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# Anyway Config
> One configuration to rule all data sources
Anyway Config is a configuration library for Ruby gems and applications.
As a library author, you can benefit from using Anyway Config by providing a better UX for your end-users:
- **Zero-code configuration** — no more boilerplate initializers.
- **Per-environment and local** settings support out-of-the-box.
For application developers, Anyway Config could be useful to:
- **Keep configuration organized** and use _named configs_ instead of bloated `.env`/`settings.yml`/whatever.
- **Free code of ENV/credentials/secrets dependency** and use configuration classes instead—your code should not rely on configuration data sources.
**NOTE:** this readme shows documentation for 2.x version.
For version 1.x see the [1-4-stable branch](https://github.com/palkan/anyway_config/tree/1-4-stable).
## Links
- [Anyway Config: Keep your Ruby configuration sane](https://evilmartians.com/chronicles/anyway-config-keep-your-ruby-configuration-sane?utm_source=anyway_config)
## Table of contents
- [Main concepts](#main-concepts)
- [Installation](#installation)
- [Usage](#usage)
- [Configuration classes](#configuration-classes)
- [Dynamic configuration](#dynamic-configuration)
- [Validation & Callbacks](#validation-and-callbacks)
- [Using with Rails applications](#using-with-rails)
- [Data population](#data-population)
- [Organizing configs](#organizing-configs)
- [Generators](#generators)
- [Using with Ruby applications](#using-with-ruby)
- [Environment variables](#environment-variables)
- [Type coercion](#type-coercion)
- [Local configuration](#local-files)
- [Data loaders](#data-loaders)
- [Doppler integration](#doppler-integration)
- [EJSON support](#ejson-support)
- [Custom loaders](#custom-loaders)
- [Source tracing](#tracing)
- [Pattern matching](#pattern-matching)
- [Test helpers](#test-helpers)
- [OptionParser integration](#optionparser-integration)
- [RBS support](#rbs-support)
## Main concepts
Anyway Config abstractize the configuration layer by introducing **configuration classes** which describe available parameters and their defaults. For [example](https://github.com/palkan/influxer/blob/master/lib/influxer/config.rb):
```ruby
module Influxer
class Config < Anyway::Config
attr_config(
host: "localhost",
username: "root",
password: "root"
)
end
end
```
Using Ruby classes to represent configuration allows you to add helper methods and computed parameters easily, makes the configuration **testable**.
The `anyway_config` gem takes care of loading parameters from **different sources** (YAML, credentials/secrets, environment variables, etc.). Internally, we use a _pipeline pattern_ and provide the [Loaders API](#data-loaders) to manage and [extend](#custom-loaders) its functionality.
Check out the libraries using Anyway Config for more examples:
- [Influxer](https://github.com/palkan/influxer)
- [AnyCable](https://github.com/anycable/anycable)
- [Sniffer](https://github.com/aderyabin/sniffer)
- [Blood Contracts](https://github.com/sclinede/blood_contracts)
- [and others](https://github.com/palkan/anyway_config/network/dependents).
## Installation
Adding to a gem:
```ruby
# my-cool-gem.gemspec
Gem::Specification.new do |spec|
# ...
spec.add_dependency "anyway_config", ">= 2.0.0"
# ...
end
```
Or adding to your project:
```ruby
# Gemfile
gem "anyway_config", "~> 2.0"
```
### Supported Ruby versions
- Ruby (MRI) >= 2.5.0
- JRuby >= 9.2.9
## Usage
### Configuration classes
Using configuration classes allows you to make configuration data a bit more than a bag of values:
you can define a schema for your configuration, provide defaults, add validations and additional helper methods.
Anyway Config provides a base class to inherit from with a few DSL methods:
```ruby
require "anyway_config"
module MyCoolGem
class Config < Anyway::Config
attr_config user: "root", password: "root", host: "localhost"
end
end
```
Here `attr_config` creates accessors and populates the default values. If you don't need default values you can write:
```ruby
attr_config :user, :password, host: "localhost", options: {}
```
**NOTE**: it's safe to use non-primitive default values (like Hashes or Arrays) without worrying about their mutation: the values would be deeply duplicated for each config instance.
