avoid conflict with extensions used as service name

loader/loader.go

@@ -313,6 +313,8 @@ func parseConfig(b []byte, opts *Options) (map[string]interface{}, error) {
 	return yml, err
 }
 
+const extensions = "#extensions" // Using # prefix, we prevent risk to conflict with an actual yaml key
+
 func groupXFieldsIntoExtensions(dict map[string]interface{}) map[string]interface{} {
 	extras := map[string]interface{}{}
 	for key, value := range dict {
@@ -325,7 +327,7 @@ func groupXFieldsIntoExtensions(dict map[string]interface{}) map[string]interfac
 		}
 	}
 	if len(extras) > 0 {
-		dict["extensions"] = extras
+		dict[extensions] = extras
 	}
 	return dict
 }
@@ -364,7 +366,7 @@ func loadSections(filename string, config map[string]interface{}, configDetails
 	if err != nil {
 		return nil, err
 	}
-	extensions := getSection(config, "extensions")
+	extensions := getSection(config, extensions)
 	if len(extensions) > 0 {
 		cfg.Extensions = extensions
 	}
@@ -526,7 +528,7 @@ func formatInvalidKeyError(keyPrefix string, key interface{}) error {
 func LoadServices(filename string, servicesDict map[string]interface{}, workingDir string, lookupEnv template.Mapping, opts *Options) ([]types.ServiceConfig, error) {
 	var services []types.ServiceConfig
 
-	x, ok := servicesDict["extensions"]
+	x, ok := servicesDict[extensions]
 	if ok {
 		// as a top-level attribute, "services" doesn't support extensions, and a service can be named `x-foo`
 		for k, v := range x.(map[string]interface{}) {

loader/loader_test.go

@@ -308,7 +308,7 @@ services:
 	assert.Check(t, is.Len(actual.Services, 1))
 	service := actual.Services[0]
 	assert.Check(t, is.Equal("busybox", service.Image))
-	extras := map[string]interface{}{
+	extras := types.Extensions{
 		"x-foo": "bar",
 	}
 	assert.Check(t, is.DeepEqual(extras, service.Extensions))
@@ -2215,3 +2215,18 @@ volumes:
 	path := project.Volumes["data"].DriverOpts["device"]
 	assert.Check(t, filepath.IsAbs(path))
 }
+
+func TestLoadServiceExtension(t *testing.T) {
+	dict := `
+services:
+  extension: # this name should be allowed
+    image: web
+    x-foo: bar
+`
+	configDetails := buildConfigDetails(dict, nil)
+
+	project, err := Load(configDetails)
+	assert.NilError(t, err)
+	assert.Equal(t, project.Services[0].Name, "extension")
+	assert.Equal(t, project.Services[0].Extensions["x-foo"], "bar")
+}

types/project.go

@@ -41,7 +41,7 @@ type Project struct {
 	Volumes      Volumes    `yaml:",omitempty" json:"volumes,omitempty"`
 	Secrets      Secrets    `yaml:",omitempty" json:"secrets,omitempty"`
 	Configs      Configs    `yaml:",omitempty" json:"configs,omitempty"`
-	Extensions   Extensions `yaml:",inline" json:"-"` // https://github.com/golang/go/issues/6213
+	Extensions   Extensions `mapstructure:"#extensions" yaml:",inline" json:"-"` // https://github.com/golang/go/issues/6213
 	ComposeFiles []string   `yaml:"-" json:"-"`
 	Environment  Mapping    `yaml:"-" json:"-"`