Description

Nix expressions usually work as you expect them to, but sometimes they do not. nix-log provides logging functionality you wish you had in the latter case without cluttering the former one.

nix-log wraps logging functionality already existing within nix and nixpkgs

By default, the logger will only print WARN level logs, unless a different log level value is set in NIX_LOG environment variable.

API

• trace - builtins.trace counterpart, which will only result in a log statement being printed in TRACE log level. Available as global lib.trace and as a trace "method" on a logger instance constructed via mkLog.

• trace' - builtins.trace counterpart, which will only result in a log statement being printed in TRACE log level. This variation takes an extra attribute-set parameter, which will be formatted using configured formatAttrs (builtins.toJSON by default) and appended to the log message. Available as global lib.trace' and as a trace' "method" on a logger instance constructed via mkLog.

• debug - prints a log statement in DEBUG log level or above. Available as global lib.debug and as a debug "method" on a logger instance constructed via mkLog.

• debug' - prints a log statement in DEBUG log level or above. This variation takes an extra attribute-set parameter, which will be formatted using configured formatAttrs (builtins.toJSON by default) and appended to the log message. Available as global lib.debug' and as a debug' "method" on a logger instance constructed via mkLog.

• info - nixpkgs.lib.info counterpart, which will only result in a log statement being printed in INFO log level. Available as global lib.info and as a info "method" on a logger instance constructed via mkLog.

• info' - nixpkgs.lib.info counterpart, which will only result in a log statement being printed in INFO log level. This variation takes an extra attribute-set parameter, which will be formatted using configured formatAttrs (builtins.toJSON by default) and appended to the log message. Available as global lib.info' and as a info' "method" on a logger instance constructed via mkLog.

• warn - nixpkgs.lib.warn counterpart, which will only result in a log statement being printed in WARN log level. Available as global lib.warn and as a warn "method" on a logger instance constructed via mkLog.

• warn' - nixpkgs.lib.warn counterpart, which will only result in a log statement being printed in WARN log level. This variation takes an extra attribute-set parameter, which will be formatted using configured formatAttrs (builtins.toJSON by default) and appended to the log message. Available as global lib.warn' and as a warn' "method" on a logger instance constructed via mkLog.

• warnIf - nixpkgs.lib.warnIf counterpart, which will only result in a log statement being printed in WARN log level. Available as global lib.warnIf and as a warnIf "method" on a logger instance constructed via mkLog.

• mkLog - constructs a new logger

• logLevel - an attribute-set of supported log level "enums"