let lib = import ./default.nix; inherit (builtins) trace attrNamesToStr isAttrs isFunction isList isInt isString head substring attrNames; 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 ${a}" v); traceVal = if builtins ? trace then x: (builtins.trace x x) else x: x; traceXMLVal = if builtins ? trace then x: (builtins.trace (builtins.toXML x) x) else x: x; # this can help debug your code as well - designed to not produce thousands of lines traceShowVal = x : trace (showVal x) x; traceShowValMarked = str: x: trace (str + showVal x) x; attrNamesToStr = a : lib.concatStringsSep "; " (map (x : "${x}=") (attrNames a)); showVal = 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 element is: ${showVal (head x)}" else if x == true then "x is boolean true" else if x == false then "x is boolean false" else if x == null then "x is null" else if isInt x then "x is an integer `${toString x}'" else if isString x then "x is a string `${substring 0 50 x}...'" else "x is probably a path `${substring 0 50 (toString x)}'"; # trace the arguments passed to function and its result traceCall = n : f : a : let t = n2 : x : traceShowValMarked "${n} ${n2}:" x; in t "result" (f (t "arg 1" a)); traceCall2 = n : f : a : b : let t = n2 : x : traceShowValMarked "${n} ${n2}:" x; in t "result" (f (t "arg 1" a) (t "arg 2" b)); traceCall3 = n : f : a : b : c : let t = n2 : x : traceShowValMarked "${n} ${n2}:" x; in t "result" (f (t "arg 1" a) (t "arg 2" b) (t "arg 3" c)); traceValIfNot = c: x: if c x then true else trace (showVal x) false; /* Evaluate a set of tests. A test is an attribute set {expr, expected}, denoting an expression and its expected result. The result is a list of failed tests, each represented as {name, expected, actual}, denoting the attribute name of the failing test and its expected and actual results. Used for regression testing of the functions in lib; see tests.nix for an example. */ runTests = tests: lib.concatLists (lib.attrValues (lib.mapAttrs (name: test: if ! lib.eqStrict test.expr test.expected then [ { inherit name; expected = test.expected; result = test.expr; } ] else [] ) tests)); }