Auto-exclude Spring Boot LiquibaseAutoConfiguration when Database Migration Plugin is present

[jamesfredley]

Summary

Automatically excludes Spring Boot's LiquibaseAutoConfiguration when the Database Migration Plugin is on the classpath, using Grails' existing AST transformation in ApplicationClassInjector. This eliminates the need for users to manually add spring.liquibase.enabled: false to their configuration.

Bug Description

When a Grails application uses the Database Migration Plugin, Spring Boot's LiquibaseAutoConfiguration creates its own SpringLiquibase bean that conflicts with the plugin's own Liquibase lifecycle management in DatabaseMigrationGrailsPlugin.doWithApplicationContext(). This causes:

• Duplicate changelog execution attempts
• Lock contention on DATABASECHANGELOGLOCK
• Startup failures or unexpected behavior

Users must currently add this workaround to application.yml:

spring:
  liquibase:
    enabled: false

Fix

Added a conditional exclusion to ApplicationClassInjector - the same AST transformation that already excludes DataSourceAutoConfiguration, ReactorAutoConfiguration, and HibernateJpaAutoConfiguration. When DatabaseMigrationGrailsPlugin is detected on the classpath via ClassUtils.isPresent(), LiquibaseAutoConfiguration is added to @EnableAutoConfiguration(excludeName=...) at compile time.

This is a single-mechanism approach that hooks into existing Grails infrastructure rather than adding new runtime components.

Opt-out

To disable the automatic exclusion, add the following to your project's gradle.properties:

systemProp.grails.dbmigration.excludeLiquibaseAutoConfiguration=false

This system property is read at compile time during the AST transformation. When set to false, the exclusion is not added and Spring Boot's Liquibase auto-configuration will run alongside the plugin.

Files Changed

• grails-core/.../ApplicationClassInjector.groovy - Added CONDITIONAL_EXCLUSIONS list and conditional exclusion logic with system property opt-out
• grails-core/.../ApplicationClassInjectorSpec.groovy - 6 new Spock tests
• grails-doc/.../automaticDatabaseMigration.adoc - Documentation for the auto-exclusion and opt-out
• grails-data-hibernate5/dbmigration/README.md - Documentation for the auto-exclusion and opt-out

Test Coverage

All 6 tests pass:

Test	Verifies
EXCLUDED_AUTO_CONFIGURE_CLASSES contains expected entries	Existing exclusions intact
CONDITIONAL_EXCLUSIONS contains LiquibaseAutoConfiguration entry	Correct plugin class, exclude class, and system property
system property defaults to true (exclusion enabled)	Default behavior is to exclude
system property set to false disables exclusion	Opt-out mechanism works
shouldInject returns false for null URL	Edge case
artefact types contains Application	Injector configuration

Example Application

https://github.com/jamesfredley/grails-liquibase-autoconfig-conflict

Environment Information

• Grails: 7.0.7
• Spring Boot: 3.5.10
• Groovy: 4.0.30
• Liquibase: 4.27.0 (managed by BOM)
• JDK: 17+

[jdaugherty]

There's already a built in way to exclude problematic autoconfiguration via the Application AST transform. Since there's a way to do this already, shoudln't we adopt the "grails way"?

[Copilot]

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[jdaugherty]

Wait, I just looked at the referenced spring security config - this PR makes it sound like we agreed on this approach and this PR is just following that approach. But that approach doesn't appear to be existing; it's new via https://github.com/apache/grails-spring-security/pull/1205/changes

As an optional, external plugin I understand that it needs to implement the exclusion logic, but we've approached the Grails autoconfiguration exclusion differently in core. We need to decide on one way and not adopt multiple ways.

ApplicationClassInjector is the class that has built in excludes. The database plugin should be added here if it's present on the classpath.

@matrei what are your thoughts?

[jamesfredley]

The readme is where the spring security config suggestion currently lives: https://github.com/apache/grails-spring-security/blame/7.0.x/README.md#L52. https://github.com/apache/grails-spring-security/pull/1205/changes suggests making it automatic instead of manual.

[jamesfredley]

@jdaugherty I agree this works, it just feels a bit odd doing it in grails-core for an optional (although often used) plugin

if (ClassUtils.isPresent('org.grails.plugins.databasemigration.DatabaseMigrationGrailsPlugin', classLoader)) {
    GrailsASTUtils.addExpressionToAnnotationMember(enableAutoConfigAnnotation, 'excludeName', 
        constX('org.springframework.boot.autoconfigure.liquibase.LiquibaseAutoConfiguration'))
}

[jdaugherty]

I think ti's reasonable for anything in core to use the core accepted solution. For independent projects, it doesn't make sense to make the change in core. I just mostly want to have 1 way of doing this instead of multiple in grails-core.

[jamesfredley]

Ok, I will switch it out.