rconfig {rconfig}

Manage R Configuration at the Command Line

Description

Manage R configuration using files (YAML, JSON, INI, TXT) JSON strings and command line arguments. Command line arguments can be used to provide commands and to override configuration. Period-separated command line flags are parsed as hierarchical lists.

Usage

rconfig(
  file = NULL,
  list = NULL,
  eval = NULL,
  flatten = NULL,
  debug = NULL,
  sep = NULL,
  sub = NULL,
  ...
)

value(x, ...)

## Default S3 method:
value(x, default = NULL, coerce = TRUE, ...)

command(x, ...)

## Default S3 method:
command(x, ...)

Arguments

file

Configuration file name or URL (NULL to not use this configuration file to override the default behavior). Can be a vector, in which case each element will be treated as a configuration file, and these will be parsed and applied in the order they appear.

list

A list to override other configs (NULL to not use this list to override the default behavior). This argument is treated as a single configuration (as opposed to file). List names need to be unique.

eval

Logical, evaluate !expr R expressions.

flatten

Logical, should config contain nested lists or should results be flat, i.e. a$b$c to flattened into the key a.b.c; like unlist() but returning a list and preserving the value types.

debug

Logical, when debug mode is on the configuration source information are attached as the "trace" attribute.

sep

Character, separator for text files.

sub

Logical, substitute environment variables (see Details).

...

Other arguments passed to file parsers: yaml::yaml.load_file() for YAML, jsonlite::fromJSON() for JSON, and utils::read.table() for text files.

x

A list, e.g. the rconfig() output.

default

A default value to be used when a configuration entry is not set.

coerce

Logical, should values of x coerced to the same type as ⁠storage.mode(default).⁠

Details

Merges configuration after parsing files, JSON strings, and command line arguments. Note that rconfig only considers trailing command line arguments from Rscript. rconfig differentiates verb/noun syntax, where verbs are sub-commands following the R script file name and preceding the command line flags (starting with - or ⁠--⁠). Configurations are merged in the following order (key-values from last element override previous values for the same key):

1. R_RCONFIG_FILE value or "rconfig.yml" from working directory

2. JSON strings (following -j and --json flags) and files (following -f and --file flags) provided as command line arguments are parsed and applied in the order they appear (key-value pairs are separated by space, only atomic values considered, i.e. file name or string) for each flag, but multiple file/JSON flags are accepted in sequence

3. the remaining other command line arguments, that can be sub-commands or command line flags (starting with - or ⁠--⁠), period-separated command line flags are parsed as hierarchical lists (key-value pairs are separated by space, flags must begin with ⁠--⁠, values are treated as vectors when contain spaces, i.e. ⁠--key 1 2 3⁠)

4. configuration from the file argument (one or multiple files, parsed and applied in the order they appear)

5. configuration from the list argument

The following environment variables and options can be set to modify the default behavior:

• R_RCONFIG_FILE: location of the default configuration file, it is assumed to be rconfig.yml in the current working directory. The file name can be an URL or it can can be missing.

• R_RCONFIG_EVAL: coerced to logical, indicating whether R expressions starting with !expr should be evaluated in the namespace environment for the base package (overrides the value of getOption("rconfig.eval")). When not set the value assumed is TRUE.

• R_RCONFIG_SUB: coerced to logical, indicating whether environment variables should be substituted (overrides the value of getOption("rconfig.sub")). When not set the value assumed is TRUE.

• R_RCONFIG_FLATTEN: coerced to logical, flatten nested lists, i.e. a$b$c becomes the key a.b.c (overrides the value of getOption("rconfig.flatten")). When not set the value assumed is FALSE.

• R_RCONFIG_DEBUG: coerced to logical, to turn on debug mode (overrides the value of getOption("rconfig.debug")). When not set the value assumed is FALSE.

• R_RCONFIG_SEP: separator for text file parser, (overrides the value of getOption("rconfig.sep")). When not set the value assumed is "=".

When the configuration is a file (file name can also be a URL), it can be nested structure in JSON or YAML format. Other text files are parsed using the separator (R_RCONFIG_SEP or getOption("rconfig.sep")) and period-separated keys are parsed as hierarchical lists (i.e. a.b.c=12 is treated as a$b$c = 12) by default.

When the configuration is a file or a JSON string, values starting with !expr will be evaluated depending on the settings R_RCONFIG_EVAL and getOption("rconfig.eval"). E.g. ⁠cores: !expr getOption("mc.cores")⁠, etc.

The rconfig package interprets 3 kinds of substitution patterns:

• environment variables (⁠${VALUE}⁠): these variables are already present when the configurations is read from the calling environment or from .Renviron file in the project specific or home folder, set variables can be null or not-null

• R global variables (⁠@{VALUE}⁠): the rconfig package looks for variables in the global environment at the time of configuration evaluation, however, expressions are not evaluated (unlike the !expr option for values)

• configuration values (⁠#{VALUE}⁠): the configuration level variables are evaluated last, thus these values can refer to existing keys that are already substituted

For additional details see the package website at https://github.com/analythium/rconfig.

Value

The configuration value (a named list, or an empty list). When debug mode is on, the "trace" attribute traces the merged configurations. The value() method returns the value of a given argument or the default value when it is not found (i.e. NULL). The command() method returns a character vector with command line sub-commands (can be of length 0).

See Also

utils::modifyList()

Examples

cfile <- function(file) {
    system.file("examples", file, package = "rconfig")
}

rconfig::rconfig()

rconfig::rconfig(
    file = cfile("rconfig.yml"))

rconfig::rconfig(
    file = c(cfile("rconfig.json"),
             cfile("rconfig-prod.txt")),
    list = list(user = list(name = "Jack")))

rconfig::rconfig(
    file = c(cfile("rconfig.json"),
             cfile("rconfig-prod.txt")),
    list = list(user = list(name = "Jack")),
    flatten = TRUE)

CONFIG <- rconfig::rconfig(
    file = cfile("rconfig.yml"))
value(CONFIG$cores, 2L)   # set to 1L
value(CONFIG$test, FALSE) # unset