Public API for getting information about build targets

Until now, SourceKit-LSP has been using a couple of internal data structures of the build plan, which were incidentally public, for this. This changes those data structures to internal and exposes a new public API for accessing information about build targets, including those for plugins.

rdar://112120976

Author: neonichu

Sources/Build/BuildDescription/ClangTargetBuildDescription.swift

@@ -21,7 +21,7 @@ import struct SPMBuildCore.PrebuildCommandResult
 import enum TSCBasic.ProcessEnv
 
 /// Target description for a Clang target i.e. C language family target.
-public final class ClangTargetBuildDescription {
+public final class ClangTargetBuildDescription: BuildTarget {
     /// The target described by this target.
     public let target: ResolvedTarget
 
@@ -425,4 +425,14 @@ public final class ClangTargetBuildDescription {
             string: headerContent
         )
     }
+
+    // MARK: - `BuildTarget`
+
+    public var sources: [AbsolutePath] {
+        return (try? compilePaths().map { $0.source }) ?? []
+    }
+
+    public func compileArguments() throws -> [String] {
+        return try self.basicArguments()
+    }
 }

Sources/Build/BuildDescription/PluginTargetBuildDescription.swift

@@ -0,0 +1,40 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift open source project
+//
+// Copyright (c) 2023 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See http://swift.org/LICENSE.txt for license information
+// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+import struct Basics.AbsolutePath
+import class PackageGraph.ResolvedTarget
+import class PackageLoading.ManifestLoader
+import struct PackageModel.ToolsVersion
+import class PackageModel.UserToolchain
+
+struct PluginTargetBuildDescription: BuildTarget {
+    public let target: ResolvedTarget
+    private let toolsVersion: ToolsVersion
+
+    init(target: ResolvedTarget, toolsVersion: ToolsVersion) {
+        assert(target.type == .plugin)
+        self.target = target
+        self.toolsVersion = toolsVersion
+    }
+
+    var sources: [AbsolutePath] {
+        return target.sources.paths
+    }
+
+    func compileArguments() throws -> [String] {
+        // FIXME: This is very odd and we should clean this up by merging `ManifestLoader` and `DefaultPluginScriptRunner` again.
+        let loader = ManifestLoader(toolchain: try UserToolchain(swiftSDK: .hostSwiftSDK()))
+        return loader.interpreterFlags(for: self.toolsVersion)
+    }
+    
+
+}

Sources/Build/BuildDescription/SwiftTargetBuildDescription.swift

@@ -21,7 +21,7 @@ import SPMBuildCore
 import struct TSCBasic.ByteString
 
 /// Target description for a Swift target.
-public final class SwiftTargetBuildDescription {
+public final class SwiftTargetBuildDescription: BuildTarget {
     /// The package this target belongs to.
     public let package: ResolvedPackage
 

Sources/Build/BuildDescription/TargetBuildDescription.swift

@@ -92,3 +92,10 @@ public enum TargetBuildDescription {
         }
     }
 }
+
+public protocol BuildTarget {
+    var target: ResolvedTarget { get }
+    var sources: [AbsolutePath] { get }
+
+    func compileArguments() throws -> [String]
+}

Sources/Build/BuildPlan.swift

@@ -186,20 +186,20 @@ public class BuildPlan: SPMBuildCore.BuildPlan {
     }
 
     /// The package graph.
-    public let graph: PackageGraph
+    let graph: PackageGraph
 
     /// The target build description map.
-    public let targetMap: [ResolvedTarget: TargetBuildDescription]
+    let targetMap: [ResolvedTarget: TargetBuildDescription]
 
     /// The product build description map.
-    public let productMap: [ResolvedProduct: ProductBuildDescription]
+    let productMap: [ResolvedProduct: ProductBuildDescription]
 
     /// The plugin descriptions. Plugins are represented in the package graph
     /// as targets, but they are not directly included in the build graph.
-    public let pluginDescriptions: [PluginDescription]
+    let pluginDescriptions: [PluginDescription]
 
     /// The build targets.
-    public var targets: AnySequence<TargetBuildDescription> {
+    var targets: AnySequence<TargetBuildDescription> {
         return AnySequence(targetMap.values)
     }
 
@@ -209,11 +209,11 @@ public class BuildPlan: SPMBuildCore.BuildPlan {
     }
 
     /// The results of invoking any build tool plugins used by targets in this build.
-    public let buildToolPluginInvocationResults: [ResolvedTarget: [BuildToolPluginInvocationResult]]
+    let buildToolPluginInvocationResults: [ResolvedTarget: [BuildToolPluginInvocationResult]]
 
     /// The results of running any prebuild commands for the targets in this build.  This includes any derived
     /// source files as well as directories to which any changes should cause us to reevaluate the build plan.
-    public let prebuildCommandResults: [ResolvedTarget: [PrebuildCommandResult]]
+    let prebuildCommandResults: [ResolvedTarget: [PrebuildCommandResult]]
 
     private var derivedTestTargetsMap: [ResolvedProduct: [ResolvedTarget]] = [:]
 
@@ -1040,6 +1040,22 @@ public class BuildPlan: SPMBuildCore.BuildPlan {
             return execInfos.filter{!$0.supportedTriples.isEmpty}
         }
     }
+
+    public func getBuildTarget(for target: ResolvedTarget) -> BuildTarget? {
+        if let description = targetMap[target] {
+            switch description {
+            case .clang(let description):
+                return description
+            case .swift(let description):
+                return description
+            }
+        } else {
+            if target.type == .plugin, let package = self.graph.package(for: target) {
+                return PluginTargetBuildDescription(target: target, toolsVersion: package.manifest.toolsVersion)
+            }
+            return nil
+        }
+    }
 }
 
 private extension PackageModel.SwiftTarget {