Commandline Args for Custom Plugins

[abrua1]

I am using our own proto plugin inside this protobuf maven plugin using the configuration jvmMavenPlugin. Is there any way I can pass args into the main method of my custom plugin?

[ascopes]

The best way to do this is to use the "option" functionality within the Protobuf API itself.

https://github.com/protocolbuffers/protobuf/blob/6bf86f01d4e9d6de4883430b96c7aad9e9fa7670/src/google/protobuf/compiler/plugin.proto#L50

This is able to be passed in via a string within the options attribute on a protoc plugin descriptor in the Maven plugin (see https://ascopes.github.io/protobuf-maven-plugin/generate-mojo.html#jvmMavenPlugins)

e.g.

<plugin>
  ...
  
  <configuration>
    ...
    <jvmMavenPlugins>
      <jvmMavenPlugin>
        ...
        <options>--debug</options>
      </jvmMavenPlugin>
    </jvmMavenPlugins>
  </configuration>
</plugin>

This is consistently supported between binary plugins and JAR-based plugins.

I have seen the Salesforce libraries support passing command line arguments directly but this appears to be just for debugging outside of being invoked via protoc directly, so I wouldn't advise you rely on that as I am not aware of a way of consistently passing those through when the plugin is actually used at runtime.

Hope that helps! 😄

[abrua1]

Thanks for your fast reply :)

I think this is not enough for our purpose, but let me give some context, maybe I am just stupid.

Currently we are using the

<groupId>org.xolstice.maven.plugins</groupId>
<artifactId>protobuf-maven-plugin</artifactId>
<version>0.6.1</version>

My configuration there is

<plugin>
  ...
  <configuration>
              <protocPlugins>
                ...
                <protocPlugin>
                  <id>gherkin-generation-proto-plugin</id>
                  <groupId>de.ivu.pto.commons</groupId>
                  <artifactId>pto-commons-gherkin-generation-proto-plugin</artifactId>
                  <version>2.1.0-SNAPSHOT</version>
                  <mainClass>
                    de.ivu.pto.commons.gherkin.proto.plugin.impl.ProtoGenerator
                  </mainClass>
                  <args>
                   <arg>defaults:${basedir}/src/test/resources/aDefaults</arg>
                    <arg>templates:${basedir}/src/test/resources/templates</arg>
                  </args>
                </protocPlugin>
  </configuration>
</plugin>

Now we want to use your protobuf-maven-plugin instead as the xolstice.maven.plugin is not maintained anymore. Therefore we still want to use our custom plugins and we need to pass arguments to the main method of our custom plugin. In the example above that would be the arguments "defaults:${basedir}/src/test/resources/aDefaults" and "templates:${basedir}/src/test/resources/templates".

So is this possible in the ascopes protobuf maven plugin?

I think this is the way of argument passing you mentioned in your sentence about Salesforce libraries, but we did not face any problems with this.

[ascopes]

Just looking through the other Maven plugin's code... looks like the arguments you describe are actually embedded in the executable that gets created to bootstrap the JVM from protoc (see https://github.com/xolstice/protobuf-maven-plugin/blob/master/src/main/java/org/xolstice/maven/plugin/protobuf/ProtocPluginAssembler.java#L154).

Right now, I don't explicitly support a way of doing this, only the parameters support that protoc provides out of the box, but I could implement this fairly easily as a new feature if you need this functionality? Worth noting that unlike the Xolstice plugin, we don't create binary executables on Windows but instead we create shell scripts or batch scripts based on the platform to provide a similar behaviour, so it should be possible to throw some new arguments in there if needed.

I'll raise an issue and see if I can get something working today.

[abrua1]

Very cool! Thanks a lot :)

[ascopes]

I've got a working solution that I'm just waiting to pass CI. Hope to get it released at some point today as v2.6.0.

It adds two new options:

• jvmArgs - a list of strings to specify commandline arguments
• jvmConfigArgs - a list of strings to let you inject custom JVM options like limiting heap size, etc.

Took a little longer than I would have liked as I realised this change would have made batch arg parsing on Windows far more fragile, so I reimplemented part of that to avoid the risk of regressions following this change.

• Issue: Support passing JVM arguments and command line arguments to JVM plugins #397
• PR: GH-397: implement ability to specify JVM arguments to plugins #399

[abrua1]

I just tested the new feature and it seems to work perfectly :)

But when using version 2.6.1 I get the error:

although everything seems to work; I can't find anything unexpected in the generation.
This happens in both cases: when using custom args via jvmArg and when using none of them.

My configuration of the plugin is:

<plugin>
  <groupId>io.github.ascopes</groupId>
  <artifactId>protobuf-maven-plugin</artifactId>
  <version>2.6.1</version>

  <configuration>
    <protocVersion>${protobuf-version}</protocVersion>
    <sourceDirectories>
      <sourceDirectory>src/main/proto/resources/port/proto</sourceDirectory>
    </sourceDirectories>
    <jvmMavenPlugins>
      <jvmMavenPlugin>
        <groupId>de.ivu.pto.commons</groupId>
        <artifactId>pto-commons-gherkin-assertion-proto-plugin</artifactId>
        <version>1.4.0-SNAPSHOT</version>
        <mainClass>
          de.ivu.pto.commons.gherkin.assertion.proto.plugin.impl.VerificationStepGenerator
        </mainClass>
      </jvmMavenPlugin>
      <jvmMavenPlugin>
        <groupId>de.ivu.pto.commons</groupId>
        <artifactId>pto-commons-gherkin-generation-proto-plugin</artifactId>
        <version>2.1.0-SNAPSHOT</version>
        <mainClass>
          de.ivu.pto.commons.gherkin.proto.plugin.impl.ProtoGenerator
        </mainClass>
        <jvmArgs>
          <jvmArg>defaults:${basedir}/src/test/resources/aDefaults</jvmArg>
          <jvmArg>templates:${basedir}/src/test/resources/templates</jvmArg>
        </jvmArgs>
      </jvmMavenPlugin>
    </jvmMavenPlugins>
  </configuration>

  <executions>
    <execution>
      <id>generate-v1-protobuf-sources</id>
      <phase>generate-sources</phase>
      <goals>
        <goal>generate-test</goal>
      </goals>
      <configuration>
        <includes>v1/**</includes>
      </configuration>
    </execution>

    <execution>
      <id>generate-v2-protobuf-sources</id>
      <phase>generate-sources</phase>
      <goals>
        <goal>generate-test</goal>
      </goals>
      <configuration>
        <excludes>v1/**</excludes>
      </configuration>
    </execution>
  </executions>

</plugin>

[ascopes]

Would you be able to post the contents of the mentioned args.txt and the generated shell/batch scripts in those directories?

If you could run Maven with the -e flag and post the stack trace, that would also be greatly appreciated.