Automatic code removal, closes #666

Package.resolved

@@ -77,8 +77,8 @@
       "kind" : "remoteSourceControl",
       "location" : "https://github.com/tuist/xcodeproj",
       "state" : {
-        "revision" : "447c159b0c5fb047a024fd8d942d4a76cf47dde0",
-        "version" : "8.16.0"
+        "revision" : "a3e5d54f8c8a2964ee54870fda33b28651416581",
+        "version" : "8.17.0"
       }
     },
     {

Package.swift

@@ -85,6 +85,10 @@ var targets: [PackageDescription.Target] = [
         ],
         path: "Tests/Fixtures/RetentionFixtures"
     ),
+    .target(
+        name: "RemovalFixtures",
+        path: "Tests/Fixtures/RemovalFixtures"
+    ),
     .target(
         name: "UnusedParameterFixtures",
         path: "Tests/Fixtures/UnusedParameterFixtures",

Sources/Frontend/Commands/ScanBehavior.swift

@@ -63,6 +63,11 @@ final class ScanBehavior {
             results = try block(project)
             let interval = logger.beginInterval("result:output")
             let filteredResults = OutputDeclarationFilter().filter(results)
+
+            if configuration.autoRemove {
+                try ScanResultRemover().remove(results: filteredResults)
+            }
+
             let output = try configuration.outputFormat.formatter.init(configuration: configuration).format(filteredResults)
 
             if configuration.outputFormat.supportsAuxiliaryOutput {

Sources/Frontend/Commands/ScanCommand.swift

@@ -90,6 +90,9 @@ struct ScanCommand: FrontendCommand {
     @Flag(help: "Retain properties on Codable types")
     var retainCodableProperties: Bool = defaultConfiguration.$retainCodableProperties.defaultValue
 
+    @Flag(help: "Automatically remove code that can be done so safely without introducing build errors (experimental)")
+    var autoRemove: Bool = defaultConfiguration.$autoRemove.defaultValue
+
     @Flag(help: "Clean existing build artifacts before building")
     var cleanBuild: Bool = defaultConfiguration.$cleanBuild.defaultValue
 
@@ -148,6 +151,7 @@ struct ScanCommand: FrontendCommand {
         configuration.apply(\.$externalEncodableProtocols, externalEncodableProtocols)
         configuration.apply(\.$externalCodableProtocols, externalCodableProtocols)
         configuration.apply(\.$externalTestCaseClasses, externalTestCaseClasses)
+        configuration.apply(\.$autoRemove, autoRemove)
         configuration.apply(\.$verbose, verbose)
         configuration.apply(\.$quiet, quiet)
         configuration.apply(\.$disableUpdateCheck, disableUpdateCheck)

Sources/Frontend/Scan.swift

@@ -58,9 +58,9 @@ final class Scan {
         logger.endInterval(analyzeInterval)
 
         let resultInterval = logger.beginInterval("result:build")
-        let result = ScanResultBuilder.build(for: graph)
+        let results = ScanResultBuilder.build(for: graph)
         logger.endInterval(resultInterval)
 
-        return result
+        return results
     }
 }

Sources/PeripheryKit/CodeRemoval/EmptyExtensionSyntaxRemover.swift

@@ -0,0 +1,35 @@
+import Foundation
+import Foundation
+import SwiftParser
+import SwiftSyntax
+import SystemPackage
+
+final class EmptyExtensionSyntaxRemover: SyntaxRewriter, TriviaSplitting {
+    private let locationBuilder: SourceLocationBuilder
+
+    init(locationBuilder: SourceLocationBuilder) {
+        self.locationBuilder = locationBuilder
+    }
+
+    func perform(syntax: SourceFileSyntax) -> SourceFileSyntax {
+        visit(syntax)
+    }
+
+    override func visit(_ node: CodeBlockItemListSyntax) -> CodeBlockItemListSyntax {
+        let newChildren = node.compactMap { child -> CodeBlockItemSyntax? in
+            guard let extDecl = child.item.as(ExtensionDeclSyntax.self) else { return child }
+
+            let members = extDecl.memberBlock.members
+            let hasMembers = !(members.count == 0 || (members.count == 1 && members.first?.decl.is(MissingDeclSyntax.self) ?? false))
+            let hasInheritance = extDecl.inheritanceClause != nil
+
+            if !hasMembers, !hasInheritance {
+                return remainingTriviaDecl(from: child.item.leadingTrivia)
+            }
+
+            return child
+        }
+
+        return CodeBlockItemListSyntax(newChildren)
+    }
+}

