Reduce main thread usage in SafeDITool (#114)

* Use complete argument list

* Reduce main thread usage in SafeDITool

* Improve code coverage

* More simplification

* Remove Requirements section from README – defer instead to Package.swift

README.md

@@ -484,14 +484,6 @@ The `SafeDITool` utility is designed to able to be integrated into projects of a
 
 The `SafeDITool` can parse all of your Swift files at once, or for even better performance, the tool can be run on each dependent module as part of the build. Running this tool on each dependent module is currently left as an exercise to the reader.
 
-### Requirements
-
-* Xcode 16.0 or later
-* iOS 13 or later
-* tvOS 13 or later
-* watchOS 6 or later
-* macOS 10.13 or later
-
 ## Under the hood
 
 SafeDI has a `SafeDITool` executable that the `SafeDIGenerator` plugin utilizes to read code and generate a dependency tree. The tool utilizes Apple‘s [SwiftSyntax](https://github.com/apple/swift-syntax) library to parse your code and find your `@Instantiable` types‘ initializers and dependencies. With this information, SafeDI creates a graph of your project‘s dependencies. This graph is validated as part of the `SafeDITool`‘s execution, and the tool emits human-readible errors if the dependency graph is not valid. Source code is only generated if the dependency graph is valid.

Sources/SafeDICore/Extensions/CollectionExtensions.swift

@@ -68,3 +68,9 @@ extension Collection {
         return try arrayToTransform.map { try transform($0) } + [lastItem]
     }
 }
+
+extension Collection<String> {
+    public func removingEmpty() -> [Element] {
+        filter { !$0.isEmpty }
+    }
+}

Sources/SafeDICore/Generators/DependencyTreeGenerator.swift

@@ -47,7 +47,7 @@ public actor DependencyTreeGenerator {
             for try await generatedRoot in taskGroup {
                 generatedRoots.append(generatedRoot)
             }
-            return generatedRoots.filter { !$0.isEmpty }.sorted().joined(separator: "\n\n")
+            return generatedRoots.removingEmpty().sorted().joined(separator: "\n\n")
         }
 
         let importsWhitespace = imports.isEmpty ? "" : "\n"
@@ -74,7 +74,7 @@ public actor DependencyTreeGenerator {
             for try await generatedRoot in taskGroup {
                 generatedRoots.append(generatedRoot)
             }
-            return generatedRoots.filter { !$0.isEmpty }.sorted().joined(separator: "\n\n")
+            return generatedRoots.removingEmpty().sorted().joined(separator: "\n\n")
         }
 
         return """

Sources/SafeDICore/Models/TypeDescription.swift

@@ -131,7 +131,7 @@ public enum TypeDescription: Codable, Hashable, Comparable, Sendable {
             }.joined(separator: ", ")))
             """
         case let .closure(arguments, isAsync, doesThrow, returnType):
-            return "(\(arguments.map(\.asSource).joined(separator: ", ")))\([isAsync ? " async" : "", doesThrow ? " throws" : ""].filter { !$0.isEmpty }.joined()) -> \(returnType.asSource)"
+            return "(\(arguments.map(\.asSource).joined(separator: ", ")))\([isAsync ? " async" : "", doesThrow ? " throws" : ""].removingEmpty().joined()) -> \(returnType.asSource)"
         case let .unknown(text):
             return text
         }
@@ -519,18 +519,10 @@ private final class GenericArgumentVisitor: SyntaxVisitor {
 
 extension TypeSpecifierListSyntax {
     fileprivate var textRepresentation: [String]? {
-        let specifiers = compactMap { specifier in
-            if case let .simpleTypeSpecifier(simpleTypeSpecifierSyntax) = specifier {
-                simpleTypeSpecifierSyntax.specifier.text
-            } else {
-                // lifetimeTypeSpecifier is SPI, so we ignore it.
-                nil
-            }
-        }
-        if specifiers.isEmpty {
-            return nil
+        if isEmpty {
+            nil
         } else {
-            return specifiers
+            compactMap(\.trimmedDescription)
         }
     }
 }

Sources/SafeDITool/SafeDITool.swift

@@ -46,7 +46,6 @@ struct SafeDITool: AsyncParsableCommand, Sendable {
 
     // MARK: Internal
 
-    @MainActor
     func run() async throws {
         if swiftSourcesFilePath == nil, include.isEmpty {
             throw ValidationError("Must provide either 'swift-sources-file-path' or '--include'.")
@@ -105,44 +104,58 @@ struct SafeDITool: AsyncParsableCommand, Sendable {
 
