Improve support for multi-platform projects

In response to #462, a check was added to detect index stores containing multiple units for any given source file, and raise an error. The ultimate cause of the issue was the use of a custom `--index-store` path and Xcode being left open on a CI machine. Still, the check seemed reasonable to include to prevent others running into the same issue.

Some users then began running into this new error on projects that contained multi-platform targets, such as those with watchOS extensions. To workaround this, a mechanism was added that attempted to identify which index store units should be indexed by computing a target triple from the output of `xcodebuild -showBuildSettings`. Unfortunately, this approach did not work in some cases as `-showBuildSettings` does not respect the `-destination` argument, resulting in incorrect computed target triples.

There doesn't appear to be a simple way to compute a target triple ahead of time, and thus any potentially fixes will further increase the complexity of an already complex mechanism. Given that the original reason for #462 was caused by a user's particular setup, rather than an inherent issue with the index store, this change reverts all checks around the nature of units contained in the index store. I think this is a reasonable trade-off, as multi-platform projects are likely more command than the situations like the one faced in #462.

A new warning has been added when using `--index-store` to inform users that Xcode should not write to the index store while Periphery runs.

CHANGELOG.md

@@ -11,6 +11,7 @@
 ##### Bug Fixes
 
 - Fix redundant public accessibility analysis for protocol members declared in extensions that are referenced cross-module where the protocol itself is not.
+- Remove checks causing errors when scanning multi-platform projects.
 
 ## 2.16.0 (2023-09-27)
 

Sources/Frontend/Scan.swift

@@ -12,9 +12,13 @@ final class Scan {
     }
 
     func perform(project: Project) throws -> [ScanResult] {
-        if !configuration.indexStorePath.isEmpty, !configuration.skipBuild {
-            logger.warn("The '--index-store-path' option implies '--skip-build', specify it to silence this warning")
-            configuration.skipBuild = true
+        if !configuration.indexStorePath.isEmpty {
+            logger.warn("When using the '--index-store-path' option please ensure that Xcode is not running. False-positives can occur if Xcode writes to the index store while Periphery is running.")
+
+            if !configuration.skipBuild {
+                logger.warn("The '--index-store-path' option implies '--skip-build', specify it to silence this warning.")
+                configuration.skipBuild = true
+            }
         }
 
         if configuration.verbose {

Sources/PeripheryKit/Indexer/IndexTarget.swift

@@ -2,10 +2,8 @@ import Foundation
 
 public struct IndexTarget: Hashable {
     public let name: String
-    public var triple: String?
 
-    public init(name: String, triple: String? = nil) {
+    public init(name: String) {
         self.name = name
-        self.triple = triple
     }
 }

Sources/PeripheryKit/Indexer/JobPool.swift

@@ -23,7 +23,7 @@ struct JobPool<T> {
         }
     }
 
-    func map<R>(_ block: @escaping (T) throws -> R) throws -> [R] {
+    func flatMap<R>(_ block: @escaping (T) throws -> [R]) throws -> [R] {
         var error: Error?
         var results: [R] = []
         let lock = UnfairLock()
@@ -36,7 +36,7 @@ struct JobPool<T> {
                 let result = try block(job)
 
                 lock.perform {
-                    results.append(result)
+                    results.append(contentsOf: result)
                 }
             } catch let e {
                 error = e
@@ -49,32 +49,4 @@ struct JobPool<T> {
 
         return results
     }
-
-    func compactMap<R>(_ block: @escaping (T) throws -> R?) throws -> [R] {
-        var error: Error?
-        var results: [R] = []
-        let lock = UnfairLock()
-
-        DispatchQueue.concurrentPerform(iterations: jobs.count) { idx in
-            guard error == nil else { return }
-
-            do {
-                let job = jobs[idx]
-                if let result = try block(job) {
-                    lock.perform {
-                        results.append(result)
-                    }
-                }
-            } catch let e {
-                error = e
-            }
-        }
-
-        if let error = error {
-            throw error
-        }
-
-        return results
-    }
-
 }

Sources/PeripheryKit/Indexer/SwiftIndexer.swift

@@ -32,47 +32,28 @@ public final class SwiftIndexer: Indexer {
         let (includedFiles, excludedFiles) = filterIndexExcluded(from: allSourceFiles)
         excludedFiles.forEach { self.logger.debug("Excluding \($0.string)") }
 
