Make build plugin communicate files via a file list rather than space-separated CLI arguments

Plugins/SafeDIGenerateDependencyTree/SafeDIGenerateDependencyTree.swift

@@ -1,3 +1,4 @@
+import Foundation
 import PackagePlugin
 
 @main
@@ -26,8 +27,20 @@ struct SafeDIGenerateDependencyTree: BuildToolPlugin {
                     .map(\.path)
             }
 
-        let arguments = (targetSwiftFiles + dependenciesSourceFiles).map(\.string)
-        + ["--dependency-tree-output", outputSwiftFile.string]
+        let inputSwiftFilesFilePath = context.pluginWorkDirectory.appending(subpath: "InputSwiftFiles.txt").string
+        try Data(
+            (targetSwiftFiles + dependenciesSourceFiles)
+                .map(\.string)
+                .joined(separator: "\n")
+                .utf8
+        )
+        .write(toPath: inputSwiftFilesFilePath)
+        let arguments = [
+            "--swift-file-paths-file-path",
+            inputSwiftFilesFilePath,
+            "--dependency-tree-output",
+            outputSwiftFile.string
+        ]
 
         return [
             .buildCommand(
@@ -93,9 +106,17 @@ extension SafeDIGenerateDependencyTree: XcodeBuildToolPlugin {
         }
 
         let outputSwiftFile = context.pluginWorkDirectory.appending(subpath: "SafeDI.swift")
-        let arguments = inputSwiftFiles
-            .map(\.string)
-        + [
+        let inputSwiftFilesFilePath = context.pluginWorkDirectory.appending(subpath: "InputSwiftFiles.txt").string
+        try Data(
+            inputSwiftFiles
+                .map(\.string)
+                .joined(separator: "\n")
+                .utf8
+        )
+        .write(toPath: inputSwiftFilesFilePath)
+        let arguments = [
+            "--swift-file-paths-file-path",
+            inputSwiftFilesFilePath,
             "--dependency-tree-output",
             outputSwiftFile.string
         ]
@@ -112,3 +133,17 @@ extension SafeDIGenerateDependencyTree: XcodeBuildToolPlugin {
     }
 }
 #endif
+
+extension Data {
+    fileprivate func write(toPath filePath: String) throws {
+#if os(Linux)
+        try write(to: URL(fileURLWithPath: filePath))
+#else
+        if #available(macOS 13.0, iOS 16.0, tvOS 16.0, watchOS 9.0, *) {
+            try write(to: URL(filePath: filePath))
+        } else {
+            try write(to: URL(fileURLWithPath: filePath))
+        }
+#endif
+    }
+}

Sources/SafeDITool/SafeDITool.swift

@@ -29,8 +29,11 @@ struct SafeDITool: AsyncParsableCommand {
 
     // MARK: Arguments
 
-    @Argument(help: "The swift files to parse")
-    var swiftFilePaths: [String]
+    @Argument(help: "The Swift files to parse.")
+    var swiftFilePaths: [String] = []
+
+    @Option(help: "A path to a file containing newline-separated Swift files to parse.")
+    var swiftFilePathsFilePath: String?
 
     @Option(parsing: .upToNextOption, help: "The names of modules to import in the generated dependency tree. This list is in addition to the import statements found in files that declare @Instantiable types.")
     var additionalImportedModules: [String] = []
@@ -123,6 +126,14 @@ struct SafeDITool: AsyncParsableCommand {
             of: String.self,
             returning: [String].self
         ) { taskGroup in
+            let swiftFilePaths: [String]
+            if let swiftFilePathsFilePath {
+                swiftFilePaths = try String(contentsOfFile: swiftFilePathsFilePath)
+                    .components(separatedBy: .newlines)
+                + self.swiftFilePaths
+            } else {
+                swiftFilePaths = self.swiftFilePaths
+            }
             for filePath in swiftFilePaths {
                 taskGroup.addTask {
                     let swiftFile = try String(contentsOfFile: filePath)