Resolving via the GEM resolver adds a reason for Gradle 4.5+ (#325)

Author: ysb33r

core-plugin/src/main/groovy/com/github/jrubygradle/internal/gems/GemVersionResolver.groovy

@@ -25,13 +25,15 @@ package com.github.jrubygradle.internal.gems
 
 import com.github.jrubygradle.api.gems.GemVersion
 import com.github.jrubygradle.api.gems.GemGroups
+import groovy.transform.CompileDynamic
 import groovy.transform.PackageScope
 import org.gradle.api.Action
 import org.gradle.api.GradleException
 import org.gradle.api.artifacts.Configuration
 import org.gradle.api.artifacts.DependencyResolveDetails
 import org.gradle.api.logging.Logger
 import org.gradle.api.logging.Logging
+import org.gradle.util.GradleVersion
 
 import static com.github.jrubygradle.api.gems.GemVersion.gemVersionFromGradleIvyRequirement
 
@@ -81,6 +83,8 @@ class GemVersionResolver {
             logger.debug("${configuration}      resolved  ${next}")
 
             details.useVersion(next.toString())
+            withReason(details,"Selected by GEM Version Resolver")
+
         } else {
             GemVersion next = gemVersionFromGradleIvyRequirement(details.requested.version)
             versions[details.requested.name] = next
@@ -113,9 +117,17 @@ class GemVersionResolver {
         )
     }
 
+    @CompileDynamic
+    void withReason(DependencyResolveDetails drd, String reason) {
+        if(HAS_BECAUSE_PROPERTY) {
+            drd.because(reason)
+        }
+    }
+
     @PackageScope
     static final GemVersionResolver NULL_RESOLVER = new GemVersionResolver()
 
+    private static final HAS_BECAUSE_PROPERTY = GradleVersion.current() >= GradleVersion.version('4.5')
     private static final String DBG_SEPARATOR = '                       ------------------------'
     private final Map versions = [:]
     private final Configuration configuration