nixpkgs/pkgs/lib/debug.nix

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let lib = import ./default.nix;
inherit (builtins) trace attrNamesToStr isAttrs isFunction isList isInt
isString isBool head substring attrNames;
inherit (lib) all id mapAttrsFlatten;
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 ${a}" v);
traceVal = if builtins ? trace then x: (builtins.trace x x) else x: x;
traceXMLVal = if builtins ? trace then x: (builtins.trace (builtins.toXML x) x) else x: x;
traceXMLValMarked = str: if builtins ? trace then x: (builtins.trace ( str + builtins.toXML x) x) else x: x;
# this can help debug your code as well - designed to not produce thousands of lines
traceShowVal = x : trace (showVal x) x;
traceShowValMarked = str: x: trace (str + showVal x) x;
attrNamesToStr = a : lib.concatStringsSep "; " (map (x : "${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 "<no name>"}, { ${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
# maybe rewrite these functions in a traceCallXml like style. Then one function is enough
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));
# evaluate everything once so that errors will occur earlier
# hacky: traverse attrs by adding a dummy
# ignores functions (should this behavior change?) See strictf
#
# Note: This should be a primop! Something like seq of haskell would be nice to
# have as well. It's used fore debugging only anyway
strict = x :
let
traverse = x :
if isString x then true
else if isAttrs x then
if x ? outPath then true
else all id (mapAttrsFlatten (n: traverse) x)
else if isList x then
all id (map traverse x)
else if isBool x then true
else if isFunction x then true
else if isInt x then true
else if x == null then true
else true; # a (store) path?
in if (traverse x) then x else throw "else never reached";
# example: (traceCallXml "myfun" id 3) will output something like
# calling myfun arg 1: 3 result: 3
# this forces deep evaluation of all arguments and the result!
# note: if result doesn't evaluate you'll get no trace at all (FIXME)
# args should be printed in any case
traceCallXml = a:
if !isInt a then
traceCallXml 1 "calling ${a}\n"
else
let nr = a;
in (str: expr:
if isFunction expr then
(arg:
traceCallXml (builtins.add 1 nr) "${str}\n arg ${builtins.toString nr} is \n ${builtins.toXML (strict arg)}" (expr arg)
)
else
let r = strict expr;
in builtins.trace "${str}\n result:\n${builtins.toXML r}" r
);
}