Due to gradle/gradle#5510, compileJava may be executed unnecessarily when not using Gradle's daemon

[display-none]

spring-boot-gradle-plugin applied to a project build with no-daemon Gradle breaks incremental build - causes a retriggering of compileJava with every run

Steps to reproduce:

• Check out https://github.com/spring-guides/gs-spring-boot
• run gradlew --no-daemon clean assemble
• run gradlew --no-daemon testClasses

Expected behaviour
Task compileJava is UP-TO-DATE as nothing has changed that should trigger recompilation.

Actual behaviour
Task compileJava is run because, as Gradle prints, "Task ':compileJava' has additional actions that have changed"

Probable cause
During up-to-date checks Gradle compares task's previously known actions with current actions for equality (see org.gradle.api.internal.changedetection.rules.TaskTypeTaskStateChanges). Spring boot's org.springframework.boot.gradle.plugin.JavaPluginAction configures a JavaCompile task in configureAdditionalMetadataLocations with an action using a labda.

When building with a daemon that configuration probably happens once and in JavaCompile task's actions we can see the same lambda instance, which makes it equal and up-to-date check passes. When executing without a daemon another run has a different lambda instance and it fails the equality check.

In our project we have multiple steps configured as separate gradle runs and each of them recompiles the whole project.

Versions
Gradle 4.9
Spring Boot 2.0.4.RELEASE

[wilkinsona]

Thanks for the report. I don't think this is quite as simple has you have described. In my testing, compileJava is sometimes up-to-date and whether or not it is considered to be up-to-date seems to change depending on whether or not --info is passed in.

Initial clean run, two tasks are executed as expected:

$ ./gradlew --no-daemon clean compileJava

BUILD SUCCESSFUL in 4s
2 actionable tasks: 2 executed

Run compileJava again and it is up-to-date:

$ ./gradlew --no-daemon compileJava

BUILD SUCCESSFUL in 3s
1 actionable task: 1 up-to-date

Run compileJava again but with --info and it is no longer up-to-date:

$ ./gradlew --no-daemon compileJava --info
Initialized native services in: /Users/awilkinson/.gradle/native
Using 8 worker leases.
Starting Build
Settings evaluated using settings file '/Users/awilkinson/dev/spring-guides/gs-spring-boot/complete/settings.gradle'.
Projects loaded. Root project using build file '/Users/awilkinson/dev/spring-guides/gs-spring-boot/complete/build.gradle'.
Included projects: [root project 'complete']

> Configure project :
Evaluating root project 'complete' using build file '/Users/awilkinson/dev/spring-guides/gs-spring-boot/complete/build.gradle'.
Applying dependency management to configuration 'annotationProcessor' in project 'complete'
Applying dependency management to configuration 'apiElements' in project 'complete'
Applying dependency management to configuration 'archives' in project 'complete'
Applying dependency management to configuration 'bootArchives' in project 'complete'
Applying dependency management to configuration 'compile' in project 'complete'
Applying dependency management to configuration 'compileClasspath' in project 'complete'
Applying dependency management to configuration 'compileOnly' in project 'complete'
Applying dependency management to configuration 'default' in project 'complete'
Applying dependency management to configuration 'implementation' in project 'complete'
Applying dependency management to configuration 'runtime' in project 'complete'
Applying dependency management to configuration 'runtimeClasspath' in project 'complete'
Applying dependency management to configuration 'runtimeElements' in project 'complete'
Applying dependency management to configuration 'runtimeOnly' in project 'complete'
Applying dependency management to configuration 'testAnnotationProcessor' in project 'complete'
Applying dependency management to configuration 'testCompile' in project 'complete'
Applying dependency management to configuration 'testCompileClasspath' in project 'complete'
Applying dependency management to configuration 'testCompileOnly' in project 'complete'
Applying dependency management to configuration 'testImplementation' in project 'complete'
Applying dependency management to configuration 'testRuntime' in project 'complete'
Applying dependency management to configuration 'testRuntimeClasspath' in project 'complete'
Applying dependency management to configuration 'testRuntimeOnly' in project 'complete'
All projects evaluated.
Selected primary task 'compileJava' from project :
Tasks to be executed: [task ':compileJava']
:compileJava (Thread[main,5,main]) started.

> Task :compileJava
Resolving global dependency management for project 'complete'
Excluding [org.apache.tomcat:tomcat-annotations-api]
Excluding []
Task ':compileJava' is not up-to-date because:
  Task ':compileJava' has additional actions that have changed
All input files are considered out-of-date for incremental task ':compileJava'.
Compiling with JDK Java compiler API.
:compileJava (Thread[main,5,main]) completed. Took 1.709 secs.

