help:effective-pom uses platform encoding and garbles non-ascii characters, emits invalid XML

As stated in http://www.w3.org/TR/REC-xml/#sec-guessing-no-ext-info XML files without a BOM and without a XML encoding declaration should read the XML as UTF-8.

help:effective-pom does use the platform encoding for writing the effective-pom without emitting an appropriate XML encoding declaration in the resulting XML file.

I have created a small sample project (available at https://github.com/mfriedenhagen/invalidpom, attached as ZIP) which will reproduce the issue.

While the parent pom (https://raw.github.com/mfriedenhagen/invalidpom/master/pom.xml) has a XML encoding declaration, https://raw.github.com/mfriedenhagen/invalidpom/master/child-invalid/pom.xml has none.

Now running:

mvn -s settings.xml -gs settings.xml clean validate

will produce an invalid character for the developer name "Jörg" in child-invalid.

Two workarounds are:

• to include a XML encoding declaration as done in child-valid.
• to use JAVA_TOOL_OPTIONS on Windows as stated in http://stackoverflow.com/a/623036/49132
• to use MAVEN_OPTS=-Dfile.encoding=utf-8 mvn -s settings.xml -gs settings.xml clean validate.

Nonetheless I consider this a Major bug, as it clearly violates the recommendations of W3C.