Then, create an instance of the config class and use it:
```ruby
MyCoolGem::Config.new.user #=> "root"
```
**Bonus:**: if you define attributes with boolean default values (`false` or `true`), Anyway Config would automatically add a corresponding predicate method. For example:
```ruby
attr_config :user, :password, debug: false
MyCoolGem::Config.new.debug? #=> false
MyCoolGem::Config.new(debug: true).debug? #=> true
```
**NOTE**: since v2.0 accessors created by `attr_config` are not `attr_accessor`, i.e. they do not populate instance variables. If you used instance variables before to override readers, you must switch to using `super` or `values` store:
```ruby
class MyConfig < Anyway::Config
attr_config :host, :port, :url, :meta
# override writer to handle type coercion
def meta=(val)
super JSON.parse(val)
end
# or override reader to handle missing values
def url
super || (self.url = "#{host}:#{port}")
end
# untill v2.1, it will still be possible to read instance variables,
# i.e. the following code would also work
def url
@url ||= "#{host}:#{port}"
end
end
```
We recommend to add a feature check and support both v1.x and v2.0 in gems for the time being:
```ruby
# Check for the class method added in 2.0, e.g., `.on_load`
if respond_to?(:on_load)
def url
super || (self.url = "#{host}:#{port}")
end
else
def url
@url ||= "#{host}:#{port}"
end
end
```
#### Config name
Anyway Config relies on the notion of _config name_ to populate data.
By default, Anyway Config uses the config class name to infer the config name using the following rules:
- if the class name has a form of `::Config` then use the module name (`SomeModule::Config => "somemodule"`)
- if the class name has a form of `Config` then use the class name prefix (`SomeConfig => "some"`)
**NOTE:** in both cases, the config name is a **downcased** module/class prefix, not underscored.
You can also specify the config name explicitly (it's required in cases when your class name doesn't match any of the patterns above):
```ruby
module MyCoolGem
class Config < Anyway::Config
config_name :cool
attr_config user: "root", password: "root", host: "localhost", options: {}
end
end
```
#### Customize env variable names prefix
By default, Anyway Config uses upper-cased config name as a prefix for env variable names (e.g.
`config_name :my_app` will result to parsing `MY_APP_` prefix).
You can set env prefix explicitly:
```ruby
module MyCoolGem
class Config < Anyway::Config
config_name :cool_gem
env_prefix :really_cool # now variables, starting wih `REALLY_COOL_`, will be parsed
attr_config user: "root", password: "root", host: "localhost", options: {}
end
end
```
#### Explicit values
Sometimes it's useful to set some parameters explicitly during config initialization.
You can do that by passing a Hash into `.new` method:
```ruby
config = MyCoolGem::Config.new(
user: "john",
password: "rubyisnotdead"
)
# The value would not be overridden from other sources (such as YML file, env)
config.user == "john"
```
#### Reload configuration
There are `#clear` and `#reload` methods that do exactly what they state.
**NOTE**: `#reload` also accepts an optional Hash for [explicit values](#explicit-values).
### Dynamic configuration
You can also fetch configuration without pre-defined schema:
```ruby
# load data from config/my_app.yml,
# credentials.my_app, secrets.my_app (if using Rails), ENV["MY_APP_*"]
#
# Given MY_APP_VALUE=42
config = Anyway::Config.for(:my_app)
config["value"] #=> 42
# you can specify the config file path or env prefix
config = Anyway::Config.for(:my_app, config_path: "my_config.yml", env_prefix: "MYAPP")
```
This feature is similar to `Rails.application.config_for` but more powerful:
| Feature | Rails | Anyway Config |
| ------------- |-------------:| -----:|
| Load data from `config/app.yml` | ✅ | ✅ |
| Load data from `secrets` | ❌ | ✅ |
| Load data from `credentials` | ❌ | ✅ |
| Load data from environment | ❌ | ✅ |
| Load data from [other sources](#data-loaders) | ❌ | ✅ |
| Local config files | ❌ | ✅ |
| Type coercion | ❌ | ✅ |
| [Source tracing](#tracing) | ❌ | ✅ |
| Return Hash with indifferent access | ❌ | ✅ |
| Support ERB\* within `config/app.yml` | ✅ | ✅ |
| Raise if file doesn't exist | ✅ | ❌ |
| Works without Rails | 😀 | ✅ |
\* Make sure that ERB is loaded
### Validation and callbacks
Anyway Config provides basic ways of ensuring that the configuration is valid.
