What is an idiomatic way to do `mapOf(...)` with c...

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[rocketraman]

What is an idiomatic way to do mapOf(...) with conditions on the existence of each pair i.e. something like this obviously broken code:

mapOf(
  if(conditionA) "a" to "b",
  if(conditionB) "b" to "c"
)

For a mutable map I could use apply but obviously that doesn't work for `mapOf`:

mutableMapOf<String, String>().apply {
  if(conditionA) put("a", "b")
  if(conditionB) put("b", "c")
}