#420: fix detection of java version when JAVA_TOOL_OPTIONS is set

[glhez]

This fix the issue I had at work (#420) by ignoring the "Picked up" based on what the JDK outputs.

[slawekjaranowski]

I would like to simplify it, as example in issue.
so split output by lines and find first line starting with javac

[glhez]

I don't see what you means and I can't work on that now (PC broken and I don't want to mess with the one I use now).

The loop seems "difficult", but as far as I remember, I looked for the error message in JDK and calls here : https://github.com/openjdk/jdk/blob/81e43114eca5199a0d816c02f50ecb6bc370135b/src/hotspot/share/runtime/arguments.cpp#L3074

I am more or less doing a job of removing the line sent by parse_options_environment_variable.

Another alternative I did not try would be probably to remove the offending env variable which might or not requires a patch to https://codehaus-plexus.github.io (if that's the good repo) or avoid inheriting them.

[slawekjaranowski]

Please look at:

• Ignore stderr when parsing javac version from toolchain apache/maven-jar-plugin#471

maybe checking only standard output will be easier

[glhez]

Ok. javac -version output to stdout, java -version to stderr...

I fixed it to only read stdout like apache/maven-jar-plugin#471

[froque]

Ok. javac -version output to stdout, java -version to stderr...

This is not true for javac 1.8.0_472 and this fix will not work for this version. It outputs to stderr.

[slawekjaranowski]

Ok. javac -version output to stdout, java -version to stderr...

This is not true for javac 1.8.0_472 and this fix will not work for this version. It outputs to stderr.

right ...

% javac -version 1>/dev/null      
javac 1.8.0_472

% javac -version 2>/dev/null
~ % 

[slawekjaranowski]

next test - everything on stderr

JAVA_TOOL_OPTIONS="-Xms256m" javac -version 1>/dev/null
Picked up JAVA_TOOL_OPTIONS: -Xms256m
javac 1.8.0_472