[Traits] Change TraitConfiguration to be an enum instead of struct (#8370)

Fixes #8355.

Since the way a `TraitConfiguration` is set up can affect how traits are
calculated and whether default traits are overridden or not, it's more
ergonomic to change this to an `enum` that lists the various possible
cases of configuration:

- No trait configuration, which defaults to using default traits if
applicable
- A configuration with an empty set of traits that overrides the default
traits
 - A configuration that enables all traits
- A configuration that specifies an exact set of traits that are enabled

This way we can avoid doing multiple checks on the properties of the
`struct` and instead rely on the exact case that describes how to
continue calculating enabled traits.

The refactoring done as a part of this change also fixes #8356.

Author: bripeticca

Sources/Build/LLBuildDescription.swift

@@ -17,6 +17,8 @@ import SPMBuildCore
 import PackageGraph
 import PackageModel
 
+import enum PackageModel.TraitConfiguration
+
 import struct TSCBasic.ByteString
 
 /// Contains the description of the build that is needed during the execution.

Sources/Commands/PackageCommands/EditCommands.swift

@@ -37,7 +37,7 @@ extension SwiftPackageCommand {
         var packageIdentity: String
 
         func run(_ swiftCommandState: SwiftCommandState) async throws {
-            try await swiftCommandState.resolve(nil)
+            try await swiftCommandState.resolve()
             let workspace = try swiftCommandState.getActiveWorkspace()
 
             // Put the dependency in edit mode.
@@ -66,7 +66,7 @@ extension SwiftPackageCommand {
         var packageIdentity: String
 
         func run(_ swiftCommandState: SwiftCommandState) async throws {
-            try await swiftCommandState.resolve(nil)
+            try await swiftCommandState.resolve()
             let workspace = try swiftCommandState.getActiveWorkspace()
 
             try await workspace.unedit(

Sources/Commands/PackageCommands/Resolve.swift

@@ -16,7 +16,7 @@ import CoreCommands
 import TSCUtility
 import Workspace
 
-import struct PackageGraph.TraitConfiguration
+import enum PackageModel.TraitConfiguration
 
 extension SwiftPackageCommand {
     struct ResolveOptions: ParsableArguments {

Sources/CoreCommands/BuildSystemSupport.swift

@@ -22,6 +22,7 @@ import class Basics.ObservabilityScope
 import struct PackageGraph.ModulesGraph
 import struct PackageLoading.FileRuleDescription
 import protocol TSCBasic.OutputByteStream
+import enum PackageModel.TraitConfiguration
 
 private struct NativeBuildSystemFactory: BuildSystemFactory {
     let swiftCommandState: SwiftCommandState

Sources/CoreCommands/Options.swift

@@ -27,7 +27,7 @@ import struct PackageModel.PackageIdentity
 import enum PackageModel.Sanitizer
 @_spi(SwiftPMInternal) import struct PackageModel.SwiftSDK
 
-import struct PackageGraph.TraitConfiguration
+import enum PackageModel.TraitConfiguration
 
 import struct SPMBuildCore.BuildParameters
 import struct SPMBuildCore.BuildSystemProvider

Sources/CoreCommands/SwiftCommandState.swift

@@ -214,14 +214,14 @@ public final class SwiftCommandState {
     }
 
     /// Get the current workspace root object.
-    public func getWorkspaceRoot(traitConfiguration: TraitConfiguration? = nil) throws -> PackageGraphRootInput {
+    public func getWorkspaceRoot(traitConfiguration: TraitConfiguration = .default) throws -> PackageGraphRootInput {
         let packages: [AbsolutePath]
 
         if let workspace = options.locations.multirootPackageDataFile {
             packages = try self.workspaceLoaderProvider(self.fileSystem, self.observabilityScope)
                 .load(workspace: workspace)
         } else {
-            packages = [try getPackageRoot()]
+            packages = try [self.getPackageRoot()]
         }
 
         return PackageGraphRootInput(packages: packages, traitConfiguration: traitConfiguration)
@@ -457,10 +457,7 @@ public final class SwiftCommandState {
     }
 
     /// Returns the currently active workspace.
-    public func getActiveWorkspace(
-        emitDeprecatedConfigurationWarning: Bool = false,
-        traitConfiguration: TraitConfiguration? = nil
-    ) throws -> Workspace {
+    public func getActiveWorkspace(emitDeprecatedConfigurationWarning: Bool = false, traitConfiguration: TraitConfiguration = .default) throws -> Workspace {
         if let workspace = _workspace {
             return workspace
         }
@@ -525,9 +522,7 @@ public final class SwiftCommandState {
         return workspace
     }
 
