Support merging with mapper annotation

context/src/test/groovy/io/micronaut/runtime/beans/MapperAnnotationSpec.groovy

@@ -6,7 +6,6 @@ import io.micronaut.context.annotation.Mapper
 import io.micronaut.core.annotation.AccessorsStyle
 import io.micronaut.core.annotation.Introspected
 import io.micronaut.core.convert.ConversionService
-import jakarta.inject.Inject
 import jakarta.inject.Singleton
 import spock.lang.AutoCleanup
 import spock.lang.Shared
@@ -142,6 +141,23 @@ class MapperAnnotationSpec extends Specification {
         result.companyId == 'rab'
         result.parts == 10
     }
+
+    void "list mapper test"() {
+        when:
+        VacuumCleanersEntity result = testBean.toEntities(
+                new VacuumCleanerCollection([
+                        new VacuumCleaner("first"),
+                        new VacuumCleaner("second"),
+                        new VacuumCleaner("third")
+                ])
+        )
+
+        then:
+        result.cleaners[0].name == 'first'
+        result.cleaners[1].name == 'second'
+        result.cleaners[2].name == 'third'
+    }
+
 }
 
 @Singleton
@@ -172,6 +188,12 @@ abstract class Test {
     String calcCompanyId(CreateRobot createRobot) {
         return createRobot.companyId.reverse()
     }
+
+    @Mapper
+    abstract VacuumCleanersEntity toEntity(VacuumCleaner cleaner)
+
+    @Mapper
+    abstract VacuumCleanersEntity toEntities(VacuumCleanerCollection cleaner)
 }
 
 @Introspected
@@ -292,3 +314,39 @@ class SimpleRobotEntity {
     }
 
 }
+
+@Introspected
+final class VacuumCleaner {
+    final String name
+
+    VacuumCleaner(String name) {
+        this.name = name
+    }
+}
+
+@Introspected
+final class VacuumCleanerEntity {
+    final String name
+
+    VacuumCleanerEntity(String name) {
+        this.name = name
+    }
+}
+
+@Introspected
+final class VacuumCleanerCollection {
+    final List<VacuumCleaner> cleaners
+
+    VacuumCleanerCollection(List<VacuumCleaner> cleaners) {
+        this.cleaners = cleaners
+    }
+}
+
+@Introspected
+final class VacuumCleanersEntity {
+    final ArrayList<VacuumCleanerEntity> cleaners
+
+    VacuumCleanersEntity(ArrayList<VacuumCleanerEntity> cleaners) {
+        this.cleaners = cleaners
+    }
+}

context/src/test/groovy/io/micronaut/runtime/beans/MapperMergingAnnotationSpec.groovy

@@ -0,0 +1,194 @@
+package io.micronaut.runtime.beans
+
+import groovy.transform.EqualsAndHashCode
+import io.micronaut.context.ApplicationContext
+import io.micronaut.context.annotation.Mapper
+import io.micronaut.core.annotation.Introspected
+import jakarta.inject.Named
+import jakarta.inject.Singleton
+import spock.lang.AutoCleanup
+import spock.lang.Shared
+import spock.lang.Specification
+
+class MapperMergingAnnotationSpec extends Specification {
+
+    @Shared @AutoCleanup ApplicationContext context = ApplicationContext.run()
+    @Shared TestMerge testMerge = context.getBean(TestMerge)
+
+    void "test merge beans"() {
+        given:
+        var a = new SkeletonPartA(description: "Spooky", age: 120)
+        var b = new SkeletonPartB(numBones: 130, height: 184)
+        var c = new SkeletonPartC(numToes: 10)
+
+        when:
+        Skeleton result = testMerge.merge(a, b, c)
+
+        then:
+        result.description == 'Spooky'
+        result.age == 120
+        result.numBones == 130
+        result.height == 184
+        result.numToes == 10
+    }
+
+    void "test merge beans with mapping"() {
+        given:
+        var a = new CustomPart(halloweenDescription: "Spooky and gloomy", aliveAge: 100, deadAge: 100)
+        var b = new SkeletonPartB(numBones: 130, height: 184)
+        var c = new SkeletonPartC(numToes: 10)
+
+        when:
+        Skeleton result = testMerge.merge(a, b, c)
+
+        then:
+        result.description == 'Spooky and gloomy'
+        result.age == 200
+        result.numBones == 130
+        result.height == 184
+        result.numToes == 10
+    }
+
+    void "test update from map"() {
+        given:
+        var s = new Skeleton(description: "Spooky", age: 102)
+        var update = ["description": "Boo!!!", "numBones": 200]
+
+        when:
+        Skeleton result = testMerge.update(s, update)
+
+        then:
+        result.description == 'Boo!!!'
+        result.age == 102
+        result.numBones == 200
+    }
+
+    void "test merge from maps with mapping"() {
+        given:
+        var a = ["description": "Spooky", deadAge: 100]
+        var b = ["halloweenDescription": "Boo!!!", "numBones": 200]
+
+        when:
+        Skeleton result = testMerge.merge(a, b)
+
+        then:
+        result.description == 'Boo!!!'
+        result.age == 100
+        result.numBones == 200
+    }
+
+    void "test update default merge strategy"() {
+        when:
+        var skeleton = new Skeleton(description: "Spooky", age: 100, numBones: 12, height: 100, numToes: 2)
+        var update = new SkeletonUpdater(halloweenDescription: "Very spooky")
+
+        then:
+        testMerge.updateNotNullOverride(skeleton, update) == new Skeleton(description: "Very spooky", age: 100, numBones: 12, height: 100, numToes: 2)
+        testMerge.updateAlwaysOverride(skeleton, update) == new Skeleton(description: "Very spooky", height: 100, numToes: 2)
+    }
+
+    void "test update custom merge strategy"() {
+        when:
+        var skeleton = new Skeleton(description: "Spooky", age: 100, numBones: 12, height: 100, numToes: 2)
+        var update1 = new SkeletonUpdater(halloweenDescription: "Very spooky", explicitlySet: [])
+        var update2 = new SkeletonUpdater(halloweenDescription: "Very spooky", explicitlySet: ["halloweenDescription"])
+        var update3 = new SkeletonUpdater(halloweenDescription: "Very spooky", explicitlySet: ["halloweenDescription", "age", "numBones"])
+
+        then:
+        // Nothing explicitly set
+        testMerge.updateExplicitlySet(skeleton, update1) == skeleton
+        // Item was explicitly set
+        testMerge.updateExplicitlySet(skeleton, update2) == new Skeleton(description: "Very spooky", age: 100, numBones: 12, height: 100, numToes: 2)
+        // Item was explicitly null-ed
+        testMerge.updateExplicitlySet(skeleton, update3) == new Skeleton(description: "Very spooky", height: 100, numToes: 2)
+    }
+
+}
+
+@Singleton
+@Mapper
+abstract class TestMerge {
+
+    @Mapper
+    abstract Skeleton merge(SkeletonPartA a, SkeletonPartB b, SkeletonPartC c);
+
+    @Mapper.Mapping(from = "a.halloweenDescription", to = "description")
+    @Mapper.Mapping(from = "#{a.deadAge + a.aliveAge}", to = "age")
+    abstract Skeleton merge(CustomPart a, SkeletonPartB b, SkeletonPartC c);
+
+    @Mapper
+    abstract Skeleton update(Skeleton skeleton, Map<String, Object> values);
+
+    @Mapper.Mapping(from = "values.halloweenDescription", to = "description")
+    @Mapper.Mapping(from = "#{skeleton.get('deadAge')}", to = "age")
+    abstract Skeleton merge(Map<String, Object> skeleton, Map<String, Object> values);
+
+    @Mapper(mergeStrategy = "EXPLICITLY_SET")
+    @Mapper.Mapping(from = "updater.halloweenDescription", to = "description")
+    abstract Skeleton updateExplicitlySet(Skeleton current, SkeletonUpdater updater)
+
+    @Mapper(mergeStrategy = Mapper.MERGE_STRATEGY_ALWAYS_OVERRIDE)
+    @Mapper.Mapping(from = "updater.halloweenDescription", to = "description")
+    abstract Skeleton updateAlwaysOverride(Skeleton current, SkeletonUpdater updater)
+
+    @Mapper(mergeStrategy = Mapper.MERGE_STRATEGY_NOT_NULL_OVERRIDE)
+    @Mapper.Mapping(from = "updater.halloweenDescription", to = "description")
+    abstract Skeleton updateNotNullOverride(Skeleton current, SkeletonUpdater updater)
+
+}
+
+@Introspected
+@EqualsAndHashCode
+final class Skeleton {
+    String description
+    Integer age
+    Integer numBones
+    Float height
+    Integer numToes
+}
+
+@Introspected
+final class SkeletonUpdater {
+    String halloweenDescription
+    Integer age
+    Integer numBones
+    Set<String> explicitlySet
+}
+
+@Introspected
+final class SkeletonPartA {
+    String description
+    Integer age
+}
+
+@Introspected
+final class SkeletonPartB {
+    Integer numBones
+    double height
+}
+
+@Introspected
+final class SkeletonPartC {
+    Integer numToes
+}
+
+@Introspected
+final class CustomPart {
+    String halloweenDescription
+    Integer deadAge
+    Integer aliveAge
+}
+
+@Singleton
+@Named("EXPLICITLY_SET")
+final class ExplicitlySetMergeStrategy implements Mapper.MergeStrategy {
+
+    @Override
+    Object merge(Object currentValue, Object value, Object valueOwner, String propertyName, String mappedPropertyName) {
+        if (valueOwner instanceof SkeletonUpdater) {
+            return valueOwner.explicitlySet.contains(mappedPropertyName) ? value : currentValue
+        } else {
+            value
+        }
+    }
+}