There is a built-in `required` class method to define the list of parameters that must be present in the
configuration after loading (where present means non-`nil` and non-empty for strings):
```ruby
class MyConfig < Anyway::Config
attr_config :api_key, :api_secret, :debug
required :api_key, :api_secret
end
MyConfig.new(api_secret: "") #=> raises Anyway::Config::ValidationError
```
`Required` method supports additional `env` parameter which indicates necessity to run validations under specified
environments. `Env` parameter could be present in symbol, string, array or hash formats:
```ruby
class EnvConfig < Anyway::Config
required :password, env: "production"
required :maps_api_key, env: :production
required :smtp_host, env: %i[production staging]
required :aws_bucket, env: %w[production staging]
required :anycable_rpc_host, env: {except: :development}
required :anycable_redis_url, env: {except: %i[development test]}
required :anycable_broadcast_adapter, env: {except: %w[development test]}
end
```
If your current `Anyway::Settings.current_environment` is mismatch keys that specified
`Anyway::Config::ValidationError` error will be raised.
If you need more complex validation or need to manipulate with config state right after it has been loaded, you can use _on load callbacks_ and `#raise_validation_error` method:
```ruby
class MyConfig < Anyway::Config
attr_config :api_key, :api_secret, :mode
# on_load macro accepts symbol method names
on_load :ensure_mode_is_valid
# or block
on_load do
# the block is evaluated in the context of the config
raise_validation_error("API key and/or secret could be blank") if
api_key.blank? || api_secret.blank?
end
def ensure_mode_is_valid
unless %w[production test].include?(mode)
raise_validation_error "Unknown mode; #{mode}"
end
end
end
```
## Using with Rails
**NOTE:** version 2.x supports Rails >= 5.0; for Rails 4.x use version 1.x of the gem.
We recommend going through [Data population](#data-population) and [Organizing configs](#organizing-configs) sections first,
and then use [Rails generators](#generators) to make your application Anyway Config-ready.
### Data population
Your config is filled up with values from the following sources (ordered by priority from low to high):
1) **YAML configuration files**: `RAILS_ROOT/config/my_cool_gem.yml`.
Rails environment is used as the namespace (required); supports `ERB`:
```yml
test:
host: localhost
port: 3002
development:
host: localhost
port: 3000
```
### Multi-env configuration
_⚡️ This feature will be turned on by default in the future releases. You can turn it on now via `config.anyway_config.future.use :unwrap_known_environments`._
If the YML does not have keys that are one of the "known" Rails environments (development, production, test)—the same configuration will be available in all environments, similar to non-Rails behavior:
```yml
host: localhost
port: 3002
# These values will be active in all environments
```
To extend the list of known environments, use the setting in the relevant part of your Rails code:
```ruby
Rails.application.config.anyway_config.known_environments << "staging"
```
If your YML defines at least a single "environmental" top-level, you _have_ to separate all your settings per-environment. You can't mix and match:
```yml
staging:
host: localhost # This value will be loaded when Rails.env.staging? is true
port: 3002 # This value will not be loaded at all
```
To provide default values you can use YAML anchors, but they do not deep-merge settings, so Anyway Config provides a way to define a special top-level key for default values like this:
```ruby
config.anyway_config.default_environmental_key = "default"
```
After that, Anyway Config will start reading settings under the `"default"` key and then merge environmental settings into them.
