lix/src/libfetchers/fetchers.cc

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#include "fetchers.hh"
#include "store-api.hh"
#include <nlohmann/json.hpp>
namespace nix::fetchers {
std::unique_ptr<std::vector<std::shared_ptr<InputScheme>>> inputSchemes = nullptr;
void registerInputScheme(std::shared_ptr<InputScheme> && inputScheme)
{
if (!inputSchemes) inputSchemes = std::make_unique<std::vector<std::shared_ptr<InputScheme>>>();
inputSchemes->push_back(std::move(inputScheme));
}
Input Input::fromURL(const std::string & url)
{
return fromURL(parseURL(url));
}
static void fixupInput(Input & input)
{
// Check common attributes.
input.getType();
input.getRef();
if (input.getRev())
input.locked = true;
input.getRevCount();
input.getLastModified();
if (input.getNarHash())
input.locked = true;
}
Input Input::fromURL(const ParsedURL & url)
{
for (auto & inputScheme : *inputSchemes) {
auto res = inputScheme->inputFromURL(url);
if (res) {
res->scheme = inputScheme;
fixupInput(*res);
return std::move(*res);
}
}
throw Error("input '%s' is unsupported", url.url);
}
Input Input::fromAttrs(Attrs && attrs)
{
for (auto & inputScheme : *inputSchemes) {
auto res = inputScheme->inputFromAttrs(attrs);
if (res) {
res->scheme = inputScheme;
fixupInput(*res);
return std::move(*res);
}
}
Input input;
input.attrs = attrs;
fixupInput(input);
return input;
}
ParsedURL Input::toURL() const
{
if (!scheme)
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throw Error("cannot show unsupported input '%s'", attrsToJSON(attrs));
return scheme->toURL(*this);
}
std::string Input::toURLString(const std::map<std::string, std::string> & extraQuery) const
{
auto url = toURL();
for (auto & attr : extraQuery)
url.query.insert(attr);
return url.to_string();
}
std::string Input::to_string() const
{
return toURL().to_string();
}
Attrs Input::toAttrs() const
{
return attrs;
}
bool Input::hasAllInfo() const
{
return getNarHash() && scheme && scheme->hasAllInfo(*this);
}
bool Input::operator ==(const Input & other) const
{
return attrs == other.attrs;
}
bool Input::contains(const Input & other) const
{
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if (*this == other) return true;
auto other2(other);
other2.attrs.erase("ref");
other2.attrs.erase("rev");
if (*this == other2) return true;
return false;
}
std::pair<Tree, Input> Input::fetch(ref<Store> store) const
{
if (!scheme)
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throw Error("cannot fetch unsupported input '%s'", attrsToJSON(toAttrs()));
/* The tree may already be in the Nix store, or it could be
substituted (which is often faster than fetching from the
original source). So check that. */
if (hasAllInfo()) {
try {
auto storePath = computeStorePath(*store);
store->ensurePath(storePath);
debug("using substituted/cached input '%s' in '%s'",
to_string(), store->printStorePath(storePath));
return {Tree { .actualPath = store->toRealPath(storePath), .storePath = std::move(storePath) }, *this};
} catch (Error & e) {
debug("substitution of input '%s' failed: %s", to_string(), e.what());
}
}
auto [storePath, input] = [&]() -> std::pair<StorePath, Input> {
try {
return scheme->fetch(store, *this);
} catch (Error & e) {
e.addTrace({}, "while fetching the input '%s'", to_string());
throw;
}
}();
Tree tree {
.actualPath = store->toRealPath(storePath),
.storePath = storePath,
};
auto narHash = store->queryPathInfo(tree.storePath)->narHash;
input.attrs.insert_or_assign("narHash", narHash.to_string(SRI, true));
if (auto prevNarHash = getNarHash()) {
if (narHash != *prevNarHash)
Merge legacy `fetchGit`-builtin with the generic `fetchTree`-function The original idea was to implement a git-fetcher in Nix's core that supports content hashes[1]. In #3549[2] it has been suggested to actually use `fetchTree` for this since it's a fairly generic wrapper over the new fetcher-API[3] and already supports content-hashes. This patch implements a new git-fetcher based on `fetchTree` by incorporating the following changes: * Removed the original `fetchGit`-implementation and replaced it with an alias on the `fetchTree` implementation. * Ensured that the `git`-fetcher from `libfetchers` always computes a content-hash and returns an "empty" revision on dirty trees (the latter one is