path: root/third_party/nix/src/libstore/builtins/buildenv.cc

#include <fcntl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <algorithm>
#include "builtins.hh"

namespace nix {

typedef std::map<Path, int> Priorities;

// FIXME: change into local variables.

static Priorities priorities;

static unsigned long symlinks;

/* For each activated package, create symlinks */
static void createLinks(const Path& srcDir, const Path& dstDir, int priority) {
  DirEntries srcFiles;

  try {
    srcFiles = readDirectory(srcDir);
  } catch (SysError& e) {
    if (e.errNo == ENOTDIR) {
      printError(
          "warning: not including '%s' in the user environment because it's "
          "not a directory",
          srcDir);
      return;
    }
    throw;
  }

  for (const auto& ent : srcFiles) {
    if (ent.name[0] == '.') /* not matched by glob */
      continue;
    auto srcFile = srcDir + "/" + ent.name;
    auto dstFile = dstDir + "/" + ent.name;

    struct stat srcSt;
    try {
      if (stat(srcFile.c_str(), &srcSt) == -1)
        throw SysError("getting status of '%1%'", srcFile);
    } catch (SysError& e) {
      if (e.errNo == ENOENT || e.errNo == ENOTDIR) {
        printError("warning: skipping dangling symlink '%s'", dstFile);
        continue;
      }
      throw;
    }

    /* The files below are special-cased to that they don't show up
     * in user profiles, either because they are useless, or
     * because they would cauase pointless collisions (e.g., each
     * Python package brings its own
     * `$out/lib/pythonX.Y/site-packages/easy-install.pth'.)
     */
    if (hasSuffix(srcFile, "/propagated-build-inputs") ||
        hasSuffix(srcFile, "/nix-support") ||
        hasSuffix(srcFile, "/perllocal.pod") ||
        hasSuffix(srcFile, "/info/dir") || hasSuffix(srcFile, "/log"))
      continue;

    else if (S_ISDIR(srcSt.st_mode)) {
      struct stat dstSt;
      auto res = lstat(dstFile.c_str(), &dstSt);
      if (res == 0) {
        if (S_ISDIR(dstSt.st_mode)) {
          createLinks(srcFile, dstFile, priority);
          continue;
        } else if (S_ISLNK(dstSt.st_mode)) {
          auto target = canonPath(dstFile, true);
          if (!S_ISDIR(lstat(target).st_mode))
            throw Error("collision between '%1%' and non-directory '%2%'",
                        srcFile, target);
          if (unlink(dstFile.c_str()) == -1)
            throw SysError(format("unlinking '%1%'") % dstFile);
          if (mkdir(dstFile.c_str(), 0755) == -1)
            throw SysError(format("creating directory '%1%'"));
          createLinks(target, dstFile, priorities[dstFile]);
          createLinks(srcFile, dstFile, priority);
          continue;
        }
      } else if (errno != ENOENT)
        throw SysError(format("getting status of '%1%'") % dstFile);
    }

    else {
      struct stat dstSt;
      auto res = lstat(dstFile.c_str(), &dstSt);
      if (res == 0) {
        if (S_ISLNK(dstSt.st_mode)) {
          auto prevPriority = priorities[dstFile];
          if (prevPriority == priority)
            throw Error(
                "packages '%1%' and '%2%' have the same priority %3%; "
                "use 'nix-env --set-flag priority NUMBER INSTALLED_PKGNAME' "
                "to change the priority of one of the conflicting packages"
                " (0 being the highest priority)",
                srcFile, readLink(dstFile), priority);
          if (prevPriority < priority) continue;
          if (unlink(dstFile.c_str()) == -1)
            throw SysError(format("unlinking '%1%'") % dstFile);
        } else if (S_ISDIR(dstSt.st_mode))
          throw Error(
              "collision between non-directory '%1%' and directory '%2%'",
              srcFile, dstFile);
      } else if (errno != ENOENT)
        throw SysError(format("getting status of '%1%'") % dstFile);
    }

    createSymlink(srcFile, dstFile);
    priorities[dstFile] = priority;
    symlinks++;
  }
}

typedef std::set<Path> FileProp;

static FileProp done;
static FileProp postponed = FileProp{};

static Path out;

static void addPkg(const Path& pkgDir, int priority) {
  if (done.count(pkgDir)) return;
  done.insert(pkgDir);
  createLinks(pkgDir, out, priority);

  try {
    for (const auto& p : tokenizeString<std::vector<string>>(
             readFile(pkgDir + "/nix-support/propagated-user-env-packages"),
             " \n"))
      if (!done.count(p)) postponed.insert(p);
  } catch (SysError& e) {
    if (e.errNo != ENOENT && e.errNo != ENOTDIR) throw;
  }
}

struct Package {
  Path path;
  bool active;
  int priority;
  Package(Path path, bool active, int priority)
      : path{path}, active{active}, priority{priority} {}
};

typedef std::vector<Package> Packages;

void builtinBuildenv(const BasicDerivation& drv) {
  auto getAttr = [&](const string& name) {
    auto i = drv.env.find(name);
    if (i == drv.env.end()) throw Error("attribute '%s' missing", name);
    return i->second;
  };

  out = getAttr("out");
  createDirs(out);

  /* Convert the stuff we get from the environment back into a
   * coherent data type. */
  Packages pkgs;
  auto derivations = tokenizeString<Strings>(getAttr("derivations"));
  while (!derivations.empty()) {
    /* !!! We're trusting the caller to structure derivations env var correctly
     */
    auto active = derivations.front();
    derivations.pop_front();
    auto priority = stoi(derivations.front());
    derivations.pop_front();
    auto outputs = stoi(derivations.front());
    derivations.pop_front();
    for (auto n = 0; n < outputs; n++) {
      auto path = derivations.front();
      derivations.pop_front();
      pkgs.emplace_back(path, active != "false", priority);
    }
  }

  /* Symlink to the packages that have been installed explicitly by the
   * user. Process in priority order to reduce unnecessary
   * symlink/unlink steps.
   */
  std::sort(pkgs.begin(), pkgs.end(), [](const Package& a, const Package& b) {
    return a.priority < b.priority ||
           (a.priority == b.priority && a.path < b.path);
  });
  for (const auto& pkg : pkgs)
    if (pkg.active) addPkg(pkg.path, pkg.priority);

  /* Symlink to the packages that have been "propagated" by packages
   * installed by the user (i.e., package X declares that it wants Y
   * installed as well). We do these later because they have a lower
   * priority in case of collisions.
   */
  auto priorityCounter = 1000;
  while (!postponed.empty()) {
    auto pkgDirs = postponed;
    postponed = FileProp{};
    for (const auto& pkgDir : pkgDirs) addPkg(pkgDir, priorityCounter++);
  }

  printError("created %d symlinks in user environment", symlinks);

  createSymlink(getAttr("manifest"), out + "/manifest.nix");
}

}  // namespace nix