Start moving generation over to Descriptors

Sources/PluginLibrary/Array+Extensions.swift

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+// Sources/PluginLibrary/Array+Extensions.swift - Additions to Arrays
+//
+// Copyright (c) 2014 - 2017 Apple Inc. and the project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See LICENSE.txt for license information:
+// https://github.com/apple/swift-protobuf/blob/master/LICENSE.txt
+//
+// -----------------------------------------------------------------------------
+
+import Foundation
+
+extension Array {
+
+  /// Like map, but calls the transform with the index and value.
+  ///
+  /// NOTE: It would seem like doing:
+  ///   return self.enumerated().map {
+  ///     return try transform($0.index, $0.element)
+  ///   }
+  /// would seem like a simple thing to avoid extension. However as of Xcode 8.3.2
+  /// (Swift 3.1), building/running 5000000 interation test (macOS) of the differences
+  /// are rather large -
+  ///   Release build:
+  ///     Using enumerated: 3.694987967
+  ///     Using enumeratedMap: 0.961241992
+  ///   Debug build:
+  ///     Using enumerated: 20.038512905
+  ///     Using enumeratedMap: 8.521299144
+  func enumeratedMap<T>(_ transform: (Int, Element) throws -> T) rethrows -> [T] {
+    var i: Int = -1
+    return try map {
+      i += 1
+      return try transform(i, $0)
+    }
+  }
+}

Sources/PluginLibrary/Descriptor+Extensions.swift

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+// Sources/PluginLibrary/Descriptor+Extensions.swift - Additions to Descriptor
+//
+// Copyright (c) 2014 - 2017 Apple Inc. and the project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See LICENSE.txt for license information:
+// https://github.com/apple/swift-protobuf/blob/master/LICENSE.txt
+//
+// -----------------------------------------------------------------------------
+
+import Foundation
+import SwiftProtobuf
+
+extension FileDescriptor: ProvidesSourceCodeLocation {
+  // True if this file should perserve unknown enums within the enum.
+  public var hasUnknownEnumPreservingSemantics: Bool {
+    return syntax == .proto3
+  }
+
+  public var sourceCodeInfoLocation: Google_Protobuf_SourceCodeInfo.Location? {
+    // google/protobuf's descriptor.cc says it should be an empty path.
+    return sourceCodeInfoLocation(path: IndexPath())
+  }
+}
+
+extension Descriptor: ProvidesLocationPath, ProvidesSourceCodeLocation {
+  public func getLocationPath(path: inout IndexPath) {
+    if let containingType = containingType {
+      containingType.getLocationPath(path: &path)
+      path.append(Google_Protobuf_DescriptorProto.FieldNumbers.nestedType)
+    } else {
+      path.append(Google_Protobuf_FileDescriptorProto.FieldNumbers.messageType)
+    }
+    path.append(index)
+  }
+}
+
+extension EnumDescriptor: ProvidesLocationPath, ProvidesSourceCodeLocation {
+  // True if this enum should perserve unknown enums within the enum.
+  public var hasUnknownEnumPreservingSemantics: Bool {
+    return file.hasUnknownEnumPreservingSemantics
+  }
+
+  public func getLocationPath(path: inout IndexPath) {
+    if let containingType = containingType {
+      containingType.getLocationPath(path: &path)
+      path.append(Google_Protobuf_DescriptorProto.FieldNumbers.enumType)
+    } else {
+      path.append(Google_Protobuf_FileDescriptorProto.FieldNumbers.enumType)
+    }
+    path.append(index)
+  }
+}
+
+extension EnumValueDescriptor: ProvidesLocationPath, ProvidesSourceCodeLocation {
+  public weak var file: FileDescriptor! { return enumType.file }
+
+  public func getLocationPath(path: inout IndexPath) {
+    enumType.getLocationPath(path: &path)
+    path.append(Google_Protobuf_EnumDescriptorProto.FieldNumbers.value)
+    path.append(index)
+  }
+}
+
+extension OneofDescriptor: ProvidesLocationPath, ProvidesSourceCodeLocation {
+  public weak var file: FileDescriptor! { return containingType.file }
+
+  public func getLocationPath(path: inout IndexPath) {
+    containingType.getLocationPath(path: &path)
+    path.append(Google_Protobuf_DescriptorProto.FieldNumbers.oneofDecl)
+    path.append(index)
+  }
+}
+
+extension FieldDescriptor: ProvidesLocationPath, ProvidesSourceCodeLocation {
+  public func getLocationPath(path: inout IndexPath) {
+    if isExtension {
+      if let extensionScope = extensionScope {
+        extensionScope.getLocationPath(path: &path)
+        path.append(Google_Protobuf_DescriptorProto.FieldNumbers.extension)
+      } else {
+        path.append(Google_Protobuf_FileDescriptorProto.FieldNumbers.extension)
+      }
+    } else {
+      containingType.getLocationPath(path: &path)
+      path.append(Google_Protobuf_DescriptorProto.FieldNumbers.field)
+    }
+    path.append(index)
+  }
+}
+
+extension ServiceDescriptor: ProvidesLocationPath, ProvidesSourceCodeLocation {
+  public func getLocationPath(path: inout IndexPath) {
+    path.append(Google_Protobuf_FileDescriptorProto.FieldNumbers.service)
+    path.append(index)
+  }
+}
+
+extension MethodDescriptor: ProvidesLocationPath, ProvidesSourceCodeLocation {
+  public weak var file: FileDescriptor! { return service.file }
+
+  public func getLocationPath(path: inout IndexPath) {
+    service.getLocationPath(path: &path)
+    path.append(Google_Protobuf_ServiceDescriptorProto.FieldNumbers.method)
+    path.append(index)
+  }
+}