fix: re-add option to switch off unique mapping keys enforcement

decode_test.go

@@ -1481,7 +1481,7 @@ func (s *S) TestMergeNestedStruct(c *C) {
 	// 2) A simple implementation might attempt to handle the key skipping
 	//    directly by iterating over the merging map without recursion, but
 	//    there are more complex cases that require recursion.
-	// 
+	//
 	// Quick summary of the fields:
 	//
 	// - A must come from outer and not overriden
@@ -1497,7 +1497,7 @@ func (s *S) TestMergeNestedStruct(c *C) {
 		A, B, C int
 	}
 	type Outer struct {
-		D, E      int
+		D, E   int
 		Inner  Inner
 		Inline map[string]int `yaml:",inline"`
 	}
@@ -1515,10 +1515,10 @@ func (s *S) TestMergeNestedStruct(c *C) {
 	// Repeat test with a map.
 
 	var testm map[string]interface{}
-	var wantm = map[string]interface {} {
-		"f":     60,
+	var wantm = map[string]interface{}{
+		"f": 60,
 		"inner": map[string]interface{}{
-		    "a": 10,
+			"a": 10,
 		},
 		"d": 40,
 		"e": 50,
@@ -1614,10 +1614,11 @@ var unmarshalStrictTests = []struct {
 	value  interface{}
 	error  string
 }{{
-	known: true,
-	data:  "a: 1\nc: 2\n",
-	value: struct{ A, B int }{A: 1},
-	error: `yaml: unmarshal errors:\n  line 2: field c not found in type struct { A int; B int }`,
+	known:  true,
+	unique: false,
+	data:   "a: 1\nc: 2\n",
+	value:  struct{ A, B int }{A: 1},
+	error:  `yaml: unmarshal errors:\n  line 2: field c not found in type struct { A int; B int }`,
 }, {
 	unique: true,
 	data:   "a: 1\nb: 2\na: 3\n",
@@ -1697,6 +1698,7 @@ func (s *S) TestUnmarshalKnownFields(c *C) {
 		value := reflect.New(t)
 		dec := yaml.NewDecoder(bytes.NewBuffer([]byte(item.data)))
 		dec.KnownFields(item.known)
+		dec.UniqueKeys(item.unique)
 		err := dec.Decode(value.Interface())
 		c.Assert(err, ErrorMatches, item.error)
 	}

go.mod

@@ -1,5 +1,5 @@
-module "gopkg.in/yaml.v3"
+module gopkg.in/yaml.v3
 
-require (
-	"gopkg.in/check.v1" v0.0.0-20161208181325-20d25e280405
-)
+go 1.17
+
+require gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405

go.sum

@@ -0,0 +1,2 @@
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=

yaml.go

@@ -86,13 +86,14 @@ type Marshaler interface {
 // supported tag options.
 //
 func Unmarshal(in []byte, out interface{}) (err error) {
-	return unmarshal(in, out, false)
+	return unmarshal(in, out)
 }
 
 // A Decoder reads and decodes YAML values from an input stream.
 type Decoder struct {
 	parser      *parser
 	knownFields bool
+	uniqueKeys  bool
 }
 
 // NewDecoder returns a new decoder that reads from r.
@@ -101,7 +102,8 @@ type Decoder struct {
 // data from r beyond the YAML values requested.
 func NewDecoder(r io.Reader) *Decoder {
 	return &Decoder{
-		parser: newParserFromReader(r),
+		parser:     newParserFromReader(r),
+		uniqueKeys: true,
 	}
 }
 
@@ -111,6 +113,12 @@ func (dec *Decoder) KnownFields(enable bool) {
 	dec.knownFields = enable
 }
 
+// UniqueKeys enforces the keys in decoded mappings to exist
+// only once inside the given mapping.
+func (dec *Decoder) UniqueKeys(enable bool) {
+	dec.uniqueKeys = enable
+}
+
 // Decode reads the next YAML-encoded value from its input
 // and stores it in the value pointed to by v.
 //
@@ -119,6 +127,7 @@ func (dec *Decoder) KnownFields(enable bool) {
 func (dec *Decoder) Decode(v interface{}) (err error) {
 	d := newDecoder()
 	d.knownFields = dec.knownFields
+	d.uniqueKeys = dec.uniqueKeys
 	defer handleErr(&err)
 	node := dec.parser.parse()
 	if node == nil {
@@ -153,7 +162,7 @@ func (n *Node) Decode(v interface{}) (err error) {
 	return nil
 }
 
-func unmarshal(in []byte, out interface{}, strict bool) (err error) {
+func unmarshal(in []byte, out interface{}) (err error) {
 	defer handleErr(&err)
 	d := newDecoder()
 	p := newParser(in)
@@ -363,7 +372,7 @@ const (
 //             Address yaml.Node
 //     }
 //     err := yaml.Unmarshal(data, &person)
-// 
+//
 // Or by itself:
 //
 //     var person Node
@@ -373,7 +382,7 @@ type Node struct {
 	// Kind defines whether the node is a document, a mapping, a sequence,
 	// a scalar value, or an alias to another node. The specific data type of
 	// scalar nodes may be obtained via the ShortTag and LongTag methods.
-	Kind  Kind
+	Kind Kind
 
 	// Style allows customizing the apperance of the node in the tree.
 	Style Style
@@ -421,7 +430,6 @@ func (n *Node) IsZero() bool {
 		n.HeadComment == "" && n.LineComment == "" && n.FootComment == "" && n.Line == 0 && n.Column == 0
 }
 
-
 // LongTag returns the long form of the tag that indicates the data type for
 // the node. If the Tag field isn't explicitly defined, one will be computed
 // based on the node properties.