[MCOMPILER-402] Not possible to exclude module-info with 'excludes'

[jira-importer]

Petr Dolezal opened MCOMPILER-402 and commented

I tried to use excludes to exclude module-info.java from build, essentially in the same way as described in the official example, but the file was always compiled anyway. I even tried to use various patterns with no effect.

This seems weird to me and with the respect to the mentioned example I consider such a behavior to be a bug.

Since I could not attach the source files, here is the listing for reproducing the issue:

 

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.example</groupId>
  <artifactId>com.example</artifactId>
  <version>1.0.0-SNAPSHOT</version>
  <packaging>jar</packaging>
  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>3.8.1</version>
        <configuration>
          <release>11</release>
          <source>11</source>
          <target>11</target>
          <excludes>
            <exclude>module-info.java</exclude>
          </excludes>
        </configuration>
      </plugin>
    </plugins>
  </build>
</project>

// src/main/java/module-info.java
module com.example {
    exports com.example;
}

// src/main/java/com/example/Main.java
package com.example;
public final class Main {
    public static void main(String... args) {
        System.out.println("Hello World");
    }
}

 

---

Affects: 3.8.0, 3.8.1

Issue Links:

• MCOMPILER-488 dedicated option for implicit javac flag

Remote Links:

• GitHub Pull Request #102

[jira-importer]

Robert Scholte commented

Interesting... output says [INFO] Compiling 1 source file to ... but in the end there are 2 class files.

[jira-importer]

Piotr Zygielo commented

Here is my guess.

The same with CLI:

$ rm -rf target/classes/* $ javac -d target/classes -sourcepath src/main/java:target/generated-sources/annotations: -s target/generated-sources/annotations -g -nowarn --release 11 src/main/java/com/example/Main.java $ tree target/classes

target/classes ├── com │ └── example │   └── Main.class └── module-info.class

So module-info.java is not sent for compilation by the plugin, but it's being found by compiler itself.

https://docs.oracle.com/javase/7/docs/technotes/tools/solaris/javac.html#searching

You can use the -implicit option to specify the behavior.

And it helps:

$ rm -rf target/classes/* $ javac -d target/classes -sourcepath src/main/java:target/generated-sources/annotations: -s target/generated-sources/annotations -g -nowarn --release 11 src/main/java/com/example/Main.java -implicit:none $ tree target/classes

target/classes └── com   └── example     └── Main.class

As there is currently no option to configure -implicit in mojo I suggest to use https://maven.apache.org/plugins/maven-compiler-plugin/compile-mojo.html#compilerArgs to do it explicitly.

[jira-importer]

Piotr Zygielo commented

 essentially in the same way as described in the official example

How I see it: reproducer in this issue is very different, not the same at all, in several aspects:

1. example sets default release as 6 (reproducer: 11)
2. example has two executions, with the first including MI, targeting release 9 where the idea of MI is known,
3. example excludes MI in separate execution, which targets release 6, where there is no such thing as MI at all.

Thus I propose to reclassify this report as New Feature/Enhancement to support implicit option in m-c-p configuration - this could be provided by PR#102.

-To complete the fix - perhaps the example could be updated then to use implicit there.-

(After having glass of cold water now I think example needs no modification as it's fine as is.)