Hello @mkoncek
How can this goal be enforced such that this build fails without the change?

maven-compiler-plugin is declared in commons-parent which also uses the encoding field. I rebased the PR so that the build reports an error the same way as javac would in our case. I don't know why the build doesn't fail, but there is an [ERROR] in the log if encoding is set and current sources are used.

commons-parent uses ISO-8859 encoding by default.

@sebbASF That would work too, but I believe it is time we can afford such luxury as using non-ASCII-only characters in sources.

I can confirm that changing the encoding causes the compile to report an ERROR, but the build succeeds:

$ mvn clean compile -Dcommons.encoding=UTF8
...
[INFO] Compiling 399 source files with javac [debug release 8] to target/classes
[ERROR] /commons/compress/src/main/java/org/apache/commons/compress/archivers/tar/TarArchiveOutputStream.java:[300,32] unmappable character (0xF6) for encoding UTF-8
...
[INFO] BUILD SUCCESS

I've tried experimenting with -Dmaven.compiler.failOnWarning=true (and failOnError), but Maven does not fail the build.

However, adding -Dcommons.compiler.fork=true does cause the build to fail.
Possible bug in Maven?

See https://issues.apache.org/jira/browse/MCOMPILER-491

Unfortunately, when using fork=true, some informational messages are not shown, see:
https://issues.apache.org/jira/browse/MCOMPILER-537

How can this goal be enforced such that this build fails without the change?

Maybe by adding a UTF-8 encoded test asset, plus a test that reads the file in binary mode and compares to the expected bytes?

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.45%. Comparing base (3605bc0) to head (00748ea).
⚠️ Report is 2643 commits behind head on master.

@@            Coverage Diff            @@
##             master     #389   +/-   ##
=========================================
  Coverage     80.45%   80.45%           
  Complexity     6723     6723           
=========================================
  Files           343      343           
  Lines         25311    25311           
  Branches       4107     4107           
=========================================
  Hits          20364    20364           
  Misses         3366     3366           
  Partials       1581     1581           

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