     // MARK: Private
 
-    @MainActor
     private func findSwiftFiles() async throws -> Set<String> {
-        var swiftFiles = Set<String>()
-        if let swiftSourcesFilePath {
-            try swiftFiles.formUnion(
-                String(contentsOfFile: swiftSourcesFilePath)
-                    .components(separatedBy: CharacterSet(arrayLiteral: ","))
-                    .filter { !$0.isEmpty }
-            )
-        }
-        for included in include {
-            let includedURL = included.asFileURL
-            let includedFileEnumerator = fileFinder
-                .enumerator(
-                    at: includedURL,
-                    includingPropertiesForKeys: nil,
-                    options: [.skipsHiddenFiles],
-                    errorHandler: nil
-                )
-            guard let files = includedFileEnumerator?.compactMap({ $0 as? URL }) else {
-                struct CouldNotEnumerateDirectoryError: Error, CustomStringConvertible {
-                    let directory: String
-
-                    var description: String {
-                        "Could not create file enumerator for directory '\(directory)'"
-                    }
+        try await withThrowingTaskGroup(
+            of: [String].self,
+            returning: Set<String>.self
+        ) { taskGroup in
+            taskGroup.addTask {
+                if let swiftSourcesFilePath {
+                    try String(contentsOfFile: swiftSourcesFilePath)
+                        .components(separatedBy: CharacterSet(arrayLiteral: ","))
+                        .removingEmpty()
+                } else {
+                    []
                 }
-                throw CouldNotEnumerateDirectoryError(directory: included)
             }
-            swiftFiles.formUnion((files + [includedURL]).compactMap {
-                if $0.pathExtension == "swift" {
-                    $0.standardizedFileURL.relativePath
-                } else {
-                    nil
+            let fileFinder = await fileFinder
+            for included in include {
+                taskGroup.addTask {
+                    let includedURL = included.asFileURL
+                    let includedFileEnumerator = fileFinder
+                        .enumerator(
+                            at: includedURL,
+                            includingPropertiesForKeys: nil,
+                            options: [.skipsHiddenFiles],
+                            errorHandler: nil
+                        )
+                    guard let files = includedFileEnumerator?.compactMap({ $0 as? URL }) else {
+                        struct CouldNotEnumerateDirectoryError: Error, CustomStringConvertible {
+                            let directory: String
+
+                            var description: String {
+                                "Could not create file enumerator for directory '\(directory)'"
+                            }
+                        }
+                        throw CouldNotEnumerateDirectoryError(directory: included)
+                    }
+                    return (files + [includedURL]).compactMap {
+                        if $0.pathExtension == "swift" {
+                            $0.standardizedFileURL.relativePath
+                        } else {
+                            nil
+                        }
+                    }
                 }
-            })
+            }
+
+            var swiftFiles = Set<String>()
+            for try await includedFiles in taskGroup {
+                swiftFiles.formUnion(includedFiles)
+            }
+
+            return swiftFiles
         }
-        return swiftFiles
     }
 
     private func loadSwiftFiles() async throws -> [String] {
@@ -201,7 +214,7 @@ struct SafeDITool: AsyncParsableCommand, Sendable {
                 try .init(
                     String(contentsOfFile: dependentModuleInfoFilePath)
                         .components(separatedBy: CharacterSet(arrayLiteral: ","))
-                        .filter { !$0.isEmpty }
+                        .removingEmpty()
                         .map(\.asFileURL)
                 )
             } else {
@@ -304,7 +317,7 @@ extension String {
     }
 }
 
-protocol FileFinder {
+protocol FileFinder: Sendable {
     func enumerator(
         at url: URL,
         includingPropertiesForKeys keys: [URLResourceKey]?,
@@ -314,5 +327,9 @@ protocol FileFinder {
 }
 
 extension FileManager: FileFinder {}
+extension FileManager: @retroactive @unchecked Sendable {
+    // FileManager is thread safe:
+    // https://developer.apple.com/documentation/foundation/nsfilemanager#1651181
+}
 
 @MainActor var fileFinder: FileFinder = FileManager.default

Tests/SafeDIToolTests/Helpers/SafeDIToolTestExecution.swift

@@ -133,11 +133,10 @@ struct StubFileFinder: FileFinder {
     let files: [URL]
 }
 
-@MainActor
 func assertThrowsError(
     _ errorDescription: String,
     line: UInt = #line,
-    block: @MainActor () async throws -> some Any
+    block: @MainActor () async throws -> some Sendable
 ) async {
     do {
         _ = try await block()

Tests/SafeDIToolTests/SafeDIToolCodeGenerationErrorTests.swift

@@ -1733,6 +1733,7 @@ final class SafeDIToolCodeGenerationErrorTests: XCTestCase {
         tool.moduleInfoOutput = nil
         tool.dependentModuleInfoFilePath = nil
         tool.dependencyTreeOutput = nil
+        tool.dotFileOutput = nil
         await assertThrowsError("Could not create file enumerator for directory 'Fake'") {
             try await tool.run()
         }
@@ -1746,6 +1747,7 @@ final class SafeDIToolCodeGenerationErrorTests: XCTestCase {
         tool.moduleInfoOutput = nil
         tool.dependentModuleInfoFilePath = nil
         tool.dependencyTreeOutput = nil
+        tool.dotFileOutput = nil
         await assertThrowsError("Must provide either 'swift-sources-file-path' or '--include'.") {
             try await tool.run()
         }