Leverage tail recursion when creating message out of Throwable

src/directMain/kotlin/io/github/oshai/kotlinlogging/Formatter.kt

@@ -29,16 +29,13 @@ public class DefaultMessageFormatter(private val includePrefix: Boolean = true)
  }
  }
 
- private fun Throwable?.throwableToString(): String {
- if (this == null) {
- return ""
- }
- var msg = ""
- var current = this
- while (current != null && current.cause != current) {
- msg += ", Caused by: '${current.message}'"
- current = current.cause
+ private fun Throwable?.throwableToString() = createThrowableMsg("", this)
+
+ private tailrec fun createThrowableMsg(msg: String, throwable: Throwable?): String {
+ return if (throwable == null || throwable.cause == throwable) {
+ msg
+ } else {
+ createThrowableMsg("$msg, Caused by: '${throwable.message}'", throwable.cause)
  }
- return msg
  }
 }

src/jsTest/kotlin/io/github/oshai/kotlinlogging/SimpleJsTest.kt

@@ -28,6 +28,19 @@ class SimpleJsTest {
  assertEquals("info", appender.lastLevel)
  }
 
+ @Test
+ fun logThrowableTest() {
+ val errorLog = "Something Bad Happened"
+ val outerMessage = "Outer Message"
+ val innerMessage = "Inner Message"
+ val throwable = Throwable(message = outerMessage, cause = Throwable(message = innerMessage))
+ logger.error(throwable) { errorLog }
+ assertEquals(
+ "ERROR: [SimpleJsTest] $errorLog, Caused by: '$outerMessage', Caused by: '$innerMessage'",
+ appender.lastMessage,
+ )
+ }
+
  @Test
  fun offLevelJsTest() {
  KotlinLoggingConfiguration.LOG_LEVEL = Level.OFF