465 lines
7.5 KiB
Nix
465 lines
7.5 KiB
Nix
/**
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Collection of functions useful for debugging
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broken nix expressions.
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* `trace`-like functions take two values, print
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the first to stderr and return the second.
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* `traceVal`-like functions take one argument
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which both printed and returned.
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* `traceSeq`-like functions fully evaluate their
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traced value before printing (not just to “weak
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head normal form” like trace does by default).
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* Functions that end in `-Fn` take an additional
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function as their first argument, which is applied
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to the traced value before it is printed.
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*/
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{ lib }:
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let
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inherit (lib)
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isList
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isAttrs
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substring
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attrValues
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concatLists
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const
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elem
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generators
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id
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mapAttrs
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trace;
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in
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rec {
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# -- TRACING --
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/**
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Conditionally trace the supplied message, based on a predicate.
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# Inputs
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`pred`
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: Predicate to check
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`msg`
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: Message that should be traced
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`x`
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: Value to return
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# Type
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```
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traceIf :: bool -> string -> a -> a
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```
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# Examples
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:::{.example}
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## `lib.debug.traceIf` usage example
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```nix
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traceIf true "hello" 3
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trace: hello
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=> 3
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```
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:::
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*/
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traceIf =
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pred:
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msg:
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x: if pred then trace msg x else x;
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/**
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Trace the supplied value after applying a function to it, and
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return the original value.
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# Inputs
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`f`
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: Function to apply
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`x`
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: Value to trace and return
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# Type
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```
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traceValFn :: (a -> b) -> a -> a
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```
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# Examples
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:::{.example}
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## `lib.debug.traceValFn` usage example
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```nix
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traceValFn (v: "mystring ${v}") "foo"
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trace: mystring foo
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=> "foo"
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```
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:::
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*/
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traceValFn =
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f:
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x: trace (f x) x;
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/**
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Trace the supplied value and return it.
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# Inputs
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`x`
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: Value to trace and return
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# Type
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```
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traceVal :: a -> a
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```
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# Examples
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:::{.example}
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## `lib.debug.traceVal` usage example
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```nix
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traceVal 42
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# trace: 42
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=> 42
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```
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:::
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*/
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traceVal = traceValFn id;
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/**
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`builtins.trace`, but the value is `builtins.deepSeq`ed first.
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# Inputs
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`x`
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: The value to trace
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`y`
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: The value to return
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# Type
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```
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traceSeq :: a -> b -> b
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```
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# Examples
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:::{.example}
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## `lib.debug.traceSeq` usage example
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```nix
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trace { a.b.c = 3; } null
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trace: { a = <CODE>; }
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=> null
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traceSeq { a.b.c = 3; } null
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trace: { a = { b = { c = 3; }; }; }
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=> null
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```
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:::
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*/
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traceSeq =
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x:
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y: trace (builtins.deepSeq x x) y;
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/**
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Like `traceSeq`, but only evaluate down to depth n.
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This is very useful because lots of `traceSeq` usages
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lead to an infinite recursion.
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# Inputs
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`depth`
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: 1\. Function argument
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`x`
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: 2\. Function argument
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`y`
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: 3\. Function argument
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# Type
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```
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traceSeqN :: Int -> a -> b -> b
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```
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# Examples
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:::{.example}
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## `lib.debug.traceSeqN` usage example
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```nix
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traceSeqN 2 { a.b.c = 3; } null
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trace: { a = { b = {…}; }; }
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=> null
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```
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:::
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*/
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traceSeqN = depth: x: y:
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let snip = v: if isList v then noQuotes "[…]" v
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else if isAttrs v then noQuotes "{…}" v
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else v;
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noQuotes = str: v: { __pretty = const str; val = v; };
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modify = n: fn: v: if (n == 0) then fn v
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else if isList v then map (modify (n - 1) fn) v
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else if isAttrs v then mapAttrs
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(const (modify (n - 1) fn)) v
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else v;
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in trace (generators.toPretty { allowPrettyValues = true; }
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(modify depth snip x)) y;
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/**
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A combination of `traceVal` and `traceSeq` that applies a
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provided function to the value to be traced after `deepSeq`ing
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it.
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# Inputs
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`f`
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: Function to apply
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`v`
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: Value to trace
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*/
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traceValSeqFn =
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f:
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v: traceValFn f (builtins.deepSeq v v);
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/**
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A combination of `traceVal` and `traceSeq`.
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# Inputs
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`v`
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: Value to trace
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*/
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traceValSeq = traceValSeqFn id;
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/**
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A combination of `traceVal` and `traceSeqN` that applies a
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provided function to the value to be traced.
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# Inputs
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`f`
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: Function to apply
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`depth`
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: 2\. Function argument
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`v`
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: Value to trace
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*/
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traceValSeqNFn =
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f:
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depth:
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v: traceSeqN depth (f v) v;
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/**
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A combination of `traceVal` and `traceSeqN`.
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# Inputs
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`depth`
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: 1\. Function argument
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`v`
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: Value to trace
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*/
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traceValSeqN = traceValSeqNFn id;
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/**
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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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# Inputs
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`depth`
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: 1\. Function argument
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`name`
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: 2\. Function argument
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`f`
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: 3\. Function argument
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`v`
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: 4\. Function argument
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# Examples
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:::{.example}
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## `lib.debug.traceFnSeqN` usage example
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```nix
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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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:::
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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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/**
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Evaluates a set of tests.
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A test is an attribute set `{expr, expected}`,
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denoting an expression and its expected result.
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The result is a `list` of __failed tests__, each represented as
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`{name, expected, result}`,
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- expected
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- What was passed as `expected`
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- result
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- The actual `result` of the test
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Used for regression testing of the functions in lib; see
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tests.nix for more examples.
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Important: Only attributes that start with `test` are executed.
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- If you want to run only a subset of the tests add the attribute `tests = ["testName"];`
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# Inputs
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`tests`
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: Tests to run
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# Type
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```
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runTests :: {
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tests = [ String ];
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${testName} :: {
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expr :: a;
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expected :: a;
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};
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}
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->
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[
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{
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name :: String;
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expected :: a;
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result :: a;
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}
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]
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```
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# Examples
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:::{.example}
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## `lib.debug.runTests` usage example
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```nix
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runTests {
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testAndOk = {
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expr = lib.and true false;
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expected = false;
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};
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testAndFail = {
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expr = lib.and true false;
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expected = true;
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};
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}
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->
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[
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{
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name = "testAndFail";
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expected = true;
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result = false;
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}
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]
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```
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:::
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*/
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runTests =
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tests: concatLists (attrValues (mapAttrs (name: test:
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let testsToRun = if tests ? tests then tests.tests else [];
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in if (substring 0 4 name == "test" || elem name testsToRun)
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&& ((testsToRun == []) || elem name tests.tests)
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&& (test.expr != test.expected)
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then [ { inherit name; expected = test.expected; result = test.expr; } ]
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else [] ) tests));
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/**
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Create a test assuming that list elements are `true`.
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# Inputs
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`expr`
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: 1\. Function argument
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# Examples
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:::{.example}
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## `lib.debug.testAllTrue` usage example
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```nix
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{ testX = allTrue [ true ]; }
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```
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:::
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*/
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testAllTrue = expr: { inherit expr; expected = map (x: true) expr; };
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}
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