fix: ensure that file references are fixed for filesystem synchronized root groups

Sources/XcodeProj/Utils/ReferenceGenerator.swift

@@ -139,6 +139,8 @@ final class ReferenceGenerator: ReferenceGenerating {
             guard let childFileElement: PBXFileElement = child.getObject() else { return }
             if let childGroup = childFileElement as? PBXGroup {
                 try generateGroupReferences(childGroup, identifiers: identifiers)
+            } else if let childSynchronizedRootGroup = childFileElement as? PBXFileSystemSynchronizedRootGroup {
+                try generateSynchronizedRootGroupReferences(childSynchronizedRootGroup, identifiers: identifiers)
             } else if let childFileReference = childFileElement as? PBXFileReference {
                 try generateFileReference(childFileReference, identifiers: identifiers)
             } else if let childReferenceProxy = childFileElement as? PBXReferenceProxy {
@@ -161,6 +163,21 @@ final class ReferenceGenerator: ReferenceGenerating {
         fixReference(for: fileReference, identifiers: identifiers)
     }
 
+    /// Generates the reference for a synchronized root group object.
+    ///
+    /// - Parameters:
+    ///   - synchronizedRootGroup: synchronized root group instance.
+    ///   - identifiers: list of identifiers.
+    private func generateSynchronizedRootGroupReferences(_ synchronizedRootGroup: PBXFileSystemSynchronizedRootGroup,
+                                                         identifiers: [String]) throws {
+        var identifiers = identifiers
+        if let groupName = synchronizedRootGroup.fileName() {
+            identifiers.append(groupName)
+        }
+
+        fixReference(for: synchronizedRootGroup, identifiers: identifiers)
+    }
+
     /// Generates the reference for a configuration list object.
     ///
     /// - Parameters:

Tests/XcodeProjTests/Utils/ReferenceGeneratorTests.swift

@@ -83,6 +83,21 @@ class ReferenceGeneratorTests: XCTestCase {
 
         XCTAssertNotEqual(firstProductsGroupUUID, secondProductsGroupUUID)
     }
+
+    func test_projectWithFilesystemSynchronizedRootGroup_convertsReferencesToPermanent() throws {
+        let project = PBXProj(rootObject: nil, objectVersion: 0, archiveVersion: 0, classes: [:], objects: [])
+        let pbxProject = project.makeProject()
+
+        let syncedGroup = project.makeSynchronizedRootGroup()
+        let target = project.makeTarget()
+        target.fileSystemSynchronizedGroups = [syncedGroup]
+        pbxProject.targets.append(target)
+
+        let referenceGenerator = ReferenceGenerator(outputSettings: PBXOutputSettings())
+        try referenceGenerator.generateReferences(proj: project)
+
+        XCTAssert(!syncedGroup.reference.temporary)
+    }
 }
 
 private extension PBXProj {
@@ -168,4 +183,23 @@ private extension PBXProj {
 
         return (target, buildFile)
     }
+
+    func makeTarget() -> PBXTarget {
+        let target = PBXNativeTarget(name: "MyApp",
+                                     productName: "MyApp.app",
+                                     productType: .application)
+        add(object: target)
+        return target
+    }
+
+    func makeSynchronizedRootGroup() -> PBXFileSystemSynchronizedRootGroup {
+        let syncedGroup = PBXFileSystemSynchronizedRootGroup(
+            sourceTree: .group,
+            path: "SyncedPath",
+            name: "SyncedGroup"
+        )
+        add(object: syncedGroup)
+        rootObject!.mainGroup.children.append(syncedGroup)
+        return syncedGroup
+    }
 }