nixd/Server: split worker in a dedicated class (#230)

This should fix some async-signal unsafe calls (causing the forked
process hangs).

lspserver/include/lspserver/DraftStore.h

@@ -47,6 +47,10 @@ class DraftStore {
 
   llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> asVFS() const;
 
+  /// LSP defines file versions as numbers that increase.
+  /// treats them as opaque and therefore uses strings instead.
+  static std::string encodeVersion(std::optional<int64_t> LSPVersion);
+
   static std::optional<int64_t> decodeVersion(llvm::StringRef Encoded);
 
 private:

lspserver/include/lspserver/LSPServer.h

@@ -10,9 +10,6 @@
 
 #include <memory>
 
-#include <llvm/ADT/StringRef.h>
-#include <llvm/Support/JSON.h>
-
 namespace lspserver {
 
 /// LSPServer wraps inputs & outputs, associate message IDs between calls/reply,

lspserver/src/DraftStore.cpp

@@ -81,6 +81,10 @@ static void updateVersion(DraftStore::Draft &D,
   }
 }
 
+std::string DraftStore::encodeVersion(std::optional<int64_t> LSPVersion) {
+  return LSPVersion ? std::to_string(*LSPVersion) : "";
+}
+
 std::string DraftStore::addDraft(PathRef File, llvm::StringRef Version,
                                  llvm::StringRef Contents) {
   std::lock_guard<std::mutex> Lock(Mutex);

nixd/include/nixd/Nix/Eval.h

@@ -0,0 +1,22 @@
+#include <nix/eval-inline.hh>
+#include <nix/shared.hh>
+
+namespace nix {
+
+// Copy-paste from nix source code, do not know why it is inlined.
+
+inline void EvalState::evalAttrs(Env &env, Expr *e, Value &v, const PosIdx pos,
+                                 std::string_view errorCtx) {
+  try {
+    e->eval(*this, env, v);
+    if (v.type() != nAttrs)
+      error("value is %1% while a set was expected", showType(v))
+          .withFrame(env, *e)
+          .debugThrow<TypeError>();
+  } catch (Error &e) {
+    e.addTrace(positions[pos], errorCtx);
+    throw;
+  }
+}
+
+} // namespace nix

nixd/include/nixd/Nix/Init.h

@@ -0,0 +1,16 @@
+#pragma once
+
+#include <nix/eval.hh>
+#include <nix/globals.hh>
+#include <nix/shared.hh>
+
+namespace nixd {
+
+inline void initEval() {
+  nix::initNix();
+  nix::initLibStore();
+  nix::initPlugins();
+  nix::initGC();
+}
+
+} // namespace nixd

nixd/include/nixd/Server/Config.h

@@ -0,0 +1,52 @@
+#pragma once
+
+#include <list>
+#include <string>
+#include <thread>
+#include <vector>
+
+namespace nixd::configuration {
+
+inline std::list<std::string> toNixArgs(const std::vector<std::string> &Args) {
+  return {Args.begin(), Args.end()};
+}
+struct InstallableConfigurationItem {
+  std::vector<std::string> args;
+  std::string installable;
+
+  [[nodiscard]] bool empty() const {
+    return args.empty() && installable.empty();
+  }
+
+  [[nodiscard]] auto nArgs() const { return toNixArgs(args); }
+};
+
+struct TopLevel {
+
+  struct Eval {
+    /// Nix installables that will be used for root translation unit.
+    InstallableConfigurationItem target;
+
+    /// The depth you'd like to eval *after* reached "installable" target.
+    int depth = 0;
+    /// Number of workers forking
+    /// defaults to std::thread::hardware_concurrency
+    int workers = static_cast<int>(std::thread::hardware_concurrency());
+  };
+
+  Eval eval;
+
+  struct Formatting {
+    std::string command = "nixpkgs-fmt";
+  };
+  Formatting formatting;
+
+  struct Options {
+    bool enable = false;
+    InstallableConfigurationItem target;
+  };
+
+  Options options;
+};
+
+} // namespace nixd::configuration

nixd/include/nixd/Server/ConfigSerialization.h

@@ -0,0 +1,31 @@
+#pragma once
+
+#include "Config.h"
+
+#include <llvm/Support/JSON.h>
+
+namespace nixd::configuration {
+
+llvm::json::Value toJSON(const TopLevel::Eval &R);
+
+llvm::json::Value toJSON(const TopLevel::Formatting &R);
+
+llvm::json::Value toJSON(const TopLevel::Options &R);
+
+llvm::json::Value toJSON(const InstallableConfigurationItem &R);
+
+bool fromJSON(const llvm::json::Value &Params, TopLevel::Eval &R,
+              llvm::json::Path P);
+
+bool fromJSON(const llvm::json::Value &Params, TopLevel::Formatting &R,
+              llvm::json::Path P);
+
+bool fromJSON(const llvm::json::Value &Params, TopLevel::Options &R,
+              llvm::json::Path P);
+
+bool fromJSON(const llvm::json::Value &Params, TopLevel &R, llvm::json::Path P);
+
+bool fromJSON(const llvm::json::Value &Params, InstallableConfigurationItem &R,
+              llvm::json::Path P);
+
+} // namespace nixd::configuration