additonal logic to skipping mandatory field

libbeat/processors/actions/alterFieldProcessor.go

@@ -59,10 +59,13 @@ func NewAlterFieldProcessor(c *conf.C, processorName string, alterFunc mapstr.Al
 	var configFields []string
 	for _, readOnly := range processors.MandatoryExportedFields {
 		readOnly = strings.ToLower(readOnly)
-		for i, field := range config.Fields {
-			if !strings.HasPrefix(strings.ToLower(field), readOnly) {
-				configFields = append(configFields, config.Fields[i])
+		for _, field := range config.Fields {
+			// Skip fields that match "readOnly" or start with "readOnly."
+			if strings.HasPrefix(strings.ToLower(field), readOnly+".") || strings.ToLower(field) == readOnly {
+				continue
 			}
+			// Add fields that do not match "readOnly" criteria
+			configFields = append(configFields, field)
 		}
 	}
 	return &alterFieldProcessor{

libbeat/processors/actions/lowercase_test.go

@@ -32,7 +32,7 @@ import (
 func TestNewLowerCaseProcessor(t *testing.T) {
 	c := conf.MustNewConfigFrom(
 		mapstr.M{
-			"fields":         []string{"field1", "type", "field2", "type.value.key"}, // "type" is our mandatory field
+			"fields":         []string{"field1", "type", "field2", "type.value.key", "typeKey"}, // "type" is our mandatory field
 			"ignore_missing": true,
 			"fail_on_error":  false,
 		},
@@ -43,7 +43,7 @@ func TestNewLowerCaseProcessor(t *testing.T) {
 
 	processor, ok := procInt.(*alterFieldProcessor)
 	assert.True(t, ok)
-	assert.Equal(t, []string{"field1", "field2"}, processor.Fields) // we discard both "type" and "typeInput" as mandatory fields
+	assert.Equal(t, []string{"field1", "field2", "typeKey"}, processor.Fields) // we discard both "type" and "type.value.key" as mandatory fields
 	assert.True(t, processor.IgnoreMissing)
 	assert.False(t, processor.FailOnError)
 }