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Git hashing for Git fetching #9025

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Git hashing for Git fetching #9025

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ce9ea7e
Experimentally return `treeHash` on git and github fetchers
Ericson2314 Mar 27, 2024
a8314ff
Git hashing for Git Fetching
Ericson2314 Sep 4, 2023
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14 changes: 11 additions & 3 deletions src/libexpr/primops/fetchTree.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -31,9 +31,13 @@ void emitTreeAttrs(

// FIXME: support arbitrary input attributes.

auto narHash = input.getNarHash();
assert(narHash);
attrs.alloc("narHash").mkString(narHash->to_string(HashFormat::SRI, true));
if (auto narHash = input.getNarHash()) {
attrs.alloc("narHash").mkString(narHash->to_string(HashFormat::SRI, true));
} else if (auto treeHash = input.getTreeHash()) {
attrs.alloc("treeHash").mkString(treeHash->to_string(HashFormat::SRI, true));
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We have two kinds of tree hashes:

  • tree hashes from git commits, which do not correspond to fetched trees in general
  • tree hashes from file system objects returned by fetchTree

Which one is this, and what is the purpose of exposing it to the expression language?

} else
/* Must have either tree hash or NAR hash */
assert(false);

if (input.getType() == "git")
attrs.alloc("submodules").mkBool(
Expand All @@ -51,6 +55,10 @@ void emitTreeAttrs(
attrs.alloc("shortRev").mkString(emptyHash.gitShortRev());
}

if (auto treeHash = input.getTreeHash()) {
attrs.alloc("treeHash").mkString(treeHash->gitRev());
}

if (auto revCount = input.getRevCount())
attrs.alloc("revCount").mkInt(*revCount);
else if (emptyRevFallback)
Expand Down
30 changes: 22 additions & 8 deletions src/libfetchers/fetchers.cc
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Expand Up @@ -301,14 +301,19 @@ std::string Input::getName() const

StorePath Input::computeStorePath(Store & store) const
{
auto narHash = getNarHash();
if (!narHash)
throw Error("cannot compute store path for unlocked input '%s'", to_string());
return store.makeFixedOutputPath(getName(), FixedOutputInfo {
.method = FileIngestionMethod::Recursive,
.hash = *narHash,
.references = {},
});
if (auto treeHash = getTreeHash())
return store.makeFixedOutputPath(getName(), FixedOutputInfo {
.method = FileIngestionMethod::Git,
.hash = *treeHash,
.references = {},
});
if (auto narHash = getNarHash())
return store.makeFixedOutputPath(getName(), FixedOutputInfo {
.method = FileIngestionMethod::Recursive,
.hash = *narHash,
.references = {},
});
throw Error("cannot compute store path for unlocked input '%s'", to_string());
}

std::string Input::getType() const
Expand Down Expand Up @@ -351,6 +356,15 @@ std::optional<Hash> Input::getRev() const
return hash;
}

std::optional<Hash> Input::getTreeHash() const
{
if (auto s = maybeGetStrAttr(attrs, "treeHash")) {
experimentalFeatureSettings.require(Xp::GitHashing);
return Hash::parseAny(*s, HashAlgorithm::SHA1);
}
return {};
}

std::optional<uint64_t> Input::getRevCount() const
{
if (auto n = maybeGetIntAttr(attrs, "revCount"))
Expand Down
1 change: 1 addition & 0 deletions src/libfetchers/fetchers.hh
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Expand Up @@ -121,6 +121,7 @@ public:
std::optional<Hash> getNarHash() const;
std::optional<std::string> getRef() const;
std::optional<Hash> getRev() const;
std::optional<Hash> getTreeHash() const;
std::optional<uint64_t> getRevCount() const;
std::optional<time_t> getLastModified() const;

Expand Down
32 changes: 23 additions & 9 deletions src/libfetchers/git-utils.cc
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Expand Up @@ -57,7 +57,7 @@ bool operator == (const git_oid & oid1, const git_oid & oid2)

namespace nix {

struct GitInputAccessor;
struct GitInputAccessorImpl;

