Source value mapped more than once inspection for @ValueMapping

For value mappings a source value can only be mapped once. For example

import org.mapstruct.Mapper;
import org.mapstruct.ValueMapping;

@Mapper
public interface ValueMapper {

    enum A {
        A,B
    }

    enum B {
        A,B
    }

    @ValueMapping(source = "A", target = "B")
    @ValueMapping(source = "A", target = "A")
    A from(B b);
}

is invalide as source A is mapped twice. MapStruct report this as

Source value mapping: "A" cannot be mapped more than once.

Currently the plugin does not recognize this as an error. An inspection should be added for this.

For normal mappings there is already an inspection implemented and could be used as an example: https://github.com/mapstruct/mapstruct-idea/blob/main/src/main/java/org/mapstruct/intellij/inspection/TargetPropertyMappedMoreThanOnceInspection.java.

既存の inspection パターンを提供している src/main/java/org/mapstruct/intellij/inspection/TargetPropertyMappedMoreThanOnceInspection.java から始めてください。通常の重複したマッピングをどのように検出しているかを追跡し、同じアプローチを @ValueMapping のソース値に適用してください。重複したソース値が認識され、期待されるエラーメッセージで報告されれば完了です。