add HandleError function to contain boilerplate

Author: keks

response.go

@@ -2,6 +2,7 @@ package cmds
 
 import (
 	"fmt"
+	"io"
 
 	"github.com/ipfs/go-ipfs-cmdkit"
 )
@@ -36,3 +37,25 @@ func (h Head) Length() uint64 {
 func (h Head) Error() *cmdkit.Error {
 	return h.Err
 }
+
+// HandleError handles the error from cmds.Response.Next(), it returns
+// true if Next() should be called again
+func HandleError(err error, res Response, re ResponseEmitter) bool {
+	if err != nil {
+		if err == io.EOF {
+			return false
+		}
+
+		if err == ErrRcvdError {
+			err = res.Error()
+		}
+
+		if e, ok := err.(*cmdkit.Error); ok {
+			re.SetError(e.Message, e.Code)
+		} else {
+			re.SetError(err, cmdkit.ErrNormal)
+		}
+		return false
+	}
+	return true
+}

response_test.go

@@ -14,6 +14,20 @@ type TestOutput struct {
 	Baz      int
 }
 
+func eqStringSlice(a, b []string) bool {
+	if len(a) != len(b) {
+		return false
+	}
+
+	for i := range a {
+		if a[i] != b[i] {
+			return false
+		}
+	}
+
+	return true
+}
+
 func TestMarshalling(t *testing.T) {
 	cmd := &Command{}
 	opts, _ := cmd.GetOptions(nil)
@@ -50,6 +64,42 @@ func TestMarshalling(t *testing.T) {
 	}
 }
 
+func TestHandleError(t *testing.T) {
+	var (
+		out []string
+		exp = []string{"1", "2", "3", "EOF"}
+	)
+
+	cmd := &Command{}
+	opts, _ := cmd.GetOptions(nil)
+
+	req, _ := NewRequest(nil, nil, nil, nil, nil, opts)
+
+	re, res := NewChanResponsePair(req)
+	go func() {
+		re.Emit(1)
+		re.Emit(2)
+		re.Emit(3)
+		re.Close()
+	}()
+
+	var err error
+	for HandleError(err, res, re) {
+		var v interface{}
+		v, err = res.Next()
+		if v != nil {
+			out = append(out, fmt.Sprint(v))
+		} else {
+			out = append(out, fmt.Sprint(err))
+		}
+
+	}
+
+	if !eqStringSlice(out, exp) {
+		t.Fatalf("expected %v, got %v", exp, out)
+	}
+}
+
 func removeWhitespace(input string) string {
 	input = strings.Replace(input, " ", "", -1)
 	input = strings.Replace(input, "\t", "", -1)