feat: make desktop FFI invocation asynchronous

bind/desktop/invoke_executor_test.go

@@ -0,0 +1,102 @@
+package main
+
+import (
+	"strconv"
+	"sync"
+	"sync/atomic"
+	"testing"
+	"time"
+)
+
+func TestInvokeConcurrency(t *testing.T) {
+	tests := []struct {
+		cpus int
+		want int
+	}{
+		{cpus: 1, want: 4},
+		{cpus: 2, want: 4},
+		{cpus: 4, want: 8},
+		{cpus: 8, want: 16},
+		{cpus: 16, want: 32},
+		{cpus: 64, want: 32},
+	}
+	for _, test := range tests {
+		t.Run(strconv.Itoa(test.cpus), func(t *testing.T) {
+			if got := invokeConcurrency(test.cpus); got != test.want {
+				t.Fatalf("invokeConcurrency(%d) = %d, want %d", test.cpus, got, test.want)
+			}
+		})
+	}
+}
+
+func TestInvokeExecutorWaitsWithoutRejecting(t *testing.T) {
+	const (
+		workerCount = 2
+		taskCount   = 6
+	)
+	release := make(chan struct{})
+	started := make(chan struct{}, taskCount)
+	var active atomic.Int32
+	var maxActive atomic.Int32
+	executor := newInvokeExecutor(workerCount, func(request invokeRequest) string {
+		current := active.Add(1)
+		for {
+			maximum := maxActive.Load()
+			if current <= maximum || maxActive.CompareAndSwap(maximum, current) {
+				break
+			}
+		}
+		started <- struct{}{}
+		<-release
+		active.Add(-1)
+		return request.path
+	})
+
+	var completed sync.WaitGroup
+	completed.Add(taskCount)
+	for i := range taskCount {
+		accepted := executor.submit(invokeTask{
+			request: invokeRequest{path: strconv.Itoa(i)},
+			complete: func(string, error) {
+				completed.Done()
+			},
+		})
+		if !accepted {
+			t.Fatalf("task %d was rejected while all workers were busy", i)
+		}
+	}
+
+	for range workerCount {
+		select {
+		case <-started:
+		case <-time.After(time.Second):
+			t.Fatal("workers did not start queued tasks")
+		}
+	}
+	if got := maxActive.Load(); got != workerCount {
+		t.Fatalf("maximum active tasks = %d, want %d", got, workerCount)
+	}
+
+	close(release)
+	completed.Wait()
+	executor.close()
+}
+
+func TestInvokeExecutorConvertsPanicsToErrors(t *testing.T) {
+	executor := newInvokeExecutor(1, func(invokeRequest) string {
+		panic("boom")
+	})
+	completed := make(chan error, 1)
+	executor.submit(invokeTask{complete: func(_ string, err error) {
+		completed <- err
+	}})
+	select {
+	case err := <-completed:
+		if err == nil || err.Error() != "invoke panic: boom" {
+			t.Fatalf("unexpected error: %v", err)
+		}
+	case <-time.After(time.Second):
+		t.Fatal("panic result was not completed")
+	}
+	executor.close()
+}