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-rw-r--r--third_party/nix/src/nix-env/nix-env.cc1546
1 files changed, 1546 insertions, 0 deletions
diff --git a/third_party/nix/src/nix-env/nix-env.cc b/third_party/nix/src/nix-env/nix-env.cc
new file mode 100644
index 000000000000..d25a4897467c
--- /dev/null
+++ b/third_party/nix/src/nix-env/nix-env.cc
@@ -0,0 +1,1546 @@
+#include <algorithm>
+#include <cerrno>
+#include <ctime>
+#include <iostream>
+#include <sstream>
+
+#include <absl/strings/match.h>
+#include <absl/strings/numbers.h>
+#include <glog/logging.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include "attr-path.hh"
+#include "common-eval-args.hh"
+#include "derivations.hh"
+#include "eval.hh"
+#include "get-drvs.hh"
+#include "globals.hh"
+#include "json.hh"
+#include "legacy.hh"
+#include "names.hh"
+#include "profiles.hh"
+#include "shared.hh"
+#include "store-api.hh"
+#include "user-env.hh"
+#include "util.hh"
+#include "value-to-json.hh"
+#include "xml-writer.hh"
+
+using namespace nix;
+using std::cout;
+
+typedef enum {
+  srcNixExprDrvs,
+  srcNixExprs,
+  srcStorePaths,
+  srcProfile,
+  srcAttrPath,
+  srcUnknown
+} InstallSourceType;
+
+struct InstallSourceInfo {
+  InstallSourceType type;
+  Path nixExprPath;         /* for srcNixExprDrvs, srcNixExprs */
+  Path profile;             /* for srcProfile */
+  std::string systemFilter; /* for srcNixExprDrvs */
+  Bindings* autoArgs;
+};
+
+struct Globals {
+  InstallSourceInfo instSource;
+  Path profile;
+  std::shared_ptr<EvalState> state;
+  bool dryRun;
+  bool preserveInstalled;
+  bool removeAll;
+  std::string forceName;
+  bool prebuiltOnly;
+};
+
+using Operation = void (*)(Globals&, Strings, Strings);
+
+static std::string needArg(Strings::iterator& i, Strings& args,
+                           const std::string& arg) {
+  if (i == args.end()) {
+    throw UsageError(format("'%1%' requires an argument") % arg);
+  }
+  return *i++;
+}
+
+static bool parseInstallSourceOptions(Globals& globals, Strings::iterator& i,
+                                      Strings& args, const std::string& arg) {
+  if (arg == "--from-expression" || arg == "-E") {
+    globals.instSource.type = srcNixExprs;
+  } else if (arg == "--from-profile") {
+    globals.instSource.type = srcProfile;
+    globals.instSource.profile = needArg(i, args, arg);
+  } else if (arg == "--attr" || arg == "-A") {
+    globals.instSource.type = srcAttrPath;
+  } else {
+    return false;
+  }
+  return true;
+}
+
+static bool isNixExpr(const Path& path, struct stat& st) {
+  return S_ISREG(st.st_mode) ||
+         (S_ISDIR(st.st_mode) && pathExists(path + "/default.nix"));
+}
+
+static void getAllExprs(EvalState& state, const Path& path, StringSet& attrs,
+                        Value& v) {
+  StringSet namesSorted;
+  for (auto& i : readDirectory(path)) {
+    namesSorted.insert(i.name);
+  }
+
+  for (auto& i : namesSorted) {
+    /* Ignore the manifest.nix used by profiles.  This is
+       necessary to prevent it from showing up in channels (which
+       are implemented using profiles). */
+    if (i == "manifest.nix") {
+      continue;
+    }
+
+    Path path2 = path + "/" + i;
+
+    struct stat st;
+    if (stat(path2.c_str(), &st) == -1) {
+      continue;  // ignore dangling symlinks in ~/.nix-defexpr
+    }
+
+    if (isNixExpr(path2, st) &&
+        (!S_ISREG(st.st_mode) || absl::EndsWith(path2, ".nix"))) {
+      /* Strip off the `.nix' filename suffix (if applicable),
+         otherwise the attribute cannot be selected with the
+         `-A' option.  Useful if you want to stick a Nix
+         expression directly in ~/.nix-defexpr. */
+      std::string attrName = i;
+      if (absl::EndsWith(attrName, ".nix")) {
+        attrName = std::string(attrName, 0, attrName.size() - 4);
+      }
+      if (attrs.find(attrName) != attrs.end()) {
+        LOG(WARNING) << "name collision in input Nix expressions, skipping '"
+                     << path2 << "'";
+        continue;
+      }
+      attrs.insert(attrName);
+      /* Load the expression on demand. */
+      Value& vFun = state.getBuiltin("import");
+      Value& vArg(*state.allocValue());
+      mkString(vArg, path2);
+      mkApp(*state.allocAttr(v, state.symbols.Create(attrName)), vFun, vArg);
+    } else if (S_ISDIR(st.st_mode)) {
+      /* `path2' is a directory (with no default.nix in it);
+         recurse into it. */
+      getAllExprs(state, path2, attrs, v);
+    }
+  }
+}
+
+static void loadSourceExpr(EvalState& state, const Path& path, Value& v) {
+  struct stat st;
+  if (stat(path.c_str(), &st) == -1) {
+    throw SysError(format("getting information about '%1%'") % path);
+  }
+
+  if (isNixExpr(path, st)) {
+    state.evalFile(path, v);
+  }
+
+  /* The path is a directory.  Put the Nix expressions in the
+     directory in a set, with the file name of each expression as
+     the attribute name.  Recurse into subdirectories (but keep the
+     set flat, not nested, to make it easier for a user to have a
+     ~/.nix-defexpr directory that includes some system-wide
+     directory). */
+  else if (S_ISDIR(st.st_mode)) {
+    state.mkAttrs(v, 1024);
+    state.mkList(*state.allocAttr(v, state.symbols.Create("_combineChannels")),
+                 0);
+    StringSet attrs;
+    getAllExprs(state, path, attrs, v);
+  }
+
+  else {
+    throw Error("path '%s' is not a directory or a Nix expression", path);
+  }
+}
+
+static void loadDerivations(EvalState& state, const Path& nixExprPath,
+                            const std::string& systemFilter, Bindings& autoArgs,
+                            const std::string& pathPrefix, DrvInfos& elems) {
+  Value vRoot;
+  loadSourceExpr(state, nixExprPath, vRoot);
+
+  Value& v(*findAlongAttrPath(state, pathPrefix, autoArgs, vRoot));
+
+  getDerivations(state, v, pathPrefix, autoArgs, elems, true);
+
+  /* Filter out all derivations not applicable to the current
+     system. */
+  for (DrvInfos::iterator i = elems.begin(), j; i != elems.end(); i = j) {
+    j = i;
+    j++;
+    if (systemFilter != "*" && i->querySystem() != systemFilter) {
+      elems.erase(i);
+    }
+  }
+}
+
+static long getPriority(EvalState& state, DrvInfo& drv) {
+  return drv.queryMetaInt("priority", 0);
+}
+
+static long comparePriorities(EvalState& state, DrvInfo& drv1, DrvInfo& drv2) {
+  return getPriority(state, drv2) - getPriority(state, drv1);
+}
+
+// FIXME: this function is rather slow since it checks a single path
+// at a time.
