Merge compose extensions.

Fixes docker/compose#12724.

Signed-off-by: Florian Apolloner <[email protected]>

Author: apollo13

loader/loader_yaml_test.go

@@ -30,6 +30,9 @@ func TestParseYAMLFiles(t *testing.T) {
 			{
 				Filename: "test.yaml",
 				Content: []byte(`
+x-extension:
+    test1: first
+
 services:
   test:
     image: foo
@@ -40,6 +43,9 @@ services:
 			{
 				Filename: "override.yaml",
 				Content: []byte(`
+x-extension:
+    test2: second
+
 services:
   test:
     image: bar
@@ -58,6 +64,10 @@ services:
 				"init":    false,
 			},
 		},
+		"x-extension": map[string]interface{}{
+			"test1": "first",
+			"test2": "second",
+		},
 	})
 }
 

override/merge.go

@@ -20,7 +20,6 @@ import (
 	"cmp"
 	"fmt"
 	"slices"
-	"strings"
 
 	"github.com/compose-spec/compose-go/v2/tree"
 )
@@ -104,7 +103,7 @@ func mergeYaml(e any, o any, p tree.Path) (any, error) {
 func mergeMappings(mapping map[string]any, other map[string]any, p tree.Path) (map[string]any, error) {
 	for k, v := range other {
 		e, ok := mapping[k]
-		if !ok || strings.HasPrefix(k, "x-") {
+		if !ok {
 			mapping[k] = v
 			continue
 		}