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persist_config
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0.1.0
Persists configurations from given files at compile time.
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lib/persist_config.ex
defmodule PersistConfig do
@moduledoc ~S"""
Persists the configurations from a list of files during compilation. Also puts
the current application name in a module attribute and provides a `get_env`
macro for concise configuration value retrieval.
## Installation
Add `persist_config` to your list of dependencies in `mix.exs`. Also include
the required configuration files in the package definition of `mix.exs`:
```elixir
def project do
[
app: :your_app,
...
deps: deps(),
package: package(),
...
]
end
...
def deps do
[
{:persist_config, "~> 0.4", runtime: false}
]
end
...
defp package do
[
files: ["lib", "mix.exs", "README*", "config/persist*.exs"],
maintainers: [...],
licenses: [...],
links: %{...}
]
end
```
## Usage
`use PersistConfig` supports the following options:
- `:app` - module attribute to hold the current application name,
defaults to `:app`
- `:files` - wildcard paths, defaults to `["config/persist*.exs"]`
Option `:files` lists the files whose configurations will be persisted.
Importing these files in `config/config.exs` is __needless__:
```elixir
import Config
import_config "persist_this_config.exs"
```
Each entry represents a wildcard path relative to the root. If the list of
paths is or ends up being empty, no configurations are persisted.
When your project is used as a dependency, this package will allow the
specified configuration files to have their configurations persisted during
compilation.
For example, you may configure some path to read an external file and you want
to still read that __very__ file when your app is a dependency (without and
despite any path configuration in the parent app). To achieve this:
__1.__ Use a module attribute as a __constant__:
```elixir
use PersistConfig
...
@path get_env(:path)
...
words = File.read!(@path)
```
__2.__ Create a config file named, say, `config/persist_path.exs`:
```elixir
import Config
config :words_cache, path: "#{File.cwd!()}/assets/words.txt"
```
__3.__ In `mix.exs`, specify a package definition like this:
```elixir
defp package do
[
files: [... "assets/words.txt", "config/persist*.exs"],
maintainers: [...],
licenses: [...],
links: %{...}
]
end
```
__Note:__ Such configurations are __global__ and should otherwise be [avoided](https://hexdocs.pm/elixir/library-guidelines.html#avoid-application-configuration).
#### Example 1
```elixir
use PersistConfig, files: ["config/persist_path.exs"]
...
@all_env Application.get_all_env(@app)
@path get_env(:path)
```
#### Example 2
```elixir
use PersistConfig, app: :my_app
...
@my_attr Application.get_env(@my_app, :my_attr)
```
#### Example 3
```elixir
use PersistConfig
...
defp log?, do: get_env(:log?, true)
```
"""
@doc """
Persists the configurations from a list of files during compilation. Also puts
the current application name in a module attribute and provides a `get_env`
macro for concise configuration value retrieval.
`use PersistConfig` supports the following options:
- `:app` - module attribute to hold the current application name,
defaults to `:app`
- `:files` - wildcard paths, defaults to `["config/persist*.exs"]`
"""
defmacro __using__(options \\ []) do
app = options[:app] || :app
files = options[:files] || ["config/persist*.exs"]
files = files |> Enum.map(&Path.wildcard/1) |> List.flatten()
quote bind_quoted: [app: app, files: files], unquote: true do
import unquote(__MODULE__)
Enum.each(files, fn file ->
file |> Config.Reader.read!() |> Application.put_all_env()
@external_resource Path.expand(file)
end)
Module.put_attribute(__MODULE__, app, Mix.Project.config()[:app])
end
end
@doc """
Returns the value for `key` in in the current application's environment.
If the configuration parameter does not exist, returns the `default` value.
"""
@doc since: "0.4.0"
defmacro get_env(key, default \\ nil) do
app = Mix.Project.config()[:app]
quote bind_quoted: [app: app, key: key, default: default] do
:application.get_env(app, key, default)
end
end
end