+static bool isPrebuilt(EvalState& state, DrvInfo& elem) {
+  Path path = elem.queryOutPath();
+  if (state.store->isValidPath(path)) {
+    return true;
+  }
+  PathSet ps = state.store->querySubstitutablePaths({path});
+  return ps.find(path) != ps.end();
+}
+
+static void checkSelectorUse(DrvNames& selectors) {
+  /* Check that all selectors have been used. */
+  for (auto& i : selectors) {
+    if (i.hits == 0 && i.fullName != "*") {
+      throw Error(format("selector '%1%' matches no derivations") % i.fullName);
+    }
+  }
+}
+
+static DrvInfos filterBySelector(EvalState& state, const DrvInfos& allElems,
+                                 const Strings& args, bool newestOnly) {
+  DrvNames selectors = drvNamesFromArgs(args);
+  if (selectors.empty()) {
+    selectors.push_back(DrvName("*"));
+  }
+
+  DrvInfos elems;
+  std::set<unsigned int> done;
+
+  for (auto& i : selectors) {
+    typedef std::list<std::pair<DrvInfo, unsigned int> > Matches;
+    Matches matches;
+    unsigned int n = 0;
+    for (auto j = allElems.begin(); j != allElems.end(); ++j, ++n) {
+      DrvName drvName(j->queryName());
+      if (i.matches(drvName)) {
+        i.hits++;
+        matches.push_back(std::pair<DrvInfo, unsigned int>(*j, n));
+      }
+    }
+
+    /* If `newestOnly', if a selector matches multiple derivations
+       with the same name, pick the one matching the current
+       system.  If there are still multiple derivations, pick the
+       one with the highest priority.  If there are still multiple
+       derivations, pick the one with the highest version.
+       Finally, if there are still multiple derivations,
+       arbitrarily pick the first one. */
+    if (newestOnly) {
+      /* Map from package names to derivations. */
+      typedef std::map<std::string, std::pair<DrvInfo, unsigned int> > Newest;
+      Newest newest;
+      StringSet multiple;
+
+      for (auto& j : matches) {
+        DrvName drvName(j.first.queryName());
+        long d = 1;
+
+        auto k = newest.find(drvName.name);
+
+        if (k != newest.end()) {
+          d = j.first.querySystem() == k->second.first.querySystem()
+                  ? 0
+                  : j.first.querySystem() == settings.thisSystem
+                        ? 1
+                        : k->second.first.querySystem() == settings.thisSystem
+                              ? -1
+                              : 0;
+          if (d == 0) {
+            d = comparePriorities(state, j.first, k->second.first);
+          }
+          if (d == 0) {
+            d = compareVersions(drvName.version,
+                                DrvName(k->second.first.queryName()).version);
+          }
+        }
+
+        if (d > 0) {
+          newest.erase(drvName.name);
+          newest.insert(Newest::value_type(drvName.name, j));
+          multiple.erase(j.first.queryName());
+        } else if (d == 0) {
+          multiple.insert(j.first.queryName());
+        }
+      }
+
+      matches.clear();
+      for (auto& j : newest) {
+        if (multiple.find(j.second.first.queryName()) != multiple.end()) {
+          LOG(WARNING) << "warning: there are multiple derivations named '"
+                       << j.second.first.queryName()
+                       << "'; using the first one";
+        }
+        matches.push_back(j.second);
+      }
+    }
+
+    /* Insert only those elements in the final list that we
+       haven't inserted before. */
+    for (auto& j : matches) {
+      if (done.find(j.second) == done.end()) {
+        done.insert(j.second);
+        elems.push_back(j.first);
+      }
+    }
+  }
+
+  checkSelectorUse(selectors);
+
+  return elems;
+}
+
+static bool isPath(const std::string& s) {
+  return s.find('/') != std::string::npos;
+}
+
+static void queryInstSources(EvalState& state, InstallSourceInfo& instSource,
+                             const Strings& args, DrvInfos& elems,
+                             bool newestOnly) {
+  InstallSourceType type = instSource.type;
+  if (type == srcUnknown && !args.empty() && isPath(args.front())) {
+    type = srcStorePaths;
+  }
+
+  switch (type) {
+    /* Get the available user environment elements from the
+       derivations specified in a Nix expression, including only
+       those with names matching any of the names in `args'. */
+    case srcUnknown:
+    case srcNixExprDrvs: {
+      /* Load the derivations from the (default or specified)
+         Nix expression. */
+      DrvInfos allElems;
+      loadDerivations(state, instSource.nixExprPath, instSource.systemFilter,
+                      *instSource.autoArgs, "", allElems);
+
+      elems = filterBySelector(state, allElems, args, newestOnly);
+
+      break;
+    }
+
+    /* Get the available user environment elements from the Nix
+       expressions specified on the command line; these should be
+       functions that take the default Nix expression file as
+       argument, e.g., if the file is `./foo.nix', then the
+       argument `x: x.bar' is equivalent to `(x: x.bar)
+       (import ./foo.nix)' = `(import ./foo.nix).bar'. */
+    case srcNixExprs: {
+      Value vArg;
+      loadSourceExpr(state, instSource.nixExprPath, vArg);
+
+      for (auto& i : args) {
+        Expr* eFun = state.parseExprFromString(i, absPath("."));
+        Value vFun;
+        Value vTmp;
+        state.eval(eFun, vFun);
+        mkApp(vTmp, vFun, vArg);
+        getDerivations(state, vTmp, "", *instSource.autoArgs, elems, true);
+      }
+
+      break;
+    }
+
+    /* The available user environment elements are specified as a
+       list of store paths (which may or may not be
+       derivations). */
+    case srcStorePaths: {
+      for (auto& i : args) {
+        Path path = state.store->followLinksToStorePath(i);
+
+        std::string name = baseNameOf(path);
+        std::string::size_type dash = name.find('-');
