Expose line and column number of parsed elements

decode.go

@@ -586,7 +586,7 @@ func (d *decoder) mappingSlice(n *node, out reflect.Value) (good bool) {
 			d.merge(n.children[i+1], out)
 			continue
 		}
-		item := MapItem{}
+		item := MapItem{Line: n.children[i].line, Col: n.children[i].column}
 		k := reflect.ValueOf(&item.Key).Elem()
 		if d.unmarshal(n.children[i], k) {
 			v := reflect.ValueOf(&item.Value).Elem()
@@ -616,6 +616,17 @@ func (d *decoder) mappingStruct(n *node, out reflect.Value) (good bool) {
 		elemType = inlineMap.Type().Elem()
 	}
 
+	for _, f := range sinfo.FieldsMap {
+		if f.LineNum {
+			field := out.Field(f.Num)
+			field.SetInt(int64(n.line))
+		}
+		if f.ColNum {
+			field := out.Field(f.Num)
+			field.SetInt(int64(n.column))
+		}
+	}
+
 	for i := 0; i < l; i += 2 {
 		ni := n.children[i]
 		if isMerge(ni) {

decode_test.go

@@ -3,7 +3,7 @@ package yaml_test
 import (
 	"errors"
 	. "gopkg.in/check.v1"
-	"gopkg.in/yaml.v2"
+	yaml "."
 	"math"
 	"net"
 	"reflect"
@@ -529,9 +529,27 @@ var unmarshalTests = []struct {
 	// Ordered maps.
 	{
 		"{b: 2, a: 1, d: 4, c: 3, sub: {e: 5}}",
-		&yaml.MapSlice{{"b", 2}, {"a", 1}, {"d", 4}, {"c", 3}, {"sub", yaml.MapSlice{{"e", 5}}}},
+		&yaml.MapSlice{
+			{"b", 2, 0, 1},
+			{"a", 1, 0, 7},
+			{"d", 4, 0, 13},
+			{"c", 3, 0, 19},
+			{"sub", yaml.MapSlice{
+				{"e", 5, 0, 31},
+			}, 0, 25},
+		},
 	},
 
+	// Line numbers on ordered maps.
+	{
+		`root:
+  sub1: apple
+  sub2: orange`,
+		&yaml.MapSlice{{"root", yaml.MapSlice{
+			{"sub1", "apple", 1, 2},
+			{"sub2", "orange", 2, 2},
+		}, 0, 0}},
+	},
 	// Issue #39.
 	{
 		"a:\n b:\n  c: d\n",
@@ -812,6 +830,50 @@ func (s *S) TestUnmarshalerRetry(c *C) {
 	c.Assert(su, DeepEquals, sliceUnmarshaler([]int{1}))
 }
 
+type testPerson struct {
+	Name       string
+	Profession string
+	YOB        int
+
+	LineNumber int `,linenum`
+	ColNumber  int `,colnum`
+}
+
+func (s *S) TestUnmarshalerWithLineNumbers(c *C) {
+
+	input := []byte(`---
+- name: Ada Lovelace
+  profession: Mathematician
+  yob: 1815
+
+- name: Ada Rogato
+  profession: Pilot and Parachutist
+  yob: 1910
+`)
+
+	var v []testPerson
+	err := yaml.Unmarshal(input, &v)
+
+	c.Assert(err, IsNil)
+
+	c.Assert(v, DeepEquals, []testPerson{
+		testPerson{
+			Name:       "Ada Lovelace",
+			Profession: "Mathematician",
+			YOB:        1815,
+			LineNumber: 1,
+			ColNumber:  2,
+		},
+		testPerson{
+			Name:       "Ada Rogato",
+			Profession: "Pilot and Parachutist",
+			YOB:        1910,
+			LineNumber: 5,
+			ColNumber:  2,
+		},
+	})
+}
+
 // From http://yaml.org/type/merge.html
 var mergeTests = `
 anchors:

encode_test.go

@@ -8,7 +8,7 @@ import (
 	"time"
 
 	. "gopkg.in/check.v1"
-	"gopkg.in/yaml.v2"
+	yaml "."
 	"net"
 	"os"
 )
@@ -287,7 +287,7 @@ var marshalTests = []struct {
 
 	// Ordered maps.
 	{
-		&yaml.MapSlice{{"b", 2}, {"a", 1}, {"d", 4}, {"c", 3}, {"sub", yaml.MapSlice{{"e", 5}}}},
+		&yaml.MapSlice{{"b", 2, 0, 0}, {"a", 1, 0, 0}, {"d", 4, 0, 0}, {"c", 3, 0, 0}, {"sub", yaml.MapSlice{{"e", 5, 0, 0}}, 0, 0}},
 		"b: 2\na: 1\nd: 4\nc: 3\nsub:\n  e: 5\n",
 	},
 

yaml.go

@@ -21,6 +21,7 @@ type MapSlice []MapItem
 // MapItem is an item in a MapSlice.
 type MapItem struct {
 	Key, Value interface{}
+	Line, Col int
 }
 
 // The Unmarshaler interface may be implemented by types to customize their
@@ -124,6 +125,12 @@ func Unmarshal(in []byte, out interface{}) (err error) {
 //                  they were part of the outer struct. For maps, keys must
 //                  not conflict with the yaml keys of other struct fields.
 //
+//     linenum      Will cause the parser to save the line number the object
+//                  was found.
+//
+//     colnum       Will cause the parser to save the column number the object
+//                  was found.
+//
 // In addition, if the key is "-", the field is ignored.
 //
 // For example:
@@ -200,6 +207,8 @@ type fieldInfo struct {
 	Num       int
 	OmitEmpty bool
 	Flow      bool
+	LineNum   bool
+	ColNum    bool
 
 	// Inline holds the field index if the field is part of an inlined struct.
 	Inline []int
@@ -247,6 +256,10 @@ func getStructInfo(st reflect.Type) (*structInfo, error) {
 					info.Flow = true
 				case "inline":
 					inline = true
+				case "linenum":
+					info.LineNum = true
+				case "colnum":
+					info.ColNum = true
 				default:
 					return nil, errors.New(fmt.Sprintf("Unsupported flag %q in tag %q of type %s", flag, tag, st))
 				}