fix(file-provider): Build XPC components with ARC

[claucambra]

Summary

Adds remaining XPC components to ARC build

Checklist

• Sign-off message is added to all commits.
• The commit messages are following The Conventional Commits specification.
• The commit history is clean with no merge commits.
  • How to rebase your commits
  • How to squash commits with rebase
• Uploaded screenshots from before and after for UI changes.
• Test(s) added to branch, with before/after results included in PR description, for performance improvements where applicable.
• Documentation has been updated or is not required.
• Backports requested where applicable (critical bugfixes).
• Labels added where applicable (bug/enhancement).
• Milestone added for target version.

AI (if applicable)

• The content of this PR was partly or fully generated using AI
  • I have read the guidelines for AI-assisted contributions.
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[claucambra]

/backport to stable-35.0

[i2h3]

Wait… No, actually, this does not compile. 😅 It looks good but there is a problem with it.

Must fix

1. The branch does not compile (src/gui/macOS/fileproviderxpc_mac_utils.mm:93, :139)

   • What this is: getFileProviderServices and connectToFileProviderServices wait on a dispatch group and then free it.
   • Problem: These two dispatch_release(group) calls were missed in the ARC conversion. Under -fobjc-arc, clang fails with 'release' is unavailable: not available in automatic reference counting mode.
   • Fix: Delete both lines, as was already done in getDomainManagers and getFileProviderDomainIdentifier.
   • If we skip it: Every build with BUILD_FILE_PROVIDER_MODULE=ON fails, and so does this commit when bisecting.

2. FileProviderXPCUtilsTest no longer compiles, and its ownership checks are now wrong (test/macOS/testfileproviderxpcutils.cpp, src/gui/macOS/fileproviderxpc_mac_utils.h:19)

   • What this is: The test checks who owns the objects that the XPC utilities return. It is built with -x objective-c++ and without -fobjc-arc (test/macOS/CMakeLists.txt:14).
   • Problem: The header now contains static_assert(__has_feature(objc_arc)), so the test fails to compile. Even without the assert, the test still calls release on values that ARC now returns at +0 ([services release] at lines 203 and 215, [domainIdentifier release] at line 228). That over-releases them and crashes.
   • Fix:
     • Compile the test with -fobjc-arc next to -x objective-c++.
     • Remove the manual release calls, and take the returned pointers back with __bridge_transfer.
     • Wrap the processClientCommunicationConnections calls in @autoreleasepool { } before the *Deallocated checks.
     • Drop or rename clientCommunicationDomainIdentifierCanBeReleasedByCaller, because the +1 contract it tests no longer exists.
     • Move the static_assert from the header into fileproviderxpc_mac_utils.mm and fileproviderxpc_mac.mm, as every other ARC file does (e.g. src/gui/macOS/fileprovider_mac.mm:18).
   • If we skip it: CI fails when tests are built, and nothing tests the new ownership contract.

Should fix

3. AGENTS.md now says every Objective-C file uses ARC, but 8 files still do not (AGENTS.md:218)
   • What this is: This rule tells agents which memory-management model to follow.
   • Problem: These files still use manual reference counting: src/gui/cocoainitializer_mac.mm, src/gui/macOS/fileproviderservice.mm, src/gui/macOS/findersyncservice.mm, src/gui/macOS/findersyncxpc_mac.mm, src/gui/macOS/localnetworkpermission.mm, src/gui/updater/sparkleupdater_mac.mm, src/libsync/settingsources_mac.mm and src/libsync/theme_mac.mm. The old warning against ARC-only features in those files is gone. An agent that edits findersyncxpc_mac.mm and follows the new rule leaves out release, so the object leaks without any warning. Or the agent converts the whole file as an unrelated side change.
   • Fix: Keep the new rule as the goal, and add one sentence: files not yet compiled with -fobjc-arc (see src/gui/CMakeLists.txt and src/common/common.cmake) still use manual reference counting until a separate change converts them.
   • If we skip it: Agents add leaks to the files that still use manual reference counting.

Nice to have

4. A copy that is no longer needed (src/gui/macOS/fileproviderxpc_mac_utils.mm:203)
   • What this is: getFileProviderDomainIdentifier returns the domain identifier as an NSString.
   • Problem: [[NSString alloc] initWithString:...] only existed to give manual-reference-counting callers a +1 object to release. Under ARC it is an extra copy.
   • Fix: return domainIdentifier.toNSString();
   • If we skip it: Each call makes one small extra copy. Nothing breaks.

[claucambra]

@i2h3 thanks for the comments

Wait… No, actually, this does not compile. 😅 It looks good but there is a problem with it.

looks like I missed what broke when I extracted this from the original xpc timeout branch
thanks, fixed

its ownership checks are now wrong

also fixed

AGENTS.md now says every Objective-C file uses ARC, but 8 files still do not

thanks, fixed

A copy that is no longer needed

also fixed

[sonarqubecloud]

Quality Gate failed

Failed conditions
0.0% Coverage on New Code (required ≥ 80%)
6 New Code Smells (required ≤ 0)
C Maintainability Rating on New Code (required ≥ A)

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