+        if (dash != std::string::npos) {
+          name = std::string(name, dash + 1);
+        }
+
+        DrvInfo elem(state, "", nullptr);
+        elem.setName(name);
+
+        if (isDerivation(path)) {
+          elem.setDrvPath(path);
+          elem.setOutPath(
+              state.store->derivationFromPath(path).findOutput("out"));
+          if (name.size() >= drvExtension.size() &&
+              std::string(name, name.size() - drvExtension.size()) ==
+                  drvExtension) {
+            name = std::string(name, 0, name.size() - drvExtension.size());
+          }
+        } else {
+          elem.setOutPath(path);
+        }
+
+        elems.push_back(elem);
+      }
+
+      break;
+    }
+
+    /* Get the available user environment elements from another
+       user environment.  These are then filtered as in the
+       `srcNixExprDrvs' case. */
+    case srcProfile: {
+      elems = filterBySelector(state, queryInstalled(state, instSource.profile),
+                               args, newestOnly);
+      break;
+    }
+
+    case srcAttrPath: {
+      Value vRoot;
+      loadSourceExpr(state, instSource.nixExprPath, vRoot);
+      for (auto& i : args) {
+        Value& v(*findAlongAttrPath(state, i, *instSource.autoArgs, vRoot));
+        getDerivations(state, v, "", *instSource.autoArgs, elems, true);
+      }
+      break;
+    }
+  }
+}
+
+static void printMissing(EvalState& state, DrvInfos& elems) {
+  PathSet targets;
+  for (auto& i : elems) {
+    Path drvPath = i.queryDrvPath();
+    if (!drvPath.empty()) {
+      targets.insert(drvPath);
+    } else {
+      targets.insert(i.queryOutPath());
+    }
+  }
+
+  printMissing(state.store, targets);
+}
+
+static bool keep(DrvInfo& drv) { return drv.queryMetaBool("keep", false); }
+
+static void installDerivations(Globals& globals, const Strings& args,
+                               const Path& profile) {
+  DLOG(INFO) << "installing derivations";
+
+  /* Get the set of user environment elements to be installed. */
+  DrvInfos newElems;
+  DrvInfos newElemsTmp;
+  queryInstSources(*globals.state, globals.instSource, args, newElemsTmp, true);
+
+  /* If --prebuilt-only is given, filter out source-only packages. */
+  for (auto& i : newElemsTmp) {
+    if (!globals.prebuiltOnly || isPrebuilt(*globals.state, i)) {
+      newElems.push_back(i);
+    }
+  }
+
+  StringSet newNames;
+  for (auto& i : newElems) {
+    /* `forceName' is a hack to get package names right in some
+       one-click installs, namely those where the name used in the
+       path is not the one we want (e.g., `java-front' versus
+       `java-front-0.9pre15899'). */
+    if (!globals.forceName.empty()) {
+      i.setName(globals.forceName);
+    }
+    newNames.insert(DrvName(i.queryName()).name);
+  }
+
+  while (true) {
+    std::string lockToken = optimisticLockProfile(profile);
+
+    DrvInfos allElems(newElems);
+
+    /* Add in the already installed derivations, unless they have
+       the same name as a to-be-installed element. */
+    if (!globals.removeAll) {
+      DrvInfos installedElems = queryInstalled(*globals.state, profile);
+
+      for (auto& i : installedElems) {
+        DrvName drvName(i.queryName());
+        if (!globals.preserveInstalled &&
+            newNames.find(drvName.name) != newNames.end() && !keep(i)) {
+          LOG(INFO) << "replacing old '" << i.queryName() << "'";
+        } else {
+          allElems.push_back(i);
+        }
+      }
+
+      for (auto& i : newElems) {
+        LOG(INFO) << "installing " << i.queryName();
+      }
+    }
+
+    printMissing(*globals.state, newElems);
+
+    if (globals.dryRun) {
+      return;
+    }
+
+    if (createUserEnv(*globals.state, allElems, profile,
+                      settings.envKeepDerivations, lockToken)) {
+      break;
+    }
+  }
+}
+
+static void opInstall(Globals& globals, Strings opFlags, Strings opArgs) {
+  for (auto i = opFlags.begin(); i != opFlags.end();) {
+    std::string arg = *i++;
+    if (parseInstallSourceOptions(globals, i, opFlags, arg)) {
+      ;
+    } else if (arg == "--preserve-installed" || arg == "-P") {
+      globals.preserveInstalled = true;
+    } else if (arg == "--remove-all" || arg == "-r") {
+      globals.removeAll = true;
+    } else {
+      throw UsageError(format("unknown flag '%1%'") % arg);
+    }
+  }
+
+  installDerivations(globals, opArgs, globals.profile);
+}
+
+typedef enum { utLt, utLeq, utEq, utAlways } UpgradeType;
+
+static void upgradeDerivations(Globals& globals, const Strings& args,
+                               UpgradeType upgradeType) {
+  DLOG(INFO) << "upgrading derivations";
+
+  /* Upgrade works as follows: we take all currently installed
+     derivations, and for any derivation matching any selector, look
+     for a derivation in the input Nix expression that has the same
+     name and a higher version number. */
+
+  while (true) {
+    std::string lockToken = optimisticLockProfile(globals.profile);
+
+    DrvInfos installedElems = queryInstalled(*globals.state, globals.profile);
+
+    /* Fetch all derivations from the input file. */
+    DrvInfos availElems;
+    queryInstSources(*globals.state, globals.instSource, args, availElems,
+                     false);
+
+    /* Go through all installed derivations. */
+    DrvInfos newElems;
+    for (auto& i : installedElems) {
+      DrvName drvName(i.queryName());
+
+      try {
+        if (keep(i)) {
+          newElems.push_back(i);
+          continue;
+        }
+
+        /* Find the derivation in the input Nix expression
+           with the same name that satisfies the version
+           constraints specified by upgradeType.  If there are
+           multiple matches, take the one with the highest
+           priority.  If there are still multiple matches,
+           take the one with the highest version.
