feature: Adds defer metadata template for codegen [2/2] (#328)

Author: calvincestari

Sources/ApolloCodegenLib/Templates/DeferredFragmentsMetadataTemplate.swift

@@ -0,0 +1,138 @@
+import GraphQLCompiler
+import IR
+import TemplateString
+
+struct DeferredFragmentsMetadataTemplate {
+
+  let operation: IR.Operation
+  let config: ApolloCodegen.ConfigurationContext
+  let renderAccessControl: () -> String
+
+  init(
+    operation: IR.Operation,
+    config: ApolloCodegen.ConfigurationContext,
+    renderAccessControl: @autoclosure @escaping () -> String
+  ) {
+    self.operation = operation
+    self.config = config
+    self.renderAccessControl = renderAccessControl
+  }
+
+  // MARK: Templates
+
+  /// Renders metadata definitions for the deferred fragments of an Operation.
+  ///
+  /// - Returns: The `TemplateString` for the deferred fragments metadata definitions.
+  func render() -> TemplateString {
+    let deferredFragmentPathTypeInfo = DeferredFragmentsPathTypeInfo(
+      from: operation.rootField.selectionSet.selections
+    )
+    guard !deferredFragmentPathTypeInfo.isEmpty else { return "" }
+
+    return """
+
+    // MARK: Deferred Fragment Metadata
+
+    \(renderAccessControl())extension \(operation.generatedDefinitionName) {
+      \(DeferredFragmentIdentifiersTemplate(deferredFragmentPathTypeInfo))
+
+      \(DeferredFragmentsPropertyTemplate(deferredFragmentPathTypeInfo))
+    }
+    """
+  }
+
+  fileprivate func DeferredFragmentIdentifiersTemplate(
+    _ deferredFragmentPathTypeInfo: [DeferredPathTypeInfo]
+  ) -> TemplateString {
+    """
+    enum DeferredFragmentIdentifiers {
+    \(deferredFragmentPathTypeInfo.map {
+      return """
+        static let \($0.deferCondition.label) = DeferredFragmentIdentifier(label: \"\($0.deferCondition.label)\", fieldPath: [\
+      \($0.path.map { "\"\($0)\"" }, separator: ", ")\
+      ])
+      """
+    }, separator: "\n")
+    }
+    """
+  }
+
+  fileprivate func DeferredFragmentsPropertyTemplate(
+    _ deferredFragmentPathTypeInfo: [DeferredPathTypeInfo]
+  ) -> TemplateString {
+    """
+    static var deferredFragments: [DeferredFragmentIdentifier: any \(config.ApolloAPITargetName).SelectionSet.Type]? {[
+    \(deferredFragmentPathTypeInfo.map {
+      return """
+        DeferredFragmentIdentifiers.\($0.deferCondition.label): \($0.typeName).self,
+      """
+    }, separator: "\n")
+    ]}
+    """
+  }
+
+  // MARK: Helpers
+
+  fileprivate struct DeferredPathTypeInfo {
+    let path: [String]
+    let deferCondition: CompilationResult.DeferCondition
+    let typeName: String
+  }
+
+  fileprivate func DeferredFragmentsPathTypeInfo(
+    from directSelections: DirectSelections?,
+    path: [String] = []
+  ) -> [DeferredPathTypeInfo] {
+    guard let directSelections, !directSelections.isEmpty else { return [] }
+
+    var deferredPathTypeInfo: [DeferredPathTypeInfo] = []
+
+    for field in directSelections.fields.values {
+      if let field = field as? EntityField {
+        let fieldPath = path + [(field.alias ?? field.name)]
+        deferredPathTypeInfo.append(contentsOf:
+          DeferredFragmentsPathTypeInfo(from: field.selectionSet.selections, path: fieldPath)
+        )
+      }
+    }
+
+    for fragment in directSelections.inlineFragments.values {
+      if let deferCondition = fragment.typeInfo.deferCondition {
+        let selectionSetName = SelectionSetNameGenerator.generatedSelectionSetName(
+          for: fragment.typeInfo,
+          format: .omittingRoot,
+          pluralizer: config.pluralizer
+        )
+
+        deferredPathTypeInfo.append(DeferredPathTypeInfo(
+          path: path,
+          deferCondition: deferCondition,
+          typeName: "Data.\(selectionSetName)"
+        ))
+      }
+
+      deferredPathTypeInfo.append(contentsOf:
+        DeferredFragmentsPathTypeInfo(from: fragment.selectionSet.selections, path: path)
+      )
+    }
+
+    for fragment in directSelections.namedFragments.values {
+      if let deferCondition = fragment.typeInfo.deferCondition {
+        deferredPathTypeInfo.append(DeferredPathTypeInfo(
+          path: path,
+          deferCondition: deferCondition,
+          typeName: fragment.definition.name.asFragmentName
+        ))
+      }
+
+      deferredPathTypeInfo.append(contentsOf:
+        DeferredFragmentsPathTypeInfo(
+          from: fragment.fragment.rootField.selectionSet.selections,
+          path: path
+        )
+      )
+    }
+
+    return deferredPathTypeInfo
+  }
+}

Sources/ApolloCodegenLib/Templates/OperationDefinitionTemplate.swift

@@ -42,7 +42,11 @@ struct OperationDefinitionTemplate: OperationTemplateRenderer {
         ).renderBody())
       }
     }
-
+    \(section: DeferredFragmentsMetadataTemplate(
+      operation: operation,
+      config: config,
+      renderAccessControl: { accessControlModifier(for: .parent) }()
+    ).render())
     """)
   }