Add helper to RequestError for unmarshaling error info to structs

sdg0919 · Apr 4, 2019 · 38b5cb5 · 38b5cb5
1 parent d8af3b6
commit 38b5cb5
Show file tree

Hide file tree

Showing 2 changed files with 77 additions and 0 deletions.
diff --git a/rpc/client.go b/rpc/client.go
@@ -4,6 +4,8 @@
 package rpc
 
 import (
+	"encoding/json"
+	"reflect"
 	"strings"
 
 	"github.com/juju/errors"
@@ -42,6 +44,27 @@ func (e *RequestError) ErrorCode() string {
 	return e.Code
 }
 
+// UnmarshalInfo attempts to unmarshal the information contained in the Info
+// field of a RequestError into an object instance a pointer to which is passed
+// via the to argument. The method will return an error if a non-pointer arg
+// is provided.
+func (e *RequestError) UnmarshalInfo(to interface{}) error {
+	if reflect.ValueOf(to).Kind() != reflect.Ptr {
+		return errors.New("UnmarshalInfo expects a pointer as an argument")
+	}
+
+	data, err := json.Marshal(e.Info)
+	if err != nil {
+		return errors.Annotate(err, "could not marshal error information")
+	}
+	err = json.Unmarshal(data, to)
+	if err != nil {
+		return errors.Annotate(err, "could not unmarshal error information to provided target")
+	}
+
+	return nil
+}
+
 func (conn *Conn) send(call *Call) {
 	conn.sending.Lock()
 	defer conn.sending.Unlock()

diff --git a/rpc/rpc_test.go b/rpc/rpc_test.go
@@ -1212,6 +1212,60 @@ func (s *rpcSuite) TestRecorderErrorPreventsRequest(c *gc.C) {
 	c.Assert(root.calls, gc.HasLen, 0)
 }
 
+func (s *rpcSuite) TestRequestErrorInfoUnmarshaling(c *gc.C) {
+	type nestedStruct struct {
+		Baz bool
+	}
+	type someStruct struct {
+		Foo    string
+		Nested nestedStruct
+	}
+
+	specs := []struct {
+		descr string
+		info  map[string]interface{}
+		to    interface{}
+		exp   interface{}
+		err   string
+	}{
+		{
+			descr: "unmarshal to struct",
+			info: map[string]interface{}{
+				"Foo": "bar",
+				"Nested": map[string]interface{}{
+					"Baz": true,
+				},
+			},
+			to: new(someStruct),
+			exp: &someStruct{
+				Foo:    "bar",
+				Nested: nestedStruct{Baz: true},
+			},
+		},
+		{
+			descr: "unmarshal to non-pointer",
+			info:  map[string]interface{}{"Foo": "bar"},
+			to:    42,
+			err:   "UnmarshalInfo expects a pointer as an argument",
+		},
+	}
+
+	for specIndex, spec := range specs {
+		c.Logf("test %d: %s", specIndex, spec.descr)
+
+		re := &rpc.RequestError{
+			Info: spec.info,
+		}
+		err := re.UnmarshalInfo(spec.to)
+		if spec.err == "" {
+			c.Assert(err, gc.IsNil)
+			c.Assert(spec.to, gc.DeepEquals, spec.exp)
+		} else {
+			c.Assert(err, gc.ErrorMatches, spec.err)
+		}
+	}
+}
+
 func chanReadError(c *gc.C, ch <-chan error, what string) error {
 	select {
 	case e := <-ch: