Change in Swift behaviour with didSet property observer for @published property in Xcode 11.4

Playground.swift

/*
In Xcode 11.3.1, the output is:

>>> setting n to -1
    sending value through valueDidChange publisher
    situation negative("hello")
<<< done
>>> setting n to 1
    sending value through valueDidChange publisher
    situation positive("hello")
<<< done
>>> setting n to 1
    sending value through valueDidChange publisher
    situation positive("hello")
<<< done
>>> setting n to 0
    sending value through valueDidChange publisher
    situation zero
<<< done

In Xcode 11.4, the output is:

>>> setting n to -1
<<< done
>>> setting n to 1
<<< done
>>> setting n to 1
<<< done
>>> setting n to 0
<<< done

*/

import Foundation
import Combine

enum Situation {
  case positive(String)
  case zero
  case negative(String)
}

struct Thing {
  var n: Int
  var s: String

  var situation: Situation {
    if n > 0 {
      return .positive(s)
    } else if n < 0 {
      return .negative(s)
    }
    return .zero
  }
}

public typealias Reducer<Value, Action> = (Value, Action) -> Value

class Store<Value, Action>: ObservableObject {

  public fileprivate(set) var reducer: Reducer<Value, Action>
  @Published public fileprivate(set) var value: Value {
    didSet {
      print("    sending value through valueDidChange publisher")
      valueDidChange.send(value)
    }
  }

  let valueDidChange = PassthroughSubject<Value, Never>()

  init(initialValue: Value, reducer: @escaping Reducer<Value, Action>) {
    self.reducer = reducer
    self.value = initialValue
  }

  func send(action: Action) {
    self.value = self.reducer(self.value, action)
  }
}

let reducer: Reducer<Thing, Int> = { value, action in
  var copy = value
  copy.n += action
  copy.s += "\(action)"
  return copy
}

let store = Store<Thing, Int>(
  initialValue: Thing(n: 0, s: "hello"),
  reducer: reducer
)

let situationCancellable = store.valueDidChange
  .map(\.situation)
  .sink { situation in print("    situation", situation) }

print(">>> setting n to -1")
store.value.n = -1
print("<<< done")

print(">>> setting n to 1")
store.value.n = 1
print("<<< done")

print(">>> setting n to 1")
store.value.n = 1
print("<<< done")

print(">>> setting n to 0")
store.value.n = 0
print("<<< done")