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feat(libstore): make cycle errors more verbose

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Co-Authored-By: Milan Hauth <milahu@gmail.com>
This commit is contained in:
Bernardo Meurer Costa 2025-10-11 18:42:18 +00:00
parent bef3c37cb2
commit d44c8c8b69
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6 changed files with 574 additions and 42 deletions
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181
src/libstore/unix/build/derivation-builder.cc
View file

@ -45,6 +45,7 @@
#include "store-config-private.hh"
#include "build/derivation-check.hh"
#include "build/find-cycles.hh"
#if NIX_WITH_AWS_AUTH
# include "nix/store/aws-creds.hh"
@ -1473,43 +1474,100 @@ SingleDrvOutputs DerivationBuilderImpl::registerOutputs()
outputStats.insert_or_assign(outputName, std::move(st));
}
auto sortedOutputNames = topoSort(
outputsToSort,
{[&](const std::string & name) {
auto orifu = get(outputReferencesIfUnregistered, name);
if (!orifu)
throw BuildError(
BuildResult::Failure::OutputRejected,
"no output reference for '%s' in build of '%s'",
name,
store.printStorePath(drvPath));
return std::visit(
overloaded{
/* Since we'll use the already installed versions of these, we
can treat them as leaves and ignore any references they
have. */
[&](const AlreadyRegistered &) { return StringSet{}; },
[&](const PerhapsNeedToRegister & refs) {
StringSet referencedOutputs;
/* FIXME build inverted map up front so no quadratic waste here */
for (auto & r : refs.refs)
for (auto & [o, p] : scratchOutputs)
if (r == p)
referencedOutputs.insert(o);
return referencedOutputs;
std::vector<std::string> sortedOutputNames;
try {
sortedOutputNames = topoSort(
outputsToSort,
{[&](const std::string & name) {
auto orifu = get(outputReferencesIfUnregistered, name);
if (!orifu)
throw BuildError(
BuildResult::Failure::OutputRejected,
"no output reference for '%s' in build of '%s'",
name,
store.printStorePath(drvPath));
return std::visit(
overloaded{
/* Since we'll use the already installed versions of these, we
can treat them as leaves and ignore any references they
have. */
[&](const AlreadyRegistered &) { return StringSet{}; },
[&](const PerhapsNeedToRegister & refs) {
StringSet referencedOutputs;
/* FIXME build inverted map up front so no quadratic waste here */
for (auto & r : refs.refs)
for (auto & [o, p] : scratchOutputs)
if (r == p)
referencedOutputs.insert(o);
return referencedOutputs;
},
},
},
*orifu);
}},
{[&](const std::string & path, const std::string & parent) {
// TODO with more -vvvv also show the temporary paths for manual inspection.
return BuildError(
BuildResult::Failure::OutputRejected,
"cycle detected in build of '%s' in the references of output '%s' from output '%s'",
store.printStorePath(drvPath),
path,
parent);
}});
*orifu);
}},
{[&](const std::string & path, const std::string & parent) {
// TODO with more -vvvv also show the temporary paths for manual inspection.
