errors: remove usage of errors.Cause

This removes usages of `errors.Cause` in favor of using `errors.As`
which is the more standard way of handling error causes. `Cause` was not
used frequently and `errors.As` is part of the standard library and is
supported by `github.com/pkg/errors`.

For one usage of `errors.Cause`, the underlying implementation itself
has a reliance on the internal implementation of the error being
returned and this method isn't guaranteed to work. Since we are relying
on an implementation detail and not an API, I've added a test to ensure
the behavior continues working as designed.

This also removes a check for an error being returned from containerd
that has since been fixed so the code is dead.

Signed-off-by: Jonathan A. Sternberg <[email protected]>

Author: jsternberg

cache/util/fsutil.go

@@ -131,16 +131,24 @@ func StatFile(ctx context.Context, mount snapshot.Mountable, path string) (*fsty
 			// The filename here is internal to the mount, so we can restore
 			// the request base path for error reporting.
 			// See os.DirFS.Open for details.
-			err1 := err
-			if err := errors.Cause(err); err != nil {
-				err1 = err
-			}
-			if pe, ok := err1.(*os.PathError); ok {
-				pe.Path = path
-			}
+			replaceErrorPath(err, path)
 			return errors.WithStack(err)
 		}
 		return nil
 	})
 	return st, err
 }
+
+// replaceErrorPath will override the path in an os.PathError in the error chain.
+// This works with the fsutil library, but it isn't necessarily the correct
+// way to do this because the error message of wrapped errors doesn't necessarily
+// update or change when a wrapped error is changed.
+//
+// Still, this method of updating the path works with the way this specific
+// library returns errors.
+func replaceErrorPath(err error, path string) {
+	var pe *os.PathError
+	if errors.As(err, &pe) {
+		pe.Path = path
+	}
+}

cache/util/fsutil_test.go

@@ -0,0 +1,31 @@
+package util
+
+import (
+	"path"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	"github.com/tonistiigi/fsutil"
+)
+
+// TestSetErrorPath ensures that modifying the os.PathError from fsutil.Stat
+// modifies the error message appropriately.
+//
+// This method of modifying the path error is an implementation
+// detail of how the error is returned. It isn't necessarily the
+// case that this will always work if the underlying library changes.
+func TestSetErrorPath(t *testing.T) {
+	// Temporary directory to reduce the chance of using stat on a real file.
+	dir := t.TempDir()
+
+	// Random path that shouldn't exist.
+	fpath := path.Join(dir, "a/b/c")
+	_, err := fsutil.Stat(fpath)
+	require.Error(t, err)
+
+	require.ErrorContains(t, err, "a/b/c")
+	// Set the path in the error to a new path.
+	replaceErrorPath(err, "/my/new/path")
+	require.NotContains(t, err.Error(), "a/b/c")
+	require.Contains(t, err.Error(), "/my/new/path")
+}

util/resolver/retryhandler/retry.go

@@ -64,11 +64,7 @@ func retryError(err error) bool {
 		return true
 	}
 	// catches TLS timeout or other network-related temporary errors
-	if ne, ok := errors.Cause(err).(net.Error); ok && ne.Temporary() { //nolint:staticcheck // ignoring "SA1019: Temporary is deprecated", continue to propagate net.Error through the "temporary" status
-		return true
-	}
-	// https://github.com/containerd/containerd/pull/4724
-	if errors.Cause(err).Error() == "no response" {
+	if ne := net.Error(nil); errors.As(err, &ne) && ne.Temporary() { //nolint:staticcheck // ignoring "SA1019: Temporary is deprecated", continue to propagate net.Error through the "temporary" status
 		return true
 	}
 

util/system/path_test.go

@@ -3,7 +3,6 @@ package system
 import (
 	"testing"
 
-	"github.com/pkg/errors"
 	"github.com/stretchr/testify/require"
 )
 
@@ -77,7 +76,7 @@ func TestNormalizeWorkdir(t *testing.T) {
 		t.Run(tc.name, func(t *testing.T) {
 			result, err := NormalizeWorkdir(tc.currentWorkdir, tc.newWorkDir, "linux")
 			if tc.err != "" {
-				require.EqualError(t, errors.Cause(err), tc.err)
+				require.ErrorContains(t, err, tc.err)
 			} else {
 				require.NoError(t, err)
 			}
@@ -300,7 +299,7 @@ func TestNormalizeWorkdirWindows(t *testing.T) {
 		t.Run(tc.name, func(t *testing.T) {
 			result, err := NormalizeWorkdir(tc.currentWorkdir, tc.newWorkDir, "windows")
 			if tc.err != "" {
-				require.EqualError(t, errors.Cause(err), tc.err)
+				require.ErrorContains(t, err, tc.err)
 			} else {
 				require.NoError(t, err)
 			}
@@ -365,7 +364,7 @@ func TestNormalizeWorkdirUnix(t *testing.T) {
 		t.Run(tc.name, func(t *testing.T) {
 			result, err := NormalizeWorkdir(tc.currentWorkdir, tc.newWorkDir, "linux")
 			if tc.err != "" {
-				require.EqualError(t, errors.Cause(err), tc.err)
+				require.ErrorContains(t, err, tc.err)
 			} else {
 				require.NoError(t, err)
 			}