lix/src/libfetchers/attrs.cc
Eelco Dolstra 12f9379123 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.
2020-04-02 14:56:20 +02:00

108 lines
3.1 KiB
C++

#include "attrs.hh"
#include "fetchers.hh"
#include <nlohmann/json.hpp>
namespace nix::fetchers {
Attrs jsonToAttrs(const nlohmann::json & json)
{
Attrs attrs;
for (auto & i : json.items()) {
if (i.value().is_number())
attrs.emplace(i.key(), i.value().get<int64_t>());
else if (i.value().is_string())
attrs.emplace(i.key(), i.value().get<std::string>());
else if (i.value().is_boolean())
attrs.emplace(i.key(), i.value().get<bool>());
else
throw Error("unsupported input attribute type in lock file");
}
return attrs;
}
nlohmann::json attrsToJson(const Attrs & attrs)
{
nlohmann::json json;
for (auto & attr : attrs) {
if (auto v = std::get_if<int64_t>(&attr.second)) {
json[attr.first] = *v;
} else if (auto v = std::get_if<std::string>(&attr.second)) {
json[attr.first] = *v;
} else if (auto v = std::get_if<Explicit<bool>>(&attr.second)) {
json[attr.first] = v->t;
} else abort();
}
return json;
}
std::optional<std::string> maybeGetStrAttr(const Attrs & attrs, const std::string & name)
{
auto i = attrs.find(name);
if (i == attrs.end()) return {};
if (auto v = std::get_if<std::string>(&i->second))
return *v;
throw Error("input attribute '%s' is not a string %s", name, attrsToJson(attrs).dump());
}
std::string getStrAttr(const Attrs & attrs, const std::string & name)
{
auto s = maybeGetStrAttr(attrs, name);
if (!s)
throw Error("input attribute '%s' is missing", name);
return *s;
}
std::optional<int64_t> maybeGetIntAttr(const Attrs & attrs, const std::string & name)
{
auto i = attrs.find(name);
if (i == attrs.end()) return {};
if (auto v = std::get_if<int64_t>(&i->second))
return *v;
throw Error("input attribute '%s' is not an integer", name);
}
int64_t getIntAttr(const Attrs & attrs, const std::string & name)
{
auto s = maybeGetIntAttr(attrs, name);
if (!s)
throw Error("input attribute '%s' is missing", name);
return *s;
}
std::optional<bool> maybeGetBoolAttr(const Attrs & attrs, const std::string & name)
{
auto i = attrs.find(name);
if (i == attrs.end()) return {};
if (auto v = std::get_if<int64_t>(&i->second))
return *v;
throw Error("input attribute '%s' is not a Boolean", name);
}
bool getBoolAttr(const Attrs & attrs, const std::string & name)
{
auto s = maybeGetBoolAttr(attrs, name);
if (!s)
throw Error("input attribute '%s' is missing", name);
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;
}
}