Dan Berindei created MCOMPILER-433:
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Summary: mvn clean compile test compiles the source files twice
Key: MCOMPILER-433
URL: https://issues.apache.org/jira/browse/MCOMPILER-433
Project: Maven Compiler Plugin
Issue Type: Bug
Affects Versions: 3.8.1
Reporter: Dan Berindei
When one invokes {{mvn clean compile test}}, the {{default-compile}} execution
runs twice.
This is because
{{org.apache.maven.lifecycle.internal.DefaultLifecycleExecutionPlanCalculator#calculateMojoExecutions()}}
(which hasn't changed in 6 years) collects the list of mojo executions in a
list, and for each phase on the command-line it adds the mojo executions for
that phase and its dependencies, even if some executions already exist in the
list. E.g.
{noformat}
mojoExecutions = {java.util.ArrayList} size = 8
0 = {org.apache.maven.plugin.MojoExecution}
"org.apache.maven.plugins:maven-clean-plugin:2.5:clean {execution:
default-clean}"
1 = {org.apache.maven.plugin.MojoExecution}
"org.apache.maven.plugins:maven-resources-plugin:2.6:resources {execution:
default-resources}"
2 = {org.apache.maven.plugin.MojoExecution}
"org.apache.maven.plugins:maven-compiler-plugin:3.8.1:compile {execution:
default-compile}"
3 = {org.apache.maven.plugin.MojoExecution}
"org.apache.maven.plugins:maven-resources-plugin:2.6:resources {execution:
default-resources}"
4 = {org.apache.maven.plugin.MojoExecution}
"org.apache.maven.plugins:maven-compiler-plugin:3.8.1:compile {execution:
default-compile}"
5 = {org.apache.maven.plugin.MojoExecution}
"org.apache.maven.plugins:maven-resources-plugin:2.6:testResources {execution:
default-testResources}"
6 = {org.apache.maven.plugin.MojoExecution}
"org.apache.maven.plugins:maven-compiler-plugin:3.8.1:testCompile {execution:
default-testCompile}"
7 = {org.apache.maven.plugin.MojoExecution}
"org.apache.maven.plugins:maven-surefire-plugin:2.12.4:test {execution:
default-test}"
{noformat}
The second execution of {{maven-compiler-plugin}} version 3.8.0 used to check
that the sources haven't changed and do nothing. But that check was wrong,
because it didn't check any class files, and MCOMPILER-349 replaced it with
another check that is also wrong, because it
({{org.apache.maven.plugin.compiler.AbstractCompilerMojo#isDependencyChanged()}})
checks for changes since the start of the build in all the classes on the
module's classpath, including {{target/classes}}.
This means the second execution of {{maven-compiler-plugin}} verison 3.8.1
deletes all the {{.class}} files from {{target/classes}}. It does not delete
the files generated by annotation processors in
{{target/generated-sources/annotations}}, but it also doesn't add them to the
Javac sources parameter because
{{org.apache.maven.plugin.compiler.AbstractCompilerMojo#getCompileSources()}}
ignores the generated sources directory:
{noformat}
compileSourceRoots = {java.util.ArrayList} size = 3
0 = "/home/dan/Work/maven-compiler-test/src/main/java"
1 = "/home/dan/Work/maven-compiler-test/target/generated-sources/annotations"
2 = "/home/dan/Work/maven-compiler-test/target/generated-sources/annotations"
{noformat}
{noformat}
sources = {java.util.HashSet} size = 2
0 = {java.io.File}
"/home/dan/Work/maven-compiler-test/src/main/java/ProtoStreamContextInitializer.java"
1 = {java.io.File} "/home/dan/Work/maven-compiler-test/src/main/java/A.java"
{noformat}
We have an annotation processor that tries to be smart and doesn't overwrite
its generated Java source files if they already exists and they have the
correct checksum. But because the generated file isn't written, it is not added
to Javac's sources, and Javac does not compile it to a {{.class}} file. I
haven't tested it, but I believe the same problem appears if the source files
were generated e.g. by another Maven plugin or by an Ant script in the
{{generate-sources}} phase.
I believe the maven-core behaviour won't change any time soon (and in fact some
users may depend on the duplicate executions). Instead
{{org.apache.maven.plugin.compiler.AbstractCompilerMojo#isDependencyChanged()}}
needs to be fixed to avoid recompilation when runs the second time.
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