internal/pkg: drop cached error on cancel

This avoids disabling the artifact when using the individual cancel method. Unfortunately this makes the method blocking.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/pkg/pkg_test.go

@@ -911,7 +911,7 @@ func TestCache(t *testing.T) {
 			var started sync.WaitGroup
 			defer started.Wait()
 
-			blockCures := func(d byte, n int) {
+			blockCures := func(d byte, e stub.UniqueError, n int) {
 				started.Add(n)
 				for i := range n {
 					wg.Go(func() {
@@ -920,9 +920,9 @@ func TestCache(t *testing.T) {
 							cure: func(t *pkg.TContext) error {
 								started.Done()
 								<-t.Unwrap().Done()
-								return stub.UniqueError(0xbad0 + i)
+								return e + stub.UniqueError(i)
 							},
-						}}); !reflect.DeepEqual(err, stub.UniqueError(0xbad0+i)) {
+						}}); !reflect.DeepEqual(err, e+stub.UniqueError(i)) {
 							panic(err)
 						}
 					})
@@ -930,15 +930,26 @@ func TestCache(t *testing.T) {
 				started.Wait()
 			}
 
-			blockCures(0xfd, 16)
+			blockCures(0xfd, 0xbad, 16)
 			c.Abort()
 			wg.Wait()
 
-			blockCures(0xff, 1)
+			blockCures(0xfd, 0xcafe, 16)
+			c.Abort()
+			wg.Wait()
+
+			blockCures(0xff, 0xbad, 1)
 			if !c.Cancel(unique.Make(pkg.ID{0xff})) {
 				t.Fatal("missed cancellation")
 			}
 			wg.Wait()
+
+			blockCures(0xff, 0xcafe, 1)
+			if !c.Cancel(unique.Make(pkg.ID{0xff})) {
+				t.Fatal("missed cancellation")
+			}
+			wg.Wait()
+
 			for c.Cancel(unique.Make(pkg.ID{0xff})) {
 			}