[pkg/ottl] Add ConvertAttributesToElementsXML Converter (open-telemet…

…ry#35328)

This adds a converter called `ElementizeAttributesXML`. This serves as
one of the granular transformations described in open-telemetry#35281 which will allow
users to migrate any arbitrary XML document into a JSON-equivalent
state.

Also see open-telemetry#35364

.chloggen/elementize-attributes-xml.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: pkg/ottl
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Add ConvertAttributesToElementsXML Converter
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [35328]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: []

pkg/ottl/e2e/e2e_test.go

@@ -347,6 +347,12 @@ func Test_e2e_converters(t *testing.T) {
 				tCtx.GetLogRecord().Attributes().PutStr("test", "FooBar")
 			},
 		},
+		{
+			statement: `set(attributes["test"], ConvertAttributesToElementsXML("<Log id=\"1\"><Message>This is a log message!</Message></Log>"))`,
+			want: func(tCtx ottllog.TransformContext) {
+				tCtx.GetLogRecord().Attributes().PutStr("test", `<Log><Message>This is a log message!</Message><id>1</id></Log>`)
+			},
+		},
 		{
 			statement: `set(attributes["test"], Double(1.0))`,
 			want: func(tCtx ottllog.TransformContext) {

pkg/ottl/ottlfuncs/README.md

@@ -413,6 +413,7 @@ Available Converters:
 - [Decode](#decode)
 - [Concat](#concat)
 - [ConvertCase](#convertcase)
+- [ConvertAttributesToElementsXML](#convertattributestoelementsxml)
 - [Day](#day)
 - [Double](#double)
 - [Duration](#duration)
@@ -547,6 +548,31 @@ Examples:
 
 - `ConvertCase(metric.name, "snake")`
 
+### ConvertAttributesToElementsXML
+
+`ConvertAttributesToElementsXML(target, Optional[xpath])`
+
+The `ConvertAttributesToElementsXML` Converter returns an edited version of an XML string where attributes are converted into child elements.
+
+`target` is a Getter that returns a string. This string should be in XML format.
+If `target` is not a string, nil, or cannot be parsed as XML, `ConvertAttributesToElementsXML` will return an error.
+
+`xpath` (optional) is a string that specifies an [XPath](https://www.w3.org/TR/1999/REC-xpath-19991116/) expression that
+selects one or more elements. Attributes will only be converted within the result(s) of the xpath.
+
+For example, `<a foo="bar"><b>baz</b></a>` will be converted to `<a><b>baz</b><foo>bar</foo></a>`.
+
+Examples:
+
+Convert all attributes in a document
+
+- `ConvertAttributesToElementsXML(body)`
+
+Convert only attributes within "Record" elements
+
+- `ConvertAttributesToElementsXML(body, "/Log/Record")`
+
+
 ### Day
 
 `Day(value)`

pkg/ottl/ottlfuncs/func_convert_attributes_to_elements_xml.go

@@ -0,0 +1,69 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package ottlfuncs // import "github.com/open-telemetry/opentelemetry-collector-contrib/pkg/ottl/ottlfuncs"
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/antchfx/xmlquery"
+
+	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/ottl"
+)
+
+type ConvertAttributesToElementsXMLArguments[K any] struct {
+	Target ottl.StringGetter[K]
+	XPath  ottl.Optional[string]
+}
+
+func NewConvertAttributesToElementsXMLFactory[K any]() ottl.Factory[K] {
+	return ottl.NewFactory("ConvertAttributesToElementsXML", &ConvertAttributesToElementsXMLArguments[K]{}, createConvertAttributesToElementsXMLFunction[K])
+}
+
+func createConvertAttributesToElementsXMLFunction[K any](_ ottl.FunctionContext, oArgs ottl.Arguments) (ottl.ExprFunc[K], error) {
+	args, ok := oArgs.(*ConvertAttributesToElementsXMLArguments[K])
+
+	if !ok {
+		return nil, fmt.Errorf("ConvertAttributesToElementsXML args must be of type *ConvertAttributesToElementsXMLAguments[K]")
+	}
+
+	xPath := args.XPath.Get()
+	if xPath == "" {
+		xPath = "//@*" // All attributes in the document
+	}
+	if err := validateXPath(xPath); err != nil {
+		return nil, err
+	}
+
+	return convertAttributesToElementsXML(args.Target, xPath), nil
+}
+
+// convertAttributesToElementsXML returns a string that is a result of converting all attributes of the
+// target XML into child elements. These new elements are added as the last child elements of the parent.
+// e.g. <a foo="bar" hello="world"><b/></a> -> <a><hello>world</hello><foo>bar</foo><b/></a>
+func convertAttributesToElementsXML[K any](target ottl.StringGetter[K], xPath string) ottl.ExprFunc[K] {
+	return func(ctx context.Context, tCtx K) (any, error) {
+		var doc *xmlquery.Node
+		if targetVal, err := target.Get(ctx, tCtx); err != nil {
+			return nil, err
+		} else if doc, err = parseNodesXML(targetVal); err != nil {
+			return nil, err
+		}
+		for _, n := range xmlquery.Find(doc, xPath) {
+			if n.Type != xmlquery.AttributeNode {
+				continue
+			}
+			xmlquery.AddChild(n.Parent, &xmlquery.Node{
+				Type: xmlquery.ElementNode,
+				Data: n.Data,
+				FirstChild: &xmlquery.Node{
+					Type: xmlquery.TextNode,
+					Data: n.InnerText(),
+				},
+			})
+			n.Parent.RemoveAttr(n.Data)
+		}
+		return doc.OutputXML(false), nil
+	}
+}

