MageConfig

MageConfig is a Go library designed for flexible configuration management. It allows for the loading of parameters from various sources such as configuration files, environment variables, and command-line arguments into a designated configuration struct. This is achieved with Go's struct tags, which enable control over the source and loading mechanism for each parameter. In addition, MageConfig offers the capability to set default values and manage required or dependencies parameters effectively.

Features

Loading Configuration: mageconfig allows you to load configuration parameters from multiple sources into a configuration struct, including files, environment variables, and command-line arguments.
Default Values: You can set default values for configuration fields using the default tag. If a value is not provided through other sources, the default value will be used.
Dependent Parameters: Using the depends tag, you can specify which parameters a certain field is dependent upon. If the dependencies are not satisfied, an error will be returned.
Required Parameters: Mark configuration fields as required using the required tag. If a required parameter is not set, an error will be returned.
Multiple Data Types: mageconfig supports various data types for configuration fields, including bool, int, []int, uint, []uint, float, []float, string, []string, time.Duration, time.Time, and map[string]bool|int|uint|float|string|time.Duration|time.Time.
Usage Help: mageconfig provides a built-in usage help functionality that can be triggered by passing the -help or --help command-line argument.
Command line arguments that come after the target argument (with the specified prefix) can be removed using DropArgsAfterTarget function.
The configuration loading process follows a specific priority order: configuration file values are overwritten by environment variable values, which in turn are overwritten by argument values. This means that if the same configuration parameter is specified in multiple places, the argument value will take precedence over the environment variable value, which will take precedence over the configuration file value.

Limitations

It's important to note that the configuration you provide to mageconfig should be a pointer to a struct or mageconfig will return an error.
When running mage -help, it will display the help information for mage itself. To view the help for a specific target in magefile.go, you can use the command mage dummy -help or invoke it after compiling it into a binary file. Also, it's worth noting that executing a command in the format mage -v -debug --arg-name=value will not be possible.
Additionally, please be aware that using mage -l to list all the build targets may currently not work due to certain complexities. When using a compiled binary, this functionality works as expected.

Supported Tags

file: Defines the name of the parameter in the configuration file.
env: Defines the name of the environment variable.
arg: Defines the name of the command-line argument.
default: Defines the default value of the parameter.
depends: Indicates a comma-separated list of parameters that the current field depends on, such as "field0,field1".
required: If set to "true", the parameter is required. If a required parameter is not set, the Load function will return an error.
desc: The description of the parameter, used for the help print.

Default Naming Convention

In mageconfig, you specify the names of configuration parameters using struct tags for each field in your configuration struct. For example, you can specify the name of a parameter in a configuration file with the file tag, an environment variable with the env tag, and a command-line argument with the arg tag.

However, if you don't specify a name using these tags, mageconfig will default to using the name of the struct field itself. The name will be converted to lower case and will be expected in this form in your configuration file, as an environment variable, and as a command-line argument.

Configuration File Format

The configuration file should be a plain text file where each line defines a parameter. The parameter name and its value should be separated by a colon.

param1: value1
param2: value2

Lines that do not conform to this format will be ignored.

Command Line Interface

You can run mage with various options and targets, followed by arguments for mageconfig:

mage [mage-options] [targets] [mageconfig-arguments]

Mageconfig arguments can be specified in two ways:

With a single dash and the argument name (e.g., -arg-name)
With two dashes and the argument name (e.g., --arg-name)

The value for an argument can be specified either by appending it directly with an equal sign, or by providing it after a space. For example:

-arg-name1="value1"
--arg-name2 "value2"

Boolean arguments can be specified in the same way, but they also have an additional feature: if you provide the argument name without a value, it will automatically be interpreted as true. For example:

--arg-bool1
--arg-bool2=false

In this case, --arg-bool1 is equivalent to --arg-bool1=true.

Installation

To use mageconfig in your Go project, you can install it using the go get command:

go get github.com/grffio/mageconfig

How to Use

An example magefile.go is located in the examples directory.

You can execute the example with the following command:

env DB_URL="postgresql://localhost:5432" mage -debug -v showconfig --api-key "abc123"

This command sets the DB_URL environment variable, runs the mage command with the showconfig target, includes mage's debug option, and specifies the --api-key argument.

License

This project is licensed under the MIT License - see the LICENSE file for details.

Support

If you encounter any issues, please open an issue on the GitHub repository. We'll do our best to address it promptly.