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Task automation by cooking recipes in a configuration file
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README.rst

configcook: task automation by cooking recipes in a configuration file

configcook is a tool to automate tasks using a configuration file. Think of Makefiles, but then with a configuration file using TOML syntax. The tool is heavily inspired by the Buildout project.

Comparison with Buildout

It aims to do the same as Buildout (the zc.buildout package). Both have:

  • extensions
  • recipes
  • extend configuration from other files

Big differences:

  • Buildout installs packages itself. configcook calls pip on the command line.
  • Buildout uses ConfigParser compatible ini-style configuration files. configcook uses TOML configuration files.

It would be great if extensions and recipes written for Buildout could work with configcook. Currently this seems impossible without changes to those extensions and recipes.

TOML configuration files

TOML is more expressive than ini-style configuration files. In Buildout config you could write this:

[buildout]
a_string = 0
a_number = 0
a_list_of_strings = 0
a_list_of_integers = 0

In TOML this would be:

[configcook]
a_string = "0"
a_number = 0
a_list_of_strings = ["0"]
a_list_of_integers = [0]

So TOML is a bit more verbose, with quotes and brackets, but it avoids tedious parsing in recipes. The tedious parsing is done by the Python toml package. Note: the pytoml package could be good too, but toml is more popular.

Also, compare how booleans are handled. In buildout config it is completely up to the recipe to make sure that false means false, instead of true because it is a non-empty string:

[buildout]
a_boolean_true = true
# or maybe true/True/TRUE/yes/1/on
a_boolean_false = false
# or maybe false/False/FALSE/no/0/off

In configcook/TOML there is just one way:

[configcook]
a_boolean_true = true
a_boolean_false = false

In Buildout you can append items with the += construction when you extend files. You need to be careful with multiple values:

# original file:
[buildout]
single = one two
multi =
    one
    two

# file extending original file:
[buildout]
single += three
multi +=
    three

# result:
[buildout]
single =
    one two
    three
multi =
    one
    two
    three

In configcook the above would give a parse error because parts + is not a valid key, so you must quote it. It gives more consistency and flexibility though:

# original file:
[configcook]
a_string = "1"
a_number = 1
a_list_of_strings = ["1"]
a_list_of_integers = [1]

# file extending original file:
[configcook]
"a_string+" = "2"
"a_number+" = 2
"a_list_of_strings+" = ["2"]
"a_list_of_integers+' = [2]

# result:
[configcook]
a_string = "12"
a_number = 3
a_list_of_strings = ["1", "2"]
a_list_of_integers = [1, 2]

Technically, you can also add booleans this way, but it is not needed and not recommended. If you do it:

  • false + false is 0.
  • false + true is 1.
  • true + true is 2.

In Buildout you can remove items with the -= construction when you extend files: Again, you need to be careful with multiple values:

# original file:
[buildout]
single = one two
multi =
    one
    two

# file extending original file:
[buildout]
single -= one
multi -=
    one

# result:
[buildout]
single = one two
multi =
    two

TODO: support -= for subtracting values.

Note: you can only add or subtract values that are of the same type. For example, adding a string to a list will give a ConfigError.

The above is the basic information you need about the TOML format and how configcook uses it. See the TOML specification for more details.

TOML and Python packages

TOML was chosen by the Python community as format for specifying how to build a Python package. A package author would do this in a pyproject.toml file. See PEP 518, which includes an overview of file formats considered.

Within the pyproject.toml file, PEP 518 reserves a few names for tables (sections) that tools are expected to recognize and respect. At the moment, these are:

  • build-system
  • tool

The PEP goes on to say: "Tables not specified in this PEP are reserved for future use by other PEPs."

So if you add configcook to your pyproject.toml file it should look something like this:

[build-system]
# Minimum requirements for the build system to execute.
# PEP 508 specifications.
requires = ["setuptools", "wheel", "configcook"]

[tool.configcook]
parts = tool.configcook.somepart

[tool.configcook.somepart]
recipe = some.recipe

If you need lots more configcook sections, it gets tedious to prepend all table names with tool.configcook. Also, configcook is definitely not only meant for Python packages.

TODO: so we want to make tool.configcook available under the configcook key as well. And maybe tool.configcook.somepart under the somepart key.

Most important URLs

Compatibility

configcook aims to work on Python 2.7, Python 3.6, Python3.7 and PyPy2/3. As long as you have a pip that still works on Python 2.7, it should work.

Design decisions

  • We never directly install or uninstall Python packages. We use pip for that.
  • We call pip on the command line. We might use some utility functions from pip in our Python code, but a package install or uninstall will always be done in a shell with pip.
  • The packages end up wherever pip installs them. By default we expect this to be in a virtualenv, and will refuse to install anything if not. There will be options to go around this safety restriction, but then you should know what you are doing, as we might pollute your global Python install.
  • We will not isolate packages. If you have one config section that installs development requirements and another for production requirements and you install them both, then you simply have both. Perhaps clever recipes could work around this limitation.
  • pip is leading. You should be able to manually do pip install -r *requirements.txt -c *constraints.txt and have the same packages and versions installed as when you would have run configcook. configcook may install more, or suggest changes to those version files.
  • Version pins are only in the requirements.txt and constraints.txt files, or variants like dev-requirements.txt.
  • Extensions and recipes are encouraged to follow our design decisions, but we cannot enforce this.

Recipes

Some hints for recipe authors who want their recipe to be a good citizen:

  • A recipe class SHOULD inherit from configcook.recipes.BaseRecipe.
  • A recipe class __init__ MUST accept a tuple of name, config, options. name is the name of the part or section.
  • A recipe class SHOULD NOT change the config. This is the parsed configcook configuration, in a dictionary of dictionaries.
  • A recipe class MAY update its recipe options. These are the parsed options in the section belonging to the recipe part.
  • A recipe class SHOULD have a packages property that returns a list of packages to install. The list MAY be empty.
  • A recipe class SHOULD have an install method.
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