From 854f6fa0392fc8a5649c1d9d6beebba7ba8ecb67 Mon Sep 17 00:00:00 2001
From: Jordan Krage <jmank88@gmail.com>
Date: Fri, 19 Jan 2018 07:49:39 -0600
Subject: [PATCH] decode: discard unknown fields

---
 decode.go      |  9 ++++++---
 decode_test.go | 23 +++++++++++++++++++++++
 2 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/decode.go b/decode.go
index cf3fde2..7046c5a 100644
--- a/decode.go
+++ b/decode.go
@@ -656,9 +656,12 @@ func objectIntoStruct(structPtr reflect.Value) func(*ObjectDecoder) error {
 			structValue := structPtr.Elem()
 			f := fieldByName(structValue, k)
 			if f == zeroValue {
-				return errors.Errorf("unable to decode entry: no field found named/tagged %q", k)
-			}
-			if err := o.Decode(f.Addr().Interface()); err != nil {
+				// Discard value with no matching field.
+				// TODO could be more efficient with custom discardValue() method
+				if _, err := o.decodeInterface(); err != nil {
+					return errors.Wrapf(err, "failed to discard value for %q with call #%d", k, o.count)
+				}
+			} else if err := o.Decode(f.Addr().Interface()); err != nil {
 				return errors.Wrapf(err, "failed to decode value for %q with call #%d", k, o.count)
 			}
 		}
diff --git a/decode_test.go b/decode_test.go
index b289f73..222e8d2 100644
--- a/decode_test.go
+++ b/decode_test.go
@@ -44,3 +44,26 @@ func (tc *testCase) unmarshalBlock(t *testing.T) {
 			expected, expected, actual.Elem().Interface(), actual.Elem().Interface())
 	}
 }
+
+func TestUnmarshalDiscardUnknownFields(t *testing.T) {
+	type val struct{ A int8 }
+
+	exp := val{8}
+	var got val
+
+	bin := []byte{'{', 'U', 0x01, 'A', 'i', 0x08, 'U', 0x01, 'b', 'i', 0x05, '}'}
+
+	if err := Unmarshal(bin, &got); err != nil {
+		t.Fatal(err)
+	} else if got != exp {
+		t.Errorf("\nexpected: %T %v \nbut got:  %T %v", exp, exp, got, got)
+	}
+
+	block := "[{]\n\t[U][1][A][i][8]\n\t[U][1][B][i][5]\n[}]"
+
+	if err := UnmarshalBlock([]byte(block), &got); err != nil {
+		t.Fatal(err)
+	} else if got != exp {
+		t.Errorf("\nexpected: %T %v \nbut got:  %T %v", exp, exp, got, got)
+	}
+}