Rework determination of virtualenv site-packages flags for v20

[PeterJCLaw]

virtualenv 20.0 removed --no-site-packages so we cannot pass that on that version. This means we have three version scenarios to cope with:

• < 1.7: site packages installed by default, with --no-site-packages to opt out

• 1.7 - 20.0: --no-site-packages present and default, --system-site-packages to opt back in

• > 20.0: no site packages by default, --system-site-packages to opt back in

This PR aims to add support for the last of these, so that all three are supported.

This was mentioned at #534 (comment) and I've hit this myself (on Fedora 33, where this patch fixes it for me).

Meta: I've not yet added any tests; I'm not sure how to do that, but if you can point me in the right direction I'm happy to give it a go.

[PeterJCLaw]

Note: I thiiink that this should probably be >=, however I believe the current spelling has the same error.

[crazymind1337]

I have tested your branch at our CI. The result is what I expected:

The CI fails due to the fact $virtualenv is not set, because it is not installed for a fresh system and the fact itself is been set in the beginning of the run and not been updated while virtualenv is been installed. Therefore the comparison which you are making is not catching up.

My PR which was based on the $OS, like: if $os == 20.04 => remove --no-site-packages parameter has not been accepted due to the fact the removal of the parameter is based on the virtualenv version.

I think we will have to modify the exec for virtualenv. Maybe we make 2 execs with an onlyif parameter which differs on the different virtualenv version.

[crazymind1337]

The actual cases are:

• $systempkgs = true and $virtualenv_version > 1.7 and $virtualenv_version < 20:
  $system_pkgs_flag = "--system-site-packages"

• $systempkgs = false and $virtualenv_version > 1.7 and $virtualenv_version < 20:
  $system_pkgs_flag = "--no-site-packages"

• $systempkgs = true and $virtualenv_version >= 20:
  $system_pkgs_flag = "--system-site-packages"

• $systempkgs = false and $virtualenv_version >= 20:
  $system_pkgs_flag = ""

Which in the end is:

• $systempkgs = true:
  $system_pkgs_flag = "--system-site-packages"

• $systempkgs = false:
  $virtualenv_version < 20:
  $system_pkgs_flag = "--no-site-packages"
  $virtualenv_version >= 20
  $system_pkgs_flag = ""

I am not sure if we still need to check on the case if $virtualenv_version < 1.7. On any OSes we are using the $virtualenv_version is > 1.7.

But still: The value for the fact $virtualenv_version is unset on the fresh installation. Therefore we only can rely on the fact if it is set.

[PeterJCLaw]

Ah, just seen that #552 was a previous attempt at this.

The actual cases are:

• $systempkgs = true and $virtualenv_version > 1.7 and $virtualenv_version < 20:
  $system_pkgs_flag = "--system-site-packages"

• $systempkgs = false and $virtualenv_version > 1.7 and $virtualenv_version < 20:
  $system_pkgs_flag = "--no-site-packages"

• $systempkgs = true and $virtualenv_version >= 20:
  $system_pkgs_flag = "--system-site-packages"

• $systempkgs = false and $virtualenv_version >= 20:
  $system_pkgs_flag = ""

so on any virtualenv version we have if $systempkgs = true we can add $system_pkgs_flag = "--system-site-packages". and based on the virtualenv version we need to figure out what to set for $system_pkgs_flag.

From a quick look these seem correct, but incomplete -- there's no handling for virtualenv before 1.7. I don't think that --system-site-packages exists in the earlier versions.

I am not sure if we still need to check on the case if $virtualenv_version < 1.7. On any OSes we are using the virtualenv_version is > 1.7.

I would expect that support is required unless the module explicitly declares that it doesn't support the version. (as a user, I'd also hope that it would warn clearly about that somewhere, perhaps at runtime when trying to use an incompatible virtualenv).

[crazymind1337]

From virtualenv --help:

  --no-site-packages    DEPRECATED. Retained only for backward compatibility.
                        Not having access to global site-packages is now the
                        default behavior.

[crazymind1337]

virtualenv in version 1.7 has been release 9 years ago. I don't find anything if it is already EOL but I think we are safe to drop its support.

https://pypi.org/project/virtualenv/1.7/

I have checked all supported OS (from metadata.json). All have virtualenv => 15 for their default repository available.

[crazymind1337]

I think we are safe to just add

  $system_pkgs_flag = $systempkgs ? {
    true    => '--system-site-packages',
    default => '',
  }

[bastelfreak]

hey people. I created #589 . can you both please take a look? I'm also open for suggestions to properly test if this is working

[bastelfreak]

hey people. Since #593 got merged, this issue can be closed?

[PeterJCLaw]

Yup, that PR has fixed it for me also.