mirror of
https://github.com/NixOS/nixpkgs.git
synced 2024-12-20 21:17:46 +00:00
41e13149f7
Immensely helpful when you want to see the changes a function makes to
its value as it passes through.
Example:
```
$ nix-instantiate --strict --eval -E '(with import ./lib; traceFnSeqN 2 "id" (x: x) { a.b.c = 3; })'
trace: {
fn = "id";
from = {
a = {
b = {…};
};
};
to = {
a = {
b = {…};
};
};
}
{ a = { b = { c = 3; }; }; }
```
292 lines
8.8 KiB
Nix
292 lines
8.8 KiB
Nix
/* Collection of functions useful for debugging
|
|
broken nix expressions.
|
|
|
|
* `trace`-like functions take two values, print
|
|
the first to stderr and return the second.
|
|
* `traceVal`-like functions take one argument
|
|
which both printed and returned.
|
|
* `traceSeq`-like functions fully evaluate their
|
|
traced value before printing (not just to “weak
|
|
head normal form” like trace does by default).
|
|
* Functions that end in `-Fn` take an additional
|
|
function as their first argument, which is applied
|
|
to the traced value before it is printed.
|
|
*/
|
|
{ lib }:
|
|
let
|
|
inherit (lib)
|
|
isInt
|
|
attrNames
|
|
isList
|
|
isAttrs
|
|
substring
|
|
addErrorContext
|
|
attrValues
|
|
concatLists
|
|
concatStringsSep
|
|
const
|
|
elem
|
|
generators
|
|
head
|
|
id
|
|
isDerivation
|
|
isFunction
|
|
mapAttrs
|
|
trace;
|
|
in
|
|
|
|
rec {
|
|
|
|
# -- TRACING --
|
|
|
|
/* Conditionally trace the supplied message, based on a predicate.
|
|
|
|
Type: traceIf :: bool -> string -> a -> a
|
|
|
|
Example:
|
|
traceIf true "hello" 3
|
|
trace: hello
|
|
=> 3
|
|
*/
|
|
traceIf =
|
|
# Predicate to check
|
|
pred:
|
|
# Message that should be traced
|
|
msg:
|
|
# Value to return
|
|
x: if pred then trace msg x else x;
|
|
|
|
/* Trace the supplied value after applying a function to it, and
|
|
return the original value.
|
|
|
|
Type: traceValFn :: (a -> b) -> a -> a
|
|
|
|
Example:
|
|
traceValFn (v: "mystring ${v}") "foo"
|
|
trace: mystring foo
|
|
=> "foo"
|
|
*/
|
|
traceValFn =
|
|
# Function to apply
|
|
f:
|
|
# Value to trace and return
|
|
x: trace (f x) x;
|
|
|
|
/* Trace the supplied value and return it.
|
|
|
|
Type: traceVal :: a -> a
|
|
|
|
Example:
|
|
traceVal 42
|
|
# trace: 42
|
|
=> 42
|
|
*/
|
|
traceVal = traceValFn id;
|
|
|
|
/* `builtins.trace`, but the value is `builtins.deepSeq`ed first.
|
|
|
|
Type: traceSeq :: a -> b -> b
|
|
|
|
Example:
|
|
trace { a.b.c = 3; } null
|
|
trace: { a = <CODE>; }
|
|
=> null
|
|
traceSeq { a.b.c = 3; } null
|
|
trace: { a = { b = { c = 3; }; }; }
|
|
=> null
|
|
*/
|
|
traceSeq =
|
|
# The value to trace
|
|
x:
|
|
# The value to return
|
|
y: trace (builtins.deepSeq x x) y;
|
|
|
|
/* Like `traceSeq`, but only evaluate down to depth n.
|
|
This is very useful because lots of `traceSeq` usages
|
|
lead to an infinite recursion.
|
|
|
|
Example:
|
|
traceSeqN 2 { a.b.c = 3; } null
|
|
trace: { a = { b = {…}; }; }
|
|
=> null
|
|
*/
|
|
traceSeqN = depth: x: y:
|
|
let snip = v: if isList v then noQuotes "[…]" v
|
|
else if isAttrs v then noQuotes "{…}" v
|
|
else v;
|
|
noQuotes = str: v: { __pretty = const str; val = v; };
|
|
modify = n: fn: v: if (n == 0) then fn v
|
|
else if isList v then map (modify (n - 1) fn) v
|
|
else if isAttrs v then mapAttrs
|
|
(const (modify (n - 1) fn)) v
|
|
else v;
|
|
in trace (generators.toPretty { allowPrettyValues = true; }
|
|
(modify depth snip x)) y;
|
|
|
|
/* A combination of `traceVal` and `traceSeq` that applies a
|
|
provided function to the value to be traced after `deepSeq`ing
|
|
it.
|
|
*/
|
|
traceValSeqFn =
|
|
# Function to apply
|
|
f:
|
|
# Value to trace
|
|
v: traceValFn f (builtins.deepSeq v v);
|
|
|
|
/* A combination of `traceVal` and `traceSeq`. */
|
|
traceValSeq = traceValSeqFn id;
|
|
|
|
/* A combination of `traceVal` and `traceSeqN` that applies a
|
|
provided function to the value to be traced. */
|
|
traceValSeqNFn =
|
|
# Function to apply
|
|
f:
|
|
depth:
|
|
# Value to trace
|
|
v: traceSeqN depth (f v) v;
|
|
|
|
/* A combination of `traceVal` and `traceSeqN`. */
|
|
traceValSeqN = traceValSeqNFn id;
|
|
|
|
/* Trace the input and output of a function `f` named `name`,
|
|
both down to `depth`.
