type-config 1.3.0

A small library that adds types and auto-validation to your config files!

Type config ⭐🐙

Type-config is a small python library that let's you add custom types and validations to your config file. The project's focus is on readability and maintainability, using a simple ini-like formatting.

This project is being tested and very young. There could be updates soon and not everything might work as expected.
If you find a problem, please write an issue, so I'll be able to solve it :)

Table of contents (for github) 📝

• Type config ⭐🐙
• Features
• Demo
• Getting started
• Installation 🔧
• Initialisation
• Adding options
• Adding types
• Getters
• Creating a file
• Parsing a file
• Validating an existing dictionary
• Merging configurations
• Healing a broken configuration
• Error handling 🔧
• Contributing 💕
• Extra 🐙

Features

• Define custom types for the validation of your config file's data, applied during parsing
• Automatic formatting of your config file
• Possibility of recovering a corrupted (badly formatted) file
• Merging configurations (useful when having CLI arguments and a config file)
• Attaching error and help messages to each option, for clear and effective communication
• Adding type hints to your configuration file to help you during development

Demo

This is how you would create a type_config object:

config = TypeConfig()
# OR, if you want type hints in your config file:
config = TypeConfig(type_hint=True)

Adding options:

config.add_option(
option="shopping list",
type="List>=3",
help="What I have to buy",
important_help="Must be a list of at least three items, separated by commas",
)

Adding a type (they can have descriptive names❗):

config.add_type(
type="List>=3",
validate=lambda list: len(list.split(",")) >= 3,
cast=lambda list: [item.trim() for item in list.split(",")],
error="The list must have at least three items"
)

This is how entries can look in a config file made with type_config:

shopping list = water, pasta, oil
# !!! Must be a list of at least three items, separated by commas
# What I have to buy

or, if you want to see what type you are applying to the option:

[List>=3] shopping list = water, pasta, oil
# !!! Must be a list of at least three items, separated by commas
# What I have to buy

When you parse this file again, each option will be tested with their type's validating function and formatted using their casting function.

If there are errors, the parsing won't crash; it will give you a list of which options failed and why, so that you can quickly understand what's wrong.

---

Getting started 🔥

Installation 🔧

Install the package using pip

pip install type_config

Initialising the TypeConfig object

The TypeConfig object is the main interface used by this library to help you handle configuration files and validation.

config = TypeConfig(type_hint:bool=False)

Parmeter	Description	Default
type_hint	Whether or not to add type hints to your config file. This initialises the class' self.type_hint, which can later on be changed directly by the user and is used by heal_config and create_config.	False

Adding options

Options are added using the method add_option of a TypeConfig object.

They hold many information useful when parsing and debugging.

Parmeter	Description	Default
option	The option's name	Required
type	The type associated with this option	Required
help	An help string used to explain what the option does or what it is for. This is showed under the option in the config file.	Required
default	A default value used when the option is left blank	Empty_string
can_be_empty	Whether or not the option can be left without a value. The value that will be given is None. Notice: default is applied when there is no value, so it's suggested using this option while leaving default empty.	False
important_help	Extra information that could be useful when writing the option's value	Empty_string

Adding types

Types are added using the method add_type of a TypeConfig object.

They are used for data validation.

Parmeter	Description	Default
type	The type's name	Required
validate	A function that returns a boolean, which is used to validate the option's value.	Required
cast	A function that "casts" a specific type upon the option's value, effectively transforming it from string to the desired type.	Required
error	A message describing what could be the reason when the option's value is considered invalid. This is showed under the option in the config file.	Required

Getters

You can get a COPY of the options and types of a TypeConfig object by using get_options and get_types. These are to be used for testing, debugging or visualization, not for modifying the existing values.

Method	Description
get_options	Get all of the options added so far to the TypeConfig object
get_types	Get all of the types added so far to the TypeConfig object

Creating a file

You can obtain the formatted text of a config file with the create_config method of a TypeConfig's object. If self.type_hint is set to True, type hints will be added before each option. This DOES NOT have any effect on the parsing are are just "hints" for the developer.