Sources/PeripheryKit/CodeRemoval/EmptyFileVisitor.swift

@@ -0,0 +1,30 @@
+import Foundation
+import Foundation
+import SwiftParser
+import SwiftSyntax
+import SystemPackage
+
+final class EmptyFileVisitor: SyntaxVisitor, TriviaSplitting {
+    private var isEmpty = false
+
+    init() {
+        super.init(viewMode: .sourceAccurate)
+    }
+
+    func perform(syntax: SourceFileSyntax) -> Bool {
+        walk(syntax)
+        return isEmpty
+    }
+
+    override func visit(_ node: SourceFileSyntax) -> SyntaxVisitorContinueKind {
+        if node.statements.count == 0 {
+            isEmpty = true
+        } else {
+            isEmpty = node.statements.allSatisfy {
+                $0.item.is(ImportDeclSyntax.self) || $0.item.is(MissingDeclSyntax.self)
+            }
+        }
+
+        return .skipChildren
+    }
+}

Sources/PeripheryKit/CodeRemoval/PublicAccessibilitySyntaxRemover.swift

@@ -0,0 +1,194 @@
+import Foundation
+import SwiftParser
+import SwiftSyntax
+import SystemPackage
+
+final class PublicAccessibilitySyntaxRemover: SyntaxRewriter, SyntaxRemover {
+    private let resultLocation: SourceLocation
+    private let locationBuilder: SourceLocationBuilder
+
+    init(resultLocation: SourceLocation, replacements: [String], locationBuilder: SourceLocationBuilder) {
+        self.resultLocation = resultLocation
+        self.locationBuilder = locationBuilder
+    }
+
+    func perform(syntax: SourceFileSyntax) -> SourceFileSyntax {
+        visit(syntax)
+    }
+
+    override func visit(_ node: ClassDeclSyntax) -> DeclSyntax {
+        let newNode = removePublicModifier(
+            from: node,
+            at: node.name.positionAfterSkippingLeadingTrivia,
+            triviaRecipient: \.classKeyword
+        )
+        return super.visit(newNode)
+    }
+
+    override func visit(_ node: StructDeclSyntax) -> DeclSyntax {
+        let newNode = removePublicModifier(
+            from: node,
+            at: node.name.positionAfterSkippingLeadingTrivia,
+            triviaRecipient: \.structKeyword
+        )
+        return super.visit(newNode)
+    }
+
+    override func visit(_ node: EnumDeclSyntax) -> DeclSyntax {
+        let newNode = removePublicModifier(
+            from: node,
+            at: node.name.positionAfterSkippingLeadingTrivia,
+            triviaRecipient: \.enumKeyword
+        )
+        return super.visit(newNode)
+    }
+
+    override func visit(_ node: ExtensionDeclSyntax) -> DeclSyntax {
+        let newNode = removePublicModifier(
+            from: node,
+            at: node.extendedType.positionAfterSkippingLeadingTrivia,
+            triviaRecipient: \.extensionKeyword
+        )
+        return super.visit(newNode)
+    }
+
+    override func visit(_ node: ProtocolDeclSyntax) -> DeclSyntax {
+        let newNode = removePublicModifier(
+            from: node,
+            at: node.name.positionAfterSkippingLeadingTrivia,
+            triviaRecipient: \.protocolKeyword
+        )
+        return super.visit(newNode)
+    }
+
+    override func visit(_ node: InitializerDeclSyntax) -> DeclSyntax {
+        let newNode = removePublicModifier(
+            from: node,
+            at: node.initKeyword.positionAfterSkippingLeadingTrivia,
+            triviaRecipient: \.initKeyword
+        )
+        return super.visit(newNode)
+    }
+
+    override func visit(_ node: FunctionDeclSyntax) -> DeclSyntax {
+        let newNode = removePublicModifier(
+            from: node,
+            at: node.name.positionAfterSkippingLeadingTrivia,
+            triviaRecipient: \.funcKeyword
+        )
+        return super.visit(newNode)
+    }
+
+    override func visit(_ node: SubscriptDeclSyntax) -> DeclSyntax {
+        let newNode = removePublicModifier(
+            from: node,
+            at: node.subscriptKeyword.positionAfterSkippingLeadingTrivia,
+            triviaRecipient: \.subscriptKeyword