+           Do not upgrade if it would decrease the priority. */
+        auto bestElem = availElems.end();
+        std::string bestVersion;
+        for (auto j = availElems.begin(); j != availElems.end(); ++j) {
+          if (comparePriorities(*globals.state, i, *j) > 0) {
+            continue;
+          }
+          DrvName newName(j->queryName());
+          if (newName.name == drvName.name) {
+            int d = compareVersions(drvName.version, newName.version);
+            if ((upgradeType == utLt && d < 0) ||
+                (upgradeType == utLeq && d <= 0) ||
+                (upgradeType == utEq && d == 0) || upgradeType == utAlways) {
+              long d2 = -1;
+              if (bestElem != availElems.end()) {
+                d2 = comparePriorities(*globals.state, *bestElem, *j);
+                if (d2 == 0) {
+                  d2 = compareVersions(bestVersion, newName.version);
+                }
+              }
+              if (d2 < 0 &&
+                  (!globals.prebuiltOnly || isPrebuilt(*globals.state, *j))) {
+                bestElem = j;
+                bestVersion = newName.version;
+              }
+            }
+          }
+        }
+
+        if (bestElem != availElems.end() &&
+            i.queryOutPath() != bestElem->queryOutPath()) {
+          const char* action =
+              compareVersions(drvName.version, bestVersion) <= 0
+                  ? "upgrading"
+                  : "downgrading";
+          LOG(INFO) << action << " '" << i.queryName() << "' to '"
+                    << bestElem->queryName() << "'";
+          newElems.push_back(*bestElem);
+        } else {
+          newElems.push_back(i);
+        }
+
+      } catch (Error& e) {
+        e.addPrefix(
+            fmt("while trying to find an upgrade for '%s':\n", i.queryName()));
+        throw;
+      }
+    }
+
+    printMissing(*globals.state, newElems);
+
+    if (globals.dryRun) {
+      return;
+    }
+
+    if (createUserEnv(*globals.state, newElems, globals.profile,
+                      settings.envKeepDerivations, lockToken)) {
+      break;
+    }
+  }
+}
+
+static void opUpgrade(Globals& globals, Strings opFlags, Strings opArgs) {
+  UpgradeType upgradeType = utLt;
+  for (auto i = opFlags.begin(); i != opFlags.end();) {
+    std::string arg = *i++;
+    if (parseInstallSourceOptions(globals, i, opFlags, arg)) {
+      ;
+    } else if (arg == "--lt") {
+      upgradeType = utLt;
+    } else if (arg == "--leq") {
+      upgradeType = utLeq;
+    } else if (arg == "--eq") {
+      upgradeType = utEq;
+    } else if (arg == "--always") {
+      upgradeType = utAlways;
+    } else {
+      throw UsageError(format("unknown flag '%1%'") % arg);
+    }
+  }
+
+  upgradeDerivations(globals, opArgs, upgradeType);
+}
+
+static void setMetaFlag(EvalState& state, DrvInfo& drv, const std::string& name,
+                        const std::string& value) {
+  Value* v = state.allocValue();
+  mkString(*v, value.c_str());
+  drv.setMeta(name, v);
+}
+
+static void opSetFlag(Globals& globals, Strings opFlags, Strings opArgs) {
+  if (!opFlags.empty()) {
+    throw UsageError(format("unknown flag '%1%'") % opFlags.front());
+  }
+  if (opArgs.size() < 2) {
+    throw UsageError("not enough arguments to '--set-flag'");
+  }
+
+  auto arg = opArgs.begin();
+  std::string flagName = *arg++;
+  std::string flagValue = *arg++;
+  DrvNames selectors = drvNamesFromArgs(Strings(arg, opArgs.end()));
+
+  while (true) {
+    std::string lockToken = optimisticLockProfile(globals.profile);
+
+    DrvInfos installedElems = queryInstalled(*globals.state, globals.profile);
+
+    /* Update all matching derivations. */
+    for (auto& i : installedElems) {
+      DrvName drvName(i.queryName());
+      for (auto& j : selectors) {
+        if (j.matches(drvName)) {
+          LOG(INFO) << "setting flag on '" << i.queryName() << "'";
+          j.hits++;
+          setMetaFlag(*globals.state, i, flagName, flagValue);
+          break;
+        }
+      }
+    }
+
+    checkSelectorUse(selectors);
+
+    /* Write the new user environment. */
+    if (createUserEnv(*globals.state, installedElems, globals.profile,
+                      settings.envKeepDerivations, lockToken)) {
+      break;
+    }
+  }
+}
+
+static void opSet(Globals& globals, Strings opFlags, Strings opArgs) {
+  auto store2 = globals.state->store.dynamic_pointer_cast<LocalFSStore>();
+  if (!store2) {
+    throw Error("--set is not supported for this Nix store");
+  }
+
+  for (auto i = opFlags.begin(); i != opFlags.end();) {
+    std::string arg = *i++;
+    if (parseInstallSourceOptions(globals, i, opFlags, arg)) {
+      ;
+    } else {
+      throw UsageError(format("unknown flag '%1%'") % arg);
+    }
+  }
+
+  DrvInfos elems;
+  queryInstSources(*globals.state, globals.instSource, opArgs, elems, true);
+
+  if (elems.size() != 1) {
+    throw Error("--set requires exactly one derivation");
+  }
+
+  DrvInfo& drv(elems.front());
+
+  if (!globals.forceName.empty()) {
+    drv.setName(globals.forceName);
+  }
+
+  if (!drv.queryDrvPath().empty()) {
+    PathSet paths = {drv.queryDrvPath()};
+    printMissing(globals.state->store, paths);
+    if (globals.dryRun) {
+      return;
+    }
+    globals.state->store->buildPaths(
+        paths, globals.state->repair != 0u ? bmRepair : bmNormal);
+  } else {
+    printMissing(globals.state->store, {drv.queryOutPath()});
+    if (globals.dryRun) {
+      return;
+    }
+    globals.state->store->ensurePath(drv.queryOutPath());
+  }
+
+  DLOG(INFO) << "switching to new user environment";
+  Path generation = createGeneration(ref<LocalFSStore>(store2), globals.profile,
+                                     drv.queryOutPath());
+  switchLink(globals.profile, generation);
+}
+
+static void uninstallDerivations(Globals& globals, Strings& selectors,
+                                 Path& profile) {
+  while (true) {
+    std::string lockToken = optimisticLockProfile(profile);
+
+    DrvInfos installedElems = queryInstalled(*globals.state, profile);
+    DrvInfos newElems;
+
+    for (auto& i : installedElems) {
+      DrvName drvName(i.queryName());
+      bool found = false;
+      for (auto& j : selectors) {
+        /* !!! the repeated calls to followLinksToStorePath()
+           are expensive, should pre-compute them. */
