From ae8df5ea87a9c4120d4777dc52bba0b3ddabd9ea Mon Sep 17 00:00:00 2001
From: Mike Farah <mikefarah@gmail.com>
Date: Tue, 21 Dec 2021 16:08:37 +1100
Subject: [PATCH] wip

---
 pkg/yqlib/doc/usage/xml.md | 21 +++++++++++
 pkg/yqlib/encoder_xml.go   | 71 ++++++++++++++++++++++++++++----------
 pkg/yqlib/xml_test.go      | 15 +++++++-
 3 files changed, 87 insertions(+), 20 deletions(-)

diff --git a/pkg/yqlib/doc/usage/xml.md b/pkg/yqlib/doc/usage/xml.md
index 02cf3566..1215047c 100644
--- a/pkg/yqlib/doc/usage/xml.md
+++ b/pkg/yqlib/doc/usage/xml.md
@@ -120,3 +120,24 @@ will output
 </pets>
 ```
 
+## Encode xml: attributes
+Fields with the matching xml-attribute-prefix are assumed to be attributes.
+
+Given a sample.yml file of:
+```yaml
+cat:
+  +name: tiger
+  meows: true
+
+```
+then
+```bash
+yq e -o=xml '.' sample.yml
+```
+will output
+```xml
+<cat name="tiger">
+  <meows>true</meows>
+</cat>
+```
+
diff --git a/pkg/yqlib/encoder_xml.go b/pkg/yqlib/encoder_xml.go
index fb19caab..b5fe832d 100644
--- a/pkg/yqlib/encoder_xml.go
+++ b/pkg/yqlib/encoder_xml.go
@@ -4,15 +4,17 @@ import (
 	"encoding/xml"
 	"fmt"
 	"io"
+	"strings"
 
 	yaml "gopkg.in/yaml.v3"
 )
 
 type xmlEncoder struct {
-	xmlEncoder *xml.Encoder
+	xmlEncoder      *xml.Encoder
+	attributePrefix string
 }
 
-func NewXmlEncoder(writer io.Writer, indent int) Encoder {
+func NewXmlEncoder(writer io.Writer, indent int, attributePrefix string) Encoder {
 	encoder := xml.NewEncoder(writer)
 	var indentString = ""
 
@@ -20,12 +22,12 @@ func NewXmlEncoder(writer io.Writer, indent int) Encoder {
 		indentString = indentString + " "
 	}
 	encoder.Indent("", indentString)
-	return &xmlEncoder{encoder}
+	return &xmlEncoder{encoder, attributePrefix}
 }
 func (e *xmlEncoder) Encode(node *yaml.Node) error {
 	switch node.Kind {
 	case yaml.MappingNode:
-		return e.encodeMap(node)
+		return e.encodeTopLevelMap(node)
 	case yaml.DocumentNode:
 		return e.Encode(unwrapDoc(node))
 	case yaml.ScalarNode:
@@ -35,18 +37,24 @@ func (e *xmlEncoder) Encode(node *yaml.Node) error {
 	return fmt.Errorf("unsupported type %v", node.Tag)
 }
 
+func (e *xmlEncoder) encodeTopLevelMap(node *yaml.Node) error {
+	for i := 0; i < len(node.Content); i += 2 {
+		key := node.Content[i]
+		value := node.Content[i+1]
+
+		start := xml.StartElement{Name: xml.Name{Local: key.Value}}
+		err := e.doEncode(value, start)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
 func (e *xmlEncoder) doEncode(node *yaml.Node, start xml.StartElement) error {
 	switch node.Kind {
 	case yaml.MappingNode:
-		err := e.xmlEncoder.EncodeToken(start)
-		if err != nil {
-			return err
-		}
-		err = e.encodeMap(node)
-		if err != nil {
-			return err
-		}
-		return e.xmlEncoder.EncodeToken(start.End())
+		return e.encodeMap(node, start)
 	case yaml.SequenceNode:
 		return e.encodeArray(node, start)
 	case yaml.ScalarNode:
@@ -77,16 +85,41 @@ func (e *xmlEncoder) encodeArray(node *yaml.Node, start xml.StartElement) error
 	return nil
 }
 
-func (e *xmlEncoder) encodeMap(node *yaml.Node) error {
+func (e *xmlEncoder) encodeMap(node *yaml.Node, start xml.StartElement) error {
+
+	//first find all the attributes and put them on the start token
 	for i := 0; i < len(node.Content); i += 2 {
 		key := node.Content[i]
 		value := node.Content[i+1]
 
-		start := xml.StartElement{Name: xml.Name{Local: key.Value}}
-		err := e.doEncode(value, start)
-		if err != nil {
-			return err
+		if strings.HasPrefix(key.Value, e.attributePrefix) {
+			if value.Kind == yaml.ScalarNode {
+				attributeName := strings.Replace(key.Value, e.attributePrefix, "", 1)
+				start.Attr = append(start.Attr, xml.Attr{Name: xml.Name{Local: attributeName}, Value: value.Value})
+			} else {
+				return fmt.Errorf("cannot use %v as attribute, only scalars are supported", value.Tag)
+			}
 		}
 	}
-	return nil
+
+	err := e.xmlEncoder.EncodeToken(start)
+	if err != nil {
+		return err
+	}
+
+	//now we encode non attribute tokens
+	for i := 0; i < len(node.Content); i += 2 {
+		key := node.Content[i]
+		value := node.Content[i+1]
+
+		if !strings.HasPrefix(key.Value, e.attributePrefix) {
+			start := xml.StartElement{Name: xml.Name{Local: key.Value}}
+			err := e.doEncode(value, start)
+			if err != nil {
+				return err
+			}
+		}
+	}
+
+	return e.xmlEncoder.EncodeToken(start.End())
 }
diff --git a/pkg/yqlib/xml_test.go b/pkg/yqlib/xml_test.go
index babe96e3..04302e68 100644
--- a/pkg/yqlib/xml_test.go
+++ b/pkg/yqlib/xml_test.go
@@ -28,7 +28,7 @@ func yamlToXml(sampleYaml string, indent int) string {
 	var output bytes.Buffer
 	writer := bufio.NewWriter(&output)
 
-	var encoder = NewXmlEncoder(writer, indent)
+	var encoder = NewXmlEncoder(writer, indent, "+")
 	inputs, err := readDocuments(strings.NewReader(sampleYaml), "sample.yml", 0, NewYamlDecoder())
 	if err != nil {
 		panic(err)
@@ -88,6 +88,19 @@ var xmlScenarios = []xmlScenario{
 		expected:       "<pets>\n  <cat>purrs</cat>\n  <cat>meows</cat>\n</pets>",
 		encodeScenario: true,
 	},
+	{
+		description:    "Encode xml: attributes",
+		subdescription: "Fields with the matching xml-attribute-prefix are assumed to be attributes.",
+		input:          "cat:\n  +name: tiger\n  meows: true\n",
+		expected:       "<cat name=\"tiger\">\n  <meows>true</meows>\n</cat>",
+		encodeScenario: true,
+	},
+	{
+		skipDoc:        true,
+		input:          "cat:\n  ++name: tiger\n  meows: true\n",
+		expected:       "<cat +name=\"tiger\">\n  <meows>true</meows>\n</cat>",
+		encodeScenario: true,
+	},
 }
 
 //encode