System.Text.Json roundtrips Stack<T> instances in reverse order

[eiriktsarpalis]

The code

var stack  = new Stack<int>(new int[] { 3, 2, 1 });

for (int i = 0; i < 5; i++)
{
    string json = JsonSerializer.Serialize(stack);
    Console.WriteLine(json);
    stack = JsonSerializer.Deserialize<Stack<int>>(json);
}

Produces

[1,2,3]
[3,2,1]
[1,2,3]
[3,2,1]
[1,2,3]

Even though this can be expected given the nature of stacks in general, it certainly violates expectations when it comes to marshalling collections. FWIW this is not specific to STJ as similar behavior can be observed when applying a stack to its own IEnumerable constructor.

[ghost]

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Issue Details

---

The code

var stack  = new Stack<int>(new int[] { 3, 2, 1 });

for (int i = 0; i < 5; i++)
{
    string json = JsonSerializer.Serialize(stack);
    Console.WriteLine(json);
    stack = JsonSerializer.Deserialize<Stack<int>>(json);
}

Produces

[1,2,3]
[3,2,1]
[1,2,3]
[3,2,1]
[1,2,3]

Even though this can be expected given the nature of stacks in general, it certainly violates expectations when it comes to marshalling collections. FWIW this is not specific to STJ as similar behavior can be observed when applying a stack to its own IEnumerable constructor.

Author:	eiriktsarpalis
Assignees:	-
Labels:	area-System.Text.Json
Milestone:	-

[eiriktsarpalis]

FWIW I'm not necessarily proposing that we fix this (users might rely on the current behavior 😱) although we should make sure that it is at least documented given that the type is officially supported.

[gregsdennis]

My opinion is that if people are depending upon bug behavior, they shouldn't be surprised when that big is fixed, even if they don't know it's a bug.

I think fix it.