+        if ((isPath(j) &&
+             i.queryOutPath() ==
+                 globals.state->store->followLinksToStorePath(j)) ||
+            DrvName(j).matches(drvName)) {
+          LOG(INFO) << "uninstalling '" << i.queryName() << "'";
+          found = true;
+          break;
+        }
+      }
+      if (!found) {
+        newElems.push_back(i);
+      }
+    }
+
+    if (globals.dryRun) {
+      return;
+    }
+
+    if (createUserEnv(*globals.state, newElems, profile,
+                      settings.envKeepDerivations, lockToken)) {
+      break;
+    }
+  }
+}
+
+static void opUninstall(Globals& globals, Strings opFlags, Strings opArgs) {
+  if (!opFlags.empty()) {
+    throw UsageError(format("unknown flag '%1%'") % opFlags.front());
+  }
+  uninstallDerivations(globals, opArgs, globals.profile);
+}
+
+static bool cmpChars(char a, char b) { return toupper(a) < toupper(b); }
+
+static bool cmpElemByName(const DrvInfo& a, const DrvInfo& b) {
+  auto a_name = a.queryName();
+  auto b_name = b.queryName();
+  return lexicographical_compare(a_name.begin(), a_name.end(), b_name.begin(),
+                                 b_name.end(), cmpChars);
+}
+
+using Table = std::list<Strings>;
+
+void printTable(Table& table) {
+  auto nrColumns = !table.empty() ? table.front().size() : 0;
+
+  std::vector<size_t> widths;
+  widths.resize(nrColumns);
+
+  for (auto& i : table) {
+    assert(i.size() == nrColumns);
+    Strings::iterator j;
+    size_t column;
+    for (j = i.begin(), column = 0; j != i.end(); ++j, ++column) {
+      if (j->size() > widths[column]) {
+        widths[column] = j->size();
+      }
+    }
+  }
+
+  for (auto& i : table) {
+    Strings::iterator j;
+    size_t column;
+    for (j = i.begin(), column = 0; j != i.end(); ++j, ++column) {
+      std::string s = *j;
+      replace(s.begin(), s.end(), '\n', ' ');
+      cout << s;
+      if (column < nrColumns - 1) {
+        cout << std::string(widths[column] - s.size() + 2, ' ');
+      }
+    }
+    cout << std::endl;
+  }
+}
+
+/* This function compares the version of an element against the
+   versions in the given set of elements.  `cvLess' means that only
+   lower versions are in the set, `cvEqual' means that at most an
+   equal version is in the set, and `cvGreater' means that there is at
+   least one element with a higher version in the set.  `cvUnavail'
+   means that there are no elements with the same name in the set. */
+
+typedef enum { cvLess, cvEqual, cvGreater, cvUnavail } VersionDiff;
+
+static VersionDiff compareVersionAgainstSet(const DrvInfo& elem,
+                                            const DrvInfos& elems,
+                                            std::string& version) {
+  DrvName name(elem.queryName());
+
+  VersionDiff diff = cvUnavail;
+  version = "?";
+
+  for (auto& i : elems) {
+    DrvName name2(i.queryName());
+    if (name.name == name2.name) {
+      int d = compareVersions(name.version, name2.version);
+      if (d < 0) {
+        diff = cvGreater;
+        version = name2.version;
+      } else if (diff != cvGreater && d == 0) {
+        diff = cvEqual;
+        version = name2.version;
+      } else if (diff != cvGreater && diff != cvEqual && d > 0) {
+        diff = cvLess;
+        if (version.empty() || compareVersions(version, name2.version) < 0) {
+          version = name2.version;
+        }
+      }
+    }
+  }
+
+  return diff;
+}
+
+static void queryJSON(Globals& globals, std::vector<DrvInfo>& elems) {
+  JSONObject topObj(cout, true);
+  for (auto& i : elems) {
+    JSONObject pkgObj = topObj.object(i.attrPath);
+
+    auto drvName = DrvName(i.queryName());
+    pkgObj.attr("name", drvName.fullName);
+    pkgObj.attr("pname", drvName.name);
+    pkgObj.attr("version", drvName.version);
+    pkgObj.attr("system", i.querySystem());
+
+    JSONObject metaObj = pkgObj.object("meta");
+    StringSet metaNames = i.queryMetaNames();
+    for (auto& j : metaNames) {
+      auto placeholder = metaObj.placeholder(j);
+      Value* v = i.queryMeta(j);
+      if (v == nullptr) {
+        LOG(ERROR) << "derivation '" << i.queryName()
+                   << "' has invalid meta attribute '" << j << "'";
+        placeholder.write(nullptr);
+      } else {
+        PathSet context;
+        printValueAsJSON(*globals.state, true, *v, placeholder, context);
+      }
+    }
+  }
+}
+
+static void opQuery(Globals& globals, Strings opFlags, Strings opArgs) {
+  Strings remaining;
+  std::string attrPath;
+
+  bool printStatus = false;
+  bool printName = true;
+  bool printAttrPath = false;
+  bool printSystem = false;
+  bool printDrvPath = false;
+  bool printOutPath = false;
+  bool printDescription = false;
+  bool printMeta = false;
+  bool compareVersions = false;
+  bool xmlOutput = false;
+  bool jsonOutput = false;
+
+  enum { sInstalled, sAvailable } source = sInstalled;
+
+  settings.readOnlyMode = true; /* makes evaluation a bit faster */
+
+  for (auto i = opFlags.begin(); i != opFlags.end();) {
+    std::string arg = *i++;
+    if (arg == "--status" || arg == "-s") {
+      printStatus = true;
+    } else if (arg == "--no-name") {
+      printName = false;
+    } else if (arg == "--system") {
+      printSystem = true;
+    } else if (arg == "--description") {
+      printDescription = true;
+    } else if (arg == "--compare-versions" || arg == "-c") {
+      compareVersions = true;
+    } else if (arg == "--drv-path") {
+      printDrvPath = true;
+    } else if (arg == "--out-path") {
+      printOutPath = true;
+    } else if (arg == "--meta") {
+      printMeta = true;
+    } else if (arg == "--installed") {
+      source = sInstalled;
+    } else if (arg == "--available" || arg == "-a") {
+      source = sAvailable;
+    } else if (arg == "--xml") {
+      xmlOutput = true;
+    } else if (arg == "--json") {
+      jsonOutput = true;
+    } else if (arg == "--attr-path" || arg == "-P") {
+      printAttrPath = true;
+    } else if (arg == "--attr" || arg == "-A") {
+      attrPath = needArg(i, opFlags, arg);
+    } else {
+      throw UsageError(format("unknown flag '%1%'") % arg);
+    }
+  }
+
+  /* Obtain derivation information from the specified source. */
+  DrvInfos availElems;
+  DrvInfos installedElems;
+
+  if (source == sInstalled || compareVersions || printStatus) {
