ronfig (version 0.0.7)

load_config: Load configuration

Description

Load a user defined configuration from file. By default (i.e. when as_is = FALSE), load_config() requires inputs to be given as uniquely-named lists. It first parses the configuration file looking for a 'default' entry. With no additional arguments this will be returned as a list to the user. If the user specifies an additional list to consider (via the config argument) then this list is layered on top (using utils::modifyList()).

list_config() returns the names of (possible) configurations within the given file. It corresponds to names(load_config(filename, as_is = TRUE)).

Usage

load_config(filename, config, crates, ..., as_is = FALSE, default = "default")
list_config(filename)

Value

If as_is = FALSE (default), load_config() returns a list contain entries corresponding to the chosen config.

If as_is = TRUE and no config value specified, a list of all entries in the evaluated configuration file. If a config value is specified, this entry is pulled from the list and returned.

list_config() returns a character vector of (possible) configurations within the given file. It corresponds to names(load_config(filename, as_is = TRUE)).

Arguments

filename

Configuration file to read from.

config

If as_is = FALSE, name of entry in configuration file to layer on top of 'default'.

If as_is = TRUE then, if specified, this entry will be selected from the configuration and returned.

crates

A list of carrier::crate objects which are used to inject functions in to the environment where the configuration file will be evaluated.

...

Not currently used.

as_is

Should the configuration file be read in as is, without layering on top of the default config?

Defaults to FALSE.

default

The default configuration to use. Not used if as_is = FALSE.

Details

Configuration files can be specified using a reduced subset of base R. By default this is restricted to the following operators and functions:

• <-, =, +, -, *, :

• $, [, [[

• $<-, [<-, [[<-

• c()

• as.Date()

• array(), matrix()

• list(), data.frame()

• Sys.Date(), Sys.time()

• seq(), sequence(), and seq_len()

• file.path()

• modifyList()

We also enable a convenience function, cc, which automatically quotes input to save typing.

Users can also inject their own functions in to the evaluation environment by supplying a list of crates as an additional argument.

Examples

# load the example configuration
file <- system.file("config.R", package = "ronfig")
cat(readChar(file, file.info(file)$size))

# default configuration
str(load_config(file))

# debug configuration
str(load_config(file, "debug"))

# forecast configuration
str(load_config(file, "forecast"))

# Injecting crated function
f <- tempfile()
cat("default <- list(a=mean(1:10))", file = f)

# will fail as mean() not available
tryCatch(with(load_config(f), a), error = conditionMessage)

# will work if we inject crated mean
crate <- carrier::crate(function(x) mean(x))
with(load_config(f, crates = list(mean = crate)), a)

unlink(f)