Add a way for the builder mechanism to provide access to the `Config` object passed to a builder

[tjquinno]

Environment Details

• Helidon Version: 4.x
• Helidon SE or Helidon MP
• JDK version:
• OS:
• Docker version (if applicable):

---

Problem Description

It would be very useful if the builder mechanism provided a way to retrieve, from the built XXXConfig object, the Config (if any) that was passed to the builder's config(Config) method.

For an example, suppose we create MetricsConfigBlueprint that starts out like this:

@ConfigBean()
@Configured(root = true, prefix = MetricsConfigBlueprint.METRICS_CONFIG_KEY)
@Prototype.Blueprint(decorator = MetricsConfigBlueprint.BuilderDecorator.class)
@Prototype.CustomMethods(MetricsConfigSupport.class)
interface MetricsConfigBlueprint {

Tomas suggested these steps as a workaround which almost worked but exposed a small bug:

• Add a method to the blueprint:

  @ConfiguredOption(builderMethod = false, configured = false)
  Config metricsConfig();

• In the builder decorator method (run as build() executes):

      class BuilderDecorator implements Prototype.BuilderDecorator<MetricsConfig.BuilderBase<?, ?>> {
  
        @Override
        public void decorate(MetricsConfig.BuilderBase<?, ?> builder) {
            if (builder.config().isEmpty()) {
                builder.config(GlobalConfig.config().get(METRICS_CONFIG_KEY));
            }
            builder.metricsConfig(target.config().get());
        }
    }

• Write a custom method for the prototype that refers to the saved config instance:

  class MetricsConfigSupport {
  
    @Prototype.PrototypeMethod
    static Optional<String> lookupConfig(MetricsConfig metricsConfig, String key) {
        return metricsConfig.metricsConfig()
                .get(key)
                .asString()
                .asOptional();
    }

Tomas provided this patch that allows this approach to work:

Subject: [PATCH] Fix prototype builder for Config type
---
Index: builder/processor/src/main/java/io/helidon/builder/processor/GenerateAbstractBuilder.java
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
diff --git a/builder/processor/src/main/java/io/helidon/builder/processor/GenerateAbstractBuilder.java b/builder/processor/src/main/java/io/helidon/builder/processor/GenerateAbstractBuilder.java
--- a/builder/processor/src/main/java/io/helidon/builder/processor/GenerateAbstractBuilder.java	(revision af5d14b8a9565af4011713a94a631748b6b87322)
+++ b/builder/processor/src/main/java/io/helidon/builder/processor/GenerateAbstractBuilder.java	(date 1691673740771)
@@ -628,7 +628,7 @@
             pw.println("private Config config;");
         }
         for (PrototypeProperty child : typeContext.propertyData().properties()) {
-            if (!isBuilder || !child.typeHandler().actualType().equals(CONFIG_TYPE)) {
+            if (!isBuilder || !(child.typeHandler().actualType().equals(CONFIG_TYPE) && child.name().equals("config"))) {
                 pw.print(spacing);
                 pw.print(child.fieldDeclaration(isBuilder));
                 pw.println(";");
Index: builder/processor/src/main/java/io/helidon/builder/processor/PrototypeProperty.java
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
diff --git a/builder/processor/src/main/java/io/helidon/builder/processor/PrototypeProperty.java b/builder/processor/src/main/java/io/helidon/builder/processor/PrototypeProperty.java
--- a/builder/processor/src/main/java/io/helidon/builder/processor/PrototypeProperty.java	(revision af5d14b8a9565af4011713a94a631748b6b87322)
+++ b/builder/processor/src/main/java/io/helidon/builder/processor/PrototypeProperty.java	(date 1691673524635)
@@ -324,7 +324,7 @@
                             .map(typeHandler::toDefaultValue)
                             .orElse(null),
                     configuredAnnotation.getValue("builderMethod").map(Boolean::parseBoolean).orElse(true),
-                    configuredAnnotation.getValue("notConfigured").map(Boolean::parseBoolean).orElse(false),
+                    !configuredAnnotation.getValue("configured").map(Boolean::parseBoolean).orElse(true),
                     provider,
                     provider ? ProviderOption.create(configuredAnnotation) : null);
         }

[tomas-langer]

The intendend approach was to allow definition of Optional<Config> config() method on prototype.
All the infrustructure code is there (the method is correctly generated on implementation), but due to some changes in the builder code (refactoring of getters, where it used to implement the prototype and now has dedicated getters), the feature got broken (and was not tested).

Solution: add a check when generating the package local Optional<Config> config() method on builder base, and if such a method is declared on prototype, generate it as public (and do not generated it during the usual processing of fields)

[tomas-langer]

Another issue with builders - if a type has static Type create(Config), treat it as a static factory method (even if the type is not a prototype)

[tomas-langer]

Waiting for #7256