Add 'path' fetcher

This fetchers copies a plain directory (i.e. not a Git/Mercurial
repository) to the store (or does nothing if the path is already a
store path).

One use case is to pin the 'nixpkgs' flake used to build the current
NixOS system, and prevent it from being garbage-collected, via a
system registry entry like this:

  {
      "from": {
          "id": "nixpkgs",
          "type": "indirect"
      },
      "to": {
          "type": "path",
          "path": "/nix/store/rralhl3wj4rdwzjn16g7d93mibvlr521-source",
          "lastModified": 1585388205,
          "rev": "b0c285807d6a9f1b7562ec417c24fa1a30ecc31a"
      },
      "exact": true
  }

Note the fake "lastModified" and "rev" attributes that ensure that the
flake gives the same evaluation results as the corresponding
Git/GitHub inputs.
This commit is contained in:
Eelco Dolstra 2020-04-02 14:56:20 +02:00
parent 00e1400eb7
commit 12f9379123
3 changed files with 147 additions and 0 deletions

View file

@ -89,4 +89,19 @@ bool getBoolAttr(const Attrs & attrs, const std::string & name)
return *s; return *s;
} }
std::map<std::string, std::string> attrsToQuery(const Attrs & attrs)
{
std::map<std::string, std::string> query;
for (auto & attr : attrs) {
if (auto v = std::get_if<int64_t>(&attr.second)) {
query.insert_or_assign(attr.first, fmt("%d", *v));
} else if (auto v = std::get_if<std::string>(&attr.second)) {
query.insert_or_assign(attr.first, *v);
} else if (auto v = std::get_if<Explicit<bool>>(&attr.second)) {
query.insert_or_assign(attr.first, v->t ? "1" : "0");
} else abort();
}
return query;
}
} }

View file

@ -34,4 +34,6 @@ std::optional<bool> maybeGetBoolAttr(const Attrs & attrs, const std::string & na
bool getBoolAttr(const Attrs & attrs, const std::string & name); bool getBoolAttr(const Attrs & attrs, const std::string & name);
std::map<std::string, std::string> attrsToQuery(const Attrs & attrs);
} }

130
src/libfetchers/path.cc Normal file
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@ -0,0 +1,130 @@
#include "fetchers.hh"
#include "store-api.hh"
namespace nix::fetchers {
struct PathInput : Input
{
Path path;
/* Allow the user to pass in "fake" tree info attributes. This is
useful for making a pinned tree work the same as the repository
from which is exported
(e.g. path:/nix/store/...-source?lastModified=1585388205&rev=b0c285...). */
std::optional<Hash> rev;
std::optional<uint64_t> revCount;
std::optional<time_t> lastModified;
std::string type() const override { return "path"; }
std::optional<Hash> getRev() const override { return rev; }
ParsedURL toURL() const override
{
auto query = attrsToQuery(toAttrsInternal());
query.erase("path");
return ParsedURL {
.scheme = "path",
.path = path,
.query = query,
};
}
Attrs toAttrsInternal() const override
{
Attrs attrs;
attrs.emplace("path", path);
if (rev)
attrs.emplace("rev", rev->gitRev());
if (revCount)
attrs.emplace("revCount", *revCount);
if (lastModified)
attrs.emplace("lastModified", *lastModified);
return attrs;
}
std::pair<Tree, std::shared_ptr<const Input>> fetchTreeInternal(nix::ref<Store> store) const override
{
auto input = std::make_shared<PathInput>(*this);
auto storePath = store->maybeParseStorePath(path);
if (storePath)
store->addTempRoot(*storePath);
if (!storePath || storePath->name() != "source" || !store->isValidPath(*storePath))
// FIXME: try to substitute storePath.
storePath = store->addToStore("name", path);
return
{
Tree {
.actualPath = store->toRealPath(*storePath),
.storePath = std::move(*storePath),
.info = TreeInfo {
.revCount = revCount,
.lastModified = lastModified
}
},
input
};
}
};
struct PathInputScheme : InputScheme
{
std::unique_ptr<Input> inputFromURL(const ParsedURL & url) override
{
if (url.scheme != "path") return nullptr;
auto input = std::make_unique<PathInput>();
input->path = url.path;
for (auto & [name, value] : url.query)
if (name == "rev")
input->rev = Hash(value, htSHA1);
else if (name == "revCount") {
uint64_t revCount;
if (!string2Int(value, revCount))
throw Error("path URL '%s' has invalid parameter '%s'", url.to_string(), name);
input->revCount = revCount;
}
else if (name == "lastModified") {
time_t lastModified;
if (!string2Int(value, lastModified))
throw Error("path URL '%s' has invalid parameter '%s'", url.to_string(), name);
input->lastModified = lastModified;
}
else
throw Error("path URL '%s' has unsupported parameter '%s'", url.to_string(), name);
return input;
}
std::unique_ptr<Input> inputFromAttrs(const Attrs & attrs) override
{
if (maybeGetStrAttr(attrs, "type") != "path") return {};
auto input = std::make_unique<PathInput>();
input->path = getStrAttr(attrs, "path");
for (auto & [name, value] : attrs)
if (name == "rev")
input->rev = Hash(getStrAttr(attrs, "rev"), htSHA1);
else if (name == "revCount")
input->revCount = getIntAttr(attrs, "revCount");
else if (name == "lastModified")
input->lastModified = getIntAttr(attrs, "lastModified");
else if (name == "type" || name == "path")
;
else
throw Error("unsupported path input attribute '%s'", name);
return input;
}
};
static auto r1 = OnStartup([] { registerInputScheme(std::make_unique<PathInputScheme>()); });
}