildFile; fileRef = 9B1CCDD82360F02C007C9032 /* Bundle+Helpers.swift */; };
@@ -1133,6 +1134,7 @@
 		54DDB0911EA045870009DD99 /* InMemoryNormalizedCache.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = InMemoryNormalizedCache.swift; sourceTree = "<group>"; };
 		5AC6CA4222AAF7B200B7C94D /* GraphQLHTTPMethod.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = GraphQLHTTPMethod.swift; sourceTree = "<group>"; };
 		5BB2C0222380836100774170 /* VersionNumberTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = VersionNumberTests.swift; sourceTree = "<group>"; };
+		66321AE62A126C4400CC35CB /* IR+Formatting.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "IR+Formatting.swift"; sourceTree = "<group>"; };
 		90690D05224333DA00FC2E54 /* Apollo-Project-Debug.xcconfig */ = {isa = PBXFileReference; lastKnownFileType = text.xcconfig; path = "Apollo-Project-Debug.xcconfig"; sourceTree = "<group>"; };
 		90690D06224333DA00FC2E54 /* Apollo-Target-Framework.xcconfig */ = {isa = PBXFileReference; lastKnownFileType = text.xcconfig; path = "Apollo-Target-Framework.xcconfig"; sourceTree = "<group>"; };
 		90690D07224333DA00FC2E54 /* Apollo-Project-Release.xcconfig */ = {isa = PBXFileReference; lastKnownFileType = text.xcconfig; path = "Apollo-Project-Release.xcconfig"; sourceTree = "<group>"; };
@@ -2471,6 +2473,7 @@
 				9B7B6F68233C2C0C00F32205 /* FileManager+Apollo.swift */,
 				9BAEEBF62346F0A000808306 /* StaticString+Apollo.swift */,
 				9B8C3FB1248DA2EA00707B13 /* URL+Apollo.swift */,
+				66321AE62A126C4400CC35CB /* IR+Formatting.swift */,
 			);
 			name = Extensions;
 			sourceTree = "<group>";
@@ -5034,6 +5037,7 @@
 				9F62E03F2590896400E6E808 /* GraphQLError.swift in Sources */,
 				E6AAA732286BC58200F4659D /* OperationIdentifiersFileGenerator.swift in Sources */,
 				9B7B6F5A233C287200F32205 /* ApolloCodegenConfiguration.swift in Sources */,
+				66321AE72A126C4400CC35CB /* IR+Formatting.swift in Sources */,
 				9F1A966B258F34BB00A06EEB /* GraphQLJSFrontend.swift in Sources */,
 				DEB05B48289C3B4000170299 /* MockInterfacesFileGenerator.swift in Sources */,
 				DE09114E27288B1F000648E5 /* SortedSelections.swift in Sources */,

Sources/ApolloCodegenLib/ApolloCodegen.swift

@@ -21,6 +21,7 @@ public class ApolloCodegen {
     case invalidConfiguration(message: String)
     case invalidSchemaName(_ name: String, message: String)
     case targetNameConflict(name: String)
+    case typeNameConflict(name: String, conflictingName: String, containingObject: String)
 
     public var errorDescription: String? {
       switch self {
@@ -53,8 +54,15 @@ public class ApolloCodegen {
         return "The schema namespace `\(name)` is invalid: \(message)"
       case let .targetNameConflict(name):
         return """
-          Target name '\(name)' conflicts with a reserved library name. Please choose a different \
-          target name.
+        Target name '\(name)' conflicts with a reserved library name. Please choose a different \
+        target name.
+        """
+      case let .typeNameConflict(name, conflictingName, containingObject):
+        return """
+        TypeNameConflict - \
+        Field '\(conflictingName)' conflicts with field '\(name)' in operation/fragment `\(containingObject)`. \
+        Recommend using a field alias for one of these fields to resolve this conflict. \
+        For more info see: https://www.apollographql.com/docs/ios/troubleshooting/codegen-troubleshooting#typenameconflict
         """
       }
     }
@@ -212,6 +220,36 @@ public class ApolloCodegen {
       throw Error.schemaNameConflict(name: context.schemaNamespace)
     }
   }
+
+  /// Validates that there are no type conflicts within a SelectionSet
+  static private func validateTypeConflicts(for selectionSet: IR.SelectionSet, with context: ConfigurationContext, in containingObject: String) throws {
+    // Check for type conflicts resulting from singularization/pluralization of fields
+    var fieldNamesByFormattedTypeName = [String: String]()
+    var fields: [IR.EntityField] = selectionSet.selections.direct?.fields.values.compactMap { $0 as? IR.EntityField } ?? []
+    fields.append(contentsOf: selectionSet.selections.merged.fields.values.compactMap { $0 as? IR.EntityField } )
+
+    try fields.forEach { field in
+      let formattedTypeName = field.formattedSelectionSetName(with: context.pluralizer)
+      if let existingFieldName = fieldNamesByFormattedTypeName[formattedTypeName] {
+        throw Error.typeNameConflict(
+          name: existingFieldName,
+          conflictingName: field.name,
+          containingObject: containingObject
+        )
+      }
+
+      fieldNamesByFormattedTypeName[formattedTypeName] = field.name
+      try validateTypeConflicts(for: field.selectionSet, with: context, in: containingObject)
+    }
+
+    // gather nested fragments to loop through and check as well
+    var nestedSelectionSets: [IR.SelectionSet] = selectionSet.selections.direct?.inlineFragments.values.elements ?? []
+    nestedSelectionSets.append(contentsOf: selectionSet.selections.merged.inlineFragments.values)
+
+    try nestedSelectionSets.forEach { nestedSet in
+      try validateTypeConflicts(for: nestedSet, with: context, in: containingObject)
+    }
+  }
 
