Add a cancellable OkHttp Call.await() extension

execute() blocks the calling thread and ignores the coroutine it runs
in -- if that coroutine is cancelled (a screen torn down mid-save, a
WorkManager-stopped fetch), the network call keeps running to
completion regardless, tying up a thread/socket for nothing. enqueue()
plus invokeOnCancellation actually aborts the in-flight HTTP call.

1 files changed, 27 insertions, 0 deletions

diff --git a/app/src/main/java/org/terst/feedreader/data/Net.kt b/app/src/main/java/org/terst/feedreader/data/Net.kt
index d3720a0..4d0c956 100644
--- a/app/src/main/java/org/terst/feedreader/data/Net.kt
+++ b/app/src/main/java/org/terst/feedreader/data/Net.kt
@@ -1,8 +1,35 @@
 package org.terst.feedreader.data
 
+import kotlinx.coroutines.suspendCancellableCoroutine
+import okhttp3.Call
+import okhttp3.Callback
 import okhttp3.OkHttpClient
+import okhttp3.Response
+import java.io.IOException
+import kotlin.coroutines.resume
+import kotlin.coroutines.resumeWithException
 
 /** Shared OkHttp client -- one connection pool for the whole app. */
 object Net {
     val client: OkHttpClient by lazy { OkHttpClient() }
 }
+
+// A plain call.execute() blocks the calling thread and knows nothing about the coroutine
+// it's running inside -- if that coroutine gets cancelled (a screen torn down mid-save, a
+// WorkManager-stopped fetch), the network call keeps right on running to completion
+// regardless, tying up a thread/socket for work nothing is waiting on anymore. enqueue()
+// registers real cancellation: cont.invokeOnCancellation { cancel() } actually aborts the
+// in-flight HTTP call (closes the socket) instead of just abandoning the coroutine.
+suspend fun Call.await(): Response = suspendCancellableCoroutine { cont ->
+    cont.invokeOnCancellation { cancel() }
+    enqueue(object : Callback {
+        override fun onResponse(call: Call, response: Response) {
+            cont.resume(response)
+        }
+
+        override fun onFailure(call: Call, e: IOException) {
+            if (cont.isCancelled) return
+            cont.resumeWithException(e)
+        }
+    })
+}