1 files changed, 240 insertions, 0 deletions
diff --git a/third_party/nix/src/libstore/builtins/buildenv.cc b/third_party/nix/src/libstore/builtins/buildenv.cc
new file mode 100644
index 0000000000..433082a0f9
--- /dev/null
+++ b/third_party/nix/src/libstore/builtins/buildenv.cc
@@ -0,0 +1,240 @@
+#include <algorithm>
+
+#include <absl/strings/match.h>
+#include <absl/strings/str_split.h>
+#include <fcntl.h>
+#include <glog/logging.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+#include "libstore/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) {
+      LOG(ERROR) << "warning: not including '" << srcDir
+                 << "' in the user environment because it's not a directory";
+      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) {
+        LOG(ERROR) << "warning: skipping dangling symlink '" << 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 (absl::EndsWith(srcFile, "/propagated-build-inputs") ||
+        absl::EndsWith(srcFile, "/nix-support") ||
+        absl::EndsWith(srcFile, "/perllocal.pod") ||
+        absl::EndsWith(srcFile, "/info/dir") ||
+        absl::EndsWith(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++;
+  }
+}
+
+using FileProp = std::set<Path>;
+
+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 (auto p : absl::StrSplit(
+             readFile(pkgDir + "/nix-support/propagated-user-env-packages"),
+             absl::ByAnyChar(" \n"), absl::SkipEmpty())) {
+      auto pkg = std::string(p);
+      if (!done.count(pkg)) {
+        postponed.insert(pkg);
+      }
+    }
+  } 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} {}
+};
+
+using Packages = std::vector<Package>;
+
+void builtinBuildenv(const BasicDerivation& drv) {
+  auto getAttr = [&](const std::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;
+  Strings derivations = absl::StrSplit(
+      getAttr("derivations"), absl::ByAnyChar(" \t\n\r"), absl::SkipEmpty());
+  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++);
+    }
+  }
+
+  LOG(INFO) << "created " << symlinks << " symlinks in user environment";
+
+  createSymlink(getAttr("manifest"), out + "/manifest.nix");
+}
+
+}  // namespace nix