fix: support base-image extension dependencies

dagger/maintenance/main.go

@@ -202,9 +202,12 @@ func (m *Maintenance) GenerateTestingValues(
 		return nil, err
 	}
 
-	extensions := make([]*ExtensionConfiguration, len(extensionInfos))
-	for i, info := range extensionInfos {
-		extensions[i] = info.Configuration
+	extensions := make([]*ExtensionConfiguration, 0, len(extensionInfos))
+	for _, info := range extensionInfos {
+		if info.Configuration == nil {
+			continue
+		}
+		extensions = append(extensions, info.Configuration)
 	}
 
 	databaseConfig := generateDatabaseConfig(extensionInfos)

dagger/maintenance/testingvalues.go

@@ -3,6 +3,7 @@ package main
 import (
 	"context"
 	"fmt"
+	"strings"
 
 	"dagger/maintenance/internal/dagger"
 )
@@ -37,6 +38,8 @@ type testingExtensionInfo struct {
 	CreateExtension bool
 }
 
+const baseImageDependencyPrefix = "base-image:"
+
 type imageLocator struct {
 	ExtensionImage string
 	PgMajor        int
@@ -64,7 +67,19 @@ func generateTestingValuesExtensions(
 		CreateExtension: metadata.CreateExtension,
 	})
 
-	for _, dep := range metadata.RequiredExtensions {
+	for _, requiredDependency := range metadata.RequiredExtensions {
+		dep, isBaseImageDependency, err := parseRequiredDependency(requiredDependency)
+		if err != nil {
+			return nil, err
+		}
+		if isBaseImageDependency {
+			out = append(out, &testingExtensionInfo{
+				SQLName:         dep,
+				CreateExtension: true,
+			})
+			continue
+		}
+
 		depExists, err := source.Exists(ctx, dep)
 		if err != nil {
 			return nil, err
@@ -108,6 +123,19 @@ func generateTestingValuesExtensions(
 	return out, nil
 }
 
+func parseRequiredDependency(dependency string) (string, bool, error) {
+	if !strings.HasPrefix(dependency, baseImageDependencyPrefix) {
+		return dependency, false, nil
+	}
+
+	name := strings.TrimPrefix(dependency, baseImageDependencyPrefix)
+	if name == "" {
+		return "", false, fmt.Errorf("base-image dependency %q has no extension name", dependency)
+	}
+
+	return name, true, nil
+}
+
 func generateExtensionConfiguration(metadata *extensionMetadata, extensionImage string) (*ExtensionConfiguration, error) {
 	targetExtensionImage := extensionImage
 	if targetExtensionImage == "" {

templates/metadata.hcl.tmpl

@@ -98,8 +98,10 @@ metadata = {
   auto_update_os_libs      = false
 
   # TODO: Remove this comment block after customizing the file.
-  # `required_extensions`: must contain the name(s) of the sibling
-  # folders in this repository that contain a required extension.
+  # `required_extensions`: names of required extensions. By default each name
+  # must identify a sibling folder in this repository. Prefix dependencies
+  # provided by the PostgreSQL base image with `base-image:` (for example,
+  # `base-image:pg_stat_statements`).
   required_extensions      = []
 
   # TODO: Remove this comment block after customizing the file.