[MNG-5800] Cannot unset Mojo parameter so that the default applies when parameter is set in the parent POM

[jira-importer]

Tobias Oberlies opened MNG-5800 and commented

In case a Mojo parameter is configured in a parent POM, it seems that there is not way to unset it in a child POM. With "unsetting" I mean provide a POM configuration so that the default value applies, without having to explicitly know the default value.

Steps to reproduce:

1. For a Mojo parameter with a default value, set an explicit value in the parent POM
2. In the child POM, try to reset the parameter either with

<configuration>
   <param></param>
</configuration>

or

<configuration>
   <param combine.self="override"></param>
</configuration>

Expected result: The parameter param is set to its default value.

Actual result: In the first case, the configuration from the parent POM still applies. In the second case, the configuration value is set to null for a String parameter.

---

Affects: 3.2.2

[jira-importer]

Tobias Oberlies commented

In the combine.self="override" case, I can see in the debug after PROJECT BUILD PLAN} that the configuration <param combine.self="override"></param> suppresses the default values that are normally printed there. So to fix this issue, there probably needs to be a fix in the logic that computes the combined xml.

With the current behaviour, I can see another issue in the code that converts the XML values and sets them on the Mojo: For a parameter of type SimpleDateFormat with a setParam(String) method, the field is set to a non-null value, but the setter is never called.

[jira-importer]

Elliotte Rusty Harold commented

Can this be changed without breaking backwards compatibility?