| Safe Haskell | None |
|---|---|
| Language | Haskell2010 |
Data.Yaml.Config
Contents
Description
Functionality for using YAML as configuration files
In particular, merging environment variables with yaml values
loadYamlSettings is a high-level API for loading YAML and merging environment variables.
A yaml value of _env:ENV_VAR:default will lookup the environment variable ENV_VAR.
On a historical note, this code was taken directly from the yesod web framework's configuration module.
Synopsis
- loadYamlSettings :: FromJSON settings => [FilePath] -> [Value] -> EnvUsage -> IO settings
- loadYamlSettingsArgs :: FromJSON settings => [Value] -> EnvUsage -> IO settings
- data EnvUsage
- ignoreEnv :: EnvUsage
- useEnv :: EnvUsage
- requireEnv :: EnvUsage
- useCustomEnv :: HashMap Text Text -> EnvUsage
- requireCustomEnv :: HashMap Text Text -> EnvUsage
- applyCurrentEnv :: Bool -> Value -> IO Value
- getCurrentEnv :: IO (HashMap Text Text)
- applyEnvValue :: Bool -> HashMap Text Text -> Value -> Value
High-level
Arguments
| :: FromJSON settings | |
| => [FilePath] | run time config files to use, earlier files have precedence |
| -> [Value] | any other values to use, usually from compile time config. overridden by files |
| -> EnvUsage | |
| -> IO settings |
Load the settings from the following three sources:
- Run time config files
- Run time environment variables
- The default compile time config file
For example, to load up settings from config/foo.yaml and allow overriding
from the actual environment, you can use:
loadYamlSettings ["config/foo.yaml"] [] useEnv
Since: 0.8.16
Arguments
| :: FromJSON settings | |
| => [Value] | any other values to use, usually from compile time config. overridden by files |
| -> EnvUsage | use environment variables |
| -> IO settings |
Same as loadYamlSettings, but get the list of runtime config files from
the command line arguments.
Since: 0.8.17
EnvUsage
Defines how we want to use the environment variables when loading a config file. Use the smart constructors provided by this module.
Since: 0.8.16
ignoreEnv :: EnvUsage Source #
Do not use any environment variables, instead relying on defaults values in the config file.
Since: 0.8.16
Use environment variables when available, otherwise use defaults.
Since: 0.8.16
requireEnv :: EnvUsage Source #
Do not use default values from the config file, but instead take all overrides from the environment. If a value is missing, loading the file will throw an exception.
Since: 0.8.16
useCustomEnv :: HashMap Text Text -> EnvUsage Source #
Same as useEnv, but instead of the actual environment, use the provided
HashMap as the environment.
Since: 0.8.16
requireCustomEnv :: HashMap Text Text -> EnvUsage Source #
Same as requireEnv, but instead of the actual environment, use the
provided HashMap as the environment.
Since: 0.8.16
Lower level
A convenience wrapper around applyEnvValue and getCurrentEnv
Since: 0.8.16
getCurrentEnv :: IO (HashMap Text Text) Source #
Get the actual environment as a HashMap from Text to Text.
Since: 0.8.16
Arguments
| :: Bool | require an environment variable to be present? |
| -> HashMap Text Text | |
| -> Value | |
| -> Value |
Override environment variable placeholders in the given Value with
values from the environment.
If the first argument is True, then all placeholders _must_ be provided by
the actual environment. Otherwise, default values from the Value will be
used.
Since: 0.8.16