// Some wrapper types that ensure that the git_*_free functions get called.
template<auto del>
Expand Down Expand Up @@ -334,9 +334,11 @@ struct GitRepoImpl : GitRepo, std::enable_shared_from_this<GitRepoImpl>
}

/**
* A 'GitInputAccessor' with no regard for export-ignore or any other transformations.
* A 'GitInputAccessorImpl' with no regard for export-ignore or any other transformations.
*/
ref<GitInputAccessor> getRawAccessor(const Hash & rev);
ref<GitInputAccessorImpl> getRawAccessor(const Hash & rev);

ref<GitInputAccessor> getPlainAccessor(const Hash & rev) override;

ref<InputAccessor> getAccessor(const Hash & rev, bool exportIgnore) override;

Expand Down Expand Up @@ -477,17 +479,24 @@ ref<GitRepo> GitRepo::openRepo(const std::filesystem::path & path, bool create,
/**
* Raw git tree input accessor.
*/
struct GitInputAccessor : InputAccessor
struct GitInputAccessorImpl : GitInputAccessor
{
ref<GitRepoImpl> repo;
Tree root;

GitInputAccessor(ref<GitRepoImpl> repo_, const Hash & rev)
GitInputAccessorImpl(ref<GitRepoImpl> repo_, const Hash & rev)
: repo(repo_)
, root(peelObject<Tree>(*repo, lookupObject(*repo, hashToOID(rev)).get(), GIT_OBJECT_TREE))
{
}

Hash getTreeHash() override
{
auto * oid = git_tree_id(root.get());
assert(oid);
return toHash(*oid);
}

std::string readBlob(const CanonPath & path, bool symlink)
{
auto blob = getBlob(path, symlink);
Expand Down Expand Up @@ -922,17 +931,22 @@ struct GitFileSystemObjectSinkImpl : GitFileSystemObjectSink
}
};

ref<GitInputAccessor> GitRepoImpl::getRawAccessor(const Hash & rev)
ref<GitInputAccessorImpl> GitRepoImpl::getRawAccessor(const Hash & rev)
{
auto self = ref<GitRepoImpl>(shared_from_this());
return make_ref<GitInputAccessor>(self, rev);
return make_ref<GitInputAccessorImpl>(self, rev);
}

ref<GitInputAccessor> GitRepoImpl::getPlainAccessor(const Hash & rev)
{
return getRawAccessor(rev);
}

ref<InputAccessor> GitRepoImpl::getAccessor(const Hash & rev, bool exportIgnore)
{
auto self = ref<GitRepoImpl>(shared_from_this());
ref<GitInputAccessor> rawGitAccessor = getRawAccessor(rev);
ref<GitInputAccessorImpl> rawGitAccessor = getRawAccessor(rev);
if (exportIgnore) {
auto self = ref<GitRepoImpl>(shared_from_this());
return make_ref<GitExportIgnoreInputAccessor>(self, rawGitAccessor, rev);
}
else {
Expand Down
12 changes: 12 additions & 0 deletions src/libfetchers/git-utils.hh
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Expand Up @@ -16,6 +16,16 @@ struct GitFileSystemObjectSink : FileSystemObjectSink
virtual Hash sync() = 0;
};

/**
* Git Input Accessor
*
* Created from `GitRepo`. Support some additional operations.
*/
struct GitInputAccessor : InputAccessor
{
virtual Hash getTreeHash() = 0;
};

struct GitRepo
{
virtual ~GitRepo()
Expand Down Expand Up @@ -75,6 +85,8 @@ struct GitRepo

virtual bool hasObject(const Hash & oid) = 0;

virtual ref<GitInputAccessor> getPlainAccessor(const Hash & rev) = 0;

virtual ref<InputAccessor> getAccessor(const Hash & rev, bool exportIgnore) = 0;

virtual ref<InputAccessor> getAccessor(const WorkdirInfo & wd, bool exportIgnore, MakeNotAllowedError makeNotAllowedError) = 0;
Expand Down
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