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Merge pull request #12809 from DeterminateSystems/handle-failed-cached-values

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Throw CachedEvalError if a cached value exists but has type "failed"
This commit is contained in:
Eelco Dolstra 2025-04-01 11:49:09 +02:00 • committed by GitHub
commit db70061f0b
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2 changed files with 27 additions and 18 deletions
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35
src/libexpr/eval-cache.cc
View file

@ -418,6 +418,14 @@ Value & AttrCursor::getValue()
return **_value;
}
void AttrCursor::fetchCachedValue()
{
if (!cachedValue)
cachedValue = root->db->getAttr(getKey());
if (cachedValue && std::get_if<failed_t>(&cachedValue->second) && parent)
throw CachedEvalError(parent->first, parent->second);
}
std::vector<Symbol> AttrCursor::getAttrPath() const
{
if (parent) {
@ -494,14 +502,13 @@ Suggestions AttrCursor::getSuggestionsForAttr(Symbol name)
std::shared_ptr<AttrCursor> AttrCursor::maybeGetAttr(Symbol name)
{
if (root->db) {
if (!cachedValue)
cachedValue = root->db->getAttr(getKey());
fetchCachedValue();
if (cachedValue) {
if (auto attrs = std::get_if<std::vector<Symbol>>(&cachedValue->second)) {
for (auto & attr : *attrs)
if (attr == name)
return std::make_shared<AttrCursor>(root, std::make_pair(shared_from_this(), attr));
return std::make_shared<AttrCursor>(root, std::make_pair(ref(shared_from_this()), attr));
return nullptr;
} else if (std::get_if<placeholder_t>(&cachedValue->second)) {
auto attr = root->db->getAttr({cachedValue->first, name});
@ -512,7 +519,7 @@ std::shared_ptr<AttrCursor> AttrCursor::maybeGetAttr(Symbol name)
throw CachedEvalError(ref(shared_from_this()), name);
else
return std::make_shared<AttrCursor>(root,
std::make_pair(shared_from_this(), name), nullptr, std::move(attr));
std::make_pair(ref(shared_from_this()), name), nullptr, std::move(attr));
}
// Incomplete attrset, so need to fall thru and
// evaluate to see whether 'name' exists
@ -547,7 +554,7 @@ std::shared_ptr<AttrCursor> AttrCursor::maybeGetAttr(Symbol name)
}
return make_ref<AttrCursor>(
root, std::make_pair(shared_from_this(), name), attr->value, std::move(cachedValue2));
root, std::make_pair(ref(shared_from_this()), name), attr->value, std::move(cachedValue2));
}
std::shared_ptr<AttrCursor> AttrCursor::maybeGetAttr(std::string_view name)
@ -585,8 +592,7 @@ OrSuggestions<ref<AttrCursor>> AttrCursor::findAlongAttrPath(const std::vector<S
std::string AttrCursor::getString()
{
if (root->db) {
if (!cachedValue)
cachedValue = root->db->getAttr(getKey());
fetchCachedValue();
if (cachedValue && !std::get_if<placeholder_t>(&cachedValue->second)) {
if (auto s = std::get_if<string_t>(&cachedValue->second)) {
debug("using cached string attribute '%s'", getAttrPathStr());
@ -607,8 +613,7 @@ std::string AttrCursor::getString()
string_t AttrCursor::getStringWithContext()
{
if (root->db) {
if (!cachedValue)
cachedValue = root->db->getAttr(getKey());
fetchCachedValue();
if (cachedValue && !std::get_if<placeholder_t>(&cachedValue->second)) {
if (auto s = std::get_if<string_t>(&cachedValue->second)) {
bool valid = true;
@ -654,8 +659,7 @@ string_t AttrCursor::getStringWithContext()
bool AttrCursor::getBool()
{
if (root->db) {
if (!cachedValue)
cachedValue = root->db->getAttr(getKey());
fetchCachedValue();
if (cachedValue && !std::get_if<placeholder_t>(&cachedValue->second)) {
if (auto b = std::get_if<bool>(&cachedValue->second)) {
debug("using cached Boolean attribute '%s'", getAttrPathStr());
@ -676,8 +680,7 @@ bool AttrCursor::getBool()
NixInt AttrCursor::getInt()
{
if (root->db) {
if (!cachedValue)
cachedValue = root->db->getAttr(getKey());
fetchCachedValue();
if (cachedValue && !std::get_if<placeholder_t>(&cachedValue->second)) {
if (auto i = std::get_if<int_t>(&cachedValue->second)) {
debug("using cached integer attribute '%s'", getAttrPathStr());
@ -698,8 +701,7 @@ NixInt AttrCursor::getInt()
std::vector<std::string> AttrCursor::getListOfStrings()
{
if (root->db) {
if (!cachedValue)
cachedValue = root->db->getAttr(getKey());
fetchCachedValue();
if (cachedValue && !std::get_if<placeholder_t>(&cachedValue->second)) {
if (auto l = std::get_if<std::vector<std::string>>(&cachedValue->second)) {
debug("using cached list of strings attribute '%s'", getAttrPathStr());
@ -731,8 +733,7 @@ std::vector<std::string> AttrCursor::getListOfStrings()
std::vector<Symbol> AttrCursor::getAttrs()
{
if (root->db) {
if (!cachedValue)
cachedValue = root->db->getAttr(getKey());
fetchCachedValue();
if (cachedValue && !std::get_if<placeholder_t>(&cachedValue->second)) {
if (auto attrs = std::get_if<std::vector<Symbol>>(&cachedValue->second)) {
debug("using cached attrset attribute '%s'", getAttrPathStr());

10
src/libexpr/include/nix/eval-cache.hh
View file

@ -90,7 +90,7 @@ class AttrCursor : public std::enable_shared_from_this<AttrCursor>
friend struct CachedEvalError;
ref<EvalCache> root;
typedef std::optional<std::pair<std::shared_ptr<AttrCursor>, Symbol>> Parent;
using Parent = std::optional<std::pair<ref<AttrCursor>, Symbol>>;
Parent parent;
RootValue _value;
std::optional<std::pair<AttrId, AttrValue>> cachedValue;
@ -99,6 +99,14 @@ class AttrCursor : public std::enable_shared_from_this<AttrCursor>
Value & getValue();
/**
* If `cachedValue` is unset, try to initialize it from the
* database. It is not an error if it does not exist. Throw a
* `CachedEvalError` exception if it does exist but has type
* `AttrType::Failed`.
*/
void fetchCachedValue();
public:
AttrCursor(