Add KnownFields()

node_test.go

@@ -19,6 +19,7 @@ import (
 	"bytes"
 	"fmt"
 	"os"
+	"reflect"
 
 	. "gopkg.in/check.v1"
 	"gopkg.in/yaml.v3"
@@ -2811,6 +2812,82 @@ func (s *S) TestNodeEncodeDecode(c *C) {
 	}
 }
 
+var nodeDecodeKnownFieldsTests = []struct {
+	knownFields bool
+	node  yaml.Node
+	value interface{}
+	error string
+}{{
+	false,
+	yaml.Node{
+		Kind: yaml.MappingNode,
+		Tag:  "!!map",
+		Content: []*yaml.Node{{
+			Kind:  yaml.ScalarNode,
+			Value: "a",
+			Tag:   "!!str",
+		}, {
+			Kind:  yaml.ScalarNode,
+			Value: "b",
+			Tag:   "!!str",
+		}, {
+			Kind:  yaml.ScalarNode,
+			Value: "c",
+			Tag:   "!!str",
+		}, {
+			Kind:  yaml.ScalarNode,
+			Value: "d",
+			Tag:   "!!str",
+		}},
+	},
+	struct{A string}{},
+	"",
+}, {
+	true,
+	yaml.Node{
+		Kind: yaml.MappingNode,
+		Tag:  "!!map",
+		Content: []*yaml.Node{{
+			Kind:  yaml.ScalarNode,
+			Value: "a",
+			Tag:   "!!str",
+		}, {
+			Kind:  yaml.ScalarNode,
+			Value: "b",
+			Tag:   "!!str",
+		}, {
+			Kind:  yaml.ScalarNode,
+			Value: "c",
+			Tag:   "!!str",
+		}, {
+			Kind:  yaml.ScalarNode,
+			Value: "d",
+			Tag:   "!!str",
+		}},
+	},
+	struct{A string}{},
+	"yaml: unmarshal errors:\n  line 0: field c not found in type struct { A string }",
+}}
+
+func (s *S) TestNodeDecodeKnownFIelds(c *C) {
+	for i, item := range nodeDecodeKnownFieldsTests {
+		c.Logf("Decode KnownFields test value #%d: %#v", i, item.knownFields)
+
+		if item.knownFields {
+			item.node.KnownFields(true)
+		}
+
+		t := reflect.ValueOf(item.value).Type()
+		value := reflect.New(t)
+		err := item.node.Decode(value.Interface())
+		if item.error != "" {
+			c.Assert(err, ErrorMatches, item.error)
+		} else {
+			c.Assert(err, IsNil)
+		}
+	}
+}
+
 func (s *S) TestNodeZeroEncodeDecode(c *C) {
 	// Zero node value behaves as nil when encoding...
 	var n yaml.Node

yaml.go

@@ -141,6 +141,7 @@ func (dec *Decoder) Decode(v interface{}) (err error) {
 // conversion of YAML into a Go value.
 func (n *Node) Decode(v interface{}) (err error) {
 	d := newDecoder()
+	d.knownFields = n.knownFields
 	defer handleErr(&err)
 	out := reflect.ValueOf(v)
 	if out.Kind() == reflect.Ptr && !out.IsNil() {
@@ -413,6 +414,8 @@ type Node struct {
 	// These fields are not respected when encoding the node.
 	Line   int
 	Column int
+
+	knownFields bool
 }
 
 // IsZero returns whether the node has all of its fields unset.
@@ -482,6 +485,12 @@ func (n *Node) SetString(s string) {
 	}
 }
 
+// KnownFields ensures that the keys in decoded mappings to
+// exist as fields in the struct being decoded into.
+func (n *Node) KnownFields(enable bool) {
+	n.knownFields = enable
+}
+
 // --------------------------------------------------------------------------
 // Maintain a mapping of keys to structure field indexes