envvar_fns: Generator functions for environment variable processors

Description

These functions return environment variable processor functions. Arguments to them are used to specify behaviors.

Usage

envvar_is(value, ...)
# S3 method for `NULL`
envvar_is(value, case_sensitive = FALSE, ...)
# S3 method for character
envvar_is(value, case_sensitive = FALSE, ...)
# S3 method for numeric
envvar_is(value, ...)
# S3 method for logical
envvar_is(value, case_sensitive = FALSE, ...)
envvar_eval(...)
envvar_eval_or_raw(...)
envvar_is_one_of(values, ...)
envvar_choice_of(values, default = NULL, ...)
envvar_is_true(...)
envvar_is_false(...)
envvar_is_set(...)
envvar_str_split(delim = ";", ...)

Value

A function to be used for processing an environment variable value

Arguments

value: A value to test against
...: Other arguments unused
case_sensitive: A logical value indicating whether string comparisons should be case-sensitive.
values: A list or vector of values to match
default: A default value used when a value cannot be coerced from the environment variable value
delim: A character value to use as a delimiter to use when splitting the environment variable value

Functions

envvar_is(): Test for equality with handlers for most atomic R types, performing sensible interpretation of environment variable values.
envvar_is(`NULL`): environment variable has value "null"
envvar_is(character): environment variable is equal to string value
envvar_is(numeric): environment variable is equal to string representation of numeric value
envvar_is(logical): environment variable is equal to string representation of logical value
envvar_eval(): Parse the environment variable value as R code and and evaluate it to produce a return value, emitting an error if the expression fails to parse or evaluate. This option is a sensible default for most R-specific environment variables, but may fail for string literals, and meaningful values that don't conform to R's syntax like "true" (see envvar_is_true()), "false" (see envvar_is_false()) or "null".
envvar_eval_or_raw(): Parse the environment variable value as R code and and evaluate it to produce a return value, or falling back to the raw value as a string if an error occurs.
envvar_is_one_of(): For meaningful string comparisons, check whether the environment variable is equal to some meaningful string. Optionally with case-sensitivity.
envvar_choice_of(): Check whether environment variable can be coerced to match one of values, returning the value if it matches or default otherwise.
envvar_is_true(): Test whether the environment variable is "truthy", that is whether it is case-insensitive "true" or 1
envvar_is_false(): Test whether the environment variable is "falsy", that is whether it is case-insensitive "false" or 0
envvar_is_set(): Test whether the environment variable is set. This is somewhat operating-system dependent, as not all operating systems can distinguish between an empty string as a value and an unset environment variable. For details see Sys.getenv()'s Details about its unset parameter.
envvar_str_split(): Interpret the environment variable as a delimited list of strings, such as PATH variables.