-        let stores = try JobPool(jobs: indexStorePaths)
-            .map { [logger] indexStorePath in
+        let unitsByFile = try JobPool(jobs: indexStorePaths)
+            .flatMap { [logger, currentFilePath] indexStorePath in
                 logger.debug("Reading \(indexStorePath)")
                 let indexStore = try IndexStore.open(store: URL(fileURLWithPath: indexStorePath.string), lib: .open())
-                return (indexStore, indexStore.units(includeSystem: false))
-            }
-
-        let units = stores.reduce(into: [(IndexStore, IndexStoreUnit)]()) { result, tuple in
-            let (indexStore, units) = tuple
-            units.forEach { result.append((indexStore, $0)) }
-        }
-
-        let unitsByFile = try JobPool(jobs: units)
-            .compactMap { [logger, sourceFiles, currentFilePath] (indexStore, unit) -> (FilePath, IndexStore, IndexStoreUnit)? in
-                guard let filePath = try indexStore.mainFilePath(for: unit) else { return nil }
+                let units = indexStore.units(includeSystem: false)
 
-                let file = FilePath.makeAbsolute(filePath, relativeTo: currentFilePath)
+                return try units.compactMap { unit  -> (FilePath, IndexStore, IndexStoreUnit)? in
+                    guard let filePath = try indexStore.mainFilePath(for: unit) else { return nil }
 
-                if includedFiles.contains(file) {
-                    // Ignore units built for other architectures/platforms.
-                    let validTargetTriples = sourceFiles[file]?.compactMapSet { $0.triple } ?? []
+                    let file = FilePath.makeAbsolute(filePath, relativeTo: currentFilePath)
 
-                    if validTargetTriples.isEmpty {
+                    if includedFiles.contains(file) {
                         return (file, indexStore, unit)
-                    } else {
-                        if let unitTargetTriple = try indexStore.target(for: unit) {
-                            if validTargetTriples.contains(unitTargetTriple) {
-                                return (file, indexStore, unit)
-                            }
-                        } else {
-                            logger.warn("No unit target triple for: \(file)")
-                        }
                     }
-                }
 
-                return nil
+                    return nil
+                }
             }
-           .reduce(into: [FilePath: [(IndexStore, IndexStoreUnit)]](), { result, tuple in
-               let (file, indexStore, unit) = tuple
-               result[file, default: []].append((indexStore, unit))
-           })
+            .reduce(into: [FilePath: [(IndexStore, IndexStoreUnit)]](), { result, tuple in
+                let (file, indexStore, unit) = tuple
+                result[file, default: []].append((indexStore, unit))
+            })
 
         let indexedFiles = Set(unitsByFile.keys)
         let unindexedFiles = allSourceFiles.subtracting(excludedFiles).subtracting(indexedFiles)
@@ -83,21 +64,9 @@ public final class SwiftIndexer: Indexer {
             throw PeripheryError.unindexedTargetsError(targets: targets, indexStorePaths: indexStorePaths)
         }
 
-        let jobs = try unitsByFile.map { (file, units) -> Job in
-            let modules = try units.reduce(into: Set<String>()) { (set, tuple) in
-                let (indexStore, unit) = tuple
-                if let name = try indexStore.moduleName(for: unit) {
-                    let (didInsert, _) = set.insert(name)
-                    if !didInsert {
-                        let targets = try units.compactMapSet { try indexStore.target(for: $0.1) }
-                        throw PeripheryError.conflictingIndexUnitsError(file: file, module: name, unitTargets: targets)
-                    }
-                }
-            }
-            let sourceFile = SourceFile(path: file, modules: modules)
-
+        let jobs = unitsByFile.map { (file, units) -> Job in
             return Job(
-                file: sourceFile,
+                file: file,
                 units: units,
                 graph: graph,
                 logger: logger,
@@ -113,7 +82,7 @@ public final class SwiftIndexer: Indexer {
                 try job.phaseOne()
             }
 
-            phaseOneLogger.debug("\(job.file.path) (\(elapsed)s)")
+            phaseOneLogger.debug("\(job.file) (\(elapsed)s)")
         }
 
         logger.endInterval(phaseOneInterval)
@@ -126,7 +95,7 @@ public final class SwiftIndexer: Indexer {
                 try job.phaseTwo()
             }
 
