Handle an interface with suspend that returns a JS friendly type

If we are KustomExporting an interface that contains a suspend that
returns a JS friendly type (e.g. Long <-> Double), we want to await
the promise result before importing the JS type back to the Kotlin
type.

> promise.toLong().await()
becomes:
> promise.await().toLong()

Author: shama

compiler/src/main/kotlin/deezer/kustomexport/compiler/js/pattern/SharedTransformer.kt

@@ -141,11 +141,12 @@ fun FunctionDescriptor.buildWrappingFunctionBody(
     body += "val result = $callStr("
     body += if (parameters.isNotEmpty()) "\n" else ""
     body += params
-    body += if (parameters.isNotEmpty()) ")\n" else ")\n"
+    body += if (parameters.isNotEmpty()) ")" else ")"
+
+    body += if (import && isSuspend) ".%M()\n".toFormatString(coroutinesAwait) else "\n".toFormatString()
 
     body += if (import || !isSuspend) "return·" else ""
     body += returnType.portMethod(import, "result".toFormatString())
-    body += if (import && isSuspend) ".%M()".toFormatString(coroutinesAwait) else "".toFormatString()
 
     if (!import && isSuspend) body += "\n}"
     return body

samples/src/commonMain/kotlin/sample/coroutines/InterfaceWithSuspend.kt

@@ -0,0 +1,21 @@
+package sample.coroutines
+
+import deezer.kustomexport.KustomExport
+
+@KustomExport
+interface IThingDoer {
+    suspend fun doThings(): List<Long>
+}
+
+class NonWebThingDoer : IThingDoer {
+    override suspend fun doThings(): List<Long> {
+        return listOf(1, 2, 3)
+    }
+}
+
+@KustomExport
+class WebThingDoer : IThingDoer {
+    override suspend fun doThings(): List<Long> {
+        return listOf(3, 2, 1)
+    }
+}

samples/src/commonMain/kotlin/sample/coroutines/InterfaceWithSuspend.ts

@@ -0,0 +1,12 @@
+import { runTest } from "../shared_ts/RunTest"
+import { assert, assertEquals, assertQuiet, assertEqualsQuiet } from "../shared_ts/Assert"
+import { sample } from '@kustom/Samples'
+
+runTest("InterfaceWithSuspend", async () : Promise<void> => {
+    var neverAbortController = new AbortController()
+    var neverAbortSignal = neverAbortController.signal
+
+    const thingDoer = new sample.coroutines.js.WebThingDoer()
+    const res = await thingDoer.doThings(neverAbortSignal)
+    assertEquals([3, 2, 1].join(","), res.join(","), "executes suspend function with JS friendly types")
+})