remove restriction for extends to refer to another resource

loader/extends.go

@@ -20,7 +20,6 @@ import (
 	"context"
 	"fmt"
 	"path/filepath"
-	"strings"
 
 	"github.com/compose-spec/compose-go/v2/consts"
 	"github.com/compose-spec/compose-go/v2/override"
@@ -106,11 +105,6 @@ func applyServiceExtends(ctx context.Context, name string, services map[string]a
 	}
 	source := deepClone(base).(map[string]any)
 
-	err = validateExtendSource(source, ref)
-	if err != nil {
-		return nil, err
-	}
-
 	for _, processor := range post {
 		processor.Apply(map[string]any{
 			"services": map[string]any{
@@ -127,30 +121,6 @@ func applyServiceExtends(ctx context.Context, name string, services map[string]a
 	return merged, nil
 }
 
-// validateExtendSource check the source for `extends` doesn't refer to another container/service
-func validateExtendSource(source map[string]any, ref string) error {
-	forbidden := []string{"links", "volumes_from", "depends_on"}
-	for _, key := range forbidden {
-		if _, ok := source[key]; ok {
-			return fmt.Errorf("service %q can't be used with `extends` as it declare `%s`", ref, key)
-		}
-	}
-
-	sharedNamespace := []string{"network_mode", "ipc", "pid", "net", "cgroup", "userns_mode", "uts"}
-	for _, key := range sharedNamespace {
-		if v, ok := source[key]; ok {
-			val := v.(string)
-			if strings.HasPrefix(val, types.ContainerPrefix) {
-				return fmt.Errorf("service %q can't be used with `extends` as it shares `%s` with another container", ref, key)
-			}
-			if strings.HasPrefix(val, types.ServicePrefix) {
-				return fmt.Errorf("service %q can't be used with `extends` as it shares `%s` with another service", ref, key)
-			}
-		}
-	}
-	return nil
-}
-
 func getExtendsBaseFromFile(ctx context.Context, name string, path string, opts *Options, ct *cycleTracker) (map[string]any, error) {
 	for _, loader := range opts.ResourceLoaders {
 		if !loader.Accept(path) {

loader/extends_test.go

@@ -306,7 +306,7 @@ services:
 	assert.Equal(t, extendsCount, 3)
 }
 
-func TestRejectExtendsWithServiceRef(t *testing.T) {
+func TestExtendsWithServiceRef(t *testing.T) {
 	tests := []struct {
 		name    string
 		yaml    string
@@ -317,54 +317,48 @@ func TestRejectExtendsWithServiceRef(t *testing.T) {
 			yaml: `
 name: test-extends_with_volumes_from
 services:
-  foo:
-    volumes_from:
-      - zot
-  bar:
+  bar: 
     extends:
-      service: foo
+      file: ./testdata/extends/depends_on.yaml
+      service: with_volumes_from
 `,
-			wantErr: "service \"foo\" can't be used with `extends` as it declare `volumes_from`",
+			wantErr: `service "bar" depends on undefined service "zot"`,
 		},
 		{
 			name: "depends_on",
 			yaml: `
 name: test-extends_with_depends_on
 services:
-  foo:
-    depends_on:
-      - zot
   bar:
     extends:
-      service: foo
+      file: ./testdata/extends/depends_on.yaml
+      service: with_depends_on
 `,
-			wantErr: "service \"foo\" can't be used with `extends` as it declare `depends_on`",
+			wantErr: `service "bar" depends on undefined service "zot"`,
 		},
 		{
 			name: "shared ipc",
 			yaml: `
 name: test-extends_with_shared_ipc
 services:
-  foo:
-    ipc: "service:zot"
   bar:
     extends:
-      service: foo
+      file: ./testdata/extends/depends_on.yaml
+      service: with_ipc
 `,
-			wantErr: "service \"foo\" can't be used with `extends` as it shares `ipc` with another service",
+			wantErr: `service "bar" depends on undefined service "zot"`,
 		},
 		{
 			name: "shared network_mode",
 			yaml: `
 name: test-extends_with_shared_network_mode
 services:
-  foo:
-    network_mode: "container:123abc"
   bar:
     extends:
-      service: foo
+      file: ./testdata/extends/depends_on.yaml
+      service: with_network_mode
 `,
-			wantErr: "service \"foo\" can't be used with `extends` as it shares `network_mode` with another container",
+			wantErr: `service "bar" depends on undefined service "zot"`,
 		},
 	}
 
@@ -376,6 +370,17 @@ services:
 				}},
 			})
 			assert.ErrorContains(t, err, tt.wantErr)
+
+			// Do the same but with a local `zot` service matching the imported reference
+			_, err = LoadWithContext(context.Background(), types.ConfigDetails{
+				ConfigFiles: []types.ConfigFile{{
+					Content: []byte(tt.yaml + `
+  zot:
+    image: zot
+`),
+				}},
+			})
+			assert.NilError(t, err)
 		})
 	}
 }

loader/testdata/extends/depends_on.yaml

@@ -0,0 +1,21 @@
+services:
+  with_depends_on:
+    image: foo
+    depends_on:
+      - zot
+
+  with_volumes_from:
+    image: foo
+    volumes_from:
+      - zot
+
+  with_ipc:
+    image: foo
+    ipc: "service:zot"
+
+  with_network_mode:
+    image: foo
+    network_mode: "service:zot"
+
+  zot:
+    image: hidden

loader/validate.go

@@ -73,7 +73,7 @@ func checkConsistency(project *types.Project) error {
 
 		for dependedService := range s.DependsOn {
 			if _, err := project.GetService(dependedService); err != nil {
-				return fmt.Errorf("service %q depends on undefined service %s: %w", s.Name, dependedService, errdefs.ErrInvalid)
+				return fmt.Errorf("service %q depends on undefined service %q: %w", s.Name, dependedService, errdefs.ErrInvalid)
 			}
 		}
 		// Check there isn't a cycle in depends_on declarations

loader/validate_test.go

@@ -258,7 +258,7 @@ func TestValidateDependsOn(t *testing.T) {
 		},
 	}
 	err := checkConsistency(&project)
-	assert.Error(t, err, `service "myservice" depends on undefined service missingservice: invalid compose project`)
+	assert.Error(t, err, `service "myservice" depends on undefined service "missingservice": invalid compose project`)
 }
 
 func TestValidateContainerName(t *testing.T) {