[Distutils] PEP DRAFT - Inclusion of pip bootstrap in Python installation

[Daniel Holth]

On Tue, Mar 19, 2013 at 2:04 PM, Richard Jones <richard at python.org> wrote:
> Hi all,
>
> I present for your deliberation a draft PEP for the inclusion of a pip
> bootstrap program in Python 3.4. Discussion of this PEP should remain
> here on the distutils SIG.
>
> The PEP is revision controlled in my bitbucket account
> https://bitbucket.org/r1chardj0n3s/pypi-pep (this is also where I'm
> intending to develop the implementation.)
>
>
>     Richard
>
> PEP: XXXX
> Title: Inclusion of pip bootstrap in Python installation
> Version:
> Last-Modified:
> Author: Richard Jones <richard at python.org>
> BDFL-Delegate:  Nick Coghlan <ncoghlan at gmail.com>
> Discussions-To: <distutils-sig at python.org>
> Status: Draft
> Type: Standards Track
> Created: 18-Mar-2013
> Python-Version: 3.4
> Post-History: 19-Mar-2013
>
> Abstract
> ========
>
> This PEP proposes the inclusion of a pip boostrap executable in the Python
> installation to simplify the use of 3rd-party modules by Python users.
>
> This PEP does not propose to include the pip implementation in the Python
> standard library. Nor does it propose to implement any package management or
> installation mechanisms beyond those provided by PEPs 470 ("The Wheel Binary
> Package Format 1.0") and TODO distlib PEP.
>
>
> Rationale
> =========
>
> Currently the user story for installing 3rd-party Python modules is
> not as simple as it could be. It requires that all 3rd-party modules inform
> the user of how to install the installer, typically via a link to the
> installer. That link may be out of date or the steps required to perform the
> install of the installer may be enough of a roadblock to prevent the user from
> further progress.
>
> Large Python projects which emphasise a low barrier to entry have shied away
> from depending on third party packages because of the introduction of this
> potential stumbling block for new users.
>
> With the inclusion of the package installer command in the standard Python
> installation the barrier to installing additional software is considerably
> reduced. It is hoped that this will therefore increase the likelihood that
> Python projects will reuse third party software.
>
> It is also hoped that this is reduces the number of proposals to include
> more and more software in the Python standard library, and therefore that
> more popular Python software is more easily upgradeable beyond requiring
> Python installation upgrades.
>
>
> Proposal
> ========
>
> Python install includes an executable called "pip" that attempts to import pip
> machinery. If it can then the pip command proceeds as normal. If it cannot it
> will bootstrap pip by downloading the pip implementation wheel file.
> Once installed, the pip command proceeds as normal.
>
> A boostrap is used in the place of a the full pip code so that we don't have
> to bundle pip and also the install tool is upgradeable outside of the regular
> Python upgrade timeframe and processes.
>
> To avoid issues with sudo we will have the bootstrap default to installing the
> pip implementation to the per-user site-packages directory defined in PEP 370
> and implemented in Python 2.6/3.0. Since we avoid installing to the system
> Python we also avoid conflicting with any other packaging system (on Linux
> systems, for example.) If the user is inside a virtual environment (TODO PEP
> ref) then the pip implementation will be installed into that virtual
> environment.
>
> The bootstrapping process will proceed as follows:
>
> 1. The user system has Python (3.4+) installed. In the "scripts" directory of
>    the Python installation there is the bootstrap script called "pip".
> 2. The user will invoke a pip command, typically "pip install <package>", for
>    example "pip install Django".
> 3. The boostrap script will attempt to import the pip implementation. If this
>    succeeds, the pip command is processed normally.
> 4. On failing to import the pip implementation the bootstrap notifies the user
>    that it is "upgrading pip" and contacts PyPI to obtain the latest download
>    wheel file (see PEP 427.)
> 5. Upon downloading the file it is installed using the distlib installation
>    machinery for wheel packages. Upon completing the installation the user
>    is notified that "pip has been upgraded." TODO how is it verified?
> 6. The pip tool may now import the pip implementation and continues to process
>    the requested user command normally.
>
> Users may be running in an environment which cannot access the public Internet
> and are relying solely on a local package repository. They would use the "-i"
> (Base URL of Python Package Index) argument to the "pip install" command. This
> use case will be handled by:
>
> 1. Recognising the command-line arguments that specify alternative or additional
>    locations to discover packages and attempting to download the package
>    from those locations.
> 2. If the package is not found there then we attempt to donwload it using
>    the standard "https://pypi.python.org/pypi/simple/pip" index.
> 3. If that also fails, for any reason, we indicate to the user the operation
>    we were attempting, the reason for failure (if we know it) and display
>    further instructions for downloading and installing the file manually.
>
> Manual installation of the pip implementation will be supported through the
> manual download of the wheel file and "pip install <downloaded wheel file>".
>
> This installation will not perform standard pip installation steps of saving the
> file to a cache directory or updating any local database of installed files.
>
> The download of the pip implementation install file should be performed
> securely. The transport from pypi.python.org will be done over HTTPS but the CA
> certificate check will most likely not be performed. Therefore we will
> utilise the embedded signature support in the wheel format to validate the
> downloaded file.
>
> Beyond those arguments controlling index location and download options, the
> "pip" boostrap command may support further standard pip options for verbosity,
> quietness and logging.
>
> The "--no-install" option to the "pip" command will not affect the bootstrapping
> process.
>
> An additional new Python package will be proposed, "pypublish", which will be a
> tool for publishing packages to PyPI. It would replace the current "python
> setup.py register" and "python setup.py upload" distutils commands. Again
> because of the measured Python release cycle and extensive existing Python
> installations these commands are difficult to bugfix and extend. Additionally
> it is desired that the "register" and "upload" commands be able to be performed
> over HTTPS with certificate validation. Since shipping CA certificate keychains
> with Python is not really feasible (updating the keychain is quite difficult to
> manage) it is desirable that those commands, and the accompanying keychain, be
> made installable and upgradeable outside of Python itself.
>
>
> Implementation
> ==============
>
> TBD
>
>
> Risks
> =====
>
> The Fedora variant of Linux has had a separate program called "pip" (a Perl
> package installer) available for install for some time. The current Python "pip"
> program is installed as "pip-python". It is hoped that the Fedora community will
> resolve this issue by renaming the Perl installer.
>
> Currently pip depends upon setuptools functionality. It is intended that before
> Python 3.4 is shipped that the required functionlity will be present in Python's
> standard library as the distlib module, and that pip would be modified to use
> that functionality when present. TODO PEP reference for distlib
>
>
> References
> ==========
>
> None, so far, beyond the PEPs.
>
>
> Acknowledgments
> ===============
>
> Nick Coghlan for his thoughts on the proposal and dealing with the Red Hat
> issue.
>
> Jannis Leidel and Carl Meyer for their thoughts.
>
>
> Copyright
> =========
>
> This document has been placed in the public domain.
> _______________________________________________
> Distutils-SIG maillist  -  Distutils-SIG at python.org
> http://mail.python.org/mailman/listinfo/distutils-sig