```yml
default:
server: # This values will be loaded in all environments by default
host: localhost
port: 3002
staging:
server:
host: staging.example.com # This value will override the defaults when Rails.env.staging? is true
# port will be set to the value from the defaults — 3002
```
You can specify the lookup path for YAML files in one of the following ways:
- By setting `config.anyway_config.default_config_path` to a target directory path:
```ruby
config.anyway_config.default_config_path = "/etc/configs"
config.anyway_config.default_config_path = Rails.root.join("etc", "configs")
```
- By setting `config.anyway_config.default_config_path` to a Proc, which accepts a config name and returns the path:
```ruby
config.anyway_config.default_config_path = ->(name) { Rails.root.join("data", "configs", "#{name}.yml") }
```
- By overriding a specific config YML file path via the `_CONF` env variable, e.g., `MYCOOLGEM_CONF=path/to/cool.yml`
2) **Rails secrets**: `Rails.application.secrets.my_cool_gem` (if `secrets.yml` present).
```yml
# config/secrets.yml
development:
my_cool_gem:
port: 4444
```
3) **Rails credentials**: `Rails.application.credentials.my_cool_gem` (if supported):
```yml
my_cool_gem:
host: secret.host
```
**NOTE:** You can backport Rails 6 per-environment credentials to Rails 5.2 app using [this patch](https://gist.github.com/palkan/e27e4885535ff25753aefce45378e0cb).
4) **Environment variables**: `ENV['MYCOOLGEM_*']`.
See [environment variables](#environment-variables).
### Organizing configs
You can store application-level config classes in `app/configs` folder just like any other Rails entities.
However, in that case you won't be able to use them during the application initialization (i.e., in `config/**/*.rb` files).
Since that's a pretty common scenario, we provide a way to do that via a custom autoloader for `config/configs` folder.
That means, that you can put your configuration classes into `config/configs` folder, use them anywhere in your code without explicitly requiring them.
Consider an example: setting the Action Mailer hostname for Heroku review apps.
We have the following config to fetch the Heroku provided [metadata](https://devcenter.heroku.com/articles/dyno-metadata):
```ruby
# This data is provided by Heroku Dyno Metadadata add-on.
class HerokuConfig < Anyway::Config
attr_config :app_id, :app_name,
:dyno_id, :release_version,
:slug_commit
def hostname
"#{app_name}.herokuapp.com"
end
end
```
Then in `config/application.rb` you can do the following:
```ruby
config.action_mailer.default_url_options = {host: HerokuConfig.new.hostname}
```
You can configure the configs folder path:
```ruby
# The path must be relative to Rails root
config.anyway_config.autoload_static_config_path = "path/to/configs"
```
**NOTE:** Configs loaded from the `autoload_static_config_path` are **not reloaded in development**. We call them _static_. So, it makes sense to keep only configs necessary for initialization in this folder. Other configs, _dynamic_, could be stored in `app/configs`.
Or you can store everything in `app/configs` by setting `config.anyway_config.autoload_static_config_path = "app/configs"`.
**NOTE 2**: Since _static_ configs are loaded before initializers, it's not possible to use custom inflection Rules (usually defined in `config/initializers/inflections.rb`) to resolve constant names from files. If you rely on custom inflection rules (see, for example, [#81](https://github.com/palkan/anyway_config/issues/81)), we recommend configuration Rails inflector before initialization as well:
```ruby
# config/application.rb
# ...
require_relative "initializers/inflections"
module SomeApp
class Application < Rails::Application
# ...
end
end
```
### Generators
Anyway Config provides Rails generators to create new config classes:
- `rails g anyway:install`—creates an `ApplicationConfig` class (the base class for all config classes) and updates `.gitignore`
You can specify the static configs path via the `--configs-path` option:
```sh
rails g anyway:install --configs-path=config/settings
# or to keep everything in app/configs
rails g anyway:install --configs-path=app/configs
```
- `rails g anyway:config param1 param2 ...`—creates a named configuration class and optionally the corresponding YAML file; creates `application_config.rb` is missing.
