configurator-pg: Reduced parser for configurator-ng config files

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This module provides a simplified and updated interface to the configuration file format of configurator and configurator-ng. Its aim is primarily to allow updating programs that depend on configurator-ng to new versions of GHC without changing the configuration file format.

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Versions,,,,,,, 0.2.0, 0.2.1, 0.2.2, 0.2.3, 0.2.4, 0.2.5, 0.2.5, 0.2.6, 0.2.7, 0.2.8, 0.2.9, 0.2.10
Change log
Dependencies base (>=4.9 && <4.15), containers (>= && <0.7), megaparsec (>=7.0.0 && <9.1), protolude (>=0.1.10 && <0.4), scientific (>= && <0.4), text (>= && <1.3) [details]
License BSD-3-Clause
Copyright Copyright 2011 MailRank, Inc. Copyright 2011-2014 Bryan O'Sullivan Copyright 2015-2016 Leon P Smith Copyright 2019 Robert Vollmert
Author Robert Vollmert
Category Configuration, Data
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Uploaded by vollmert at 2020-10-26T10:43:33Z


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Readme for configurator-pg-0.2.5

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What is this?

This is a simplified version of the resting configurator-ng, aimed particularly to offer users of configurator-ng such as PostgREST an easy path to migrate to a package that compiles with modern GHC versions and that continues to read existing configuration files.


configurator-pg skips some of configurator-ng's features, and changes the API in other places:


The original configurator-ng is due to MailRank, Inc., Bryan O'Sullivan and Leon P Smith.

The low-level parser (Data.Configurator.Syntax) was initially mostly unchanged, but has since been rewritten with Megaparsec for better error messages. The evaluation (Data.Configurator.Load) is still close to the original. The high-level parser (Data.Configurator.Parser) is original.

File format

In short, the file format supports:

The format is more fully documented in the packages configurator and configurator-ng.

Here's an example:

# listen address
hostname = "localhost"
port = 8000

logdir = "$(HOME)/logs"
logfile = "$(logdir)/log.txt"
loglevels = [1, 4, 5]

users {
  alice = ""
  bob   = ""

# passwords.txt might contain
#   alice = "12345"
#   bob   = "sesame"
passwords {
  import "secrets/passwords.txt"


The following code can be used to parse the example above.

import Data.Configurator

data Settings = Settings
  { hostname  :: Text
  , port      :: Int
  , logfile   :: Maybe FilePath
  , loglevels :: Maybe [Int]
  , users     :: [(Text, Text)]
  , passwords :: [(Text, Text)]

settingsParser :: Parser Config Settings
settingsParser =
    <$> required "hostname" string
    <*> (Maybe.withDefault 1234 <$> optional "port" int)
    <*> optional "logfile" (pack <$> string)
    <*> optional "loglevels" (list int)
    <*> subassocs "users" string
    <*> subassocs "passwords" string

loadSettings :: IO Settings
loadSettings = do
  cfg <- load "settings.cfg"
  case runParser settingsParser cfg of
    Left err       -> die $ "reading config: " <> err
    Right settings -> return settings

Though note that for no apparent reason, subassocs returns the full key, whence the parsed list of users will be

    [ ("users.alice", "")
    , ("users.bob", "")