Cherry-pick #5077 to 6.0: Combine fields.yml properties when they are defined in different sources

CHANGELOG.asciidoc

@@ -31,6 +31,7 @@ https://github.com/elastic/beats/compare/v6.0.0-beta2...master[Check the HEAD di
 *Affecting all Beats*
 
 - Fix the `/usr/bin/beatname` script to accept `-d "*"` as a parameter. {issue}5040[5040]
+- Combine `fields.yml` properties when they are defined in different sources. {issue}5075[5075]
 
 *Auditbeat*
 

libbeat/template/field.go

@@ -125,7 +125,9 @@ func (f *Field) text() common.MapStr {
 	}
 
 	if len(f.MultiFields) > 0 {
-		properties["fields"] = f.MultiFields.process("", f.esVersion)
+		fields := common.MapStr{}
+		f.MultiFields.process("", f.esVersion, fields)
+		properties["fields"] = fields
 	}
 
 	return properties

libbeat/template/field_test.go

@@ -3,9 +3,9 @@ package template
 import (
 	"testing"
 
-	"github.com/stretchr/testify/assert"
-
 	"github.com/elastic/beats/libbeat/common"
+
+	"github.com/stretchr/testify/assert"
 )
 
 func TestField(t *testing.T) {

libbeat/template/fields.go

@@ -1,6 +1,7 @@
 package template
 
 import (
+	"errors"
 	"strings"
 
 	"github.com/elastic/beats/libbeat/common"
@@ -12,9 +13,7 @@ var (
 
 type Fields []Field
 
-func (f Fields) process(path string, esVersion common.Version) common.MapStr {
-	output := common.MapStr{}
-
+func (f Fields) process(path string, esVersion common.Version, output common.MapStr) error {
 	for _, field := range f {
 
 		var mapping common.MapStr
@@ -50,9 +49,26 @@ func (f Fields) process(path string, esVersion common.Version) common.MapStr {
 			} else {
 				newPath = path + "." + field.Name
 			}
-			mapping = common.MapStr{
-				"properties": field.Fields.process(newPath, esVersion),
+			mapping = common.MapStr{}
+
+			// Combine properties with previous field definitions (if any)
+			properties := common.MapStr{}
+			key := generateKey(field.Name) + ".properties"
+			currentProperties, err := output.GetValue(key)
+			if err == nil {
+				var ok bool
+				properties, ok = currentProperties.(common.MapStr)
+				if !ok {
+					// This should never happen
+					return errors.New(key + " is expected to be a MapStr")
+				}
+			}
+
+			if err := field.Fields.process(newPath, esVersion, properties); err != nil {
+				return err
 			}
+			mapping["properties"] = properties
+
 		default:
 			mapping = field.other()
 		}
@@ -62,7 +78,7 @@ func (f Fields) process(path string, esVersion common.Version) common.MapStr {
 		}
 	}
 
-	return output
+	return nil
 }
 
 // HasKey checks if inside fields the given key exists

libbeat/template/fields_test.go

@@ -4,6 +4,8 @@ import (
 	"testing"
 
 	"github.com/stretchr/testify/assert"
+
+	"github.com/elastic/beats/libbeat/common"
 )
 
 func TestHasKey(t *testing.T) {
@@ -57,3 +59,52 @@ func TestHasKey(t *testing.T) {
 		assert.Equal(t, test.result, test.fields.HasKey(test.key))
 	}
 }
+
+func TestPropertiesCombine(t *testing.T) {
+	// Test common fields are combined even if they come from different objects
+	fields := Fields{
+		Field{
+			Name: "test",
+			Type: "group",
+			Fields: Fields{
+				Field{
+					Name: "one",
+					Type: "text",
+				},
+			},
+		},
+		Field{
+			Name: "test",
+			Type: "group",
+			Fields: Fields{
+				Field{
+					Name: "two",
+					Type: "text",
+				},
+			},
+		},
+	}
+
+	output := common.MapStr{}
+	version, err := common.NewVersion("6.0.0")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = fields.process("", *version, output)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	v1, err := output.GetValue("test.properties.one")
+	if err != nil {
+		t.Fatal(err)
+	}
+	v2, err := output.GetValue("test.properties.two")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	assert.Equal(t, v1, common.MapStr{"type": "text", "norms": false})
+	assert.Equal(t, v2, common.MapStr{"type": "text", "norms": false})
+}

libbeat/template/template.go

@@ -99,7 +99,10 @@ func (t *Template) Load(file string) (common.MapStr, error) {
 	}
 
 	// Start processing at the root
-	properties := fields.process("", t.esVersion)
+	properties := common.MapStr{}
+	if err := fields.process("", t.esVersion, properties); err != nil {
+		return nil, err
+	}
 	output := t.generate(properties, dynamicTemplates)
 
 	return output, nil