Post by brouwyka on JSONByteArrayWriter string result incorrect order ^{CODESYS Forge talk (Post)}
Hi @TimvH, As discussed in our email contact, your example does not actually test/reproduce the bug I am describing: Adding to the JSON builder on later cycles works fine. Your example works because you do the following: 1. You finish the first cycle (xFirst) with adding an object to the array with 2 fields; 2. When the next cycle is triggered (xAdd), you immediately start with adding another object to that array. This works fine as the last thing you did before #2 was the addition of the array and an object to it. To reproduce the bug you should be doing the following instead, as I showed with the code I shared with my first post: 1. Create the array - save the index that is returned; 2. Add an item, either a primitive or an object, to the array; 3. Add an item outside the array (anything: a primitive, a new array, a nested object, etc); 4. Add another item to the array using the index you saved at #1. You will now see, as I shared in my initial post, that the second item is placed completely outside the root JSON object. This also happens to anything else you try to add after step #4: everything after this point will be added outside the root JSON object: the JSON is completely broken. Important to note is that this not only happens with arrays, but also with nested JSON objects. Once you add something outside of a nested JSON object, you can no longer add anything to that nested JSON object, as that causes the exact same bug. This also applies to arrays of objects, so if in your test you had tried adding a new key-value pair to the first nested object in your array after you created the second nested object, you would also run into this bug. It seems that the JSONByteArrayWriter (I haven't tested the other writers in the JSON Utilities SL library, so I don't know if they suffer from the same problem) simply does not handle any JSON fields that add brackets (so arrays with "[" & "]" and nested objects with "{" & "}") well, and closes them prematurely instead of checking if any later JSONElements in the JSONData's array belong to any of these bracketed fields. After reviewing the objects & functions of the JSON Utilities SL library, my guess is that either the JSONByteArrayWriter linearly goes through the array of JSONElements in the JSONData and only checks the diParentIndex of each JSONElement in direct ascending order, OR if it does use the JSONElement.GetChildren(); method, that this method is either broken and doesn't give all children correctly to the writer. Neither explains why everything completely breaks, and you cannot even add to the root JSON object anymore, however, so there is probably more than just that going wrong in the writer. To me, after a full week of testing and attempting workarounds, this seems like a bug in the library that needs to be fixed by Codesys, as I cannot see anything wrong in the JSONData constructed by the JSONBuilder - this seems purely a problem in the writer.
Last updated: 2026-06-15

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