CORDA-3381 Make internalUtilsKt Observer tee not wrap with SafeSubscriber (#5913)

* Make tee not wrap PublishSubjects in SafeSubscribers, otherwise a non Rx exception from an unsafe observer shuts down all other observers under the same PublishSubject

* Throw SQLException or PersistenceException plain, that may come out of an unsafe subscriber

* Revert "Throw SQLException or PersistenceException plain, that may come out of an unsafe subscriber"

This reverts commit c7b8af3fa6.

* Update Detekt baseline

core/src/main/kotlin/net/corda/core/internal/InternalUtils.kt

@@ -15,6 +15,7 @@ import net.corda.core.utilities.seconds
 import org.slf4j.Logger
 import rx.Observable
 import rx.Observer
+import rx.observers.Subscribers
 import rx.subjects.PublishSubject
 import rx.subjects.UnicastSubject
 import java.io.ByteArrayOutputStream
@@ -172,8 +173,8 @@ fun <T> Observable<T>.bufferUntilSubscribed(): Observable<T> {
 @DeleteForDJVM
 fun <T> Observer<T>.tee(vararg teeTo: Observer<T>): Observer<T> {
     val subject = PublishSubject.create<T>()
-    subject.subscribe(this)
-    teeTo.forEach { subject.subscribe(it) }
+    subject.unsafeSubscribe(Subscribers.from(this))
+    teeTo.forEach { subject.unsafeSubscribe(Subscribers.from(it)) }
     return subject
 }
 

node/src/test/kotlin/net/corda/node/utilities/ObservablesTests.kt

@@ -10,9 +10,13 @@ import org.assertj.core.api.Assertions.assertThat
 import org.junit.After
 import org.junit.Test
 import rx.Observable
+import rx.observers.Subscribers
 import rx.subjects.PublishSubject
 import java.io.Closeable
+import java.lang.RuntimeException
 import java.util.*
+import kotlin.test.assertEquals
+import kotlin.test.assertFailsWith
 
 class ObservablesTests {
     private fun isInDatabaseTransaction() = contextTransactionOrNull != null
@@ -186,6 +190,30 @@ class ObservablesTests {
         assertThat(source3.hasCompleted()).isTrue()
     }
 
+    /**
+     * tee combines [PublishSubject]s under one PublishSubject. We need to make sure that they are not wrapped with a [SafeSubscriber].
+     * Otherwise, if a non Rx exception gets thrown from a subscriber under one of the PublishSubject it will get caught by the
+     * SafeSubscriber wrapping that PublishSubject and will call [PublishSubject.PublishSubjectState.onError], which will
+     * eventually shut down all of the subscribers under that PublishSubjectState.
+     */
+    @Test
+    fun `error in unsafe subscriber won't shutdown subscribers under same publish subject, after tee`() {
+        val source1 = PublishSubject.create<Int>()
+        val source2 = PublishSubject.create<Int>()
+        var count = 0
+
+        source1.subscribe { count += it } // safe subscriber
+        source1.unsafeSubscribe(Subscribers.create { throw RuntimeException() }) // this subscriber should not shut down the above subscriber
+
+        assertFailsWith<RuntimeException> {
+            source1.tee(source2).onNext(1)
+        }
+        assertFailsWith<RuntimeException> {
+            source1.tee(source2).onNext(1)
+        }
+        assertEquals(2, count)
+    }
+
     @Test
     fun `combine tee and bufferUntilDatabaseCommit`() {
         val database = createDatabase()