++1 on including a bootstrap wheel-only installer for getting pip

-1 on giving it the same name

-1 on scripts that start with "py". "python -m something"?

Wheel's builtin signature checking is both controversial and awesome.
Its most important properties are that it is key centric (signatures
ONLY mean the signer possessed the private signing key and do not by
themselves assert any other hard-to-verify information like e-mail,
timestamps etc.); keys are short and referenced literally;   it has a
simple ~500 line pure-Python implementation including the crypto math
with optional C speedups. The reference uses a highly convenient
elliptic curve scheme called Ed25519 developed by respected
cryptographers Bernstein et al.

I would be OK with trusting the cheeseshop to make all decisions
needed for "get me the newest version of pip" to simplify the
bootstrap installer and to trust that version based only on the
integrity of the SSL connection. Would it be feasible/helpful to
include a short root CA list "the 3 that pypi is allowed to buy
certificates from" for this purpose?

It's also possible to use the downloaded archive to initiate a more
complete install. Wheel's own installer can do this but it may be too
circular for some: "python wheel-1.0.0-py2.py3-none-any.whl/wheel
install wheel-1.0.0-py2.py3-none-any.whl". With some form of distlib
in the standard library this might not be needed.

It would be a weekend project to include a vendorized version of
pkg_resources with pip. This version of pip would be able to do
everything pip does now, except install from sdist. The hardest part
would be complaining in all the right places when setuptools wasn't
installed.

We will want something to replace setup.py register / upload / ... and
pip definitely isn't the place for it. I'm not too worried about this
since you will be able to download it once we have the bootstrap
install feature in place.