[MPH-168] effective-pom should support multi-module project

[broodjetom]

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This PR closes https://issues.apache.org/jira/browse/MPH-168.

I have chosen to solve this issue using a new parameter individual. I chose this name because you are generating an effective POM for each project/module individually. It is already possible to generate an effective POM across for each project/module, but it will put it in a single result/file. Please, advice on this naming if you like it or what it should be changed to.

I have not yet built the support of specifying output in combination with individual. For now, it will always output the effective POM to ${projectDirectory}/target/effective.pom.xml. In the issue it mentions setting the output to ${project.build.directory}/effective-pom.xml, but I'm not sure how to transform the variable part in it per project.

IMO the code does not look very clean, I think some of it could be refactored, but I'm not sure in what way.

[broodjetom]

I have tried some things with the output. The problem is that variables in the command line parameters are resolved before reaching the Mojo. So, when I do:

mvn clean help:effective-pom -Dindividual -Doutput="${project.build.directory}/effective.pom.xml"

I get the following output:

[INFO] --- maven-help-plugin:3.3.1-SNAPSHOT:effective-pom (default-cli) @ triplem ---
[INFO] Effective-POM written to: C:\Users\TomS\TempProjects\triplem\target\effective.pom.xml
[INFO] Effective-POM written to: C:\Users\TomS\TempProjects\triplem\target\effective.pom.xml
[INFO] Effective-POM written to: C:\Users\TomS\TempProjects\triplem\target\effective.pom.xml
[INFO] Effective-POM written to: C:\Users\TomS\TempProjects\triplem\target\effective.pom.xml
[INFO] Effective-POM written to: C:\Users\TomS\TempProjects\triplem\target\effective.pom.xml
[INFO] Effective-POM written to: C:\Users\TomS\TempProjects\triplem\target\effective.pom.xml
[INFO] Effective-POM written to: C:\Users\TomS\TempProjects\triplem\target\effective.pom.xml

Therefore, I currently have the output path hardcoded set to the target directory of the relevant module. We could go for the option of making the output parameter relative to the target directory. But that would not really make sense.

We could also choose to allow to specify a directory as output and give each of the effective POMs a reference to the module name. That way, they do not overwrite each other. But in that case, you might bump into modules having the same name.

Please, let me know what your preferred solution is.

[broodjetom]

If have changed it to where the effective POMs are written to standard out when the output flag is not set.

When the output flag is set, we need to interpret that as relative to the build directory of the (sub)project. A problem is actually that output flag will be parsed as a file, and thus contains the full absolute path (including the drive on Windows). Luckily, the project where we run the command from is available and provides a basedir.

I have used this to do some testing: You can see the full path on top (triplem).

If you run the following command from the main module:

mvn clean help:effective-pom -Dindividual -Doutput="effective/effective.pom.xml"

Parameter	Value
basedir	C:\Users\TomS\TempProjects\triplem
output	C:\Users\TomS\TempProjects\triplem\effective\effective.pom.xml

To then get the relative output I made it to remove the basedir from the output path, meaning you are left with effective\effective.pom.xml.

[INFO] Effective POM written to: C:\Users\TomS\TempProjects\triplem\target\effective\effective.pom.xml
[INFO] Effective POM written to: C:\Users\TomS\TempProjects\triplem\drinks\cola\target\effective\effective.pom.xml
[INFO] Effective POM written to: C:\Users\TomS\TempProjects\triplem\drinks\fanta\target\effective\effective.pom.xml
[INFO] Effective POM written to: C:\Users\TomS\TempProjects\triplem\drinks\target\effective\effective.pom.xml
[INFO] Effective POM written to: C:\Users\TomS\TempProjects\triplem\chocolate\bounty\target\effective\effective.pom.xml
[INFO] Effective POM written to: C:\Users\TomS\TempProjects\triplem\chocolate\mars\target\effective\effective.pom.xml
[INFO] Effective POM written to: C:\Users\TomS\TempProjects\triplem\chocolate\target\effective\effective.pom.xml

Now run the following command from the main module:

mvn clean help:effective-pom -Dindividual -Doutput="../effective.pom.xml"

Parameter	Value
basedir	C:\Users\TomS\TempProjects\triplem
output	C:\Users\TomS\TempProjects\effective.pom.xml

Now the output does not actually contain the basedir. In that case I have currently implemented it to just look at the name of the output path, which now is effective.pom.xml and use that as a file name in the build directory.

[INFO] Effective POM written to: C:\Users\TomS\TempProjects\triplem\target\effective.pom.xml
[INFO] Effective POM written to: C:\Users\TomS\TempProjects\triplem\drinks\cola\target\effective.pom.xml
[INFO] Effective POM written to: C:\Users\TomS\TempProjects\triplem\drinks\fanta\target\effective.pom.xml
[INFO] Effective POM written to: C:\Users\TomS\TempProjects\triplem\drinks\target\effective.pom.xml
[INFO] Effective POM written to: C:\Users\TomS\TempProjects\triplem\chocolate\bounty\target\effective.pom.xml
[INFO] Effective POM written to: C:\Users\TomS\TempProjects\triplem\chocolate\mars\target\effective.pom.xml
[INFO] Effective POM written to: C:\Users\TomS\TempProjects\triplem\chocolate\target\effective.pom.xml

As a conclusion, you are now able to specify a relative path, but there is a constraint on relative paths going up the file tree. Please let me know if you see another solution?