internal/pkg: lock on-filesystem cache

Any fine-grained file-based locking here significantly hurts performance and is not part of the use case of the package. This change guarantees exclusive access to prevent inconsistent state on the filesystem.

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

internal/pkg/pkg_test.go

@@ -28,6 +28,15 @@ import (
 	"hakurei.app/message"
 )
 
+//go:linkname unsafeOpen hakurei.app/internal/pkg.open
+func unsafeOpen(
+	ctx context.Context,
+	msg message.Msg,
+	cures int,
+	base *check.Absolute,
+	lock bool,
+) (*pkg.Cache, error)
+
 func TestMain(m *testing.M) { container.TryArgv0(nil); os.Exit(m.Run()) }
 
 // overrideIdent overrides the ID method of [Artifact].
@@ -213,7 +222,7 @@ func TestIdent(t *testing.T) {
 	var cache *pkg.Cache
 	if a, err := check.NewAbs(t.TempDir()); err != nil {
 		t.Fatal(err)
-	} else if cache, err = pkg.New(t.Context(), msg, 0, a); err != nil {
+	} else if cache, err = pkg.Open(t.Context(), msg, 0, a); err != nil {
 		t.Fatal(err)
 	}
 	t.Cleanup(cache.Close)
@@ -274,8 +283,8 @@ func checkWithCache(t *testing.T, testCases []cacheTestCase) {
 			msg.SwapVerbose(testing.Verbose())
 
 			var scrubFunc func() error // scrub after hashing
-			if c, err := pkg.New(t.Context(), msg, 0, base); err != nil {
-				t.Fatalf("New: error = %v", err)
+			if c, err := pkg.Open(t.Context(), msg, 0, base); err != nil {
+				t.Fatalf("Open: error = %v", err)
 			} else {
 				t.Cleanup(c.Close)
 				if tc.early != nil {
@@ -294,6 +303,11 @@ func checkWithCache(t *testing.T, testCases []cacheTestCase) {
 				restoreTemp = true
 			}
 
+			// destroy lock file to avoid changing cache checksums
+			if err := os.Remove(base.Append("lock").String()); err != nil {
+				t.Fatal(err)
+			}
+
 			var checksum pkg.Checksum
 			if err := pkg.HashDir(&checksum, base); err != nil {
 				t.Fatalf("HashDir: error = %v", err)
@@ -522,12 +536,12 @@ func TestCache(t *testing.T) {
 				)},
 			})
 
-			if c0, err := pkg.New(
+			if c0, err := unsafeOpen(
 				t.Context(),
 				message.New(nil),
-				0, base,
+				0, base, false,
 			); err != nil {
-				t.Fatalf("New: error = %v", err)
+				t.Fatalf("open: error = %v", err)
 			} else {
 				t.Cleanup(c.Close) // check doubled cancel
 				cureMany(t, c0, []cureStep{
@@ -1017,12 +1031,12 @@ func TestNew(t *testing.T) {
 			Path: container.Nonexistent,
 			Err:  syscall.ENOENT,
 		}
-		if _, err := pkg.New(
+		if _, err := pkg.Open(
 			t.Context(),
 			message.New(nil),
 			0, check.MustAbs(container.Nonexistent),
 		); !reflect.DeepEqual(err, wantErr) {
-			t.Errorf("New: error = %#v, want %#v", err, wantErr)
+			t.Errorf("Open: error = %#v, want %#v", err, wantErr)
 		}
 	})
 
@@ -1045,12 +1059,12 @@ func TestNew(t *testing.T) {
 			Path: tempDir.Append("cache").String(),
 			Err:  syscall.EACCES,
 		}
-		if _, err := pkg.New(
+		if _, err := pkg.Open(
 			t.Context(),
 			message.New(nil),
 			0, tempDir.Append("cache"),
 		); !reflect.DeepEqual(err, wantErr) {
-			t.Errorf("New: error = %#v, want %#v", err, wantErr)
+			t.Errorf("Open: error = %#v, want %#v", err, wantErr)
 		}
 	})
 }