log: avoid panic marshaling nil error (#131)

opentracing · Dec 31, 2016 · 5e5abf8 · 5e5abf8
1 parent ac5446f
commit 5e5abf8
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Showing 2 changed files with 9 additions and 1 deletion.
diff --git a/log/field.go b/log/field.go
@@ -194,7 +194,11 @@ func (lf Field) Marshal(visitor Encoder) {
 	case float64Type:
 		visitor.EmitFloat64(lf.key, math.Float64frombits(uint64(lf.numericVal)))
 	case errorType:
-		visitor.EmitString(lf.key, lf.interfaceVal.(error).Error())
+		if err, ok := lf.interfaceVal.(error); ok {
+			visitor.EmitString(lf.key, err.Error())
+		} else {
+			visitor.EmitString(lf.key, "<nil>")
+		}
 	case objectType:
 		visitor.EmitObject(lf.key, lf.interfaceVal)
 	case lazyLoggerType:

diff --git a/log/field_test.go b/log/field_test.go
@@ -26,6 +26,10 @@ func TestFieldString(t *testing.T) {
 			field:    Error(fmt.Errorf("err msg")),
 			expected: "error:err msg",
 		},
+		{
+			field:    Error(nil),
+			expected: "error:<nil>",
+		},
 	}
 	for i, tc := range testCases {
 		if str := tc.field.String(); str != tc.expected {