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Use std::variant to enforce BuildResult invariants

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There is now a clean separation between successful and failing build
results.
This commit is contained in:
John Ericson 2025-09-23 18:09:56 -04:00
parent 43550e8edb
commit e731c43eae
29 changed files with 568 additions and 397 deletions
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60
src/libstore/serve-protocol.cc
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@ -16,32 +16,62 @@ namespace nix {
BuildResult ServeProto::Serialise<BuildResult>::read(const StoreDirConfig & store, ServeProto::ReadConn conn)
{
BuildResult status;
status.status = (BuildResult::Status) readInt(conn.from);
conn.from >> status.errorMsg;
BuildResult::Success success;
BuildResult::Failure failure;
auto rawStatus = readInt(conn.from);
conn.from >> failure.errorMsg;
if (GET_PROTOCOL_MINOR(conn.version) >= 3)
conn.from >> status.timesBuilt >> status.isNonDeterministic >> status.startTime >> status.stopTime;
conn.from >> status.timesBuilt >> failure.isNonDeterministic >> status.startTime >> status.stopTime;
if (GET_PROTOCOL_MINOR(conn.version) >= 6) {
auto builtOutputs = ServeProto::Serialise<DrvOutputs>::read(store, conn);
for (auto && [output, realisation] : builtOutputs)
status.builtOutputs.insert_or_assign(std::move(output.outputName), std::move(realisation));
success.builtOutputs.insert_or_assign(std::move(output.outputName), std::move(realisation));
}
if (BuildResult::Success::statusIs(rawStatus)) {
success.status = static_cast<BuildResult::Success::Status>(rawStatus);
status.inner = std::move(success);
} else {
failure.status = static_cast<BuildResult::Failure::Status>(rawStatus);
status.inner = std::move(failure);
}
return status;
}
void ServeProto::Serialise<BuildResult>::write(
const StoreDirConfig & store, ServeProto::WriteConn conn, const BuildResult & status)
const StoreDirConfig & store, ServeProto::WriteConn conn, const BuildResult & res)
{
conn.to << status.status << status.errorMsg;
if (GET_PROTOCOL_MINOR(conn.version) >= 3)
conn.to << status.timesBuilt << status.isNonDeterministic << status.startTime << status.stopTime;
if (GET_PROTOCOL_MINOR(conn.version) >= 6) {
DrvOutputs builtOutputs;
for (auto & [output, realisation] : status.builtOutputs)
builtOutputs.insert_or_assign(realisation.id, realisation);
ServeProto::write(store, conn, builtOutputs);
}
/* The protocol predates the use of sum types (std::variant) to
separate the success or failure cases. As such, it transits some
success- or failure-only fields in both cases. This helper
function helps support this: in each case, we just pass the old
default value for the fields that don't exist in that case. */
auto common = [&](std::string_view errorMsg, bool isNonDeterministic, const auto & builtOutputs) {
conn.to << errorMsg;
if (GET_PROTOCOL_MINOR(conn.version) >= 3)
conn.to << res.timesBuilt << isNonDeterministic << res.startTime << res.stopTime;
if (GET_PROTOCOL_MINOR(conn.version) >= 6) {
DrvOutputs builtOutputsFullKey;
for (auto & [output, realisation] : builtOutputs)
builtOutputsFullKey.insert_or_assign(realisation.id, realisation);
ServeProto::write(store, conn, builtOutputsFullKey);
}
};
std::visit(
overloaded{
[&](const BuildResult::Failure & failure) {
conn.to << failure.status;
common(failure.errorMsg, failure.isNonDeterministic, decltype(BuildResult::Success::builtOutputs){});
},
[&](const BuildResult::Success & success) {
conn.to << success.status;
common(/*errorMsg=*/"", /*isNonDeterministic=*/false, success.builtOutputs);
},
},
res.inner);
}
UnkeyedValidPathInfo ServeProto::Serialise<UnkeyedValidPathInfo>::read(const StoreDirConfig & store, ReadConn conn)