maven-enforcer-plugin and child pom - maven

Question

I am trying to use the maven-enforcer-plugin to ensure that one profile is activated (requireActiveProfile rule). See the second example on this page: Require Active Profile
It works well with a single pom file. When I try to use it with 2 pom files (a parent and a child) this do not work anymore when I try to build the child module.
I have any idea why it doesn’t work?
Complete example:
EXAMPLE
| pom.xml <1> (parent pom)
|
\---child
pom.xml <2> (child pom)
Parent pom file <1>:
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.mycompany.app</groupId>
<artifactId>my-app.parent</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>pom</packaging>
<profiles>
<profile>
<id>first</id>
<properties>
<my-name>Alice</my-name>
</properties>
</profile>
<profile>
<id>second</id>
<properties>
<my-name>Bob</my-name>
</properties>
</profile>
</profiles>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-enforcer-plugin</artifactId>
<version>1.4.1</version>
<executions>
<execution>
<id>enforce-first-or-second-profile-is-active</id>
<goals>
<goal>enforce</goal>
</goals>
<configuration>
<rules>
<requireActiveProfile>
<profiles>first,second</profiles>
<all>false</all>
</requireActiveProfile>
</rules>
<fail>true</fail>
</configuration>
</execution>
</executions>
</plugin>
<plugin>
<artifactId>maven-antrun-plugin</artifactId>
<executions>
<execution>
<phase>compile</phase>
<goals>
<goal>run</goal>
</goals>
<configuration>
<tasks>
<echo>Hello ${my-name}!</echo>
</tasks>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>
Child pom file <2>:
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>com.mycompany.app</groupId>
<artifactId>my-app.parent</artifactId>
<version>1.0-SNAPSHOT</version>
</parent>
<artifactId>my-app</artifactId>
<packaging>pom</packaging>
</project>
Now I run:
EXAMPLE>cd child
EXAMPLE\child>mvn compile -Psecond
And the output looks like that:
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building my-app 1.0-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO]
[INFO] --- maven-enforcer-plugin:1.4.1:enforce (enforce-first-or-second-profile-is-active) # my-app ---
[WARNING] Rule 0: org.apache.maven.plugins.enforcer.RequireActiveProfile failed with message:
Profile "first" is not activated.
Profile "second" is not activated.
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 1.178 s
[INFO] Finished at: 2015-10-30T18:03:50+01:00
[INFO] Final Memory: 24M/989M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-enforcer-plugin:1.4.1:enforce (enforce-first-or-second-profile-is-active) on project my-app: Some Enforcer rules have failed. Look above for specific messages explaining why the rule failed. -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoExecutionException
When I run maven on the parent pom, it works. What did I miss?

Answer 1

Maven Profiles are a bit confusing, but I'll venture an explanation based on my experiences.
The profile definitions is not inherited, but the effects of them are.
If you jump to the child directory and run mvn -Pfirst help:active-profiles you'll see that the effect of the parent's profile is indeed there:
Part of the output:
...
<properties>
<my-name>Alice</my-name>
</properties>
...
but you won't see the profiles definition in there.
The bad news is that your enforcer rule won't work in this scenario, unless every child also defines the required profiles.
The good news is that, armed with this new knowledge, you can use another enforcer rule (requireProperty) to achieve what you want:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-enforcer-plugin</artifactId>
<version>1.4.1</version>
<executions>
<execution>
<id>enforce-property</id>
<goals>
<goal>enforce</goal>
</goals>
<configuration>
<rules>
<requireProperty>
<property>my-name</property>
<message>You must set a my-name property! Did you activate the right profile?</message>
</requireProperty>
</rules>
<fail>true</fail>
</configuration>
</execution>
</executions>
</plugin>