+    installedElems = queryInstalled(*globals.state, globals.profile);
+  }
+
+  if (source == sAvailable || compareVersions) {
+    loadDerivations(*globals.state, globals.instSource.nixExprPath,
+                    globals.instSource.systemFilter,
+                    *globals.instSource.autoArgs, attrPath, availElems);
+  }
+
+  DrvInfos elems_ = filterBySelector(
+      *globals.state, source == sInstalled ? installedElems : availElems,
+      opArgs, false);
+
+  DrvInfos& otherElems(source == sInstalled ? availElems : installedElems);
+
+  /* Sort them by name. */
+  /* !!! */
+  std::vector<DrvInfo> elems;
+  for (auto& i : elems_) {
+    elems.push_back(i);
+  }
+  sort(elems.begin(), elems.end(), cmpElemByName);
+
+  /* We only need to know the installed paths when we are querying
+     the status of the derivation. */
+  PathSet installed; /* installed paths */
+
+  if (printStatus) {
+    for (auto& i : installedElems) {
+      installed.insert(i.queryOutPath());
+    }
+  }
+
+  /* Query which paths have substitutes. */
+  PathSet validPaths;
+  PathSet substitutablePaths;
+  if (printStatus || globals.prebuiltOnly) {
+    PathSet paths;
+    for (auto& i : elems) {
+      try {
+        paths.insert(i.queryOutPath());
+      } catch (AssertionError& e) {
+        DLOG(WARNING) << "skipping derivation named '" << i.queryName()
+                      << "' which gives an assertion failure";
+        i.setFailed();
+      }
+    }
+    validPaths = globals.state->store->queryValidPaths(paths);
+    substitutablePaths = globals.state->store->querySubstitutablePaths(paths);
+  }
+
+  /* Print the desired columns, or XML output. */
+  if (jsonOutput) {
+    queryJSON(globals, elems);
+    return;
+  }
+
+  bool tty = isatty(STDOUT_FILENO) != 0;
+  RunPager pager;
+
+  Table table;
+  std::ostringstream dummy;
+  XMLWriter xml(true, *(xmlOutput ? &cout : &dummy));
+  XMLOpenElement xmlRoot(xml, "items");
+
+  for (auto& i : elems) {
+    try {
+      if (i.hasFailed()) {
+        continue;
+      }
+
+      // Activity act(*logger, lvlDebug, format("outputting query result '%1%'")
+      // % i.attrPath);
+
+      if (globals.prebuiltOnly &&
+          validPaths.find(i.queryOutPath()) == validPaths.end() &&
+          substitutablePaths.find(i.queryOutPath()) ==
+              substitutablePaths.end()) {
+        continue;
+      }
+
+      /* For table output. */
+      Strings columns;
+
+      /* For XML output. */
+      XMLAttrs attrs;
+
+      if (printStatus) {
+        Path outPath = i.queryOutPath();
+        bool hasSubs =
+            substitutablePaths.find(outPath) != substitutablePaths.end();
+        bool isInstalled = installed.find(outPath) != installed.end();
+        bool isValid = validPaths.find(outPath) != validPaths.end();
+        if (xmlOutput) {
+          attrs["installed"] = isInstalled ? "1" : "0";
+          attrs["valid"] = isValid ? "1" : "0";
+          attrs["substitutable"] = hasSubs ? "1" : "0";
+        } else {
+          columns.push_back((std::string)(isInstalled ? "I" : "-") +
+                            (isValid ? "P" : "-") + (hasSubs ? "S" : "-"));
+        }
+      }
+
+      if (xmlOutput) {
+        attrs["attrPath"] = i.attrPath;
+      } else if (printAttrPath) {
+        columns.push_back(i.attrPath);
+      }
+
+      if (xmlOutput) {
+        auto drvName = DrvName(i.queryName());
+        attrs["name"] = drvName.fullName;
+        attrs["pname"] = drvName.name;
+        attrs["version"] = drvName.version;
+      } else if (printName) {
+        columns.push_back(i.queryName());
+      }
+
+      if (compareVersions) {
+        /* Compare this element against the versions of the
+           same named packages in either the set of available
+           elements, or the set of installed elements.  !!!
+           This is O(N * M), should be O(N * lg M). */
+        std::string version;
+        VersionDiff diff = compareVersionAgainstSet(i, otherElems, version);
+
+        char ch;
+        switch (diff) {
+          case cvLess:
+            ch = '>';
+            break;
+          case cvEqual:
+            ch = '=';
+            break;
+          case cvGreater:
+            ch = '<';
+            break;
+          case cvUnavail:
+            ch = '-';
+            break;
+          default:
+            abort();
+        }
+
+        if (xmlOutput) {
+          if (diff != cvUnavail) {
+            attrs["versionDiff"] = ch;
+            attrs["maxComparedVersion"] = version;
+          }
+        } else {
+          std::string column = (std::string) "" + ch + " " + version;
+          if (diff == cvGreater && tty) {
+            column = ANSI_RED + column + ANSI_NORMAL;
+          }
+          columns.push_back(column);
+        }
+      }
+
+      if (xmlOutput) {
+        if (!i.querySystem().empty()) {
+          attrs["system"] = i.querySystem();
+        }
+      } else if (printSystem) {
+        columns.push_back(i.querySystem());
+      }
+
+      if (printDrvPath) {
+        std::string drvPath = i.queryDrvPath();
+        if (xmlOutput) {
+          if (!drvPath.empty()) {
+            attrs["drvPath"] = drvPath;
+          }
+        } else {
+          columns.push_back(drvPath.empty() ? "-" : drvPath);
+        }
+      }
+
+      if (printOutPath && !xmlOutput) {
+        DrvInfo::Outputs outputs = i.queryOutputs();
+        std::string s;
+        for (auto& j : outputs) {
+          if (!s.empty()) {
+            s += ';';
+          }
+          if (j.first != "out") {
+            s += j.first;
+            s += "=";
+          }
+          s += j.second;
+        }
+        columns.push_back(s);
+      }
+
+      if (printDescription) {
+        std::string descr = i.queryMetaString("description");
+        if (xmlOutput) {
+          if (!descr.empty()) {
+            attrs["description"] = descr;
+          }
+        } else {
+          columns.push_back(descr);
+        }
+      }
+
+      if (xmlOutput) {
+        if (printOutPath || printMeta) {
+          XMLOpenElement item(xml, "item", attrs);
+          if (printOutPath) {
+            DrvInfo::Outputs outputs = i.queryOutputs();
+            for (auto& j : outputs) {
+              XMLAttrs attrs2;
+              attrs2["name"] = j.first;