+        )
+        return super.visit(newNode)
+    }
+
+    override func visit(_ node: TypeAliasDeclSyntax) -> DeclSyntax {
+        let newNode = removePublicModifier(
+            from: node,
+            at: node.name.positionAfterSkippingLeadingTrivia,
+            triviaRecipient: \.typealiasKeyword
+        )
+        return super.visit(newNode)
+    }
+
+    override func visit(_ node: VariableDeclSyntax) -> DeclSyntax {
+        let newNode = removePublicModifier(
+            from: node,
+            at: node.bindings.positionAfterSkippingLeadingTrivia,
+            triviaRecipient: \.bindingSpecifier
+        )
+        return super.visit(newNode)
+    }
+
+    override func visit(_ node: ActorDeclSyntax) -> DeclSyntax {
+        let newNode = removePublicModifier(
+            from: node,
+            at: node.name.positionAfterSkippingLeadingTrivia,
+            triviaRecipient: \.actorKeyword
+        )
+        return super.visit(newNode)
+    }
+
+    override func visit(_ node: AssociatedTypeDeclSyntax) -> DeclSyntax {
+        let newNode = removePublicModifier(
+            from: node,
+            at: node.name.positionAfterSkippingLeadingTrivia,
+            triviaRecipient: \.associatedtypeKeyword
+        )
+        return super.visit(newNode)
+    }
+
+    override func visit(_ node: PrecedenceGroupDeclSyntax) -> DeclSyntax {
+        let newNode = removePublicModifier(
+            from: node,
+            at: node.name.positionAfterSkippingLeadingTrivia,
+            triviaRecipient: \.precedencegroupKeyword
+        )
+        return super.visit(newNode)
+    }
+
+    // MARK: - Private
+
+    private func removePublicModifier<T: PublicModifiedDecl, Output: SyntaxProtocol>(
+        from node: T,
+        at position: AbsolutePosition,
+        triviaRecipient: WritableKeyPath<T, Output>
+    ) -> T {
+        var removedLeadingTrivia = Trivia(pieces: [])
+        var didRemove = false
+
+        var newModifiers = node.modifiers.filter { modifier in
+            if locationBuilder.location(at: position) == resultLocation,
+               modifier.name.text == "public" {
+                didRemove = true
+                removedLeadingTrivia = modifier.leadingTrivia
+                return false
+            }
+
+            return true
+        }
+
+        var newNode = node
+
+        if didRemove {
+            if newModifiers.count == 0 {
+                let triviaRecipientNode = node[keyPath: triviaRecipient]
+                let newTriviaRecipientNode = triviaRecipientNode
+                    .with(\.leadingTrivia, removedLeadingTrivia + newModifiers.leadingTrivia)
+                newNode = newNode.with(triviaRecipient, newTriviaRecipientNode)
+            } else {
+                newModifiers = newModifiers
+                    .with(\.leadingTrivia, removedLeadingTrivia + newModifiers.leadingTrivia)
+            }
+
+            return newNode.with(\.modifiers, newModifiers)
+        } else {
+            return node
+        }
+    }
+}
+
+protocol PublicModifiedDecl: SyntaxProtocol {
+    var modifiers: DeclModifierListSyntax { get set }
+}
+
+extension ClassDeclSyntax: PublicModifiedDecl {}
+extension StructDeclSyntax: PublicModifiedDecl {}
+extension EnumDeclSyntax: PublicModifiedDecl {}
+extension EnumCaseDeclSyntax: PublicModifiedDecl {}
+extension ExtensionDeclSyntax: PublicModifiedDecl {}
+extension ProtocolDeclSyntax: PublicModifiedDecl {}
+extension InitializerDeclSyntax: PublicModifiedDecl {}
+extension FunctionDeclSyntax: PublicModifiedDecl {}
+extension SubscriptDeclSyntax: PublicModifiedDecl {}
+extension TypeAliasDeclSyntax: PublicModifiedDecl {}
+extension VariableDeclSyntax: PublicModifiedDecl {}
+extension ActorDeclSyntax: PublicModifiedDecl {}
+extension AssociatedTypeDeclSyntax: PublicModifiedDecl {}
+extension PrecedenceGroupDeclSyntax: PublicModifiedDecl {}