fix(client): prevent IOException when closing stream early (#241)

Author: stainless-app[bot]

openai-java-core/src/main/kotlin/com/openai/core/handlers/StreamHandler.kt

@@ -16,17 +16,44 @@ internal fun <T> streamHandler(
     object : Handler<StreamResponse<T>> {
         override fun handle(response: HttpResponse): StreamResponse<T> {
             val reader = response.body().bufferedReader()
-            val sequence = sequence { reader.useLines { block(it) } }.constrainOnce()
+            val sequence =
+                // Wrap in a `CloseableSequence` to avoid performing a read on the `reader`
+                // after it has been closed, which would throw an `IOException`.
+                CloseableSequence(sequence { reader.useLines { block(it) } }.constrainOnce())
 
             return PhantomReachableClosingStreamResponse(
                 object : StreamResponse<T> {
                     override fun stream(): Stream<T> = sequence.asStream()
 
                     override fun close() {
+                        sequence.close()
                         reader.close()
                         response.close()
                     }
                 }
             )
         }
     }
+
+/**
+ * A sequence that can be closed.
+ *
+ * Once [close] is called, it will not yield more elements. It will also no longer consult the
+ * underlying [Iterator.hasNext] method.
+ */
+private class CloseableSequence<T>(private val sequence: Sequence<T>) : Sequence<T> {
+    private var isClosed: Boolean = false
+
+    override fun iterator(): Iterator<T> {
+        val iterator = sequence.iterator()
+        return object : Iterator<T> {
+            override fun next(): T = iterator.next()
+
+            override fun hasNext(): Boolean = !isClosed && iterator.hasNext()
+        }
+    }
+
+    fun close() {
+        isClosed = true
+    }
+}