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.

Note that this API is part of a new module called `SwiftPM` which could be the sstart of a "proper" public API for SwiftPM. That said, right now it depends on several types of existing modules in its public interface and that isn't likely to be resolved as part of this particular change.

rdar://112120976

Author: neonichu

Package.swift

@@ -42,6 +42,7 @@ let swiftPMDataModelProduct = (
         "PackageMetadata",
         "PackageModel",
         "SourceControl",
+        "SwiftPM",
         "Workspace",
     ]
 )
@@ -148,6 +149,15 @@ let package = Package(
             linkerSettings: packageLibraryLinkSettings
         ),
 
+        // SwiftPM public API
+        .target(
+            name: "SwiftPM",
+            dependencies: [
+                "Build",
+                "SPMBuildCore"
+            ]
+        ),
+
         // MARK: SwiftPM specific support libraries
 
         .systemLibrary(name: "SPMSQLite3", pkgConfig: systemSQLitePkgConfig),

Sources/SwiftPM/BuildDescription.swift

@@ -0,0 +1,82 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 Foundation
+
+// FIXME: should not import this module
+import Build
+// FIXME: should be internal imports
+import PackageGraph
+
+public protocol BuildTarget {
+    // FIXME: should not use `ResolvedTarget` in the public interface
+     var target: ResolvedTarget { get }
+     var sources: [URL] { get }
+
+     func compileArguments() throws -> [String]
+ }
+
+extension ClangTargetBuildDescription: BuildTarget {
+    public var sources: [URL] {
+        return (try? compilePaths().map { URL(fileURLWithPath: $0.source.pathString) }) ?? []
+    }
+
+    public func compileArguments() throws -> [String] {
+        return try self.basicArguments()
+    }
+}
+
+private struct WrappedSwiftTargetBuildDescription: BuildTarget {
+    private let description: SwiftTargetBuildDescription
+
+    init(_ description: SwiftTargetBuildDescription) {
+        self.description = description
+    }
+
+    var target: ResolvedTarget {
+        return description.target
+    }
+
+    var sources: [URL] {
+        return description.sources.map { URL(fileURLWithPath: $0.pathString) }
+    }
+
+    func compileArguments() throws -> [String] {
+        return try description.compileArguments()
+    }
+}
+
+public struct BuildDescription {
+    private let buildPlan: BuildPlan
+
+    // FIXME: should not use `BuildPlan` in the public interface
+    public init(buildPlan: BuildPlan) {
+        self.buildPlan = buildPlan
+    }
+
+    // FIXME: should not use `ResolvedTarget` in the public interface
+    public func getBuildTarget(for target: ResolvedTarget) -> BuildTarget? {
+        if let description = buildPlan.targetMap[target] {
+            switch description {
+            case .clang(let description):
+                return description
+            case .swift(let description):
+                return WrappedSwiftTargetBuildDescription(description)
+            }
+        } else {
+            if target.type == .plugin, let package = self.buildPlan.graph.package(for: target) {
+                return PluginTargetBuildDescription(target: target, toolsVersion: package.manifest.toolsVersion)
+            }
+            return nil
+        }
+    }
+}

Sources/SwiftPM/PluginTargetBuildDescription.swift

@@ -0,0 +1,44 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 Foundation
+
+// FIXME: should be an internal import
+import class PackageGraph.ResolvedTarget
+
+/*private*/ import class PackageLoading.ManifestLoader
+/*private*/ import struct PackageModel.ToolsVersion
+/*private*/ import class PackageModel.UserToolchain
+
+struct PluginTargetBuildDescription: BuildTarget {
+    // FIXME: should not use `ResolvedTarget` in the public interface
+    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: [URL] {
+        return target.sources.paths.map { URL(fileURLWithPath: $0.pathString) }
+    }
+
+    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)
+    }
+
+
+}