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lib/debug: traceSeqN & traceSeqValN

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Strict trace functions that only go down to a specified depth.
Handy to get a better picture and prevent infinite recursions.
This commit is contained in:
Profpatsch 2017-06-06 22:42:30 +02:00
parent b1ffe5e4c0
commit feb8cbdc38
1 changed files with 24 additions and 0 deletions
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lib/debug.nix
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@ -20,8 +20,32 @@ rec {
traceXMLValMarked = str: x: trace (str + builtins.toXML x) x; traceXMLValMarked = str: x: trace (str + builtins.toXML x) x;
# strict trace functions (traced structure is fully evaluated and printed) # strict trace functions (traced structure is fully evaluated and printed)
/* `builtins.trace`, but the value is `builtins.deepSeq`ed first. */
traceSeq = x: y: trace (builtins.deepSeq x x) y; traceSeq = x: y: trace (builtins.deepSeq x x) y;
/* Like `traceSeq`, but only down to depth n.
* This is very useful because lots of `traceSeq` usages
* lead to an infinite recursion.
*/
traceSeqN = depth: x: y: with lib;
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;
/* `traceSeq`, but the same value is traced and returned */
traceValSeq = v: traceVal (builtins.deepSeq v v); traceValSeq = v: traceVal (builtins.deepSeq v v);
/* `traceValSeq` but with fixed depth */
traceValSeqN = depth: v: traceSeqN depth v v;
# this can help debug your code as well - designed to not produce thousands of lines # this can help debug your code as well - designed to not produce thousands of lines
traceShowVal = x: trace (showVal x) x; traceShowVal = x: trace (showVal x) x;