Show mix compile Warnings Every Time

When I compile my project with mix compile, there warnings are shown on the commandline. When I run the command again, the warnings do not show up anymore.

How can I make mix compile show the warnings every time?

The compiler will only show warnings for things it compiles. You can force it to compile everything by doing mix compile --force

I see.
Is there a static code analysis tool, that can show me the warnings on the basis of compiled modules?