Removing a target referenced by PBXFileSystemSynchronizedBuildFileExceptionSet crashes serialization

[Alexis-Fab]

Summary

Calling removeFromProject() on a PBXNativeTarget does not cascade to PBXFileSystemSynchronizedBuildFileExceptionSet objects that reference that target. The orphaned exception sets retain a nil target reference, which crashes during serialization when generating the plist annotation (target.name on nil).

Minimal reproduction

Setup (Xcode 16+):

1. Create a project with two app targets: AppA and AppB
2. Create a folder SharedSrc/ containing Shared.swift and Info.plist
3. In Xcode, drag SharedSrc/ into the project as a synchronized folder reference, with both targets checked
4. Select Info.plist in the navigator, open the File Inspector, and uncheck AppB from Target Membership

This creates a PBXFileSystemSynchronizedBuildFileExceptionSet with target = AppB inside the SharedSrc synchronized root group — meaning "exclude Info.plist from AppB's build."

Reproduction (Ruby xcodeproj gem v1.27.0):

require "xcodeproj"

proj = Xcodeproj::Project.open("Repro.xcodeproj")

# Removing AppA works fine (not referenced by any exception set)
proj.targets.find { |t| t.name == "AppA" }.remove_from_project
proj.save  # => OK

# Removing AppB crashes (referenced by the exception set)
proj.targets.find { |t| t.name == "AppB" }.remove_from_project
proj.save  # => CRASH

Crash:

PBXFileSystemSynchronizedBuildFileExceptionSet#display_name: undefined method 'name' for nil (NoMethodError)
  "Exceptions for \"#{GroupableHelper.parent(self).display_name}\" in \"#{target.name}\" target"

What happens

• removeFromProject() on the target removes the PBXNativeTarget object, its build configuration list, and its build phases
• It does not remove PBXFileSystemSynchronizedBuildFileExceptionSet objects whose target property pointed to the removed target
• On save, the serializer calls display_name on each exception set, which accesses target.name — now nil — and crashes

What should happen

removeFromProject() on a PBXNativeTarget should also remove any PBXFileSystemSynchronizedBuildFileExceptionSet whose target references the removed target. Xcode's UI does this cleanup when deleting a target — the programmatic API should match.

Additional incomplete cascading

Beyond exception sets, removeFromProject() also leaves behind:

• PBXFileReference for the target's product (.app, .xctest)
• The product reference in the Products group
• PBXGroup entries for the target's source directory

These don't crash serialization but leave orphaned entries in the project file.

Workaround

Clean up orphaned exception sets manually before saving:

proj.objects.select { |o|
  o.isa == "PBXFileSystemSynchronizedBuildFileExceptionSet" &&
  o.respond_to?(:target) && o.target.nil?
}.each { |o| o.remove_from_project }

Environment

• Ruby xcodeproj gem 1.27.0
• Project created with Xcode 26 beta (uses synchronized folders / PBXFileSystemSynchronizedRootGroup)
• Also reproduced via xcodeproj-mcp-server v1.5.0, which uses the Swift tuist/XcodeProj library — same crash (exit code 133 / SIGTRAP, the Swift equivalent of nil access)

[dosubot]

Hi @Alexis-Fab! I'm Dosu and I’m helping the XcodeProj team.

Thanks for the detailed bug report! This is a confirmed gap in XcodeProj's object lifecycle management.

Root Cause: The Swift XcodeProj library doesn't have a high-level removeFromProject() method with cascade deletion. It only provides PBXObjects.delete(reference:) which removes objects from internal dictionaries without cleaning up related references [1]. The PBXFileSystemSynchronizedBuildFileExceptionSet.target property is a force-unwrapped PBXTarget! that crashes when the referenced target no longer exists [2].

Swift Workaround (equivalent to your Ruby fix):

let exceptionSetsToRemove = proj.pbxproj.objects.fileSystemSynchronizedBuildFileExceptionSets.values.filter {
    $0.targetReference == targetToDelete.reference
}
for exceptionSet in exceptionSetsToRemove {
    proj.pbxproj.delete(object: exceptionSet)
}
proj.pbxproj.delete(object: targetToDelete)

This pattern aligns with recent fixes like PR #1044 which addressed similar orphaned reference issues for XCLocalSwiftPackageReference objects by adding explicit cleanup handling.

A proper fix would involve either:

1. Making target optional (PBXTarget?) to fail gracefully
2. Adding cascade deletion logic in PBXObjects.delete() to automatically clean up exception sets when targets are removed

Would you be interested in contributing a PR for this?

To reply, just mention @dosu.

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[Alexis-Fab]

Thanks for confirming the root cause! I'll try to find a moment to contribute the fix, probably scoping it to the PBXFileSystemSynchronizedBuildFileExceptionSet cascade in removeFromProject() as described, without touching the other orphaned objects for now to keep the PR reviewable. No ETA I can commit to, but I'll post here if I open something.