let lib = import ./default.nix; in rec { # Wrapper aroung the primop `addErrorContext', which shouldn't used # directly. It evaluates and returns `val', but if an evaluation # error occurs, the text in `msg' is added to the error context # (stack trace) printed by Nix. addErrorContext = if builtins ? addErrorContext then builtins.addErrorContext else msg: val: val; addErrorContextToAttrs = lib.mapAttrs (a : v : lib.addErrorContext "while evaluating ${a}" v); debugVal = if builtins ? trace then x: (builtins.trace x x) else x: x; debugXMLVal = if builtins ? trace then x: (builtins.trace (builtins.toXML x) x) else x: x; # this can help debug your code as well - designed to not produce thousands of lines traceWhatis = x : __trace (whatis x) x; traceMarked = str: x: __trace (str + (whatis x)) x; attrNamesToStr = a : lib.concatStringsSep "; " (map (x : "${x}=") (__attrNames a)); whatis = x : if (__isAttrs x) then if (x ? outPath) then "x is a derivation, name ${if x ? name then x.name else ""}, { ${attrNamesToStr x} }" else "x is attr set { ${attrNamesToStr x} }" else if (__isFunction x) then "x is a function" else if (x == []) then "x is an empty list" else if (__isList x) then "x is a list, first item is : ${whatis (__head x)}" else if (x == true) then "x is boolean true" else if (x == false) then "x is boolean false" else if (x == null) then "x is null" else "x is probably a string starting, starting characters: ${__substring 0 50 x}.."; # trace the arguments passed to function and its result traceCall = n : f : a : let t = n2 : x : traceMarked "${n} ${n2}:" x; in t "result" (f (t "arg 1" a)); traceCall2 = n : f : a : b : let t = n2 : x : traceMarked "${n} ${n2}:" x; in t "result" (f (t "arg 1" a) (t "arg 2" b)); traceCall3 = n : f : a : b : c : let t = n2 : x : traceMarked "${n} ${n2}:" x; in t "result" (f (t "arg 1" a) (t "arg 2" b) (t "arg 3" c)); }