Annotation processor should validate final primitive and String fields (was: Annotation processor not working)

[xehpuk]

Source

@Option(names = {"-h", "--host"})
private final String hostname = "localhost"; // <-- notice the final

pom.xml

<build>
    <pluginManagement>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <!-- annotationProcessorPaths requires maven-compiler-plugin version 3.5 or higher -->
                <version>3.8.1</version>
                <configuration>
                  <annotationProcessorPaths>
                    <path>
                      <groupId>info.picocli</groupId>
                      <artifactId>picocli-codegen</artifactId>
                      <version>4.6.1</version>
                    </path>
                  </annotationProcessorPaths>
                  <compilerArgs>
                    <arg>-Aproject=${project.groupId}/${project.artifactId}</arg>
                  </compilerArgs>
                </configuration>
            </plugin>
        </plugins>
    </pluginManagement>
</build>

mvn compile

[INFO] Scanning for projects...
[INFO]
[INFO] --------------------------------< ... >---------------------------------
[INFO] Building ... 1.0-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO]
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ ... ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] skip non existing resourceDirectory ...\src\main\resources
[INFO]
[INFO] --- maven-compiler-plugin:3.8.1:compile (default-compile) @ ... ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling 1 source file to ...\target\classes
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  1.627 s
[INFO] Finished at: 2021-07-09T22:10:22+02:00
[INFO] ------------------------------------------------------------------------

Running

Exception in thread "main" picocli.CommandLine$InitializationException: Constant (final) primitive and String fields like private final java.lang.String ....hostname cannot be used as an @Option: compile-time constant inlining may hide new values written to it.
	at picocli.CommandLine$Model$CommandReflection.validateArgSpecMember(CommandLine.java:11571)
	at picocli.CommandLine$Model$CommandReflection.initFromAnnotatedTypedMembers(CommandLine.java:11516)
	at picocli.CommandLine$Model$CommandReflection.initFromAnnotatedFields(CommandLine.java:11466)
	at picocli.CommandLine$Model$CommandReflection.extractCommandSpec(CommandLine.java:11399)
	at picocli.CommandLine$Model$CommandSpec.forAnnotatedObject(CommandLine.java:6202)
	at picocli.CommandLine.<init>(CommandLine.java:227)
	at picocli.CommandLine.<init>(CommandLine.java:221)
	at picocli.CommandLine.<init>(CommandLine.java:196)
	at ....main(....java:44)

[remkop]

Yes, I programmed the annotation processor to throw this exception for @Option-annotated final String fields and final primitive fields.

This is by design. :-)

[xehpuk]

The processor didn't throw any exception. It was thrown at runtime. Or am I misunderstanding?

[remkop]

Yes you are right.
The exception is only thrown at runtime, not by the annotation processor. Thanks for pointing that out.

So, I guess that is the problem: this exception should not only be thrown at runtime, but also at compile time by the annotation processor. The current implementation is inconsistent. I agree.

Are you interested in providing a pull request for this?