   /// Performs GraphQL source validation and compiles the schema and operation source documents.
   static func compileGraphQLResult(
@@ -304,6 +342,7 @@ public class ApolloCodegen {
     for fragment in compilationResult.fragments {
       try autoreleasepool {
         let irFragment = ir.build(fragment: fragment)
+        try validateTypeConflicts(for: irFragment.rootField.selectionSet, with: config, in: irFragment.definition.name)
         try FragmentFileGenerator(irFragment: irFragment, config: config)
           .generate(forConfig: config, fileManager: fileManager)
       }
@@ -314,6 +353,7 @@ public class ApolloCodegen {
     for operation in compilationResult.operations {
       try autoreleasepool {
         let irOperation = ir.build(operation: operation)
+        try validateTypeConflicts(for: irOperation.rootField.selectionSet, with: config, in: irOperation.definition.name)
         try OperationFileGenerator(irOperation: irOperation, config: config)
           .generate(forConfig: config, fileManager: fileManager)
 

Sources/ApolloCodegenLib/IR+Formatting.swift

@@ -0,0 +1,40 @@
+import Foundation
+
+extension GraphQLType {
+
+  var isListType: Bool {
+    switch self {
+    case .list: return true
+    case let .nonNull(innerType): return innerType.isListType
+    case .entity, .enum, .inputObject, .scalar: return false
+    }
+  }
+
+}
+
+extension IR.EntityField {
+
+  /// Takes the associated ``IR.EntityField`` and formats it into a selection set name
+  func formattedSelectionSetName(
+    with pluralizer: Pluralizer
+  ) -> String {
+    IR.Entity.FieldPathComponent(name: responseKey, type: type)
+      .formattedSelectionSetName(with: pluralizer)
+  }
+
+}
+
+extension IR.Entity.FieldPathComponent {
+
+  /// Takes the associated ``IR.Entity.FieldPathComponent`` and formats it into a selection set name
+  func formattedSelectionSetName(
+    with pluralizer: Pluralizer
+  ) -> String {
+    var fieldName = name.firstUppercased
+    if type.isListType {
+      fieldName = pluralizer.singularize(fieldName)
+    }
+    return fieldName.asSelectionSetName
+  }
+
+}

Sources/ApolloCodegenLib/Templates/SelectionSetTemplate.swift

@@ -626,43 +626,6 @@ fileprivate extension IR.SelectionSet {
 
 }
 
-fileprivate extension IR.EntityField {
-
-  func formattedSelectionSetName(
-    with pluralizer: Pluralizer
-  ) -> String {
-    IR.Entity.FieldPathComponent(name: responseKey, type: type)
-      .formattedSelectionSetName(with: pluralizer)
-  }
-
-}
-
-fileprivate extension IR.Entity.FieldPathComponent {
-
-  func formattedSelectionSetName(
-    with pluralizer: Pluralizer
-  ) -> String {
-    var fieldName = name.firstUppercased
-    if type.isListType {
-      fieldName = pluralizer.singularize(fieldName)
-    }    
-    return fieldName.asSelectionSetName
-  }
-
-}
-
-fileprivate extension GraphQLType {
-
-  var isListType: Bool {
-    switch self {
-    case .list: return true
-    case let .nonNull(innerType): return innerType.isListType
-    case .entity, .enum, .inputObject, .scalar: return false
-    }
-  }
-
-}
-
 fileprivate extension IR.MergedSelections.MergedSource {
 
   func generatedSelectionSetName(

Sources/SubscriptionAPI/SubscriptionAPI/Sources/Schema/SchemaConfiguration.swift

@@ -8,7 +8,7 @@
 import ApolloAPI
 
 public enum SchemaConfiguration: ApolloAPI.SchemaConfiguration {
-  public static func cacheKeyInfo(for type: Object, object: some ObjectData) -> CacheKeyInfo? {
+  public static func cacheKeyInfo(for type: Object, object: ObjectData) -> CacheKeyInfo? {
     // Implement this function to configure cache key resolution for your schema types.
     return nil
   }