return BuildError(
BuildResult::Failure::OutputRejected,
"cycle detected in build of '%s' in the references of output '%s' from output '%s'",
store.printStorePath(drvPath),
path,
parent);
}});
} catch (std::exception & e) {
debug("cycle detected during topoSort, analyzing for detailed error report");
// Scan all outputs for cycle edges with exact file paths
StoreCycleEdgeVec edges;
for (auto & [outputName, _] : drv.outputs) {
auto scratchOutput = get(scratchOutputs, outputName);
if (!scratchOutput)
continue;
auto actualPath = realPathInSandbox(store.printStorePath(*scratchOutput));
debug("scanning output '%s' at path '%s' for cycle edges", outputName, actualPath);
scanForCycleEdges(actualPath, referenceablePaths, edges);
}
if (edges.empty()) {
debug("no detailed cycle edges found, re-throwing original error");
throw;
}
debug("found %lu cycle edges, transforming to connected paths", edges.size());
// Transform individual edges into connected multi-edges (paths)
StoreCycleEdgeVec multiedges;
transformEdgesToMultiedges(edges, multiedges);
// Build detailed error message
std::string cycleDetails = fmt("Detailed cycle analysis found %d cycle path(s):", multiedges.size());
for (size_t i = 0; i < multiedges.size(); i++) {
auto & multiedge = multiedges[i];
cycleDetails += fmt("\n\nCycle %d:", i + 1);
for (auto & file : multiedge) {
cycleDetails += fmt("\n → %s", file);
}
}
cycleDetails +=
fmt("\n\nThis means there are circular references between output files.\n"
"The build cannot proceed because the outputs reference each other.");
// Add hint with temp paths for debugging
if (settings.keepFailed || verbosity >= lvlDebug) {
cycleDetails +=
fmt("\n\nNote: Build outputs are kept for inspection.\n"
"You can examine the files listed above to understand the cycle.");
}
// Throw new error with original message + cycle details
BuildError * buildErr = dynamic_cast<BuildError *>(&e);
std::string originalMsg = buildErr ? std::string(buildErr->msg()) : std::string(e.what());
throw BuildError(BuildResult::Failure::OutputRejected, "%s\n\n%s", originalMsg, cycleDetails);
}
std::reverse(sortedOutputNames.begin(), sortedOutputNames.end());
@ -1848,12 +1906,61 @@ SingleDrvOutputs DerivationBuilderImpl::registerOutputs()
/* Register each output path as valid, and register the sets of
paths referenced by each of them. If there are cycles in the
outputs, this will fail. */
{
try {
ValidPathInfos infos2;
for (auto & [outputName, newInfo] : infos) {
infos2.insert_or_assign(newInfo.path, newInfo);
}
store.registerValidPaths(infos2);
} catch (BuildError & e) {
debug("cycle detected during registerValidPaths, analyzing for detailed error report");
// Scan all outputs for cycle edges with exact file paths
StoreCycleEdgeVec edges;
for (auto & [outputName, newInfo] : infos) {
auto actualPath = store.toRealPath(store.printStorePath(newInfo.path));
debug("scanning registered output '%s' at path '%s' for cycle edges", outputName, actualPath);
scanForCycleEdges(actualPath, referenceablePaths, edges);
}
if (edges.empty()) {
debug("no detailed cycle edges found, re-throwing original error");
throw;
}
debug("found %lu cycle edges, transforming to connected paths", edges.size());
// Transform individual edges into connected multi-edges (paths)
StoreCycleEdgeVec multiedges;
transformEdgesToMultiedges(edges, multiedges);
// Build detailed error message
std::string cycleDetails = fmt("Detailed cycle analysis found %d cycle path(s):", multiedges.size());
for (size_t i = 0; i < multiedges.size(); i++) {
auto & multiedge = multiedges[i];
cycleDetails += fmt("\n\nCycle %d:", i + 1);
for (auto & file : multiedge) {
cycleDetails += fmt("\n → %s", file);
}
}
cycleDetails +=
fmt("\n\nThis means there are circular references between output files.\n"
"The build cannot proceed because the outputs reference each other.");
// Add hint with temp paths for debugging
if (settings.keepFailed || verbosity >= lvlDebug) {
cycleDetails +=
fmt("\n\nNote: Build outputs were kept for inspection.\n"
"You can examine the files listed above to understand the cycle.");
}
// Throw new error with original message + cycle details
BuildError * buildErr = dynamic_cast<BuildError *>(&e);
std::string originalMsg = buildErr ? std::string(buildErr->msg()) : std::string(e.what());
throw BuildError(BuildResult::Failure::OutputRejected, "%s\n\n%s", originalMsg, cycleDetails);
}
/* If we made it this far, we are sure the output matches the