regex-property goal doesn't interpret <replacement> correctly, corrupting output

[garretwilson]

I'm using org.codehaus.mojo:build-helper-maven-plugin:3.3.0 on Windows.

Let's say I want to use the regex-property goal to replace some value with the build directory path:

<execution>
  <id>test</id>
  <phase>validate</phase>
  <goals>
    <goal>regex-property</goal>
  </goals>
  <configuration>
    <name>bar</name>
    <value>foo</value>
    <regex>.*</regex>
    <replacement>${project.build.directory}</replacement>
    <failIfNoMatch>false</failIfNoMatch>
  </configuration>
</execution>

I'm on Windows, and my ${project.build.directory} happens to be something like C:\projects\foobar\target.

Expected bar: C:\projects\foobar\target
Actual bar: C:projectsfoobartargetC:projectsfoobartarget

Not only has Build Helper Plugin removed all the backslashes, it has strangely duplicated the output!

I can only make a wild guess why this is happening. Perhaps the plugin is recursively evaluating the result until there are no unevaluated expressions. But the <replacement> should not be evaluated as a regular expression; it should be evaluated as a normal Maven interpolation string (i.e. substituting any {$variable}). I don't believe backslashes have any significance in normal interpolations strings, do they?

Why the output is being duplicated I have no idea.