stack: remove helper functions from error stack traces

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

util/grpcerrors/grpcerrors.go

@@ -181,6 +181,10 @@ func FromGRPC(err error) error {
 		err = d.WrapError(err)
 	}
 
+	if err != nil {
+		stack.Helper()
+	}
+
 	return stack.Enable(err)
 }
 

util/grpcerrors/intercept.go

@@ -5,6 +5,7 @@ import (
 	"log"
 	"os"
 
+	"github.com/moby/buildkit/util/stack"
 	"github.com/pkg/errors"
 	"google.golang.org/grpc"
 )
@@ -13,6 +14,7 @@ func UnaryServerInterceptor(ctx context.Context, req interface{}, info *grpc.Una
 	resp, err = handler(ctx, req)
 	oldErr := err
 	if err != nil {
+		stack.Helper()
 		err = ToGRPC(err)
 	}
 	if oldErr != nil && err == nil {
@@ -28,14 +30,25 @@ func UnaryServerInterceptor(ctx context.Context, req interface{}, info *grpc.Una
 }
 
 func StreamServerInterceptor(srv interface{}, ss grpc.ServerStream, info *grpc.StreamServerInfo, handler grpc.StreamHandler) error {
-	return ToGRPC(handler(srv, ss))
+	err := ToGRPC(handler(srv, ss))
+	if err != nil {
+		stack.Helper()
+	}
+	return err
 }
 
 func UnaryClientInterceptor(ctx context.Context, method string, req, reply interface{}, cc *grpc.ClientConn, invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error {
-	return FromGRPC(invoker(ctx, method, req, reply, cc, opts...))
+	err := FromGRPC(invoker(ctx, method, req, reply, cc, opts...))
+	if err != nil {
+		stack.Helper()
+	}
+	return err
 }
 
 func StreamClientInterceptor(ctx context.Context, desc *grpc.StreamDesc, cc *grpc.ClientConn, method string, streamer grpc.Streamer, opts ...grpc.CallOption) (grpc.ClientStream, error) {
 	s, err := streamer(ctx, desc, cc, method, opts...)
+	if err != nil {
+		stack.Helper()
+	}
 	return s, ToGRPC(err)
 }

util/stack/stack.go

@@ -4,15 +4,22 @@ import (
 	"fmt"
 	io "io"
 	"os"
+	"runtime"
 	"strconv"
 	"strings"
+	"sync"
 
 	"github.com/containerd/typeurl"
 	"github.com/pkg/errors"
 )
 
+var helpers map[string]struct{}
+var helpersMu sync.RWMutex
+
 func init() {
 	typeurl.Register((*Stack)(nil), "github.com/moby/buildkit", "stack.Stack+json")
+
+	helpers = map[string]struct{}{}
 }
 
 var version string
@@ -23,6 +30,19 @@ func SetVersionInfo(v, r string) {
 	revision = r
 }
 
+func Helper() {
+	var pc [1]uintptr
+	n := runtime.Callers(2, pc[:])
+	if n == 0 {
+		return
+	}
+	frames := runtime.CallersFrames(pc[:n])
+	frame, _ := frames.Next()
+	helpersMu.Lock()
+	helpers[frame.Function] = struct{}{}
+	helpersMu.Unlock()
+}
+
 func Traces(err error) []*Stack {
 	var st []*Stack
 
@@ -52,6 +72,7 @@ func Enable(err error) error {
 	if err == nil {
 		return nil
 	}
+	Helper()
 	if !hasLocalStackTrace(err) {
 		return errors.WithStack(err)
 	}
@@ -112,6 +133,8 @@ func (w *formatter) Format(s fmt.State, verb rune) {
 
 func convertStack(s errors.StackTrace) *Stack {
 	var out Stack
+	helpersMu.RLock()
+	defer helpersMu.RUnlock()
 	for _, f := range s {
 		dt, err := f.MarshalText()
 		if err != nil {
@@ -121,6 +144,9 @@ func convertStack(s errors.StackTrace) *Stack {
 		if len(p) != 2 {
 			continue
 		}
+		if _, ok := helpers[p[0]]; ok {
+			continue
+		}
 		idx := strings.LastIndexByte(p[1], ':')
 		if idx == -1 {
 			continue