+              attrs2["path"] = j.second;
+              xml.writeEmptyElement("output", attrs2);
+            }
+          }
+          if (printMeta) {
+            StringSet metaNames = i.queryMetaNames();
+            for (auto& j : metaNames) {
+              XMLAttrs attrs2;
+              attrs2["name"] = j;
+              Value* v = i.queryMeta(j);
+              if (v == nullptr) {
+                LOG(ERROR) << "derivation '" << i.queryName()
+                           << "' has invalid meta attribute '" << j << "'";
+              } else {
+                if (v->type == tString) {
+                  attrs2["type"] = "string";
+                  attrs2["value"] = v->string.s;
+                  xml.writeEmptyElement("meta", attrs2);
+                } else if (v->type == tInt) {
+                  attrs2["type"] = "int";
+                  attrs2["value"] = (format("%1%") % v->integer).str();
+                  xml.writeEmptyElement("meta", attrs2);
+                } else if (v->type == tFloat) {
+                  attrs2["type"] = "float";
+                  attrs2["value"] = (format("%1%") % v->fpoint).str();
+                  xml.writeEmptyElement("meta", attrs2);
+                } else if (v->type == tBool) {
+                  attrs2["type"] = "bool";
+                  attrs2["value"] = v->boolean ? "true" : "false";
+                  xml.writeEmptyElement("meta", attrs2);
+                } else if (v->isList()) {
+                  attrs2["type"] = "strings";
+                  XMLOpenElement m(xml, "meta", attrs2);
+                  for (unsigned int j = 0; j < v->listSize(); ++j) {
+                    if (v->listElems()[j]->type != tString) {
+                      continue;
+                    }
+                    XMLAttrs attrs3;
+                    attrs3["value"] = v->listElems()[j]->string.s;
+                    xml.writeEmptyElement("string", attrs3);
+                  }
+                } else if (v->type == tAttrs) {
+                  attrs2["type"] = "strings";
+                  XMLOpenElement m(xml, "meta", attrs2);
+                  Bindings& attrs = *v->attrs;
+                  for (auto& [name, a] : attrs) {
+                    if (a.value->type != tString) {
+                      continue;
+                    }
+                    XMLAttrs attrs3;
+                    attrs3["type"] = name;
+                    attrs3["value"] = a.value->string.s;
+                    xml.writeEmptyElement("string", attrs3);
+                  }
+                }
+              }
+            }
+          }
+        } else {
+          xml.writeEmptyElement("item", attrs);
+        }
+      } else {
+        table.push_back(columns);
+      }
+
+      cout.flush();
+
+    } catch (AssertionError& e) {
+      DLOG(WARNING) << "skipping derivation named '" << i.queryName()
+                    << "' which gives an assertion failure";
+    } catch (Error& e) {
+      e.addPrefix(
+          fmt("while querying the derivation named '%1%':\n", i.queryName()));
+      throw;
+    }
+  }
+
+  if (!xmlOutput) {
+    printTable(table);
+  }
+}
+
+static void opSwitchProfile(Globals& globals, Strings opFlags, Strings opArgs) {
+  if (!opFlags.empty()) {
+    throw UsageError(format("unknown flag '%1%'") % opFlags.front());
+  }
+  if (opArgs.size() != 1) {
+    throw UsageError(format("exactly one argument expected"));
+  }
+
+  Path profile = absPath(opArgs.front());
+  Path profileLink = getHome() + "/.nix-profile";
+
+  switchLink(profileLink, profile);
+}
+
+static const int prevGen = -2;
+
+static void switchGeneration(Globals& globals, int dstGen) {
+  PathLocks lock;
+  lockProfile(lock, globals.profile);
+
+  int curGen;
+  Generations gens = findGenerations(globals.profile, curGen);
+
+  Generation dst;
+  for (auto& i : gens) {
+    if ((dstGen == prevGen && i.number < curGen) ||
+        (dstGen >= 0 && i.number == dstGen)) {
+      dst = i;
+    }
+  }
+
+  if (!dst) {
+    if (dstGen == prevGen) {
+      throw Error(format("no generation older than the current (%1%) exists") %
+                  curGen);
+    }
+    throw Error(format("generation %1% does not exist") % dstGen);
+  }
+
+  LOG(INFO) << "switching from generation " << curGen << " to " << dst.number;
+
+  if (globals.dryRun) {
+    return;
+  }
+
+  switchLink(globals.profile, dst.path);
+}
+
+static void opSwitchGeneration(Globals& globals, Strings opFlags,
+                               Strings opArgs) {
+  if (!opFlags.empty()) {
+    throw UsageError(format("unknown flag '%1%'") % opFlags.front());
+  }
+  if (opArgs.size() != 1) {
+    throw UsageError(format("exactly one argument expected"));
+  }
+
+  int dstGen;
+  if (!absl::SimpleAtoi(opArgs.front(), &dstGen)) {
+    throw UsageError(format("expected a generation number"));
+  }
+
+  switchGeneration(globals, dstGen);
+}
+
+static void opRollback(Globals& globals, Strings opFlags, Strings opArgs) {
+  if (!opFlags.empty()) {
+    throw UsageError(format("unknown flag '%1%'") % opFlags.front());
+  }
+  if (!opArgs.empty()) {
+    throw UsageError(format("no arguments expected"));
+  }
+
+  switchGeneration(globals, prevGen);
+}
+
+static void opListGenerations(Globals& globals, Strings opFlags,
+                              Strings opArgs) {
+  if (!opFlags.empty()) {
+    throw UsageError(format("unknown flag '%1%'") % opFlags.front());
+  }
+  if (!opArgs.empty()) {
+    throw UsageError(format("no arguments expected"));
+  }
+
+  PathLocks lock;
+  lockProfile(lock, globals.profile);
+
+  int curGen;
+  Generations gens = findGenerations(globals.profile, curGen);
+
+  RunPager pager;
+
+  for (auto& i : gens) {
+    tm t;
+    if (localtime_r(&i.creationTime, &t) == nullptr) {
+      throw Error("cannot convert time");
+    }
+    cout << format("%|4|   %|4|-%|02|-%|02| %|02|:%|02|:%|02|   %||\n") %
+                i.number % (t.tm_year + 1900) % (t.tm_mon + 1) % t.tm_mday %
+                t.tm_hour % t.tm_min % t.tm_sec %
+                (i.number == curGen ? "(current)" : "");
+  }
+}
+
+static void opDeleteGenerations(Globals& globals, Strings opFlags,
+                                Strings opArgs) {
+  if (!opFlags.empty()) {
+    throw UsageError(format("unknown flag '%1%'") % opFlags.front());
+  }
+
+  if (opArgs.size() == 1 && opArgs.front() == "old") {
