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Simplify "final" inputs

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We now just check that the fetcher doesn't change any attributes in
the input, and return all the original attributes (i.e. discarding any
new attributes and keeping any attributes that the fetcher didn't
keep).
This commit is contained in:
Eelco Dolstra 2024-11-01 16:33:51 +01:00
parent 5c49d0b5d2
commit f314e35b37
3 changed files with 51 additions and 38 deletions
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50
src/libfetchers/fetchers.cc
View File

@ -193,7 +193,7 @@ std::pair<StorePath, Input> Input::fetchToStore(ref<Store> store) const
assert(final.isFinal());
scheme->checkLocks(*this, final);
checkLocks(*this, final);
return {storePath, final};
} catch (Error & e) {
@ -205,8 +205,35 @@ std::pair<StorePath, Input> Input::fetchToStore(ref<Store> store) const
return {std::move(storePath), input};
}
void InputScheme::checkLocks(const Input & specified, const Input & final) const
void Input::checkLocks(Input specified, Input & final)
{
/* If the original input is final, then we just return the
original attributes, dropping any new fields returned by the
fetcher. However, any fields that are in both the original and
final input must be identical. */
if (specified.isFinal()) {
/* Backwards compatibility hack: we had some lock files in the
past that 'narHash' fields with incorrect base-64
formatting (lacking the trailing '=', e.g. 'sha256-ri...Mw'
instead of ''sha256-ri...Mw='). So fix that. */
if (auto prevNarHash = specified.getNarHash())
specified.attrs.insert_or_assign("narHash", prevNarHash->to_string(HashFormat::SRI, true));
for (auto & field : specified.attrs) {
auto field2 = final.attrs.find(field.first);
if (field2 != final.attrs.end() && field.second != field2->second)
throw Error("mismatch in field '%s' of final input '%s', got '%s'",
field.first,
attrsToJSON(specified.attrs),
attrsToJSON(final.attrs));
}
final.attrs = specified.attrs;
return;
}
if (auto prevNarHash = specified.getNarHash()) {
if (final.getNarHash() != prevNarHash) {
if (final.getNarHash())
@ -235,23 +262,6 @@ void InputScheme::checkLocks(const Input & specified, const Input & final) const
throw Error("'revCount' attribute mismatch in input '%s', expected %d",
final.to_string(), *prevRevCount);
}
/* If the original input is final, then the result must be the
same (i.e. cannot remove, add or change fields. */
if (specified.isFinal()) {
/* Backwards compatibility hack: we had some lock files in the
past that 'narHash' fields with incorrect base-64
formatting (lacking the trailing '=', e.g. 'sha256-ri...Mw'
instead of ''sha256-ri...Mw='). So fix */
auto specified2 = specified;
if (auto prevNarHash = specified2.getNarHash())
specified2.attrs.insert_or_assign("narHash", prevNarHash->to_string(HashFormat::SRI, true));
if (specified2.attrs != final.attrs)
throw Error("fetching final input '%s' resulted in different input '%s'",
attrsToJSON(specified2.attrs), attrsToJSON(final.attrs));
}
}
std::pair<ref<SourceAccessor>, Input> Input::getAccessor(ref<Store> store) const
@ -259,7 +269,7 @@ std::pair<ref<SourceAccessor>, Input> Input::getAccessor(ref<Store> store) const
try {
auto [accessor, final] = getAccessorUnchecked(store);
scheme->checkLocks(*this, final);
checkLocks(*this, final);
return {accessor, std::move(final)};
} catch (Error & e) {

27
src/libfetchers/fetchers.hh
View File

@ -91,9 +91,9 @@ public:
bool isLocked() const;
/**
* Return whether this is a "final" input, meaning that fetching it
* will not add or change any attributes. For instance, a Git
* input with a `rev` attribute but without a `lastModified`
* Return whether this is a "final" input, meaning that fetching
* it will not add, remove or change any attributes. For instance,
* a Git input with a `rev` attribute but without a `lastModified`
* attribute is considered locked but not final. Only "final"
* inputs can be substituted from a binary cache.
*
@ -113,6 +113,19 @@ public:
*/
std::pair<StorePath, Input> fetchToStore(ref<Store> store) const;
/**
* Check the locking attributes in `final` against
* `specified`. E.g. if `specified` has a `rev` attribute, then
* `final` must have the same `rev` attribute. Throw an exception
* if there is a mismatch.
*
* If `specified` is marked final (i.e. has the `__final`
* attribute), then the intersection of attributes in `specified`
* and `final` must be equal, and `final.attrs` is set to
* `specified.attrs` (i.e. we discard any new attributes).
*/
static void checkLocks(Input specified, Input & final);
/**
* Return a `SourceAccessor` that allows access to files in the
* input without copying it to the store. Also return a possibly
@ -238,14 +251,6 @@ struct InputScheme
virtual bool isLocked(const Input & input) const
{ return false; }
/**
* Check the locking attributes in `final` against
* `specified`. E.g. if `specified` has a `rev` attribute, then
* `final` must have the same `rev` attribute. Throw an exception
* if there is a mismatch.
*/
virtual void checkLocks(const Input & specified, const Input & final) const;
};
void registerInputScheme(std::shared_ptr<InputScheme> && fetcher);

12
src/libfetchers/tarball.cc
View File

@ -384,13 +384,11 @@ struct TarballInputScheme : CurlInputScheme
input = immutableInput;
}
/* If we got a lastModified, then return it. But for
compatibility with old lock files that didn't include
lastModified, don't do this if the original input was final
and didn't contain a lastModified. */
if (result.lastModified
&& !input.attrs.contains("lastModified")
&& (!_input.isFinal() || _input.attrs.contains("lastModified")))
/* If we got a lastModified and the input is not final and
doesn't have one, then return it. Note that we don't do
this if the input is final for compatibility with old lock
files that didn't include lastModified. */
if (result.lastModified && !_input.isFinal() && !input.attrs.contains("lastModified"))
input.attrs.insert_or_assign("lastModified", uint64_t(result.lastModified));
input.attrs.insert_or_assign("narHash",