Steven Schlansker created MNG-6016:
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Summary: Maven incorrectly builds POM when you override Shade
transformers in a child
Key: MNG-6016
URL: https://issues.apache.org/jira/browse/MNG-6016
Project: Maven
Issue Type: Bug
Components: Inheritance and Interpolation, POM
Affects Versions: 3.3.9
Reporter: Steven Schlansker
Consider the project:
https://github.com/stevenschlansker/maven-configure-transformer-bug/
Simple 2 module project. Parent defines some Shade plugin configuration,
notably a {{ResourceTransformer}} with a {{mainClass}} declaration.
Child then tries to add a {{PropertiesMergingResourceTransformer}}, but somehow
the {{mainClass}} declaration from the parent gets merged into this other
transformer, causing a build failure:
{quote}
[ERROR] Failed to execute goal
org.apache.maven.plugins:maven-shade-plugin:2.4.3:shade (assemble-app) on
project maven-configure-transformer-bug-child: Unable to parse configuration of
mojo org.apache.maven.plugins:maven-shade-plugin:2.4.3:shade for parameter
mainClass: Cannot find 'mainClass' in class
org.springframework.boot.maven.PropertiesMergingResourceTransformer -> [Help 1]
{quote}
The effective POM shows that something extremely unintuitive is going on with
resource merging:
{code}
<plugin>
<artifactId>maven-shade-plugin</artifactId>
<version>2.4.3</version>
<executions>
<execution>
<id>assemble-app</id>
<phase>package</phase>
<goals>
<goal>shade</goal>
</goals>
<configuration>
<transformers>
<transformer
implementation="org.apache.maven.plugins.shade.resource.AppendingTransformer">
<resource>META-INF/spring.handlers</resource>
</transformer>
<transformer
implementation="org.springframework.boot.maven.PropertiesMergingResourceTransformer">
<resource>META-INF/spring.factories</resource>
<mainClass>foo</mainClass>
<collectSections>true</collectSections>
</transformer>
<transformer
implementation="org.apache.maven.plugins.shade.resource.AppendingTransformer">
<resource>META-INF/spring.schemas</resource>
</transformer>
<transformer
implementation="org.apache.maven.plugins.shade.resource.ServicesResourceTransformer"
/>
<transformer
implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer"
/>
</transformers>
</configuration>
</execution>
</executions>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<version>1.3.3.RELEASE</version>
<scope>compile</scope>
</dependency>
</dependencies>
<configuration>
<transformers>
<transformer
implementation="org.apache.maven.plugins.shade.resource.AppendingTransformer">
<resource>META-INF/spring.handlers</resource>
</transformer>
<transformer
implementation="org.springframework.boot.maven.PropertiesMergingResourceTransformer">
<resource>META-INF/spring.factories</resource>
<mainClass>foo</mainClass>
<collectSections>true</collectSections>
</transformer>
<transformer
implementation="org.apache.maven.plugins.shade.resource.AppendingTransformer">
<resource>META-INF/spring.schemas</resource>
</transformer>
<transformer
implementation="org.apache.maven.plugins.shade.resource.ServicesResourceTransformer"
/>
<transformer
implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer"
/>
</transformers>
</configuration>
</plugin>
{code}
It is possible to escape this by adding {{combine.self="override}} to the
{{<transformers>}} node. But I think the configuration ending up on the wrong
transformer is a bug, and the fact that it causes duplicate configuration
sections is also extremely confusing.
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