needed to retain backwards-compatibility). * The hash-mismatch error in the fetcher-API exits with code 102 as it usually happens whenever a hash-mismatch is detected by Nix. * Removed the `flakes`-feature-flag: I didn't see a reason why this API is so tightly coupled to the flakes-API and at least `fetchGit` should remain usable without any feature-flags. * It's only possible to specify a `narHash` for a `git`-tree if either a `ref` or a `rev` is given[4]. * It's now possible to specify an URL without a protocol. If it's missing, `file://` is automatically added as it was the case in the original `fetchGit`-implementation. [1] https://github.com/NixOS/nix/pull/3216 [2] https://github.com/NixOS/nix/pull/3549#issuecomment-625194383 [3] https://github.com/NixOS/nix/pull/3459 [4] https://github.com/NixOS/nix/pull/3216#issuecomment-553956703
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throw Error((unsigned int) 102, "NAR hash mismatch in input '%s' (%s), expected '%s', got '%s'",
to_string(), tree.actualPath, prevNarHash->to_string(SRI, true), narHash.to_string(SRI, true));
}
if (auto prevLastModified = getLastModified()) {
if (input.getLastModified() != prevLastModified)
throw Error("'lastModified' attribute mismatch in input '%s', expected %d",
input.to_string(), *prevLastModified);
}
if (auto prevRevCount = getRevCount()) {
if (input.getRevCount() != prevRevCount)
throw Error("'revCount' attribute mismatch in input '%s', expected %d",
input.to_string(), *prevRevCount);
}
input.locked = true;
assert(input.hasAllInfo());
return {std::move(tree), input};
}
Input Input::applyOverrides(
std::optional<std::string> ref,
std::optional<Hash> rev) const
{
if (!scheme) return *this;
return scheme->applyOverrides(*this, ref, rev);
}
void Input::clone(const Path & destDir) const
{
assert(scheme);
scheme->clone(*this, destDir);
}
std::optional<Path> Input::getSourcePath() const
{
assert(scheme);
return scheme->getSourcePath(*this);
}
void Input::markChangedFile(
std::string_view file,
std::optional<std::string> commitMsg) const
{
assert(scheme);
return scheme->markChangedFile(*this, file, commitMsg);
}
std::string Input::getName() const
{
return maybeGetStrAttr(attrs, "name").value_or("source");
}
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(FileIngestionMethod::Recursive, *narHash, getName());
}
std::string Input::getType() const
{
return getStrAttr(attrs, "type");
}
std::optional<Hash> Input::getNarHash() const
{
if (auto s = maybeGetStrAttr(attrs, "narHash")) {
auto hash = s->empty() ? Hash(htSHA256) : Hash::parseSRI(*s);
if (hash.type != htSHA256)
throw UsageError("narHash must use SHA-256");
return hash;
}
return {};
}
std::optional<std::string> Input::getRef() const
{
if (auto s = maybeGetStrAttr(attrs, "ref"))
return *s;
return {};
}
std::optional<Hash> Input::getRev() const
{
std::optional<Hash> hash = {};
if (auto s = maybeGetStrAttr(attrs, "rev")) {
try {
hash = Hash::parseAnyPrefixed(*s);
} catch (BadHash &e) {
// Default to sha1 for backwards compatibility with existing flakes
hash = Hash::parseAny(*s, htSHA1);
}
}
return hash;
}
std::optional<uint64_t> Input::getRevCount() const
{
if (auto n = maybeGetIntAttr(attrs, "revCount"))
return *n;
return {};
}
std::optional<time_t> Input::getLastModified() const
{
if (auto n = maybeGetIntAttr(attrs, "lastModified"))
return *n;
return {};
}
ParsedURL InputScheme::toURL(const Input & input)
{
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throw Error("don't know how to convert input '%s' to a URL", attrsToJSON(input.attrs));
}
Input InputScheme::applyOverrides(
const Input & input,
std::optional<std::string> ref,
std::optional<Hash> rev)
{
if (ref)
throw Error("don't know how to set branch/tag name of input '%s' to '%s'", input.to_string(), *ref);
if (rev)
throw Error("don't know how to set revision of input '%s' to '%s'", input.to_string(), rev->gitRev());
return input;
}
std::optional<Path> InputScheme::getSourcePath(const Input & input)
{
return {};
}
void InputScheme::markChangedFile(const Input & input, std::string_view file, std::optional<std::string> commitMsg)
{
assert(false);
}
void InputScheme::clone(const Input & input, const Path & destDir)
{
throw Error("do not know how to clone input '%s'", input.to_string());
}
}