-            phaseTwoLogger.debug("\(job.file.path) (\(elapsed)s)")
+            phaseTwoLogger.debug("\(job.file) (\(elapsed)s)")
         }
 
         logger.endInterval(phaseTwoInterval)
@@ -135,15 +104,16 @@ public final class SwiftIndexer: Indexer {
     // MARK: - Private
 
     private class Job {
-        let file: SourceFile
+        let file: FilePath
 
         private let units: [(IndexStore, IndexStoreUnit)]
         private let graph: SourceGraph
         private let logger: ContextualLogger
         private let configuration: Configuration
+        private var sourceFile: SourceFile?
 
         required init(
-            file: SourceFile,
+            file: FilePath,
             units: [(IndexStore, IndexStoreUnit)],
             graph: SourceGraph,
             logger: ContextualLogger,
@@ -203,7 +173,7 @@ public final class SwiftIndexer: Indexer {
 
                     try indexStore.forEachOccurrences(for: record, language: .swift) { occurrence in
                         guard let usr = occurrence.symbol.usr,
-                              let location = transformLocation(occurrence.location)
+                              let location = try transformLocation(occurrence.location)
                               else { return true }
 
                         if !occurrence.roles.intersection([.definition, .declaration]).isEmpty {
@@ -262,13 +232,14 @@ public final class SwiftIndexer: Indexer {
 
         /// Phase two associates latent references, and performs other actions that depend on the completed source graph.
         func phaseTwo() throws {
-            let multiplexingSyntaxVisitor = try MultiplexingSyntaxVisitor(file: file)
+            let sourceFile = try getSourceFile()
+            let multiplexingSyntaxVisitor = try MultiplexingSyntaxVisitor(file: sourceFile)
             let declarationSyntaxVisitor = multiplexingSyntaxVisitor.add(DeclarationSyntaxVisitor.self)
             let importSyntaxVisitor = multiplexingSyntaxVisitor.add(ImportSyntaxVisitor.self)
 
             multiplexingSyntaxVisitor.visit()
 
-            file.importStatements = importSyntaxVisitor.importStatements
+            sourceFile.importStatements = importSyntaxVisitor.importStatements
 
             associateLatentReferences()
             associateDanglingReferences()
@@ -277,12 +248,29 @@ public final class SwiftIndexer: Indexer {
             applyCommentCommands(using: multiplexingSyntaxVisitor)
         }
 
+        // MARK: - Private
+
         private var declarations: [Declaration] = []
         private var childDeclsByParentUsr: [String: Set<Declaration>] = [:]
         private var referencesByUsr: [String: Set<Reference>] = [:]
         private var danglingReferences: [Reference] = []
         private var varParameterUsrs: Set<String> = []
 
+        private func getSourceFile() throws -> SourceFile {
+            if let sourceFile { return sourceFile }
+
+            let modules = try units.reduce(into: Set<String>()) { (set, tuple) in
+                let (indexStore, unit) = tuple
+                if let name = try indexStore.moduleName(for: unit) {
+                    set.insert(name)
+                }
+            }
+
+            let sourceFile = SourceFile(path: file, modules: modules)
+            self.sourceFile = sourceFile
+            return sourceFile
+        }
+
         private func establishDeclarationHierarchy() {
             graph.withLock {
                 for (parent, decls) in childDeclsByParentUsr {
@@ -446,7 +434,7 @@ public final class SwiftIndexer: Indexer {
 
             let analyzer = UnusedParameterAnalyzer()
             let paramsByFunction = analyzer.analyze(
-                file: file,
+                file: syntaxVisitor.sourceFile,
                 syntax: syntaxVisitor.syntax,
                 locationConverter: syntaxVisitor.locationConverter,
                 parseProtocols: true)
@@ -661,8 +649,8 @@ public final class SwiftIndexer: Indexer {
             return refs
         }
 
-        private func transformLocation(_ input: IndexStoreOccurrence.Location) -> SourceLocation? {
-            return SourceLocation(file: file, line: Int(input.line), column: Int(input.column))
+        private func transformLocation(_ input: IndexStoreOccurrence.Location) throws -> SourceLocation? {
+            return SourceLocation(file: try getSourceFile(), line: Int(input.line), column: Int(input.column))
         }
 
         private func transformDeclarationKind(_ kind: IndexStoreSymbol.Kind, _ subKind: IndexStoreSymbol.SubKind) -> Declaration.Kind? {