The generator command for the Heroku example above would be:
```sh
$ rails g anyway:config heroku app_id app_name dyno_id release_version slug_commit
generate anyway:install
rails generate anyway:install
create config/configs/application_config.rb
append .gitignore
create config/configs/heroku_config.rb
Would you like to generate a heroku.yml file? (Y/n) n
```
You can also specify the `--app` option to put the newly created class into `app/configs` folder.
Alternatively, you can call `rails g anyway:app_config name param1 param2 ...`.
**NOTE:** The generated `ApplicationConfig` class uses a singleton pattern along with `delegate_missing_to` to re-use the same instance across the application. However, the delegation can lead to unexpected behaviour and break Anyway Config internals if you have attributes named as `Anyway::Config` class methods. See [#120](https://github.com/palkan/anyway_config/issues/120).
## Using with Ruby
The default data loading mechanism for non-Rails applications is the following (ordered by priority from low to high):
1) **YAML configuration files**: `./config/.yml`.
In pure Ruby apps, we also can load data under specific _environments_ (`test`, `development`, `production`, etc.).
If you want to enable this feature you must specify `Anyway::Settings.current_environment` variable for load config under specific environment.
```ruby
Anyway::Settings.current_environment = "development"
```
YAML files should be in this format:
```yml
development:
host: localhost
port: 3000
```
If `Anyway::Settings.current_environment` is missed we assume that the YAML contains values for a single environment:
```yml
host: localhost
port: 3000
```
`ERB` is supported if `erb` is loaded (thus, you need to call `require "erb"` somewhere before loading configuration).
You can specify the lookup path for YAML files in one of the following ways:
- By setting `Anyway::Settings.default_config_path` to a target directory path:
```ruby
Anyway::Settings.default_config_path = "/etc/configs"
```
- By setting `Anyway::Settings.default_config_path` to a Proc, which accepts a config name and returns the path:
```ruby
Anyway::Settings.default_config_path = ->(name) { Rails.root.join("data", "configs", "#{name}.yml") }
```
- By overriding a specific config YML file path via the `_CONF` env variable, e.g., `MYCOOLGEM_CONF=path/to/cool.yml`
2) **Environment variables**: `ENV['MYCOOLGEM_*']`.
See [environment variables](#environment-variables).
## Environment variables
Environmental variables for your config should start with your config name, upper-cased.
For example, if your config name is "mycoolgem", then the env var "MYCOOLGEM_PASSWORD" is used as `config.password`.
By default, environment variables are automatically type cast\*:
- `"True"`, `"t"` and `"yes"` to `true`;
- `"False"`, `"f"` and `"no"` to `false`;
- `"nil"` and `"null"` to `nil` (do you really need it?);
- `"123"` to 123 and `"3.14"` to 3.14.
\* See below for coercion customization.
*Anyway Config* supports nested (_hashed_) env variables—just separate keys with double-underscore.
For example, "MYCOOLGEM_OPTIONS__VERBOSE" is parsed as `config.options["verbose"]`.
Array values are also supported:
```ruby
# Suppose ENV["MYCOOLGEM_IDS"] = '1,2,3'
config.ids #=> [1,2,3]
```
If you want to provide a text-like env variable which contains commas then wrap it into quotes:
```ruby
MYCOOLGEM = "Nif-Nif, Naf-Naf and Nouf-Nouf"
```
## Type coercion
> 🆕 v2.2.0
You can define custom type coercion rules to convert string data to config values. To do that, use `.coerce_types` method:
```ruby
class CoolConfig < Anyway::Config
config_name :cool
attr_config port: 8080,
host: "localhost",
user: {name: "admin", password: "admin"}
coerce_types port: :string, user: {dob: :date}
end
ENV["COOL_USER__DOB"] = "1989-07-01"
config = CoolConfig.new
config.port == "8080" # Even though we defined the default value as int, it's converted into a string
config.user["dob"] == Date.new(1989, 7, 1) #=> true
```
Type coercion is especially useful to deal with array values:
```ruby
# To define an array type, provide a hash with two keys:
# - type — elements type
# - array: true — mark the parameter as array
coerce_types list: {type: :string, array: true}
```
You can use `type: nil` in case you don't want to coerce values, just convert a value into an array:
```ruby
# From AnyCable config (sentinels could be represented via strings or hashes)
coerce_types redis_sentinels: {type: nil, array: true}
```
It's also could be useful to explicitly define non-array types (to avoid confusion):
```ruby
coerce_types non_list: :string
```
Finally, it's possible to disable auto-casting for a particular config completely:
```ruby
class CoolConfig < Anyway::Config
attr_config port: 8080,
host: "localhost",
user: {name: "admin", password: "admin"}
disable_auto_cast!
