Field from a Kotlin data class gets ignored if it's prefixed with "is" but not a boolean.

[Arrem]

Describe the bug
When attempting to serialize a Kotlin data class which has a property prefixed with "is", but not a boolean, Jackson will ignore the property.

Version information
Tested on jackson-databind:2.13.1

To Reproduce
If you have a way to reproduce this with:

1. In a Kotlin project, create a dummy data class with a field that is not a boolean but is prefixed with is.
2. Create a Jackson object mapper and attempt to write the object to a string.
3. The property prefixed with is will be ignored.

For example, the following snippet is self-contained:

import com.fasterxml.jackson.module.kotlin.jacksonObjectMapper

data class Person(
    val name: String,
    val isAlive: Int,
    val isDead: Boolean,
)

fun main() {
    val mapper = jacksonObjectMapper()

    val actual = mapper.writeValueAsString(Person("Dave", 0, true))
    val expected = """{"name":"Dave","isAlive":0,"isDead":true}"""

    assert(expected == actual) { "Expected $expected but got $actual." }
}

Produces

Exception in thread "main" java.lang.AssertionError: Expected {"name":"Dave","isAlive":0,"isDead":true} but got {"name":"Dave","isDead":true}.

Expected behavior
All three properties should be included, but the produced output is {"name":"Dave","isDead":true}, with the isAlive property ignored.

Additional context
I am unfamiliar with the internals of Jackson but I've found the following two pieces of information that might be helpful:

• When looking at the generated bytecode, Kotlin generates a getter named isAlive for the integer property, instead of getIsAlive which might be expected by Jackson. Manually adding in a getter of that format to the class (fun getIsAlive() = isAlive) fixes the wrong behavior.
• In BeanSerializerFactory.java, on line 595, properties correctly contains all three properties, but these are then removed by the call to removeIgnorableTypes, since property.getAccessor() on line 763 returns null for the offending property. I did not investigate further to see how the getters in POJOPropertyBuilder are computed, so I am unsure what the root cause is.

[Arrem]

I just noticed that the Kotlin module is a separate repository, so it would be nice if a maintainer could transfer the issue.

[Richie94]

See #575

[k163377]

I verified on branch 2.15 and the submitted test case seems to be fixed.
This is probably a duplicate of #340, which appears to have been fixed in #641.

Therefore, this issue is closed.