nix-gh/src/libstore/builtins/buildenv.cc

#include "builtins.hh"

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

namespace nix {

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

static bool isDirectory(const Path & path)
{
    struct stat st;
    if (stat(path.c_str(), &st) == -1)
        throw SysError(format("getting status of '%1%'") % path);
    return S_ISDIR(st.st_mode);
}

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

        /* 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 (isDirectory(srcFile)) {
            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 = readLink(dstFile);
                    if (!isDirectory(target))
                        throw Error(format("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 target = readLink(dstFile);
                    auto prevPriority = priorities[dstFile];
                    if (prevPriority == priority)
                        throw Error(format(
                                "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 % target % priority);
                    if (prevPriority < priority)
                        continue;
                    if (unlink(dstFile.c_str()) == -1)
                        throw SysError(format("unlinking '%1%'") % 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.find(pkgDir) != done.end())
        return;
    done.insert(pkgDir);
    createLinks(pkgDir, out, priority);
    auto propagatedFN = pkgDir + "/nix-support/propagated-user-env-packages";
    std::string propagated;
    {
        AutoCloseFD fd = open(propagatedFN.c_str(), O_RDONLY | O_CLOEXEC);
        if (!fd) {
            if (errno == ENOENT)
                return;
            throw SysError(format("opening '%1%'") % propagatedFN);
        }
        propagated = readFile(fd.get());
    }
    for (const auto & p : tokenizeString<std::vector<string>>(propagated, " \n"))
        if (done.find(p) == done.end())
            postponed.insert(p);
}

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");
}

}