Development.Shake.Config

A module for parsing and using config files in a Shake build system. Config files consist of variable bindings, for example:

# This is my Config file
HEADERS_DIR = /path/to/dir
CFLAGS = -g -I${HEADERS_DIR}
CFLAGS = $CFLAGS -O2
include extra/file.cfg

This defines the variable HEADERS_DIR (equal to /path/to/dir), and CFLAGS (equal to -g -I/path/to/dir -O2), and also includes the configuration statements in the file extra/file.cfg. The full lexical syntax for configuration files is defined here: https://ninja-build.org/manual.html#_lexical_syntax. The use of Ninja file syntax is due to convenience and the desire to reuse an externally-defined specification (but the choice of configuration language is mostly arbitrary).

To use the configuration file either use readConfigFile to parse the configuration file and use the values directly, or usingConfigFile and getConfig to track the configuration values, so they become build dependencies.

Documentation

readConfigFile :: FilePath -> IO (HashMap String String)

Read a config file, returning a list of the variables and their bindings. Config files use the Ninja lexical syntax: https://ninja-build.org/manual.html#_lexical_syntax

readConfigFileWithEnv :: [(String, String)] -> FilePath -> IO (HashMap String String)

Read a config file with an initial environment, returning a list of the variables and their bindings. Config files use the Ninja lexical syntax: https://ninja-build.org/manual.html#_lexical_syntax

usingConfigFile :: FilePath -> Rules ()

Specify the file to use with getConfig.

usingConfig :: HashMap String String -> Rules ()

Specify the values to use with getConfig, generally prefer usingConfigFile unless you also need access to the values of variables outside Action.

getConfig :: String -> Action (Maybe String)

Obtain the value of a configuration variable, returns Nothing to indicate the variable has no binding. Any build system using getConfig must call either usingConfigFile or usingConfig. The getConfig function will introduce a dependency on the configuration variable (but not the whole configuration file), and if the configuration variable changes, the rule will be rerun. As an example:

usingConfigFile "myconfiguration.cfg"
"*.o" %> \out -> do
    cflags <- getConfig "CFLAGS"
    cmd "gcc" [out -<.> "c"] (fromMaybe "" cflags)

getConfigKeys :: Action [String]

Obtain the configuration keys. Any build system using getConfigKeys must call either usingConfigFile or usingConfig. The getConfigKeys function will introduce a dependency on the configuration keys (but not the whole configuration file), and if the configuration keys change, the rule will be rerun. Usually use as part of an action. As an example:

usingConfigFile "myconfiguration.cfg"
action $ need =<< getConfigKeys