[venv] Add ~/.venvrc to change module defaults

[cooperlees]

BPO	38483
Nosy	@brettcannon, @vsajip, @eryksun, @cooperlees, @EpicWink
PRs	bpo-38483: Add support for venv.ini #16802

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2019-11-23.16:44:56.407>
created_at = <Date 2019-10-15.10:51:40.499>
labels = ['type-feature', 'library', '3.9']
title = '[venv] Add ~/.venvrc to change module defaults'
updated_at = <Date 2019-11-23.16:44:56.406>
user = 'https://github.com/cooperlees'

bugs.python.org fields:

activity = <Date 2019-11-23.16:44:56.406>
actor = 'cooperlees'
assignee = 'none'
closed = True
closed_date = <Date 2019-11-23.16:44:56.407>
closer = 'cooperlees'
components = ['Library (Lib)']
creation = <Date 2019-10-15.10:51:40.499>
creator = 'cooperlees'
dependencies = []
files = []
hgrepos = []
issue_num = 38483
keywords = ['patch']
message_count = 7.0
messages = ['354712', '355115', '355116', '355117', '355592', '357348', '357360']
nosy_count = 5.0
nosy_names = ['brett.cannon', 'vinay.sajip', 'eryksun', 'cooperlees', 'Epic_Wink']
pr_nums = ['16802']
priority = 'normal'
resolution = 'rejected'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue38483'
versions = ['Python 3.9']

[cooperlees]

I'd like to propose adding a run commands (.venvrc) file support to the venv library.

File Location: ~/.venvrc

This file will support all current CLI arguments and override the defaults for each CLI if present in the file. I will also endeavour to add test for POSIX + Windows systems.

I propose using configparser and an .ini style config for the .venvrc.

My main use for this is to allow myself to default to always using --upgrade-deps when I create new venvs.

Thoughts? Concerns?

[EpicWink]

".xxxxxrc" usually means a file to be run (by a shell) at shell start, and therefore is a script of command to run ("rc" seems to come from "runcom", ie run commands).

INI files usually have a ".ini" or ".cfg" suffix. virtualenv, for example, used an INI file similar to your proposal: https://virtualenv.pypa.io/en/stable/reference/#configuration-file.

[cooperlees]

Good point. Happy to match the virtualenv module and use .ini if others agree.

[eryksun]

In Windows, dot files cannot be hidden (i.e. set the hidden file attribute), unlike how they're conventionally hidden in Unix. Doing so breaks normal access. A directory such as ".venv" can be hidden, but that's still going against convention. For Windows, I suggest using "$APPDATA/Python/venv.ini" as the default path.

Note that, while "$APPDATA/Python" happens to be the base directory for per-user package installations, i.e. site.getuserbase(), I'm not suggesting to use the user base directory as the default in Unix and macOS systems.

For comparison, pip uses "$APPDATA/pip/pip.ini" in Windows and "$HOME/.config/pip/pip.conf" in Unix. In macOS it prefers "$HOME/Library/Application Support/pip" over "$HOME/.config/pip" if the former exists.

[cooperlees]

Updated PR to use venv.ini. Will fix any CI errors encountered.

[brettcannon]

Is this best served in the stdlib or in an external tool like how virtualenvwrapper is separate from virtualenv? While I get the convenience of not having to install another tool to do this, it does bring in some complexity that does not directly tie into the metadata required by venv to write out to pyvenv.cfg or the directories and files that it creates.

[cooperlees]

I vote in the stdlib. This is the biggest win of venv over virtualenv The aim of this request is to allow developers to customize some of the venv defaults to make it easier to move from project to project.

To ensure a clean development environment, some days I create multiple venvs (virtual environments) a day. I treat my venv's ephemeral, and I am sure many other do too. Being able to set --upgrade-deps and/or other defaults via a config file just saves a few more key strokes and allows Python to be even more delightful to develop in over other languages.

In regards to you bringing up pyenv.cfg + metadata, this attacks a totally different problem. This is allowing developers to set some defaults for venv creation. It does not change any internal meta data and is just an optional optimization developers can choose to use.