Fix false positives for SPM packages using custom path: argument

Sources/SPMParsing/PackageSwiftFileVisitor.swift

@@ -55,6 +55,10 @@ final class PackageSwiftFileVisitor: SyntaxVisitor {
                 targetType = .regular
             }
 
+            let pathArgument = targetCall.argumentList.first(where: { $0.label?.text == "path" })?
+                .expression.as(StringLiteralExprSyntax.self)?.segments.description
+                .trimmingCharacters(in: .punctuationCharacters)
+
             let dependenciesArray = targetCall.argumentList.first(where: { $0.label?.text == "dependencies" })?.expression.as(ArrayExprSyntax.self)?.elements
             let dependencies = dependenciesArray?.compactMap { element -> String? in
                 if let stringLiteral = element.expression.as(StringLiteralExprSyntax.self) {
@@ -76,7 +80,8 @@ final class PackageSwiftFileVisitor: SyntaxVisitor {
                 type: targetType,
                 dependencies: dependenciesSet,
                 duplicateDependencies: findDuplicateDependencies(dependencies),
-                layerNumber: layers[targetName]
+                layerNumber: layers[targetName],
+                path: pathArgument
             )
             targets.append(target)
         }

Sources/SPMParsing/PackagesParser.swift

@@ -45,9 +45,28 @@ final class PackagesParser {
                     guard target.duplicateDependencies.isEmpty else {
                         throw PackagesParser.Error.duplicateDependencies(targetName: target.name, dependencies: target.duplicateDependencies)
                     }
-                    var swiftFilesPath = path + "/" + package.name + target.type.intermediatePath + target.name
-                    if !FileManager.default.fileExists(atPath: swiftFilesPath) {
-                        swiftFilesPath = path + "/" + package.name + target.type.intermediatePath
+                    var swiftFilesPath: String
+                    if let customPath = target.path {
+                        // Normalize path: strip leading/trailing slashes to avoid double-slash issues
+                        let normalizedPath = customPath
+                            .trimmingCharacters(in: CharacterSet(charactersIn: "/"))
+                        // Use explicit path from Package.swift
+                        swiftFilesPath = path + "/" + package.name + "/" + normalizedPath
+                        // Error if custom path doesn't exist - don't silently scan nothing
+                        guard FileManager.default.fileExists(atPath: swiftFilesPath) else {
+                            throw PackagesParser.Error.customPathNotFound(
+                                targetName: target.name,
+                                path: customPath,
+                                resolvedPath: swiftFilesPath
+                            )
+                        }
+                    } else {
+                        // Fall back to convention: Sources/TargetName or Tests/TargetName
+                        swiftFilesPath = path + "/" + package.name + target.type.intermediatePath + target.name
+                        // Only fall back to parent directory if convention path doesn't exist
+                        if !FileManager.default.fileExists(atPath: swiftFilesPath) {
+                            swiftFilesPath = path + "/" + package.name + target.type.intermediatePath
+                        }
                     }
                     let swiftFilesParser = SwiftFilesParser(
                         rootURL: URL(fileURLWithPath: swiftFilesPath),
@@ -95,13 +114,16 @@ extension PackagesParser {
     enum Error: Swift.Error, CustomStringConvertible, Equatable {
         case failedToParsePackage(path: String)
         case duplicateDependencies(targetName: String, dependencies: [String])
+        case customPathNotFound(targetName: String, path: String, resolvedPath: String)
 
         var description: String {
             switch self {
             case .failedToParsePackage(let path):
                 "Failed to parse Package.swift at path: \(path)"
             case .duplicateDependencies(let targetName, let dependencies):
                 "❌ Target \(targetName) has duplicate dependencies: \(dependencies.joined(separator: ", "))"
+            case .customPathNotFound(let targetName, let path, let resolvedPath):
+                "❌ Target \(targetName) specifies path: \"\(path)\" but directory not found at: \(resolvedPath)"
             }
         }
     }

Sources/SPMParsing/SwiftPackageTarget.swift

@@ -11,4 +11,5 @@ struct SwiftPackageTarget: Equatable {
     let dependencies: Set<String>
     let duplicateDependencies: [String]
     let layerNumber: Int?
+    let path: String?
 }

Tests/SwiftImportChecksTests/DiagramBuilder/DiagramBuilderTests.swift

@@ -137,7 +137,8 @@ struct DiagramBuilderTests {
                     type: .test,
                     dependencies: [],
                     duplicateDependencies: [],
-                    layerNumber: nil
+                    layerNumber: nil,
+                    path: nil
                 )
             ]
         )
@@ -173,7 +174,8 @@ struct DiagramBuilderTests {
                     type: .regular,
                     dependencies: [],
                     duplicateDependencies: [],
-                    layerNumber: nil
+                    layerNumber: nil,
+                    path: nil
                 )
             ]
         )
@@ -212,7 +214,8 @@ struct DiagramBuilderTests {
                     type: .regular,
                     dependencies: [],
                     duplicateDependencies: [],
-                    layerNumber: 0
+                    layerNumber: 0,
+                    path: nil
                 )
             ]
         )

