Remove duplicate entries while modifying PATH-like environment variables

[db4]

Changelog: Fix: Remove duplicate entries while modifying PATH-like environment variables internally. Especially important for Windows where system PATH size is limited by 8192 charachers (when using cmd.exe).
Docs: omit

• I've read the Contributing guide.
• I've followed the PEP8 style guides for Python code.

Partially solves #7587, especially when conan is launched from MSVC develper command prompt.

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[memsharded]

Could you please add a test that will cover this case? Ask for guidance if it is not evident how/where.

Thanks for the contribution!

[memsharded]

It seems that it can be done in place with a more common python idiom like:

items = apply_vars[name].split(os.pathsep)
apply_vars[name] = os.pathsep.join(OrderedDict.fromkeys(items))

[db4]

It seems that it can be done in place with a more common python idiom like:

items = apply_vars[name].split(os.pathsep)
apply_vars[name] = os.pathsep.join(OrderedDict.fromkeys(items))

Yes, indeed. I was under the impression that OrderedDict was the Python3-only thing but actually it's included in Python 2.7 as well.

[memsharded]

Great. If you could manage to add some test (ask for help if necessary), this can be merged for next Conan 1.31.

[db4]

Could you please add a test that will cover this case? Ask for guidance if it is not evident how/where.

Yes, please. I'm not familiar with Conan testing framework. Is

conan/conans/test/unittests/client/tools/win/vcvars_test.py

Line 60 in 4f9822d

def vcvars_env_not_duplicated_path_test(self):

the correct place for these additional tests? And how to run Conan tests locally?

[memsharded]

It seems that the VirtualEnvGeneratorTest in conans/test/unittests/client/generators/virtualenv_test.py would be a good place, adding another variable with repeated paths.

Locally, you can run it with: nosetests conans/test/unittests/client/generators/virtualenv_test.py. You might need to pip install -r requirements_dev.txt and pip install -r requirements_server.txt if missing deps. Please let me know if this helps, otherwise I can contribute the test myself. Thanks again for the contribution!

[db4]

Please let me know if this helps, otherwise I can contribute the test myself.

Looks like sorting it out needs some time but right now I'm a little bit busy. If you can write tests yourself with little efforts please do!

[jgsogo]

Thanks a lot for the contribution, @db4 🎉