BUILD SUCCESSFUL in 4s
1 actionable task: 1 executed

Repeat the run with --info and compileJava is up-to-date again:

./gradlew --no-daemon compileJava --info
Initialized native services in: /Users/awilkinson/.gradle/native
Using 8 worker leases.
Starting Build
Settings evaluated using settings file '/Users/awilkinson/dev/spring-guides/gs-spring-boot/complete/settings.gradle'.
Projects loaded. Root project using build file '/Users/awilkinson/dev/spring-guides/gs-spring-boot/complete/build.gradle'.
Included projects: [root project 'complete']

> Configure project :
Evaluating root project 'complete' using build file '/Users/awilkinson/dev/spring-guides/gs-spring-boot/complete/build.gradle'.
Applying dependency management to configuration 'annotationProcessor' in project 'complete'
Applying dependency management to configuration 'apiElements' in project 'complete'
Applying dependency management to configuration 'archives' in project 'complete'
Applying dependency management to configuration 'bootArchives' in project 'complete'
Applying dependency management to configuration 'compile' in project 'complete'
Applying dependency management to configuration 'compileClasspath' in project 'complete'
Applying dependency management to configuration 'compileOnly' in project 'complete'
Applying dependency management to configuration 'default' in project 'complete'
Applying dependency management to configuration 'implementation' in project 'complete'
Applying dependency management to configuration 'runtime' in project 'complete'
Applying dependency management to configuration 'runtimeClasspath' in project 'complete'
Applying dependency management to configuration 'runtimeElements' in project 'complete'
Applying dependency management to configuration 'runtimeOnly' in project 'complete'
Applying dependency management to configuration 'testAnnotationProcessor' in project 'complete'
Applying dependency management to configuration 'testCompile' in project 'complete'
Applying dependency management to configuration 'testCompileClasspath' in project 'complete'
Applying dependency management to configuration 'testCompileOnly' in project 'complete'
Applying dependency management to configuration 'testImplementation' in project 'complete'
Applying dependency management to configuration 'testRuntime' in project 'complete'
Applying dependency management to configuration 'testRuntimeClasspath' in project 'complete'
Applying dependency management to configuration 'testRuntimeOnly' in project 'complete'
All projects evaluated.
Selected primary task 'compileJava' from project :
Tasks to be executed: [task ':compileJava']
:compileJava (Thread[Task worker for ':' Thread 2,5,main]) started.

> Task :compileJava UP-TO-DATE
Resolving global dependency management for project 'complete'
Excluding [org.apache.tomcat:tomcat-annotations-api]
Excluding []
Skipping task ':compileJava' as it is up-to-date.
:compileJava (Thread[Task worker for ':' Thread 2,5,main]) completed. Took 1.064 secs.

BUILD SUCCESSFUL in 3s
1 actionable task: 1 up-to-date

When Gradle's comparing task actions it uses the class loader for the action and the type name. It's JavaPluginAction$$Lambda$22 that we're interested in.

Here is the name (as captured from the output of -verbose:class) when built without --info:

[Loaded org.springframework.boot.gradle.plugin.JavaPluginAction$$Lambda$22/165631567 from org.springframework.boot.gradle.plugin.JavaPluginAction]

And here's the name with --info:

[Loaded org.springframework.boot.gradle.plugin.JavaPluginAction$$Lambda$22/639343159 from org.springframework.boot.gradle.plugin.JavaPluginAction]

And the names from another run with --info:

[Loaded org.springframework.boot.gradle.plugin.JavaPluginAction$$Lambda$22/639343159 from org.springframework.boot.gradle.plugin.JavaPluginAction]

In this last build compileJava was up-to-date as the type name of the action hasn't changed.

If --info is removed, the name goes back to what it was in the first run:

[Loaded org.springframework.boot.gradle.plugin.JavaPluginAction$$Lambda$22/165631567 from org.springframework.boot.gradle.plugin.JavaPluginAction]

For reasons that I do not yet understand, the type names appear to change depending on the command line that's used to launch Gradle, and appears to do so predictably.

We could work around this behaviour in the plugin by using anonymous inner classes rather than lambdas for task actions, but it feels like it would be better if that was addressed in Gradle so that all plugin authors can safely use lambdas for task actions.

[wilkinsona]

This is a known problem: gradle/gradle#5510. I'm going to see if I can create a minimal example that reproduces the problem.

[display-none]

You're right, for some reason in my test runs I always had a recompilation, but now I ran
gradlew --no-daemon compileJava --console=plain
and got 2 up-to-dates in 5 runs. No --info was needed. So it looks like it's not directly dependent on that.

Originally I used the following to see that the lambda changes:

gradle.buildFinished {
	tasks['compileJava'].actions.forEach {
		logger.info(it.getDisplayName())
		logger.info(it.getActionClassName())
	}
}

[wilkinsona]

Irrespective of a change in Gradle, we should probably do something about this in our plugin. If we don't, users on current versions of Gradle will still be affected by the problem.

[david-noel]

Thanks for swapping out the lambdas. I'm looking forward to this being released.