nix-super/src/libexpr/eval-settings.cc
John Ericson 9b908fa70a Factor out nix-defexpr path computation
Avoid duplicated code, and also avoid "on the fly" path construction
(which makes it harder to keep track of which paths we use).

The factored out code doesn't create the Nix state dir anymore, but this
is fine because other in nix-env and nix-channel does:

- nix-channel: Line 158 in this commit

- nix-env: Line 1407 in this commit
2023-08-02 12:54:48 -04:00

102 lines
2.5 KiB
C++

#include "globals.hh"
#include "profiles.hh"
#include "eval.hh"
#include "eval-settings.hh"
namespace nix {
/* Very hacky way to parse $NIX_PATH, which is colon-separated, but
can contain URLs (e.g. "nixpkgs=https://bla...:foo=https://"). */
static Strings parseNixPath(const std::string & s)
{
Strings res;
auto p = s.begin();
while (p != s.end()) {
auto start = p;
auto start2 = p;
while (p != s.end() && *p != ':') {
if (*p == '=') start2 = p + 1;
++p;
}
if (p == s.end()) {
if (p != start) res.push_back(std::string(start, p));
break;
}
if (*p == ':') {
auto prefix = std::string(start2, s.end());
if (EvalSettings::isPseudoUrl(prefix) || hasPrefix(prefix, "flake:")) {
++p;
while (p != s.end() && *p != ':') ++p;
}
res.push_back(std::string(start, p));
if (p == s.end()) break;
}
++p;
}
return res;
}
EvalSettings::EvalSettings()
{
auto var = getEnv("NIX_PATH");
if (var) nixPath = parseNixPath(*var);
}
Strings EvalSettings::getDefaultNixPath()
{
Strings res;
auto add = [&](const Path & p, const std::string & s = std::string()) {
if (pathAccessible(p)) {
if (s.empty()) {
res.push_back(p);
} else {
res.push_back(s + "=" + p);
}
}
};
if (!evalSettings.restrictEval && !evalSettings.pureEval) {
add(getNixDefExpr() + "/channels");
add(rootChannelsDir() + "/nixpkgs", "nixpkgs");
add(rootChannelsDir());
}
return res;
}
bool EvalSettings::isPseudoUrl(std::string_view s)
{
if (s.compare(0, 8, "channel:") == 0) return true;
size_t pos = s.find("://");
if (pos == std::string::npos) return false;
std::string scheme(s, 0, pos);
return scheme == "http" || scheme == "https" || scheme == "file" || scheme == "channel" || scheme == "git" || scheme == "s3" || scheme == "ssh";
}
std::string EvalSettings::resolvePseudoUrl(std::string_view url)
{
if (hasPrefix(url, "channel:"))
return "https://nixos.org/channels/" + std::string(url.substr(8)) + "/nixexprs.tar.xz";
else
return std::string(url);
}
EvalSettings evalSettings;
static GlobalConfig::Register rEvalSettings(&evalSettings);
Path getNixDefExpr()
{
return settings.useXDGBaseDirectories
? getStateDir() + "/nix/defexpr"
: getHome() + "/.nix-defexpr";
}
}