When split expression includes an extension, dont add .yml automatically

.gitignore

@@ -41,6 +41,7 @@ yq*.snap
 
 test.yml
 test*.yml
+test*.yaml
 0.yml
 1.yml
 2.yml

acceptance_tests/split-printer.sh

@@ -25,6 +25,31 @@ EOM
   assertEquals "$expectedDoc2" "$doc2"
 }
 
+testBasicSplitWithNameCustomExtension() {
+  rm test*.yaml || true
+  cat >test.yml <<EOL
+a: test_doc1
+--- 
+a: test_doc2
+EOL
+
+  ./yq e test.yml -s '.a + ".yaml"'
+
+  doc1=$(cat test_doc1.yaml)
+  
+  assertEquals "a: test_doc1" "$doc1"
+
+  doc2=$(cat test_doc2.yaml)
+  read -r -d '' expectedDoc2 << EOM
+---
+a: test_doc2
+EOM
+  assertEquals "$expectedDoc2" "$doc2"
+}
+
+
+
+
 testSplitFromFile() {
   cat >test.yml <<EOL
 a: test_doc1

pkg/yqlib/printer_writer.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"regexp"
 
 	"gopkg.in/yaml.v3"
 )
@@ -67,7 +68,10 @@ func (sp *multiPrintWriter) GetWriter(node *CandidateNode) (*bufio.Writer, error
 	if result.MatchingNodes.Len() > 0 {
 		name = result.MatchingNodes.Front().Value.(*CandidateNode).Node.Value
 	}
+	var extensionRegexp = regexp.MustCompile(`\.[a-zA-Z0-9]+$`)
+	if !extensionRegexp.MatchString(name) {
 		name = fmt.Sprintf("%v.%v", name, sp.extension)
+	}
 
 	f, err := os.Create(name)