Why does Gradle downgrade my transitive dependencies in a Grails 3.1 application?

Question

I am having a problem with a transitive dependency of my grails-flyway plugin. org.grails.plugins:grails-flyway:0.2.1 declares a dependency to org.flywaydb:flyway-core:4.0.1. When I include the plugin into my Grails 3.1.6 project Gradle downgrades Flyway to version 3.2.1.

+--- org.grails.plugins:grails-flyway:0.2.1 |    \--- org.flywaydb:flyway-core:4.0.1 -> 3.2.1 

My Gradle build file looks like this

buildscript {     ext {         grailsVersion = project.grailsVersion     }     repositories {         maven { url "https://repo.grails.org/grails/core" }     }     dependencies {         classpath "org.grails:grails-gradle-plugin:$grailsVersion"         classpath "com.bertramlabs.plugins:asset-pipeline-gradle:${assetPipelinePluginVersion}"         classpath "org.grails.plugins:hibernate5:5.0.5"         classpath 'com.github.ben-manes:gradle-versions-plugin:0.12.0'     } }  version "0.40.15" group "zsc.supporter"  apply plugin: "war" apply plugin: "org.grails.grails-web" apply plugin: "org.grails.grails-gsp" apply plugin: "org.grails.grails-doc" apply plugin: "asset-pipeline" apply plugin: 'com.github.ben-manes.versions'  ext {     grailsVersion = project.grailsVersion     gradleWrapperVersion = project.gradleWrapperVersion }  repositories {     maven { url "https://repo.grails.org/grails/core" }     maven { url "https://dl.bintray.com/saw303/plugins" } }  dependencyManagement {     imports {         mavenBom "org.grails:grails-bom:$grailsVersion"     }     applyMavenExclusions false }  dependencies {     compile "org.springframework.boot:spring-boot-starter-logging"     compile "org.springframework.boot:spring-boot-autoconfigure"     compile "org.grails:grails-core"     compile "org.springframework.boot:spring-boot-starter-actuator"     compile "org.springframework.boot:spring-boot-starter-tomcat"     compile "org.grails:grails-dependencies"     compile "org.grails:grails-web-boot"     compile "org.grails.plugins:cache"     compile "org.grails.plugins:scaffolding"     compile "org.grails.plugins:hibernate4"     compile "org.hibernate:hibernate-ehcache"     console "org.grails:grails-console"     profile "org.grails.profiles:web:3.1.6"     runtime "com.bertramlabs.plugins:asset-pipeline-grails:${assetPipelinePluginVersion}"     runtime "com.h2database:h2"     testCompile "org.grails:grails-plugin-testing"     testCompile "org.grails.plugins:geb"     testRuntime "org.seleniumhq.selenium:selenium-htmlunit-driver:2.52.0"     testRuntime "net.sourceforge.htmlunit:htmlunit:2.21"      compile "org.grails.plugins:spring-security-core:3.0.4"     compile "org.grails.plugins:quartz:2.0.8"     compile "org.grails.plugins:mail:2.0.0.RC4"     compile "eu.bitwalker:UserAgentUtils:1.18"     compile 'org.mnode.ical4j:ical4j:1.0.7'     compile 'org.grails.plugins:browser-detection:3.1.0'     compile "com.googlecode.libphonenumber:libphonenumber:7.3.1"     runtime 'org.grails.plugins:grails-flyway:0.2.1'      testCompile "org.grails.plugins:grails-wizer:0.3"     testCompile 'org.grails:grails-datastore-test-support:5.0.5.RELEASE'      runtime 'mysql:mysql-connector-java:5.1.29' }  task wrapper(type: Wrapper) {     gradleVersion = gradleWrapperVersion }  assets {     minifyJs = true     minifyCss = true } 

Currently I do not understand why Gradle downgrades my transitive dependency. Can someone provide on this?

I am aware that I can force the flyway-core:4.0.1 dependency in my build.gradle but I would like to understand what the downgrade causes.

UPDATE-1

When I run gradle dependencies | grep flyway I get the following output.

+--- org.grails.plugins:grails-flyway:0.2.1 |    \--- org.flywaydb:flyway-core:4.0.1 -> 3.2.1 +--- org.grails.plugins:grails-flyway:0.2.1 |    \--- org.flywaydb:flyway-core:4.0.1 -> 3.2.1 +--- org.grails.plugins:grails-flyway:0.2.1 |    \--- org.flywaydb:flyway-core:4.0.1 -> 3.2.1 +--- org.grails.plugins:grails-flyway:0.2.1 |    \--- org.flywaydb:flyway-core:4.0.1 -> 3.2.1 

Please find the complete output at pastebin. The grails-flyway plugin and its pom.xml can be found at Bintray.

UPDATE-2

I tried to force Gradle to use org.flywaydb:flyway-core:4.0.1 according to Gradles Reference.

configurations.all {     resolutionStrategy.force 'org.flywaydb:flyway-core:4.0.1' } 

That does not affect the problem. The dependency tree still uses version 3.2.1 of flyway-core.

+--- org.grails.plugins:grails-flyway:0.2.1 |    \--- org.flywaydb:flyway-core:4.0.1 -> 3.2.1 

UPDATE-3

Gradles dependencyInsight command

gradle dependencyInsight --dependency flyway-core --configuration runtime 

results in

:dependencyInsight org.flywaydb:flyway-core:3.2.1 (selected by rule)  org.flywaydb:flyway-core:4.0.1 -> 3.2.1 \--- org.grails.plugins:grails-flyway:0.2.1      \--- runtime  

What means (selected by rule)?

"Solution" - or how to work it around

I was not able to find the rule that causes Gradle to use flyway-core:3.2.1 instead of flyway-core:4.0.1. But I found a way to work around the problem.

I added the following to my build.gradle to modify my Gradle runtime resolution strategy.

configurations.runtime.resolutionStrategy {      eachDependency { DependencyResolveDetails det ->          if (det.requested.name == 'flyway-core' && det.requested.group == 'org.flywaydb') {             det.useVersion(det.requested.version)         }     } } 

Answer 1

The thing causing it is the spring-boot-dependencies-1.3.3.RELEASE.pom

This forcing the flyway version to 3.2.1

According to the Spring Boot docs you should be able to add a line like this to your build.gradle: ext['flyway.version'] = '4.0.1'