Sources/PeripheryKit/Syntax/MultiplexingSyntaxVisitor.swift

@@ -86,13 +86,15 @@ extension PeripherySyntaxVisitor {
 }
 
 final class MultiplexingSyntaxVisitor: SyntaxVisitor {
+    let sourceFile: SourceFile
     let syntax: SourceFileSyntax
     let locationConverter: SourceLocationConverter
     let sourceLocationBuilder: SourceLocationBuilder
 
     private var visitors: [PeripherySyntaxVisitor] = []
 
     required init(file: SourceFile) throws {
+        self.sourceFile = file
         let source = try String(contentsOf: file.path.url)
         self.syntax = Parser.parse(source: source)
         self.locationConverter = SourceLocationConverter(fileName: file.path.string, tree: syntax)

Sources/PeripheryKit/Syntax/UnusedParameterAnalyzer.swift

@@ -1,5 +1,6 @@
 import Foundation
 import SwiftSyntax
+import SystemPackage
 
 final class UnusedParameterAnalyzer {
     private enum UsageType {

Sources/Shared/Extensions/Sequence+Extension.swift

@@ -30,11 +30,4 @@ public extension Sequence {
             }
         }
     }
-
-    func mapDict<Key, Value>(_ transform: (Element) throws -> (Key, Value)) rethrows -> Dictionary<Key, Value> {
-        try reduce(into: .init()) { result, element in
-            let pair = try transform(element)
-            result[pair.0] = pair.1
-        }
-    }
 }

Sources/Shared/Logger.swift

@@ -146,10 +146,6 @@ public struct ContextualLogger {
         logger.debug("[\(context)] \(text)")
     }
 
-    public func warn(_ text: String) {
-        logger.warn("[\(context)] \(text)")
-    }
-
     public func beginInterval(_ name: StaticString) -> SignpostInterval {
         logger.beginInterval(name)
     }

Sources/Shared/PeripheryError.swift

@@ -20,8 +20,6 @@ public enum PeripheryError: Error, LocalizedError, CustomStringConvertible {
     case unindexedTargetsError(targets: Set<String>, indexStorePaths: [FilePath])
     case jsonDeserializationError(error: Error, json: String)
     case indexStoreNotFound(derivedDataPath: String)
-    case conflictingIndexUnitsError(file: FilePath, module: String, unitTargets: Set<String>)
-    case invalidTargetTriple(target: String, arch: String, vendor: String, osVersion: String)
 
     public var errorDescription: String? {
         switch self {
@@ -67,15 +65,6 @@ public enum PeripheryError: Error, LocalizedError, CustomStringConvertible {
             return "JSON deserialization failed: \(describe(error))\nJSON:\n\(json)"
         case let .indexStoreNotFound(derivedDataPath):
             return "Failed to find index datastore at path: \(derivedDataPath)"
-        case let .conflictingIndexUnitsError(file, module, targets):
-            var parts = ["Found conflicting index store units for '\(file)' in module '\(module)'."]
-            if targets.count > 1 {
-                parts.append("The units have conflicting build targets: \(targets.sorted().joined(separator: ", ")).")
-            }
-            parts.append("If you passed the '--index-store-path' option, ensure that Xcode is not open with a project that may write to this index store while Periphery is running.")
-            return parts.joined(separator: " ")
-        case let .invalidTargetTriple(target, arch, vendor, osVersion):
-            return "Failed to construct triple for target '\(target)': \(arch), \(vendor), \(osVersion)"
         }
     }
 

Sources/XcodeSupport/XcodeProjectDriver.swift

@@ -113,19 +113,6 @@ public final class XcodeProjectDriver {
 
 extension XcodeProjectDriver: ProjectDriver {
     public func build() throws {
-        // Copy target triples to the targets. The triple is used by the indexer to ignore index store units built for
-        // other architectures/platforms.
-        let targetTriples = try xcodebuild.buildSettings(targets: targets)
-            .mapDict { action in
-                (action.target, try action.makeTargetTriple())
-            }
-
-        for target in targets {
-            if let triple = targetTriples[target.name] {
-                target.triple = triple
-            }
-        }
-
         guard  !configuration.skipBuild else { return }
 
         if configuration.cleanBuild {
@@ -164,7 +151,7 @@ extension XcodeProjectDriver: ProjectDriver {
 
         for target in targets {
             target.files(kind: .swift).forEach {
-                let indexTarget = IndexTarget(name: target.name, triple: target.triple)
+                let indexTarget = IndexTarget(name: target.name)
                 sourceFiles[$0, default: []].insert(indexTarget)
             }
         }