kraken-wrapper 0.1.21

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kraken-wrapper

Provides the krakenw command which is a wrapper around Kraken to construct an isolated and reproducible build environment.

Features

• Produces isolated environments in PEX format
• Reads build requirements from the .kraken.py file header
• Produces lock files (.kraken.lock) that can be used to reconstruct an exact build environment ¹⁾
• Store Python package index credentials in a keychain

^{1) The lock files do not contain hashes for installed distributions, but only the exact version numbers from the resolved build environment.}

Documentation

Table of Contents

• Requirements header
• Environment variables
• Recommendations
• Index credentials

Requirements header

If no .kraken.lock file is present, Kraken wrapper will read the header of the .kraken.py file to obtain the requirements to install into the build environment. The format of this header is demonstrated below:

# ::requirements kraken-std>=0.3.0,<0.4.0 --extra-index-url https://...
# ::pythonpath build-support

The available options are:

Option	Description
#::requirements	The content on this line will be parsed similar to the arguments for pip install. Every positional argument is a Python requirement specifier. The following options are supported: --index-url, --extra-index-url and --interpreter-constraint.
#::pythonpath	One or more paths to prepend to sys.path when the build environment is created/executed. This is already supported by kraken-core but will be used to generate a .pth file when using the VENV environment type. The ./build-support/ will always be added to sys.path.

Environment variables

The following environment variables are handled by kraken-wrapper:

Variable	Description
KRAKENW_USE	If set, it will behave as if the --use flag was specified (although the --use flag if given will still take precedence over the environment variable). Can be used to enforce a certain type of build environment to use. Available values are PEX_ZIPAPP, PEX_PACKED, PEX_LOOSE and VENV (default).
KRAKENW_REINSTALL	If set to 1, behaves as if --reinstall was specified.
KRAKENW_INCREMENTAL	If set to 1, virtual environment build environments are "incremental", i.e. they will be reused if they already exist and their installed distributions will be upgraded.

Recommendations

• When using local requirements, using the VENV type is a lot fast because it can leverage Pip's in-tree-build feature. Pex does not currently support in-tree builds.

Index credentials

Pip doesn't really have a good way to globally configure credentials for Python package indexes when they are not configured as an alias in .piprc aside from ~/.netrc. Both of these methods have the drawback that the password is stored in plain text on disk. Pip does technically support looking up a password from the system keychain using the keyring package, but it doesn't store the username and so will have to ask for it via stdin.

To work around this limitation, kraken-wrapper offers the auth command which allows you to configure credentials where the username is stored in ~/.config/krakenw/config.toml and the password is stored in the system keychain (also using the keyring package).

$ krakenw auth example.jfrog.io -u [e-mail] 
Password for [e-mail]:

Important note: If no backend for the keyring package is available, kraken-wrapper will fall back to writing the password as plain text into the same configuration file.