Vavr annotation procession tool doesn't kick-in

Question

I am trying to replicate a simple Object Decomposition example from here. I've added the following dependencies to my project:

      <dependency>
        <groupId>io.vavr</groupId>
        <artifactId>vavr</artifactId>
        <version>${vavr.version}</version>
      </dependency>
      <dependency>
        <groupId>io.vavr</groupId>
        <artifactId>vavr-match</artifactId>
        <version>${vavr.version}</version>
      </dependency>
      <dependency>
        <groupId>io.vavr</groupId>
        <artifactId>vavr-match-processor</artifactId>
        <version>${vavr.version}</version>
      </dependency>

...where vavr.version is 0.10.3 and have copy-pasted the example from the above source:

import io.vavr.Tuple;
import io.vavr.Tuple2;
import io.vavr.match.annotation.Patterns;
import io.vavr.match.annotation.Unapply;
import lombok.AllArgsConstructor;
import lombok.Getter;

import static io.vavr.API.$;
import static io.vavr.API.Match;
import static io.vavr.API.Match.*;

public class Example {

  @Getter
  @AllArgsConstructor
  public static class Employee {
    private String name;
    private String id;
  }

  @Patterns
  public static class Demo {
    @Unapply
    static Tuple2<String, String> Employee(Employee Employee) {
      return Tuple.of(Employee.getName(), Employee.getId());
    }
  }

  public static void main(String[] args) {
    Employee person = new Employee("Carl", "89696D8");

    String result = Match(person).of(
      Case(Demo.Employee($("Carl"), $()), (name, id) -> ""),
      Case($(), () -> "notfound")
    );
  }
}

However the first Case yields a compile error Expected 1 argument but found 2 which suggests to me that the annotation processing didn't work and the corresponding pattern hasn't been generated. Correct me if I am wrong.

I am working with Intellij 2020.1 and have annotation processing enabled in it

Can you please share the sample project with dependencies where the case is reproduced for you. There seems to be some issues with the 0.10.3 dependency version. Only 0.9.2 includes the Tuple class for me. — Olga Klisho, Dec 14 '20 at 16:42

score 3 · Accepted Answer · answered May 06 '21 at 04:31

The reason is that you have used invalid name of the generated class in this line:

Case(Demo.Employee($("Carl"), $()), (name, id) -> "")

It should be replaced with:

Case(Example_DemoPatterns.$Employee($("Carl"), $()), (name, id) -> name + " " + id)

since Demo is a static nested class it needs to be prefixed with Example_ and because this is how the generator works it needs to suffixed with Patterns.

Here is a complete, buildable example that you can clone and try it out. It contains examples for both maven and gradle. To verify how it works change the mentioned line to e.g.:

Case(Example_DemoPatternsWhatever.$Employee($("Carl"), $()), (name, id) -> name + " " + id)

and then run:

mvn exec:java

It fails (there's no such class generated) but when you run tree target/ you will get something like:

target
├── classes
├── generated-sources
│   └── annotations
│       └── Example_DemoPatterns.java
└── maven-status
    └── maven-compiler-plugin
        └── compile
            └── default-compile
                ├── createdFiles.lst
                └── inputFiles.lst

which means that the class was indeed generated. This is the class you need to use.

Vavr annotation procession tool doesn't kick-in

1 Answers1