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55ea29fd8c
When having e.g. recursive attr-set, it cannot be printed which is
solved by Nix itself like this:
$ nix-instantiate --eval -E 'let a.b = 1; a.c = a; in builtins.trace a 1'
trace: { b = 1; c = <CYCLE>; }
1
However, `generators.toPretty` tries to evaluate something until it's
done which can result in a spurious `stack-overflow`-error:
$ nix-instantiate --eval -E 'with import <nixpkgs/lib>; generators.toPretty { } (mkOption { type = types.str; })'
error: stack overflow (possible infinite recursion)
Those attr-sets are in fact rather common, one example is shown above, a
`types.<type>`-declaration is such an example. By adding an optional
`depthLimit`-argument, `toPretty` will stop evaluating as soon as the
limit is reached:
$ nix-instantiate --eval -E 'with import ./Projects/nixpkgs-update-int/lib; generators.toPretty { depthLimit = 2; } (mkOption { type = types.str; })' |xargs -0 echo -e
"{
_type = \"option\";
type = {
_type = \"option-type\";
check = <function>;
deprecationMessage = null;
description = \"string\";
emptyValue = { };
functor = {
binOp = <unevaluated>;
name = <unevaluated>;
payload = <unevaluated>;
type = <unevaluated>;
wrapped = <unevaluated>;
};
getSubModules = null;
getSubOptions = <function>;
merge = <function>;
name = \"str\";
nestedTypes = { };
substSubModules = <function>;
typeMerge = <function>;
};
}"
Optionally, it's also possible to let `toPretty` throw an error if the
limit is exceeded.
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| .. | ||
| systems | ||
| tests | ||
| asserts.nix | ||
| attrsets.nix | ||
| cli.nix | ||
| customisation.nix | ||
| debug.nix | ||
| default.nix | ||
| deprecated.nix | ||
| fetchers.nix | ||
| filesystem.nix | ||
| fixed-points.nix | ||
| flake.nix | ||
| generators.nix | ||
| kernel.nix | ||
| licenses.nix | ||
| lists.nix | ||
| meta.nix | ||
| minver.nix | ||
| modules.nix | ||
| options.nix | ||
| sources.nix | ||
| strings-with-deps.nix | ||
| strings.nix | ||
| trivial.nix | ||
| types.nix | ||
| versions.nix | ||
| zip-int-bits.nix | ||