mirror of
https://github.com/NixOS/nixpkgs.git
synced 2024-12-15 10:12:58 +00:00
61852b7faa
all of these have been deprecated and raising warnings since 18.09. it's about time we actually made good on "will be removed in the next release".
254 lines
6.0 KiB
Nix
254 lines
6.0 KiB
Nix
/* 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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isInt
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attrNames
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isList
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isAttrs
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substring
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addErrorContext
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attrValues
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concatLists
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concatStringsSep
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const
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elem
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generators
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head
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id
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isDerivation
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isFunction
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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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/* Conditionally trace the supplied message, based on a predicate.
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Type: traceIf :: bool -> string -> a -> a
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Example:
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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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traceIf =
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# Predicate to check
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pred:
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# Message that should be traced
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msg:
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# Value to return
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x: if pred then trace msg x else x;
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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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Type: traceValFn :: (a -> b) -> a -> a
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Example:
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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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traceValFn =
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# Function to apply
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f:
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# Value to trace and return
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x: trace (f x) x;
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/* Trace the supplied value and return it.
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Type: traceVal :: a -> a
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Example:
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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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traceVal = traceValFn id;
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/* `builtins.trace`, but the value is `builtins.deepSeq`ed first.
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Type: traceSeq :: a -> b -> b
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Example:
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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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traceSeq =
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# The value to trace
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x:
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# The value to return
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y: trace (builtins.deepSeq x x) y;
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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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Example:
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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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Type: traceSeqN :: Int -> a -> b -> b
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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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/* 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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*/
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traceValSeqFn =
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# Function to apply
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f:
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# Value to trace
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v: traceValFn f (builtins.deepSeq v v);
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/* A combination of `traceVal` and `traceSeq`. */
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traceValSeq = traceValSeqFn id;
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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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traceValSeqNFn =
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# Function to apply
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f:
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depth:
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# Value to trace
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v: traceSeqN depth (f v) v;
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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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/* 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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Example:
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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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Type:
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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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runTests =
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# Tests to run
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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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/* Create a test assuming that list elements are `true`.
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Example:
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{ testX = allTrue [ true ]; }
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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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