|
|
|
|
This is useful for adding around a function call,
|
|
to see the before/after of values as they are transformed.
|
|
|
|
Example:
|
|
traceFnSeqN 2 "id" (x: x) { a.b.c = 3; }
|
|
trace: { fn = "id"; from = { a.b = {…}; }; to = { a.b = {…}; }; }
|
|
=> { a.b.c = 3; }
|
|
*/
|
|
traceFnSeqN = depth: name: f: v:
|
|
let res = f v;
|
|
in lib.traceSeqN
|
|
(depth + 1)
|
|
{
|
|
fn = name;
|
|
from = v;
|
|
to = res;
|
|
}
|
|
res;
|
|
|
|
|
|
# -- TESTING --
|
|
|
|
/* 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. Only tests having names starting with
|
|
"test" are run.
|
|
|
|
Add attr { tests = ["testName"]; } to run these tests only.
|
|
*/
|
|
runTests =
|
|
# Tests to run
|
|
tests: concatLists (attrValues (mapAttrs (name: test:
|
|
let testsToRun = if tests ? tests then tests.tests else [];
|
|
in if (substring 0 4 name == "test" || elem name testsToRun)
|
|
&& ((testsToRun == []) || elem name tests.tests)
|
|
&& (test.expr != test.expected)
|
|
|
|
then [ { inherit name; expected = test.expected; result = test.expr; } ]
|
|
else [] ) tests));
|
|
|
|
/* Create a test assuming that list elements are `true`.
|
|
|
|
Example:
|
|
{ testX = allTrue [ true ]; }
|
|
*/
|
|
testAllTrue = expr: { inherit expr; expected = map (x: true) expr; };
|
|
|
|
|
|
# -- DEPRECATED --
|
|
|
|
traceShowVal = x: trace (showVal x) x;
|
|
traceShowValMarked = str: x: trace (str + showVal x) x;
|
|
|
|
attrNamesToStr = a:
|
|
trace ( "Warning: `attrNamesToStr` is deprecated "
|
|
+ "and will be removed in the next release. "
|
|
+ "Please use more specific concatenation "
|
|
+ "for your uses (`lib.concat(Map)StringsSep`)." )
|
|
(concatStringsSep "; " (map (x: "${x}=") (attrNames a)));
|
|
|
|
showVal =
|
|
trace ( "Warning: `showVal` is deprecated "
|
|
+ "and will be removed in the next release, "
|
|
+ "please use `traceSeqN`" )
|
|
(let
|
|
modify = v:
|
|
let pr = f: { __pretty = f; val = v; };
|
|
in if isDerivation v then pr
|
|
(drv: "<δ:${drv.name}:${concatStringsSep ","
|
|
(attrNames drv)}>")
|
|
else if [] == v then pr (const "[]")
|
|
else if isList v then pr (l: "[ ${go (head l)}, … ]")
|
|
else if isAttrs v then pr
|
|
(a: "{ ${ concatStringsSep ", " (attrNames a)} }")
|
|
else v;
|
|
go = x: generators.toPretty
|
|
{ allowPrettyValues = true; }
|
|
(modify x);
|
|
in go);
|
|
|
|
traceXMLVal = x:
|
|
trace ( "Warning: `traceXMLVal` is deprecated "
|
|
+ "and will be removed in the next release. "
|
|
+ "Please use `traceValFn builtins.toXML`." )
|
|
(trace (builtins.toXML x) x);
|
|
traceXMLValMarked = str: x:
|
|
trace ( "Warning: `traceXMLValMarked` is deprecated "
|
|
+ "and will be removed in the next release. "
|
|
+ "Please use `traceValFn (x: str + builtins.toXML x)`." )
|
|
(trace (str + builtins.toXML x) x);
|
|
|
|
# trace the arguments passed to function and its result
|
|
# maybe rewrite these functions in a traceCallXml like style. Then one function is enough
|
|
traceCall = n: f: a: let t = n2: x: traceShowValMarked "${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:
|
|
trace ( "Warning: `traceValIfNot` is deprecated "
|
|
+ "and will be removed in the next release. "
|
|
+ "Please use `if/then/else` and `traceValSeq 1`.")
|
|
(if c x then true else traceSeq (showVal x) false);
|
|
|
|
|
|
addErrorContextToAttrs = attrs:
|
|
trace ( "Warning: `addErrorContextToAttrs` is deprecated "
|
|
+ "and will be removed in the next release. "
|
|
+ "Please use `builtins.addErrorContext` directly." )
|
|
(mapAttrs (a: v: addErrorContext "while evaluating ${a}" v) attrs);
|
|
|
|
# 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:
|
|
trace ( "Warning: `traceCallXml` is deprecated "
|
|
+ "and will be removed in the next release. "
|
|
+ "Please complain if you use the function regularly." )
|
|
(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 ${builtins.toXML (builtins.seq arg arg)}" (expr arg)
|
|
)
|
|
else
|
|
let r = builtins.seq expr expr;
|
|
in trace "${str}\n result:\n${builtins.toXML r}" r
|
|
));
|
|
}
|