end
ENV["COOL_PORT"] = "443"
CoolConfig.new.port == "443" #=> true
```
**IMPORTANT**: Values provided explicitly (via attribute writers) are not coerced. Coercion is only happening during the load phase.
The following types are supported out-of-the-box: `:string`, `:integer`, `:float`, `:date`, `:datetime`, `:uri`, `:boolean`.
You can use custom deserializers by passing a callable object instead of a type name:
```ruby
COLOR_TO_HEX = lambda do |raw|
case raw
when "red"
"#ff0000"
when "green"
"#00ff00"
when "blue"
"#0000ff"
end
end
class CoolConfig < Anyway::Config
attr_config :color
coerce_types color: COLOR_TO_HEX
end
CoolConfig.new({color: "red"}).color #=> "#ff0000"
```
## Local files
It's useful to have a personal, user-specific configuration in development, which extends the project-wide one.
We support this by looking at _local_ files when loading the configuration data:
- `.local.yml` files (next to\* the _global_ `.yml`)
- `config/credentials/local.yml.enc` (for Rails >= 6, generate it via `rails credentials:edit --environment local`).
\* If the YAML config path is not a default one (i.e., set via `_CONF`), we look up the local
config at this location, too.
Local configs are meant for using in development and only loaded if `Anyway::Settings.use_local_files` is `true` (which is true by default if `RACK_ENV` or `RAILS_ENV` env variable is equal to `"development"`).
**NOTE:** in Rails apps you can use `Rails.application.configuration.anyway_config.use_local_files`.
Don't forget to add `*.local.yml` (and `config/credentials/local.*`) to your `.gitignore`.
**NOTE:** local YAML configs for a Rails app must be environment-free (i.e., you shouldn't have top-level `development:` key).
## Data loaders
### Doppler integration
Anyway Config can pull configuration data from [Doppler](https://www.doppler.com/). All you need is to specify the `DOPPLER_TOKEN` environment variable with the **service token**, associated with the specific content (read more about [service tokens](https://docs.doppler.com/docs/service-tokens)).
You can also configure Doppler loader manually if needed:
```ruby
# Add loader
Anyway.loaders.append :Doppler, Anyway::Loaders::Doppler
# Configure API URL and token (defaults are shown)
Anyway::Loaders::Doppler.download_url = "https://api.doppler.com/v3/configs/config/secrets/download"
Anyway::Loaders::Doppler.token = ENV["DOPPLER_TOKEN"]
```
**NOTE:** You can opt-out from Doppler loader by specifying the`ANYWAY_CONFIG_DISABLE_DOPPLER=true` env var (in case you have the `DOPPLER_TOKEN` env var, but don't want to use it with Anyway Config).
### EJSON support
Anyway Config allows you to keep your configuration also in encrypted `.ejson` files. More information
about EJSON format you can read [here](https://github.com/Shopify/ejson).