pkg/ottl/ottlfuncs/func_convert_attributes_to_elements_xml_test.go

@@ -0,0 +1,126 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package ottlfuncs // import "github.com/open-telemetry/opentelemetry-collector-contrib/pkg/ottl/ottlfuncs"
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/ottl"
+)
+
+func Test_ConvertAttributesToElementsXML(t *testing.T) {
+	tests := []struct {
+		name     string
+		document string
+		xPath    string
+		want     string
+	}{
+		{
+			name:     "nop",
+			document: `<a><b/></a>`,
+			want:     `<a><b></b></a>`,
+		},
+		{
+			name:     "nop declaration",
+			document: `<?xml version="1.0" encoding="UTF-8"?><a><b/></a>`,
+			want:     `<?xml version="1.0" encoding="UTF-8"?><a><b></b></a>`,
+		},
+		{
+			name:     "single attribute",
+			document: `<a foo="bar"/>`,
+			want:     `<a><foo>bar</foo></a>`,
+		},
+		{
+			name:     "multiple attributes - order 1",
+			document: `<a foo="bar" hello="world"/>`,
+			want:     `<a><foo>bar</foo><hello>world</hello></a>`,
+		},
+		{
+			name:     "multiple attributes - order 2",
+			document: `<a hello="world" foo="bar"/>`,
+			want:     `<a><hello>world</hello><foo>bar</foo></a>`,
+		},
+		{
+			name:     "with child elements",
+			document: `<a hello="world" foo="bar"><b/><c/><b/></a>`,
+			want:     `<a><b></b><c></c><b></b><hello>world</hello><foo>bar</foo></a>`,
+		},
+		{
+			name:     "with child value",
+			document: `<a hello="world" foo="bar">free value</a>`,
+			want:     `<a>free value<hello>world</hello><foo>bar</foo></a>`,
+		},
+		{
+			name:     "with child elements and values",
+			document: `<a hello="world" foo="bar">free value<b/>2<c/></a>`,
+			want:     `<a>free value<b></b>2<c></c><hello>world</hello><foo>bar</foo></a>`,
+		},
+		{
+			name:     "multiple levels",
+			document: `<a hello="world" foo="bar"><b href="www.example.com"></b></a>`,
+			want:     `<a><b><href>www.example.com</href></b><hello>world</hello><foo>bar</foo></a>`,
+		},
+		{
+			name:     "xpath filtered",
+			document: `<a hello="world" foo="bar"><b href="www.example.com"></b></a>`,
+			xPath:    "/a/b/@*", // only convert attributes of b
+			want:     `<a hello="world" foo="bar"><b><href>www.example.com</href></b></a>`,
+		},
+		{
+			name:     "attributes found with non-attributes xpath",
+			document: `<a hello="world" foo="bar"><b href="www.example.com"></b></a>`,
+			xPath:    "/a/b", // convert b (the attributes of b, even though the element b was selected)
+			want:     `<a hello="world" foo="bar"><b href="www.example.com"></b></a>`,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			args := &ConvertAttributesToElementsXMLArguments[any]{
+				Target: ottl.StandardStringGetter[any]{
+					Getter: func(_ context.Context, _ any) (any, error) {
+						return tt.document, nil
+					},
+				},
+				XPath: ottl.NewTestingOptional(tt.xPath),
+			}
+			exprFunc, err := createConvertAttributesToElementsXMLFunction[any](ottl.FunctionContext{}, args)
+			assert.NoError(t, err)
+
+			result, err := exprFunc(context.Background(), nil)
+			assert.NoError(t, err)
+			assert.Equal(t, tt.want, result)
+		})
+	}
+}
+
+func TestCreateConvertAttributesToElementsXMLFunc(t *testing.T) {
+	factory := NewConvertAttributesToElementsXMLFactory[any]()
+	fCtx := ottl.FunctionContext{}
+
+	// Invalid arg type
+	exprFunc, err := factory.CreateFunction(fCtx, nil)
+	assert.Error(t, err)
+	assert.Nil(t, exprFunc)
+
+	// Invalid XPath should error on function creation
+	exprFunc, err = factory.CreateFunction(
+		fCtx, &ConvertAttributesToElementsXMLArguments[any]{
+			XPath: ottl.NewTestingOptional("!"),
+		})
+	assert.Error(t, err)
+	assert.Nil(t, exprFunc)
+
+	// Invalid XML should error on function execution
+	exprFunc, err = factory.CreateFunction(
+		fCtx, &ConvertAttributesToElementsXMLArguments[any]{
+			Target: invalidXMLGetter(),
+		})
+	assert.NoError(t, err)
+	assert.NotNil(t, exprFunc)
+	_, err = exprFunc(context.Background(), nil)
+	assert.Error(t, err)
+}

pkg/ottl/ottlfuncs/functions.go

@@ -40,6 +40,7 @@ func converters[K any]() []ottl.Factory[K] {
 		NewDecodeFactory[K](),
 		NewConcatFactory[K](),
 		NewConvertCaseFactory[K](),
+		NewConvertAttributesToElementsXMLFactory[K](),
 		NewDayFactory[K](),
 		NewDoubleFactory[K](),
 		NewDurationFactory[K](),