-    public func getRootPackageInformation(traitConfiguration: TraitConfiguration? = nil) async throws
-        -> (dependencies: [PackageIdentity: [PackageIdentity]], targets: [PackageIdentity: [String]])
-    {
+    public func getRootPackageInformation(traitConfiguration: TraitConfiguration = .default) async throws -> (dependencies: [PackageIdentity: [PackageIdentity]], targets: [PackageIdentity: [String]]) {
         let workspace = try self.getActiveWorkspace(traitConfiguration: traitConfiguration)
         let root = try self.getWorkspaceRoot(traitConfiguration: traitConfiguration)
         let rootManifests = try await workspace.loadRootManifests(
@@ -652,7 +647,7 @@ public final class SwiftCommandState {
     }
 
     /// Resolve the dependencies.
-    public func resolve(_ traitConfiguration: TraitConfiguration?) async throws {
+    public func resolve(_ traitConfiguration: TraitConfiguration = .default) async throws {
         let workspace = try getActiveWorkspace(traitConfiguration: traitConfiguration)
         let root = try getWorkspaceRoot(traitConfiguration: traitConfiguration)
 
@@ -682,7 +677,7 @@ public final class SwiftCommandState {
     ) async throws -> ModulesGraph {
         try await self.loadPackageGraph(
             explicitProduct: explicitProduct,
-            traitConfiguration: nil,
+            traitConfiguration: .default,
             testEntryPointPath: testEntryPointPath
         )
     }
@@ -695,7 +690,7 @@ public final class SwiftCommandState {
     @discardableResult
     package func loadPackageGraph(
         explicitProduct: String? = nil,
-        traitConfiguration: TraitConfiguration? = nil,
+        traitConfiguration: TraitConfiguration = .default,
         testEntryPointPath: AbsolutePath? = nil
     ) async throws -> ModulesGraph {
         do {
@@ -750,7 +745,7 @@ public final class SwiftCommandState {
         try self._manifestLoader.get()
     }
 
-    public func canUseCachedBuildManifest(_ traitConfiguration: TraitConfiguration? = nil) async throws -> Bool {
+    public func canUseCachedBuildManifest(_ traitConfiguration: TraitConfiguration = .default) async throws -> Bool {
         if !self.options.caching.cacheBuildManifest {
             return false
         }

Sources/PackageGraph/CMakeLists.txt

@@ -19,7 +19,6 @@ add_library(PackageGraph
   PackageModel+Extensions.swift
   PackageRequirement.swift
   ResolvedPackagesStore.swift
-  TraitConfiguration.swift
   Resolution/PubGrub/Assignment.swift
   Resolution/PubGrub/ContainerProvider.swift
   Resolution/PubGrub/DiagnosticReportBuilder.swift

Sources/PackageGraph/ModulesGraph+Loading.swift

@@ -1035,7 +1035,7 @@ private func calculateEnabledTraits(
         }
     }
 
-    if let parentPackage, !(explictlyEnabledTraits == nil || areDefaultsEnabled) && manifest.traits.isEmpty {
+    if let parentPackage, !(explictlyEnabledTraits == nil || areDefaultsEnabled) && !manifest.supportsTraits {
         // We throw an error when default traits are disabled for a package without any traits
         // This allows packages to initially move new API behind traits once.
         throw ModuleError.disablingDefaultTraitsOnEmptyTraits(

Sources/PackageGraph/ModulesGraph.swift

@@ -458,7 +458,7 @@ public func loadModulesGraph(
     useXCBuildFileRules: Bool = false,
     customXCTestMinimumDeploymentTargets: [PackageModel.Platform: PlatformVersion]? = .none,
     observabilityScope: ObservabilityScope,
-    traitConfiguration: TraitConfiguration? = nil
+    traitConfiguration: TraitConfiguration = .default
 ) throws -> ModulesGraph {
     let rootManifests = manifests.filter(\.packageKind.isRoot).spm_createDictionary { ($0.path, $0) }
     let externalManifests = try manifests.filter { !$0.packageKind.isRoot }
@@ -471,7 +471,7 @@ public func loadModulesGraph(
 
     let packages = Array(rootManifests.keys)
     let input = PackageGraphRootInput(packages: packages, traitConfiguration: traitConfiguration)
-    let graphRoot = PackageGraphRoot(
+    let graphRoot = try PackageGraphRoot(
         input: input,
         manifests: rootManifests,
         explicitProduct: explicitProduct,

Sources/PackageGraph/PackageContainer.swift

@@ -102,7 +102,7 @@ public protocol PackageContainer {
     /// Fetch the enabled traits of a package container.
     ///
     /// NOTE: This method should only be called on root packages.
-    func getEnabledTraits(traitConfiguration: TraitConfiguration?, version: Version?) async throws -> Set<String>
+    func getEnabledTraits(traitConfiguration: TraitConfiguration, version: Version?) async throws -> Set<String>
 }
 
 extension PackageContainer {
@@ -118,7 +118,7 @@ extension PackageContainer {
         return true
     }
 
-    public func getEnabledTraits(traitConfiguration: TraitConfiguration?, version: Version? = nil) async throws -> Set<String> {
+    public func getEnabledTraits(traitConfiguration: TraitConfiguration, version: Version? = nil) async throws -> Set<String> {
         return []
     }
 }