apply override during extend

loader/extends.go

@@ -81,13 +81,12 @@ func applyServiceExtends(ctx context.Context, name string, services map[string]a
 
 	var (
 		base      any
-		processor PostProcessor
+		processor PostProcessor = NoopPostProcessor{}
 	)
 
 	if file != nil {
 		refFilename := file.(string)
 		services, processor, err = getExtendsBaseFromFile(ctx, name, ref, filename, refFilename, opts, tracker)
-		post = append(post, processor)
 		if err != nil {
 			return nil, err
 		}
@@ -105,7 +104,7 @@ func applyServiceExtends(ctx context.Context, name string, services map[string]a
 	}
 
 	// recursively apply `extends`
-	base, err = applyServiceExtends(ctx, ref, services, opts, tracker, post...)
+	base, err = applyServiceExtends(ctx, ref, services, opts, tracker, processor)
 	if err != nil {
 		return nil, err
 	}

loader/loader.go

@@ -260,12 +260,14 @@ func WithProfiles(profiles []string) func(*Options) {
 // PostProcessor is used to tweak compose model based on metadata extracted during yaml Unmarshal phase
 // that hardly can be implemented using go-yaml and mapstructure
 type PostProcessor interface {
-	yaml.Unmarshaler
-
 	// Apply changes to compose model based on recorder metadata
 	Apply(interface{}) error
 }
 
+type NoopPostProcessor struct{}
+
+func (NoopPostProcessor) Apply(interface{}) error { return nil }
+
 // LoadConfigFiles ingests config files with ResourceLoader and returns config details with paths to local copies
 func LoadConfigFiles(ctx context.Context, configFiles []string, workingDir string, options ...func(*Options)) (*types.ConfigDetails, error) {
 	if len(configFiles) < 1 {

loader/loader_test.go

@@ -3917,3 +3917,65 @@ services:
 	assert.Equal(t, build.Provenance, "mode=max")
 	assert.Equal(t, build.SBOM, "true")
 }
+
+func TestOverrideMiddle(t *testing.T) {
+	pwd := t.TempDir()
+	base := filepath.Join(pwd, "base.yaml")
+	err := os.WriteFile(base, []byte(`
+services:
+  base:
+    volumes:
+      - /foo:/foo
+`), 0o700)
+	assert.NilError(t, err)
+
+	override := filepath.Join(pwd, "override.yaml")
+	err = os.WriteFile(override, []byte(`
+services:
+  override:
+    extends:
+      file: ./base.yaml
+      service: base
+    volumes: !override
+      -  /bar:/bar
+`), 0o700)
+	assert.NilError(t, err)
+
+	compose := filepath.Join(pwd, "compose.yaml")
+	err = os.WriteFile(compose, []byte(`
+name: test
+services:
+  test:
+    image: test
+    extends:
+      file: ./override.yaml
+      service: override
+    volumes:
+      - /zot:/zot
+`), 0o700)
+	assert.NilError(t, err)
+
+	project, err := LoadWithContext(context.TODO(), types.ConfigDetails{
+		WorkingDir: pwd,
+		ConfigFiles: []types.ConfigFile{
+			{Filename: compose},
+		},
+	})
+	assert.NilError(t, err)
+	test := project.Services["test"]
+	assert.Equal(t, len(test.Volumes), 2)
+	assert.DeepEqual(t, test.Volumes, []types.ServiceVolumeConfig{
+		{
+			Type:   "bind",
+			Source: "/bar",
+			Target: "/bar",
+			Bind:   &types.ServiceVolumeBind{CreateHostPath: true},
+		},
+		{
+			Type:   "bind",
+			Source: "/zot",
+			Target: "/zot",
+			Bind:   &types.ServiceVolumeBind{CreateHostPath: true},
+		},
+	})
+}