grpcerrors: choose the error code from the error chain in a depth-first order

util/errutil/errutil.go

@@ -0,0 +1,81 @@
+package errutil
+
+type Iterator struct {
+	// unvisited is a stack structure where the last element
+	// is the top of the stack.
+	unvisited []error
+}
+
+// Iterate will iterate through the error chain in a depth-first order.
+func Iterate(err error) *Iterator {
+	i := &Iterator{}
+	if err != nil {
+		i.unvisited = []error{err}
+	}
+	return i
+}
+
+// IsValid returns if this iterator is valid.
+func (i *Iterator) IsValid() bool {
+	return len(i.unvisited) > 0
+}
+
+// Next will retrieve the next error in the chain.
+func (i *Iterator) Next() {
+	if len(i.unvisited) == 0 {
+		return
+	}
+
+	err := i.pop()
+	switch err := err.(type) {
+	case interface{ Unwrap() error }:
+		if child := err.Unwrap(); child != nil {
+			i.push(child)
+		}
+	case interface{ Unwrap() []error }:
+		children := err.Unwrap()
+		if len(children) == 0 {
+			// Fast path although unlikely.
+			return
+		}
+		i.push(children...)
+	}
+}
+
+// Err will return the current error for the Iterator.
+// It is only valid to invoke this method if IsValid returns true.
+func (i *Iterator) Err() error {
+	last := len(i.unvisited) - 1
+	return i.unvisited[last]
+}
+
+func (i *Iterator) pop() (err error) {
+	err, i.unvisited = pop(i.unvisited)
+	return err
+}
+
+func (i *Iterator) push(elems ...error) {
+	i.unvisited = push(i.unvisited, elems...)
+}
+
+func pop[T any](s []T) (elem T, rest []T) {
+	elem = s[len(s)-1]
+	rest = s[:len(s)-1]
+	return elem, rest
+}
+
+func push[T any](s []T, elems ...T) []T {
+	if len(elems) == 1 {
+		return append(s, elems...)
+	}
+
+	// If there are multiple elements, batch
+	// add them and reverse the order so the first
+	// element is the last in the array (FIFO).
+	i := len(s)
+	s = append(s, elems...)
+	for j := len(s) - 1; i < j; i, j = i+1, j-1 {
+		s[i], s[j] = s[j], s[i]
+	}
+	return s
+}

util/grpcerrors/grpcerrors.go

@@ -10,8 +10,8 @@ import (
 	gogotypes "github.com/gogo/protobuf/types"
 	"github.com/golang/protobuf/proto" //nolint:staticcheck
 	"github.com/golang/protobuf/ptypes/any"
-	"github.com/moby/buildkit/errdefs"
 	"github.com/moby/buildkit/util/bklog"
+	"github.com/moby/buildkit/util/errutil"
 	"github.com/moby/buildkit/util/stack"
 	spb "google.golang.org/genproto/googleapis/rpc/status"
 	"google.golang.org/grpc/codes"
@@ -95,31 +95,26 @@ func withDetails(ctx context.Context, s *status.Status, details ...proto.Message
 }
 
 func Code(err error) codes.Code {
-	if errdefs.IsInternal(err) {
-		return codes.Internal
-	}
-
-	if se, ok := err.(interface {
-		Code() codes.Code
-	}); ok {
-		return se.Code()
-	}
-
-	if se, ok := err.(interface {
-		GRPCStatus() *status.Status
-	}); ok {
-		return se.GRPCStatus().Code()
-	}
+	for i := errutil.Iterate(err); i.IsValid(); i.Next() {
+		switch err := i.Err().(type) {
+		case interface{ System() }:
+			return codes.Internal
+		case interface{ GRPCStatus() *status.Status }:
+			if st := err.GRPCStatus(); st != nil {
+				return st.Code()
+			}
+		case interface{ Code() codes.Code }:
+			return err.Code()
+		}
 
-	wrapped, ok := err.(interface {
-		Unwrap() error
-	})
-	if ok {
-		if err := wrapped.Unwrap(); err != nil {
-			return Code(err)
+		switch i.Err() {
+		case context.Canceled:
+			return codes.Canceled
+		case context.DeadlineExceeded:
+			return codes.DeadlineExceeded
 		}
 	}
-	return status.FromContextError(err).Code()
+	return codes.Unknown
 }
 
 func WrapCode(err error, code codes.Code) error {