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lib/debug: add traceFnSeqN
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; }; }; } ```
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@ -148,6 +148,28 @@ rec {
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/* A combination of `traceVal` and `traceSeqN`. */
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traceValSeqN = traceValSeqNFn id;
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/* Trace the input and output of a function `f` named `name`,
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both down to `depth`.
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This is useful for adding around a function call,
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to see the before/after of values as they are transformed.
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Example:
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traceFnSeqN 2 "id" (x: x) { a.b.c = 3; }
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trace: { fn = "id"; from = { a.b = {…}; }; to = { a.b = {…}; }; }
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=> { a.b.c = 3; }
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*/
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traceFnSeqN = depth: name: f: v:
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let res = f v;
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in lib.traceSeqN
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(depth + 1)
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{
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fn = name;
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from = v;
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to = res;
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}
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res;
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# -- TESTING --
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@ -130,7 +130,7 @@ let
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assertMsg assertOneOf;
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inherit (self.debug) addErrorContextToAttrs traceIf traceVal traceValFn
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traceXMLVal traceXMLValMarked traceSeq traceSeqN traceValSeq
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traceValSeqFn traceValSeqN traceValSeqNFn traceShowVal
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traceValSeqFn traceValSeqN traceValSeqNFn traceFnSeqN traceShowVal
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traceShowValMarked showVal traceCall traceCall2 traceCall3
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traceValIfNot runTests testAllTrue traceCallXml attrNamesToStr;
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inherit (self.misc) maybeEnv defaultMergeArg defaultMerge foldArgs
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