The optional argument values_to_inject can be very useful for testing; this can allow you to have a json file with values that have to be set but do not have a default value (or have an invalid value), and test your application dynamically, reducing the amount of maintainance required when adding or removing options (since you can generate a new config file in each test session).

values_to_inject overwrites only options that are present and only for that ouput; extra arguments are simply not taken into account and the TypeConfig instance's configuration is left untouched.

Parmeter	Description	Default
values_to_inject	A dictionary containing {option:value} pairs, which overwrite the default value written to the output.	{}

Notice: the library doesn't write directly to a file, instead it returns a string that can be written to an ini file. This is done so that the user has more control over the output path and exceptions handling.

Parsing a file

You can extract your {option: value} pairs from a configuration file's content by using the parse_config method of a TypeConfig object.

This method returns a tuple of two values, containing the configuration data (yet to be validated), represented as {option:value}, and a dictionary with errors that happened during parsing, represented as {option: error}.

Notice: the library doesn't read directly from a file, instead it reads a string. This is done so that the user has more control over the input path and exceptions handling.

Parmeter	Description	Default
file_content	A string representing the content config file to be parsed.	Required

Validating an existing dictionary

To validate a dictionary containing your options, you can use the validate_config method of a TypeConfig object. This can be useful for configurations coming from a file formatted by type_config and for options coming from the argparse library.

It returns a dictionary with the validated data and a dictionary with errors that happened during validation (using the error linked to the option's type). Errors are also raised when an option or a type are not part of the TypeConfig's instance's options and types.

Parmeter	Description	Default
config	A dictionary containing keys that are part of the TypeConfig's options.	Required

Merging configurations

To merge two configurations, you can use the merge_config method of a TypeConfig object.
This method creates a new dictionary containing {option:value}.

The options' values priority is:

1. Overwriting_config's value
2. Overwritable_config's value
3. Default value from the TypeConfig object
4. raise ParsingError if option can't be empty, else value is None

Notice: Falsy options are considered valid values. Only None values are overwritten: to make sure the merging goes as expected, you might want to specify a default=None if parsing cli arguments with argparse and using store_true or store_false. Notice: no validation is done during this operation and only options present in the input configurations will be written to the result.

Parmeter	Description	Default
Overwriting_config	The configuration dictionary which values will be preferred when merging.	Required
Overwritable_config	The configuration dictionary which values will be overwritten, if possible.	Required

Healing a broken configuration

The library has a method for "healing" badly formatted configurations, which is the heal_config method of a TypeConfig object. This method maintains {option: value} pairs if the option, equal sign and value are formatted correctly and the option is part of the TypeConfig object. This method also restores comments and whitespaces.

Another use for this method is switching between a configuration file with type hints and one without. This behaviour is set by self.type_hint's value and can be useful during debugging.

The returning value is a string (the healed configuration).

Example:

BrokenType] with a broken option #Added an inline comment

I'm an option that dones't exist = ahah

option = my value # another inline comment
# I changed the help line

will become:

[BrokenType] with a broken option = default
# !!! This are the important_help
# And this is the help line

[BrokenType] option = my value
# !!! This are the important_help
# And this is the original help line

Parmeter	Description	Default
file_content	A string representing the broken file content to restore.	Required

Known bugs:

• Heal_config does not remove duplicate options for now; a fix is planned.

Error Handling 🔧

This library has only two kinds of errors: ParsingError and ValidationError.
They can be imported using:

from type_config.errors import ParsingError, ValidationError

This is a list of when they are used (all of these errors should be handled internally):

Error	Situations	Methods
ParsingError	- When an option isn't part of the TypeConfig's object configuration - When an option that can't be left empty is None/Falsy	parse_config
ValidationError	- When a type or an option isn't part of the TypeConfig's object configuration - When an option that can't be left empty is None/Falsy - When a value is invalid (Custom error message)	prase_config, validate_config

Contributing 💕

Feel free to open issues asking for more information or to reach out to me!

• Please make sure all the tests are passing before opening a pull request. You can use pytest for this.
• Please use types when possible (you can be helped by pyright or mypy).
• Please don't reformat the file in the same commit as your refactoring/contribution (if you want to, use black); this is best done in its own commit, to make clear what changed in which commit.
• Please do not use abbreviations when naming variables or functions (I have an hard time understanding them :( ).
• Please append Feat, Refactor, Fix, Format to make clear what you've contributed on.

Extra 🐙

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