Configuration will be loaded only if you have `ejson` executable in your PATH. Easiest way to do this - install `ejson` as a gem into project:
```ruby
# Gemfile
gem "ejson"
```
Loading order of configuration is next:
- `config/secrets.local.ejson` (see [Local files](#local-files) for more information)
- `config//secrets.ejson` (if you have any multi-environment setup, e.g Rails environments)
- `config/secrets.ejson`
Example of `config/secrets.ejson` file content for your `MyConfig`:
```json
{
"_public_key": "0843d33f0eee994adc66b939fe4ef569e4c97db84e238ff581934ee599e19d1a",
"my":
{
"_username": "root",
"password": "EJ[1:IC1d347GkxLXdZ0KrjGaY+ljlsK1BmK7CobFt6iOLgE=:Z55OYS1+On0xEBvxUaIOdv/mE2r6lp44:T7bE5hkAbazBnnH6M8bfVcv8TOQJAgUDQffEgw==]"
}
}
```
To debug any problems with loading configurations from `.ejson` files you can directly call `ejson decrypt`:
```sh
ejson decrypt config/secrets.ejson
```
You can customize the JSON namespace under which a loader searches for configuration via `loader_options`:
```ruby
class MyConfig < Anyway::Config
# To look under the key "foo" instead of the default key of "my"
loader_options ejson_namespace: "foo"
# Or to disable namespacing entirely, and instead search in the root object
loader_options ejson_namespace: false
end
```
### Custom loaders
You can provide your own data loaders or change the existing ones using the Loaders API (which is very similar to Rack middleware builder):
```ruby
# remove env loader => do not load params from ENV
Anyway.loaders.delete :env
# add custom loader before :env (it's better to keep the ENV loader the last one)
Anyway.loaders.insert_before :env, :my_loader, MyLoader
```
Loader is a _callable_ Ruby object (module/class responding to `.call` or lambda/proc), which `call` method
accepts the following keyword arguments:
```ruby
def call(
name:, # config name
env_prefix:, # prefix for env vars if any
config_path:, # path to YML config
local:, # true|false, whether to load local configuration
**options # custom options can be passed via Anyway::Config.loader_options example: "custom", option: "blah"
)
#=> must return Hash with configuration data
end
```
You can use `Anyway::Loaders::Base` as a base class for your loader and define a `#call` method.
For example, the [Chamber](https://github.com/thekompanee/chamber) loader could be written as follows:
```ruby
class ChamberConfigLoader < Anyway::Loaders::Base
def call(name:, **_opts)
Chamber.env.to_h[name] || {}
end
end
```
In order to support [source tracing](#tracing), you need to wrap the resulting Hash via the `#trace!` method with metadata:
```ruby
def call(name:, **_opts)
trace!(:chamber) do
Chamber.env.to_h[name] || {}
end
end
```
## Tracing
Since Anyway Config loads data from multiple source, it could be useful to know where a particular value came from.
Each `Anyway::Config` instance contains _tracing information_ which you can access via `#to_source_trace` method:
```ruby
conf = ExampleConfig.new
conf.to_source_trace
# returns the following hash
{
"host" => {value: "test.host", source: {type: :yml, path: "config/example.yml"}},
"user" => {
"name" => {value: "john", source: {type: :env, key: "EXAMPLE_USER__NAME"}},
"password" => {value: "root", source: {type: :credentials, store: "config/credentials/production.enc.yml"}}
},
"port" => {value: 9292, source: {type: :defaults}}
}
# if you change the value manually in your code,
# that would be reflected in the trace
conf.host = "anyway.host"
conf.to_source_trace["host"]
#=> {type: :user, called_from: "/path/to/caller.rb:15"}
```
You can disable tracing functionality by setting `Anyway::Settings.tracing_enabled = false` or `config.anyway_config.tracing_enabled = false` in Rails.
### Pretty print
You can use `pp` to print a formatted information about the config including the sources trace.
Example:
```ruby
pp CoolConfig.new
# # 3334 (type=load),
# host => "test.host" (type=yml path=./config/cool.yml),
# user =>
# name => "john" (type=env key=COOL_USER__NAME),
# password => "root" (type=yml path=./config/cool.yml)>
```
## Pattern matching
You can use config instances in Ruby 2.7+ pattern matching:
```ruby
case AWSConfig.new
in bucket:, region: "eu-west-1"
setup_eu_storage(bucket)
in bucket:, region: "us-east-1"
setup_us_storage(bucket)
end
```
If the attribute wasn't populated, the key won't be returned for pattern matching, i.e. you can do something line:
```ruby
aws_configured =
case AWSConfig.new
in access_key_id:, secret_access_key:
true
else
false
end
```
## Test helpers
We provide the `with_env` test helper to test code in the context of the specified environment variables values:
