refactor(3p/nix/libexpr): Move EvalState:* implementations out of parser.y r/1323

Several definitions of functions declared in eval.hh were previously
implemented in parser.y, this moves them over to parser.cc.

While this still isn't a reasonable place to keep them, the long-term
fix is more likely to be that eval.hh needs to be split up.

Before we get to that point however, this already gives us the ability
to use tooling with this code.

Change-Id: If06fb655325fe281564047ffab0a0a640428a0ee
Reviewed-on: https://cl.tvl.fyi/c/depot/+/1219
Tested-by: BuildkiteCI
Reviewed-by: isomer <isomer@tvl.fyi>

1 files changed, 140 insertions, 0 deletions

diff --git a/third_party/nix/src/libexpr/parser.cc b/third_party/nix/src/libexpr/parser.cc
index 50b7cc3ff8e3..a96d345cc126 100644
--- a/third_party/nix/src/libexpr/parser.cc
+++ b/third_party/nix/src/libexpr/parser.cc
@@ -1,5 +1,14 @@
 #include "libexpr/parser.hh"
 
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include "libexpr/eval.hh"
+#include "libstore/download.hh"
+#include "libstore/store-api.hh"
+
 namespace nix {
 
 void addAttr(ExprAttrs* attrs, AttrPath& attrPath, Expr* e, const Pos& pos) {
@@ -182,5 +191,136 @@ Expr* stripIndentation(const Pos& pos, SymbolTable& symbols,
              : new ExprConcatStrings(pos, true, es2);
 }
 
+Path resolveExprPath(Path path) {
+  assert(path[0] == '/');
+
+  /* If `path' is a symlink, follow it.  This is so that relative
+     path references work. */
+  struct stat st;
+  while (true) {
+    if (lstat(path.c_str(), &st))
+      throw SysError(format("getting status of '%1%'") % path);
+    if (!S_ISLNK(st.st_mode)) {
+      break;
+    }
+    path = absPath(readLink(path), dirOf(path));
+  }
+
+  /* If `path' refers to a directory, append `/default.nix'. */
+  if (S_ISDIR(st.st_mode)) path = canonPath(path + "/default.nix");
+
+  return path;
+}
+
+// These methods are actually declared in eval.hh, and were - for some
+// reason - previously implemented in parser.y.
+
+Expr* EvalState::parseExprFromFile(const Path& path) {
+  return parseExprFromFile(path, staticBaseEnv);
+}
+
+Expr* EvalState::parseExprFromFile(const Path& path, StaticEnv& staticEnv) {
+  return parse(readFile(path).c_str(), path, dirOf(path), staticEnv);
+}
+
+Expr* EvalState::parseExprFromString(const std::string& s, const Path& basePath,
+                                     StaticEnv& staticEnv) {
+  return parse(s.c_str(), "(std::string)", basePath, staticEnv);
+}
+
+Expr* EvalState::parseExprFromString(const std::string& s,
+                                     const Path& basePath) {
+  return parseExprFromString(s, basePath, staticBaseEnv);
+}
+
+Expr* EvalState::parseStdin() {
+  // Activity act(*logger, lvlTalkative, format("parsing standard input"));
+  return parseExprFromString(drainFD(0), absPath("."));
+}
+
+void EvalState::addToSearchPath(const std::string& s) {
+  size_t pos = s.find('=');
+  std::string prefix;
+  Path path;
+  if (pos == std::string::npos) {
+    path = s;
+  } else {
+    prefix = std::string(s, 0, pos);
+    path = std::string(s, pos + 1);
+  }
+
+  searchPath.emplace_back(prefix, path);
+}
+
+Path EvalState::findFile(const std::string& path) {
+  return findFile(searchPath, path);
+}
+
+Path EvalState::findFile(SearchPath& searchPath, const std::string& path,
+                         const Pos& pos) {
+  for (auto& i : searchPath) {
+    std::string suffix;
+    if (i.first.empty())
+      suffix = "/" + path;
+    else {
+      auto s = i.first.size();
+      if (path.compare(0, s, i.first) != 0 ||
+          (path.size() > s && path[s] != '/'))
+        continue;
+      suffix = path.size() == s ? "" : "/" + std::string(path, s);
+    }
+    auto r = resolveSearchPathElem(i);
+    if (!r.first) {
+      continue;
+    }
+    Path res = r.second + suffix;
+    if (pathExists(res)) {
+      return canonPath(res);
+    }
+  }
+  format f = format(
+      "file '%1%' was not found in the Nix search path (add it using $NIX_PATH "
+      "or -I)" +
+      std::string(pos ? ", at %2%" : ""));
+  f.exceptions(boost::io::all_error_bits ^ boost::io::too_many_args_bit);
+  throw ThrownError(f % path % pos);
+}
+
+std::pair<bool, std::string> EvalState::resolveSearchPathElem(
+    const SearchPathElem& elem) {
+  auto i = searchPathResolved.find(elem.second);
+  if (i != searchPathResolved.end()) {
+    return i->second;
+  }
+
+  std::pair<bool, std::string> res;
+
+  if (isUri(elem.second)) {
+    try {
+      CachedDownloadRequest request(elem.second);
+      request.unpack = true;
+      res = {true, getDownloader()->downloadCached(store, request).path};
+    } catch (DownloadError& e) {
+      LOG(WARNING) << "Nix search path entry '" << elem.second
+                   << "' cannot be downloaded, ignoring";
+      res = {false, ""};
+    }
+  } else {
+    auto path = absPath(elem.second);
+    if (pathExists(path)) {
+      res = {true, path};
+    } else {
+      LOG(WARNING) << "Nix search path entry '" << elem.second
+                   << "' does not exist, ignoring";
+      res = {false, ""};
+    }
+  }
+
+  DLOG(INFO) << "resolved search path element '" << elem.second << "' to '"
+             << res.second << "'";
+
+  searchPathResolved[elem.second] = res;
+  return res;
+}
 
 }  // namespace nix