Unknown Error when adding an CSSearchableItem to Core Spotlight (MacOS)

Question

I recently wanted to power the search in one of my projects with Core Spotlight. However, whenever I add an CSSearchableItem to the SearchIndex, I get an error in the completion handler with the description:

The operation couldn’t be completed. (CSIndexErrorDomain error -1.)

According to Apple's reference, the error code -1 refers to Unknown Error, which isn't exactly helpful. I added both CoreSpotlight and CoreServices frameworks to my app and I really have no idea of what I might have done wrong.

I put together a minimal example:

import Foundation
import CoreSpotlight

print("Start indexing...")
let attributeSet = CSSearchableItemAttributeSet(itemContentType: kUTTypeText as String)
attributeSet.title = "test element"
attributeSet.contentDescription = "This is a description."
attributeSet.keywords =  ["test1", "test2", "test3"]
let item = CSSearchableItem(uniqueIdentifier: "123455", domainIdentifier: "TestDomain", attributeSet: attributeSet)
var ready = false
CSSearchableIndex.default().indexSearchableItems([item]) { (error) in
    if error == nil {
        print("Success")
    } else {
        print(error?.localizedDescription)
    }
    ready = true
}
//Wait for the block to finish
while (ready == false) {
    sleep(1)
}
print("Finish indexing...")

I managed to compile Apple's example project for Core Spotlight from WWDC17, and it does in fact work without an error. However, I can't obtain the indexed items with the systemwide Spotlight search.

Does anyone have an idea what might be off? By the way, I'm running the latest High Sierra release.

[Edit] Just saw, that there is in fact someone else with this question. However, the question isn't answered yet: Error while using CoreSpotlight

[Edit2] After updating to 10.13.2, the behaviour changed. This piece of code put in a playground is working now; however, the very same code put in my app does still produce an error, it does contain more information though. Printing the error object results in:

Error Domain=CSIndexErrorDomain Code=-1003 "(null)" 
UserInfo={NSUnderlyingError=0x60000105f6e0 
{Error Domain=NSCocoaErrorDomain Code=4097 
"Couldn’t communicate with a helper application."}}

As it displays to me, this is clearly a bug in the framework, or what do you think about that?

Answer 1

With macOS 10.13, SIP and the App Sandbox seem to have become a little more strict. After a lot of digging to get this work, here's what I did, and should work for others reading this too:

1. In Xcode, toggle the "App Sandbox" capability for your target in which your CoreSpotlight code runs. If this is in a framework, it needs to be the hosting application's target. This shouldn't be necessary for new projects (for details, see this bug report).
2. Enable development signing for the application/binary which will run the CoreSpotlight code. In my case, it was the test host.

Answer 2

Eventually I managed to resolve the problem somehow, I followed the hint that the code was working in a playground. So I did what I wanted to do anyway and put the code in a framework. Without any further changes, it started to work. So apparently it had to do with the project configuration but it would be great if somebody came up with an idea what's the underlying reason for Spotlight to fail.