ObjectMapper serialization for boolean fields named isFieldName changed between versions 2.10.5 and 2.12.4

(NOTE: transferred from “jackson-databind”, assumed Kotlin-module specific)

Describe the bug I’m upgrading a project from Jackson 2.10.5 to 2.12.4 and one of the classes started serializing differently. The class has a field named isOpen which is not a boolean. In 2.10.5 this serialized as "isOpen": { } In 2.12.4 the field is dropped entirely.

Version information 2.12.4

To Reproduce

This first test passes with Jackson 2.10.5 and fails in 2.12.4. The second test passes in both versions.

class JacksonTest {
    @Test
    fun `will serialize a data class with a property named isOpen if it is not a boolean`() {
        data class Thing(val isOpen: Map<String, Boolean>)

        val data = Thing(isOpen = mapOf(Pair("a", true)))

        ObjectMapper().writeValueAsString(data) shouldBe """{"isOpen":{"a":true}}"""
    }

    @Test
    fun `will serialize a data class with a property named isOpen if it is a boolean`() {
        data class Thing(val isOpen: Boolean)

        val data = Thing(isOpen = true)

        ObjectMapper().writeValueAsString(data) shouldBe """{"open":true}"""
    }
}

[sudo-nan0-RaySK]

Same happening with Java as well.

[cowtowncoder]

@sudo-nan0-RaySK I don’t think this should be the case, unless Kotlin module is registered. If it does occur, this would belong here, but for now I assume it is Kotlin-MODULE specific (not necessarily language/value however; but module does not discriminate).