```ruby
describe HerokuConfig, type: :config do
subject { described_class.new }
specify do
# Ensure that the env vars are set to the specified
# values within the block and reset to the previous values
# outside of it.
with_env(
"HEROKU_APP_NAME" => "kin-web-staging",
"HEROKU_APP_ID" => "abc123",
"HEROKU_DYNO_ID" => "ddyy",
"HEROKU_RELEASE_VERSION" => "v0",
"HEROKU_SLUG_COMMIT" => "3e4d5a"
) do
is_expected.to have_attributes(
app_name: "kin-web-staging",
app_id: "abc123",
dyno_id: "ddyy",
release_version: "v0",
slug_commit: "3e4d5a"
)
end
end
end
```
If you want to delete the env var, pass `nil` as the value.
This helper is automatically included to RSpec if `RAILS_ENV` or `RACK_ENV` env variable is equal to "test". It's only available for the example with the tag `type: :config` or with the path `spec/configs/...`.
You can add it manually by requiring `"anyway/testing/helpers"` and including the `Anyway::Testing::Helpers` module (into RSpec configuration or Minitest test class).
## OptionParser integration
It's possible to use config as option parser (e.g., for CLI apps/libraries). It uses
[`optparse`](https://ruby-doc.org/stdlib-2.5.1/libdoc/optparse/rdoc/OptionParser.html) under the hood.
Example usage:
```ruby
class MyConfig < Anyway::Config
attr_config :host, :log_level, :concurrency, :debug, server_args: {}
# specify which options shouldn't be handled by option parser
ignore_options :server_args
# provide description for options
describe_options(
concurrency: "number of threads to use"
)
# mark some options as flag
flag_options :debug
# extend an option parser object (i.e. add banner or version/help handlers)
extend_options do |parser, config|
parser.banner = "mycli [options]"
parser.on("--server-args VALUE") do |value|
config.server_args = JSON.parse(value)
end
parser.on_tail "-h", "--help" do
puts parser
end
end
end
config = MyConfig.new
config.parse_options!(%w[--host localhost --port 3333 --log-level debug])
config.host # => "localhost"
config.port # => 3333
config.log_level # => "debug"
# Get the instance of OptionParser
config.option_parser
```
**NOTE:** values are automatically type cast using the same rules as for [environment variables](#environment-variables).
If you want to specify the type explicitly, you can do that using `describe_options`:
```ruby
describe_options(
# In this case, you should specify a hash with `type`
# and (optionally) `desc` keys
concurrency: {
desc: "number of threads to use",
type: String
}
)
```
## RBS support
Anyway Config comes with Ruby type signatures (RBS).
To use them with Steep, add `library "anyway_config"` to your Steepfile.
We also provide an API to generate a type signature for your config class:
```ruby
class MyGem::Config < Anyway::Config
attr_config :host, port: 8080, tags: [], debug: false
coerce_types host: :string, port: :integer,
tags: {type: :string, array: true}
required :host
end
```
Then calling `MyGem::Config.to_rbs` will return the following signature:
```rbs
module MyGem
interface _Config
def host: () -> String
def host=: (String) -> void
def port: () -> String?
def port=: (String) -> void
def tags: () -> Array[String]?
def tags=: (Array[String]) -> void
def debug: () -> bool
def debug?: () -> bool
def debug=: (bool) -> void
end
class Config < Anyway::Config
include _Config
end
end
```
### Handling `on_load`
When we use `on_load` callback with a block, we switch the context (via `instance_eval`), and we need to provide type hints for the type checker. Here is an example:
```ruby
class MyConfig < Anyway::Config
on_load do
# @type self : MyConfig
raise_validation_error("host is invalid") if host.start_with?("localhost")
end
end
```
Yeah, a lot of annotations 😞 Welcome to the type-safe world!
## Contributing
Bug reports and pull requests are welcome on GitHub at [https://github.com/palkan/anyway_config](https://github.com/palkan/anyway_config).
## License
The gem is available as open source under the terms of the [MIT License](http://opensource.org/licenses/MIT).