Using `$set` with nested integer keys breaks the structure

[zeapo]

Given the following class (kotlin)

@Document(collection = "nested_hell")
@TypeAlias("hell")
data class NestedHell(
    @Id val eyeDee: String,
    val levelOne: HashMap<String, HashMap<String, HashMap<String, Any>>>
)

Update queries where the keys in these nested hashmaps are integers, will not go deeper than the second level:

        ops.save(
            NestedHell(
                eyeDee = "id1",
                levelOne = hashMapOf("0" to hashMapOf("1" to hashMapOf("2" to 3)))
            )
        )
        val updateQuery = Update().set("levelOne.0.1.3", 4)
        println(updateQuery.updateObject.toJson())
        ops.updateFirst(
            Query(NestedHell::eyeDee isEqualTo "id1"),
            updateQuery,
            NestedHell::class.java
        )

The result of the save is:

{
        "_id" : "id1",
        "levelOne" : {
                "0" : {
                        "1" : {
                                "2" : 3
                        }
                }
        },
        "_class" : "hell"
}

The update query object is:

{"$set": {"levelOne.0.1.3": 4}}

The result given by the updateFirst is however

{ "_id" : "id1", "levelOne" : { "0" : 4 }, "_class" : "hell" }

Notice that the level "levelOne.0.1" has gone.

Doing the same thing in Mongo Shell gives the expected result:

> db.nested_hell.findOne()
{
        "_id" : "id1",
        "levelOne" : {
                "0" : {
                        "1" : {
                                "2" : 3
                        }
                }
        },
        "_class" : "hell"
}
> db.nested_hell.update({_id: 'id1'}, {"$set": {"levelOne.0.1.3": 4}})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.nested_hell.findOne()
{
        "_id" : "id1",
        "levelOne" : {
                "0" : {
                        "1" : {
                                "2" : 3,
                                "3" : 4
                        }
                }
        },
        "_class" : "hell"
}

When using non-numeric keys, the result is as one would expect:

        ops.save(
            NestedHell(
                eyeDee = "id2",
                levelOne = hashMapOf("a" to hashMapOf("b" to hashMapOf("c" to "d")))
            )
        )
        val updateQueryTwo = Update().set("levelOne.a.b.d", "e")
        println(updateQueryTwo.updateObject.toJson())
        val modified = ops.updateFirst(
            Query(NestedHell::eyeDee isEqualTo "id2"),
            updateQueryTwo,
            NestedHell::class.java
        )

Gives

{ "_id" : "id2", "levelOne" : { "a" : { "b" : { "c" : "d", "d" : "e" } } }, "_class" : "hell" }

[christophstrobl]

Thanks for reporting - we'll look into this.

[divyajnu08]

Hi Christoph

Please find the below pull request for the solution.
Issue-3775 - Using $set with nested integer keys breaks the structure

I tried to replicate in java and found out the following :
Method: getPath(...) line 1186 , file : QueryMapper
It uses the pattern DOT_POSITIONAL_PATTERN = Pattern.compile("\.\d+"); to remove nested integer keys.

while removing the nested integer keys , it removes the leaf key also in the query expression.
E.g: for path , levelOne.0.1.3 , it removes all the matching dots followed by integer ( becomes "levelOne" ) which removes the leaf key as well due to which we lose the information of leaf index. The result of which the expression rendered is {"$set": {"levelOne.0": 4}}
So I excluded the last key which contains the information of the path to set i.e
DOT_POSITIONAL_PATTERN = Pattern.compile("\.\d+(?!$)")
The result of which the expression rendered correctly as {"$set": {"levelOne.0.1.3": 4}}

I don't know if I am going in the right direction kindly assist. If it is correct I will make the change in Kotlin as well.
I have also added the test cases for this problem.

Thanks
Divya