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Make rootFS's showPath() render the paths from the original accessors

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This makes paths in error messages behave similar to lazy-trees,
e.g. instead of store paths like

       error: attribute 'foobar' missing
       at /nix/store/ddzfiipzqlrh3gnprmqbadnsnrxsmc9i-source/machine/configuration.nix:209:7:
          208|
          209|       pkgs.foobar
             |       ^
          210|     ];

you now get

       error: attribute 'foobar' missing
       at /home/eelco/Misc/eelco-configurations/machine/configuration.nix:209:7:
          208|
          209|       pkgs.foobar
             |       ^
          210|     ];
This commit is contained in:
Eelco Dolstra 2025-02-20 01:09:49 +01:00
parent 5506428e67
commit b28bc7ae64
10 changed files with 122 additions and 22 deletions
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32
src/libexpr/eval.cc
View file

@ -14,6 +14,7 @@
#include "profiles.hh"
#include "print.hh"
#include "filtering-source-accessor.hh"
#include "forwarding-source-accessor.hh"
#include "memory-source-accessor.hh"
#include "gc-small-vector.hh"
#include "url.hh"
@ -180,6 +181,34 @@ static Symbol getName(const AttrName & name, EvalState & state, Env & env)
}
}
struct PathDisplaySourceAccessor : ForwardingSourceAccessor
{
ref<EvalState::StorePathAccessors> storePathAccessors;
PathDisplaySourceAccessor(
ref<SourceAccessor> next,
ref<EvalState::StorePathAccessors> storePathAccessors)
: ForwardingSourceAccessor(next)
, storePathAccessors(storePathAccessors)
{
}
std::string showPath(const CanonPath & path) override
{
/* Find the accessor that produced `path`, if any, and use it
to render a more informative path
(e.g. `«github:foo/bar»/flake.nix` rather than
`/nix/store/hash.../flake.nix`). */
auto ub = storePathAccessors->upper_bound(path);
if (ub != storePathAccessors->begin())
ub--;
if (ub != storePathAccessors->end() && path.isWithin(ub->first))
return ub->second->showPath(path.removePrefix(ub->first));
else
return next->showPath(path);
}
};
static constexpr size_t BASE_ENV_SIZE = 128;
EvalState::EvalState(
@ -245,6 +274,7 @@ EvalState::EvalState(
}
, repair(NoRepair)
, emptyBindings(0)
, storePathAccessors(make_ref<StorePathAccessors>())
, rootFS(
({
/* In pure eval mode, we provide a filesystem that only
@ -270,6 +300,8 @@ EvalState::EvalState(
: makeUnionSourceAccessor({accessor, storeFS});
}
accessor = make_ref<PathDisplaySourceAccessor>(accessor, storePathAccessors);
/* Apply access control if needed. */
if (settings.restrictEval || settings.pureEval)
accessor = AllowListSourceAccessor::create(accessor, {},