Invalid variable reference in maven-shade-plugin configuration

[scheerer]

This should fix my prior PR #20052. I am pretty sure this is correct, but sadly I seem to be unable to fully build the project to verify for sure. Might need a couple eyes from build masters to ensure. I am so sorry for the bad fix in #20052.

History:

1. after the Gradle migration it was incorrectly left as ${revision}
2. I blindly used Maven conventions to set it to ${project.version}
3. After trying to 2.3.0.BUILD-SNAPSHOT build with my change I discovered ${project.version} always resolves to 0.0.1-SNAPSHOT.
4. Here is where I think I found the rest of the Gradle setup uses ${version} for the current SpringBoot build version. So I used that. :)

In order to know for sure a simple child project inheriting from the spring-boot-starter-parent 2.3.0.BUILD-SNAPSHOT must use the shade plugin like so:

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-shade-plugin</artifactId>
            <configuration>
                <createDependencyReducedPom>false</createDependencyReducedPom>
            </configuration>
            <executions>
                <execution>
                    <phase>package</phase>
                    <goals>
                        <goal>shade</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>

Then simply execute ./mvnw package to see the error.

[snicoll]

Thanks for the follow-up. It's my mistake not properly retesting the outcome. ${project.version} looked legit to me and I missed the context of the plugin dependency.

Unfortunately, what we need there is to expand the token rather than writing it as is. Your proposal on an empty project leads to:

[WARNING]
[WARNING] Some problems were encountered while building the effective model for com.example:demo:jar:0.0.1-SNAPSHOT
[WARNING] The expression ${version} is deprecated. Please use ${project.version} instead.
[WARNING]
[WARNING] It is highly recommended to fix these problems because they threaten the stability of your build.
[WARNING]
[WARNING] For this reason, future Maven versions might no longer support building such malformed projects.
[WARNING]

and

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-shade-plugin:3.2.1:shade (default-cli) on project demo: Execution default-cli of goal org.apache.maven.plugins:maven-shade-plugin:3.2.1:shade failed: Plugin org.apache.maven.plugins:maven-shade-plugin:3.2.1 or one of its dependencies could not be resolved: Could not find artifact org.springframework.boot:spring-boot-maven-plugin:jar:0.0.1-SNAPSHOT in spring-milestones (https://repo.spring.io/milestone)

I don't know yet what we need to add there to expand the version but I'll investigate tomorrow if nobody else is beating me to it.

[snicoll]

gradle publishToMavenLocal generates the following for me:

<dependencies>
            <dependency>
              <groupId>org.springframework.boot</groupId>
              <artifactId>spring-boot-maven-plugin</artifactId>
              <version>${version}</version>
            </dependency>
          </dependencies>

I believe it should generate the following:

<dependencies>
            <dependency>
              <groupId>org.springframework.boot</groupId>
              <artifactId>spring-boot-maven-plugin</artifactId>
              <version>2.3.0.BUILD-SNAPSHOT</version>
            </dependency>
          </dependencies>

[wilkinsona]

The following will work:

delegate.version("${project.version}")

This aligns with how the parent version is configured earlier in the same build.gradle file:

parent {
	delegate.groupId("${project.group}")
	delegate.artifactId("spring-boot-dependencies")
	delegate.version("${project.version}")
}

The change can be verified with the following command:

./gradlew spring-boot-project:spring-boot-starters:spring-boot-starter-parent:generatePom

This will write the generated pom to spring-boot-project/spring-boot-starters/spring-boot-starter-parent/build/publications/maven/pom-default.xml

[scheerer]

@wilkinsona If I'm understanding you correctly does that mean this PR is simply not needed?

[wilkinsona]

No, I think it's still needed, but in a modified form. We currently have '${project.version}'. We need "${project.version}" instead. Note the use of " rather than '.

[wilkinsona]

The following will work:

delegate.version("${project.version}")

This aligns with how the parent version is configured earlier in the same build.gradle file:

parent {
	delegate.groupId("${project.group}")
	delegate.artifactId("spring-boot-dependencies")
	delegate.version("${project.version}")
}

The change can be verified with the following command:

./gradlew spring-boot-project:spring-boot-starters:spring-boot-starter-parent:generatePom

This will write the generated pom to spring-boot-project/spring-boot-starters/spring-boot-starter-parent/build/publications/maven/pom-default.xml

[snicoll]

@scheerer thanks for letting us know about the issue. I took the liberty of applying Andy's suggestion myself as we are releasing M2 today and I'd like to make sure the starter has a valid POM.