Remove mutation requirement for command line actions (#1076)

rdar://139495161

Author: d-ronnqvist

Sources/SwiftDocCUtilities/Action/Action.swift

@@ -16,11 +16,11 @@ import SwiftDocC
 /// An action represents a discrete documentation task; it takes options and inputs, performs its work, reports any problems it encounters, and outputs it generates.
 package protocol AsyncAction {
     /// Performs the action and returns an ``ActionResult``.
-    mutating func perform(logHandle: inout LogHandle) async throws -> ActionResult
+    func perform(logHandle: inout LogHandle) async throws -> ActionResult
 }
 
 package extension AsyncAction {
-    mutating func perform(logHandle: LogHandle) async throws -> ActionResult {
+    func perform(logHandle: LogHandle) async throws -> ActionResult {
         var logHandle = logHandle
         return try await perform(logHandle: &logHandle)
     }

Sources/SwiftDocCUtilities/Action/Actions/Convert/ConvertAction.swift

@@ -271,7 +271,7 @@ public struct ConvertAction: AsyncAction {
             indexHTML = nil
         }
 
-        var coverageAction = CoverageAction(
+        let coverageAction = CoverageAction(
             documentationCoverageOptions: documentationCoverageOptions,
             workingDirectory: temporaryFolder,
             fileManager: fileManager)

Sources/SwiftDocCUtilities/Action/Actions/CoverageAction.swift

@@ -27,7 +27,7 @@ public struct CoverageAction: AsyncAction {
     let workingDirectory: URL
     private let fileManager: FileManagerProtocol
 
-    public mutating func perform(logHandle: inout LogHandle) async throws -> ActionResult {
+    public func perform(logHandle: inout LogHandle) async throws -> ActionResult {
         switch documentationCoverageOptions.level {
         case .brief, .detailed:
             print("   --- Experimental coverage output enabled. ---", to: &logHandle)

Sources/SwiftDocCUtilities/Action/Actions/EmitGeneratedCurationAction.swift

@@ -41,7 +41,7 @@ struct EmitGeneratedCurationAction: AsyncAction {
         self.fileManager = fileManager
     }
 
-    mutating func perform(logHandle: inout LogHandle) async throws -> ActionResult {
+    func perform(logHandle: inout LogHandle) async throws -> ActionResult {
         let inputProvider = DocumentationContext.InputsProvider(fileManager: fileManager)
         let (bundle, dataProvider) = try inputProvider.inputsAndDataProvider(
             startingPoint: catalogURL,

Sources/SwiftDocCUtilities/Action/Actions/IndexAction.swift

@@ -18,8 +18,6 @@ public struct IndexAction: AsyncAction {
     let bundleIdentifier: String
 
     var diagnosticEngine: DiagnosticEngine
-    
-    private var dataProvider: LocalFileSystemDataProvider!
 
     /// Initializes the action with the given validated options, creates or uses the given action workspace & context.
     public init(documentationBundleURL: URL, outputURL: URL, bundleIdentifier: String, diagnosticEngine: DiagnosticEngine = .init()) throws {
@@ -34,15 +32,15 @@ public struct IndexAction: AsyncAction {
 
     /// Converts each eligible file from the source documentation bundle,
     /// saves the results in the given output alongside the template files.
-    mutating public func perform(logHandle: inout LogHandle) async throws -> ActionResult {
+    public func perform(logHandle: inout LogHandle) async throws -> ActionResult {
         let problems = try buildIndex()
         diagnosticEngine.emit(problems)
 
         return ActionResult(didEncounterError: !diagnosticEngine.problems.isEmpty, outputs: [outputURL])
     }
 
-    mutating private func buildIndex() throws -> [Problem] {
-        dataProvider = try LocalFileSystemDataProvider(rootURL: rootURL)
+    private func buildIndex() throws -> [Problem] {
+        let dataProvider = try LocalFileSystemDataProvider(rootURL: rootURL)
         let indexBuilder = NavigatorIndex.Builder(renderNodeProvider: FileSystemRenderNodeProvider(fileSystemProvider: dataProvider),
                                                   outputURL: outputURL,
                                                   bundleIdentifier: bundleIdentifier,

Sources/SwiftDocCUtilities/Action/Actions/Init/InitAction.swift

@@ -72,7 +72,7 @@ public struct InitAction: AsyncAction {
     /// Generates a documentation catalog from a catalog template.
     ///
     /// - Parameter logHandle: The file handle that the convert and preview actions will print debug messages to.
-    public mutating func perform(logHandle: inout LogHandle) async throws -> ActionResult {
+    public func perform(logHandle: inout LogHandle) async throws -> ActionResult {
         let diagnosticEngine: DiagnosticEngine = DiagnosticEngine(treatWarningsAsErrors: false)
         diagnosticEngine.filterLevel = .warning
         diagnosticEngine.add(DiagnosticConsoleWriter(formattingOptions: []))

Sources/SwiftDocCUtilities/Action/Actions/Merge/MergeAction.swift

@@ -33,7 +33,7 @@ struct MergeAction: AsyncAction {
         }
     }
 
-    mutating func perform(logHandle: inout LogHandle) async throws -> ActionResult {
+    func perform(logHandle: inout LogHandle) async throws -> ActionResult {
         guard let firstArchive = archives.first else {
             // A validation warning should have already been raised in `Docc/Merge/InputAndOutputOptions/validate()`.
             return ActionResult(didEncounterError: true, outputs: [])

Sources/SwiftDocCUtilities/Action/Actions/TransformForStaticHostingAction.swift

@@ -44,12 +44,12 @@ struct TransformForStaticHostingAction: AsyncAction {
 
     /// Converts each eligible file from the source archive and
     /// saves the results in the given output folder.
-    mutating func perform(logHandle: inout LogHandle) async throws -> ActionResult {
+    func perform(logHandle: inout LogHandle) async throws -> ActionResult {
         try emit()
         return ActionResult(didEncounterError: false, outputs: [outputURL])
     }
 
-    mutating private func emit() throws {
+    private func emit() throws {
         // If the emit is to create the static hostable content outside of the source archive
         // then the output folder needs to be set up and the archive data copied
         // to the new folder.

Tests/SwiftDocCUtilitiesTests/ConvertActionStaticHostableTests.swift

@@ -32,7 +32,7 @@ class ConvertActionStaticHostableTests: StaticHostingBaseTests {
         let basePath = "test/folder"
         let indexHTML = Folder.testHTMLTemplate(basePath: "test/folder")
 
-        var action = try ConvertAction(
+        let action = try ConvertAction(
             documentationBundleURL: bundleURL,
             outOfProcessResolver: nil,
             analyze: false,