Demonstration of a bug some unintuitive behavior in conan-io/conan

This demonstrates issue conan-io/conan#1509.

NOTE: As discussed in the issue, the behavior demonstrated here is actually intentional and has now been documented (see conan-io/docs@46f10a1 and conan-io/docs@72b1fcb).

Build this test package with

conan test_package

The message "Test!" should be displayed twice in conan's output. That indicates that the package() method of conanfile.py is executed twice during a single build.

Change the line

no_copy_source = True

in conanfile.py to

no_copy_source = False

and build the package again:

conan test_package

Now "Test!" should be displayed only once.