+    deleteOldGenerations(globals.profile, globals.dryRun);
+  } else if (opArgs.size() == 1 &&
+             opArgs.front().find('d') != std::string::npos) {
+    deleteGenerationsOlderThan(globals.profile, opArgs.front(), globals.dryRun);
+  } else if (opArgs.size() == 1 &&
+             opArgs.front().find('+') != std::string::npos) {
+    if (opArgs.front().size() < 2) {
+      throw Error(format("invalid number of generations ‘%1%’") %
+                  opArgs.front());
+    }
+    std::string str_max = std::string(opArgs.front(), 1, opArgs.front().size());
+    int max;
+    if (!absl::SimpleAtoi(str_max, &max) || max == 0) {
+      throw Error(format("invalid number of generations to keep ‘%1%’") %
+                  opArgs.front());
+    }
+    deleteGenerationsGreaterThan(globals.profile, max, globals.dryRun);
+  } else {
+    std::set<unsigned int> gens;
+    for (auto& i : opArgs) {
+      unsigned int n;
+      if (!absl::SimpleAtoi(i, &n)) {
+        throw UsageError(format("invalid generation number '%1%'") % i);
+      }
+      gens.insert(n);
+    }
+    deleteGenerations(globals.profile, gens, globals.dryRun);
+  }
+}
+
+static void opVersion(Globals& globals, Strings opFlags, Strings opArgs) {
+  printVersion("nix-env");
+}
+
+static int _main(int argc, char** argv) {
+  {
+    Strings opFlags;
+    Strings opArgs;
+    Operation op = nullptr;
+    RepairFlag repair = NoRepair;
+    std::string file;
+
+    Globals globals;
+
+    globals.instSource.type = srcUnknown;
+    globals.instSource.nixExprPath = getHome() + "/.nix-defexpr";
+    globals.instSource.systemFilter = "*";
+
+    if (!pathExists(globals.instSource.nixExprPath)) {
+      try {
+        createDirs(globals.instSource.nixExprPath);
+        replaceSymlink(fmt("%s/profiles/per-user/%s/channels",
+                           settings.nixStateDir, getUserName()),
+                       globals.instSource.nixExprPath + "/channels");
+        if (getuid() != 0) {
+          replaceSymlink(
+              fmt("%s/profiles/per-user/root/channels", settings.nixStateDir),
+              globals.instSource.nixExprPath + "/channels_root");
+        }
+      } catch (Error&) {
+      }
+    }
+
+    globals.dryRun = false;
+    globals.preserveInstalled = false;
+    globals.removeAll = false;
+    globals.prebuiltOnly = false;
+
+    struct MyArgs : LegacyArgs, MixEvalArgs {
+      using LegacyArgs::LegacyArgs;
+    };
+
+    MyArgs myArgs(baseNameOf(argv[0]), [&](Strings::iterator& arg,
+                                           const Strings::iterator& end) {
+      Operation oldOp = op;
+
+      if (*arg == "--help") {
+        showManPage("nix-env");
+      } else if (*arg == "--version") {
+        op = opVersion;
+      } else if (*arg == "--install" || *arg == "-i") {
+        op = opInstall;
+      } else if (*arg ==
+                 "--force-name") {  // undocumented flag for nix-install-package
+        globals.forceName = getArg(*arg, arg, end);
+      } else if (*arg == "--uninstall" || *arg == "-e") {
+        op = opUninstall;
+      } else if (*arg == "--upgrade" || *arg == "-u") {
+        op = opUpgrade;
+      } else if (*arg == "--set-flag") {
+        op = opSetFlag;
+      } else if (*arg == "--set") {
+        op = opSet;
+      } else if (*arg == "--query" || *arg == "-q") {
+        op = opQuery;
+      } else if (*arg == "--profile" || *arg == "-p") {
+        globals.profile = absPath(getArg(*arg, arg, end));
+      } else if (*arg == "--file" || *arg == "-f") {
+        file = getArg(*arg, arg, end);
+      } else if (*arg == "--switch-profile" || *arg == "-S") {
+        op = opSwitchProfile;
+      } else if (*arg == "--switch-generation" || *arg == "-G") {
+        op = opSwitchGeneration;
+      } else if (*arg == "--rollback") {
+        op = opRollback;
+      } else if (*arg == "--list-generations") {
+        op = opListGenerations;
+      } else if (*arg == "--delete-generations") {
+        op = opDeleteGenerations;
+      } else if (*arg == "--dry-run") {
+        LOG(INFO) << "(dry run; not doing anything)";
+        globals.dryRun = true;
+      } else if (*arg == "--system-filter") {
+        globals.instSource.systemFilter = getArg(*arg, arg, end);
+      } else if (*arg == "--prebuilt-only" || *arg == "-b") {
+        globals.prebuiltOnly = true;
+      } else if (*arg == "--repair") {
+        repair = Repair;
+      } else if (*arg != "" && arg->at(0) == '-') {
+        opFlags.push_back(*arg);
+        /* FIXME: hacky */
+        if (*arg == "--from-profile" ||
+            (op == opQuery && (*arg == "--attr" || *arg == "-A"))) {
+          opFlags.push_back(getArg(*arg, arg, end));
+        }
+      } else {
+        opArgs.push_back(*arg);
+      }
+
+      if ((oldOp != nullptr) && oldOp != op) {
+        throw UsageError("only one operation may be specified");
+      }
+
+      return true;
+    });
+
+    myArgs.parseCmdline(argvToStrings(argc, argv));
+
+    initPlugins();
+
+    if (op == nullptr) {
+      throw UsageError("no operation specified");
+    }
+
+    auto store = openStore();
+
+    globals.state =
+        std::shared_ptr<EvalState>(new EvalState(myArgs.searchPath, store));
+    globals.state->repair = repair;
+
+    if (!file.empty()) {
+      globals.instSource.nixExprPath = lookupFileArg(*globals.state, file);
+    }
+
+    globals.instSource.autoArgs = myArgs.getAutoArgs(*globals.state);
+
+    if (globals.profile.empty()) {
+      globals.profile = getEnv("NIX_PROFILE", "");
+    }
+
+    if (globals.profile.empty()) {
+      Path profileLink = getHome() + "/.nix-profile";
+      try {
+        if (!pathExists(profileLink)) {
+          replaceSymlink(getuid() == 0
+                             ? settings.nixStateDir + "/profiles/default"
+                             : fmt("%s/profiles/per-user/%s/profile",
+                                   settings.nixStateDir, getUserName()),
+                         profileLink);
+        }
+        globals.profile = absPath(readLink(profileLink), dirOf(profileLink));
+      } catch (Error&) {
+        globals.profile = profileLink;
+      }
+    }
+
+    op(globals, opFlags, opArgs);
+
+    globals.state->printStats();
+
+    return 0;
+  }
+}
+
+static RegisterLegacyCommand s1("nix-env", _main);