feat: add cluster context support in Compose with x-context extension

pkg/client/compose/context.go

@@ -0,0 +1,22 @@
+package compose
+
+import (
+	"github.com/compose-spec/compose-go/v2/types"
+)
+
+// ContextExtensionKey is the top-level Compose extension key for specifying the cluster context.
+const ContextExtensionKey = "x-context"
+
+// ClusterContext extracts the x-context value from the project's top-level extensions.
+// Returns an empty string if x-context is not set.
+func ClusterContext(project *types.Project) string {
+	v, ok := project.Extensions[ContextExtensionKey]
+	if !ok {
+		return ""
+	}
+	s, ok := v.(string)
+	if !ok {
+		return ""
+	}
+	return s
+}

pkg/client/compose/context_test.go

@@ -0,0 +1,45 @@
+package compose
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestClusterContext(t *testing.T) {
+	tests := []struct {
+		name    string
+		content string
+		want    string
+	}{
+		{
+			name: "no x-context",
+			content: `
+services:
+  web:
+    image: nginx
+`,
+			want: "",
+		},
+		{
+			name: "x-context set",
+			content: `
+x-context: prod
+services:
+  web:
+    image: nginx
+`,
+			want: "prod",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			project, err := LoadProjectFromContent(context.Background(), tt.content)
+			require.NoError(t, err)
+			assert.Equal(t, tt.want, ClusterContext(project))
+		})
+	}
+}