Tests/SwiftImportChecksTests/Example/CustomPathPackage/CustomPathPackage/CustomTests/TestFile.swift

@@ -0,0 +1,2 @@
+import Foundation
+import XCTest

Tests/SwiftImportChecksTests/Example/CustomPathPackage/CustomPathPackage/Sources/Core/CoreFile.swift

@@ -0,0 +1,2 @@
+import Foundation
+import CoreDependency

Tests/SwiftImportChecksTests/Example/CustomPathPackage/CustomPathPackage/Sources/UI/UIFile.swift

@@ -0,0 +1,2 @@
+import Foundation
+import UndeclaredDependency

Tests/SwiftImportChecksTests/Example/CustomPathPackage/Package.swift

@@ -0,0 +1,21 @@
+// swift-tools-version: 6.0
+// The swift-tools-version declares the minimum version of Swift required to build this package.
+
+import PackageDescription
+
+let package = Package(
+    name: "CustomPathPackage",
+    dependencies: [],
+    targets: [
+        .target(
+            name: "TestModule",
+            dependencies: ["CoreDependency"],
+            path: "Sources/Core"
+        ),
+        .testTarget(
+            name: "TestModuleTests",
+            dependencies: ["XCTest"],
+            path: "CustomTests"
+        )
+    ]
+)

Tests/SwiftImportChecksTests/Example/InvalidCustomPathPackage/Package.swift

@@ -0,0 +1,16 @@
+// swift-tools-version: 6.0
+// The swift-tools-version declares the minimum version of Swift required to build this package.
+
+import PackageDescription
+
+let package = Package(
+    name: "InvalidPathPackage",
+    dependencies: [],
+    targets: [
+        .target(
+            name: "MissingModule",
+            dependencies: [],
+            path: "Sources/DoesNotExist"
+        )
+    ]
+)

Tests/SwiftImportChecksTests/SPMParsing/PackagesParserTests.swift

@@ -144,6 +144,63 @@ struct PackagesParserTests {
         )
         #expect(messages == expectedMessages)
     }
+
+    @Test("test parsePackages given valid path with custom path argument uses correct target path")
+    func parsePackagesGivenValidPathWithCustomPathArgument() throws {
+        // Given
+        // This test verifies that:
+        // 1. Files in Sources/Core are scanned for TestModule (has CoreDependency import)
+        // 2. Files in Sources/UI are NOT scanned (has UndeclaredDependency import that would fail)
+        // 3. Files in CustomTests are scanned for TestModuleTests (testTarget with custom path)
+        let path: String = URL.Mock.customPathPackageFileDir.relativePath
+        var messages: [String] = []
+        let expectedMessages: [String] = [
+            "Package: CustomPathPackage Target: TestModule - Type: regular",
+            "✅ All imports for target TestModule are explicit",
+            "Package: CustomPathPackage Target: TestModuleTests - Type: test",
+            "✅ All imports for target TestModuleTests are explicit"
+        ]
+        let sut = makeSUT(path: path)
+
+        // When
+        try sut.parsePackages(
+            configs: configs,
+            verbose: verbose,
+            print: { messages.append($0) }
+        )
+
+        // Then
+        // If Sources/UI was incorrectly scanned, this would fail with UndeclaredDependency error
+        #expect(messages == expectedMessages)
+    }
+
+    @Test("test parsePackages given custom path that does not exist throws error")
+    func parsePackagesGivenCustomPathNotFoundThrowsError() throws {
+        // Given
+        let path: String = URL.Mock.invalidCustomPathPackageFileDir.relativePath
+        var messages: [String] = []
+        let expectedMessages: [String] = [
+            "Package: InvalidPathPackage Target: MissingModule - Type: regular"
+        ]
+        let sut = makeSUT(path: path)
+
+        // When, Then
+        #expect(
+            throws: PackagesParser.Error.customPathNotFound(
+                targetName: "MissingModule",
+                path: "Sources/DoesNotExist",
+                resolvedPath: path + "/InvalidPathPackage/Sources/DoesNotExist"
+            ),
+            performing: {
+                try sut.parsePackages(
+                    configs: configs,
+                    verbose: verbose,
+                    print: { messages.append($0) }
+                )
+            }
+        )
+        #expect(messages == expectedMessages)
+    }
 }
 
 extension PackagesParserTests {
@@ -162,5 +219,7 @@ private extension URL {
         static let secondPackageFileDir = Bundle.module.url(forResource: "Example/SecondPackage/Package", withExtension: "swift")!.deletingLastPathComponent()
         static let duplicatesPackageFileDir = Bundle.module.url(forResource: "Example/DuplicatesPackage/Package", withExtension: "swift")!.deletingLastPathComponent()
         static let failurePackageFileDir = Bundle.module.url(forResource: "Example/FailurePackage/Package", withExtension: "swift")!.deletingLastPathComponent()
+        static let customPathPackageFileDir = Bundle.module.url(forResource: "Example/CustomPathPackage/Package", withExtension: "swift")!.deletingLastPathComponent()
+        static let invalidCustomPathPackageFileDir = Bundle.module.url(forResource: "Example/InvalidCustomPathPackage/Package", withExtension: "swift")!.deletingLastPathComponent()
     }
 }