nixd/tools/nixd-attrset-eval: support completion for "builtins"

libnixt/include/nixt/Value.h

@@ -70,4 +70,10 @@ selectStringViews(nix::EvalState &State, nix::Value &V,
   return selectSymbols(State, V, toSymbols(State.symbols, AttrPath));
 }
 
+/// TODO: use https://github.com/NixOS/nix/pull/11914 on nix version bump
+/// \brief Get nix's `builtins` constant
+inline nix::Value &getBuiltins(const nix::EvalState &State) {
+  return *State.baseEnv.values[0];
+}
+
 } // namespace nixt

nixd/include/nixd/Eval/AttrSetProvider.h

@@ -66,6 +66,14 @@ class AttrSetProvider : public lspserver::LSPServer {
   /// FIXME: suppport list names. i.e.    `foo.*.submodule`
   void onOptionComplete(const AttrPathCompleteParams &Params,
                         lspserver::Callback<OptionCompleteResponse> Reply);
+
+  /// \brief Provide information on builtin values.
+  void onBuiltinInfo(const AttrPathInfoParams &AttrPath,
+                     lspserver::Callback<BuiltinInfoResponse> Reply);
+
+  /// \brief Complete builtin values.
+  void onBuiltinComplete(const AttrPathCompleteParams &Params,
+                         lspserver::Callback<BuiltinCompleteResponse> Reply);
 };
 
 } // namespace nixd

nixd/include/nixd/Protocol/AttrSet.h

@@ -3,6 +3,7 @@
 
 #pragma once
 
+#include <cstdint>
 #include <optional>
 #include <string>
 #include <vector>
@@ -31,6 +32,13 @@ constexpr inline std::string_view AttrPathInfo = "attrset/attrpathInfo";
 constexpr inline std::string_view AttrPathComplete = "attrset/attrpathComplete";
 constexpr inline std::string_view OptionInfo = "attrset/optionInfo";
 constexpr inline std::string_view OptionComplete = "attrset/optionComplete";
+
+/// \brief ↩︎ Request information
+constexpr inline std::string_view BuiltinInfo = "attrset/builtinInfo";
+
+/// \brief ↩︎ Request completion of builtins.
+constexpr inline std::string_view BuiltinComplete = "attrset/builtinComplete";
+
 constexpr inline std::string_view Exit = "exit";
 
 } // namespace rpcMethod
@@ -136,4 +144,16 @@ using OptionInfoResponse = OptionDescription;
 
 using OptionCompleteResponse = std::vector<OptionField>;
 
+struct BuiltinDescription {
+  std::string Doc;
+  std::int64_t Arity;
+};
+
+llvm::json::Value toJSON(const BuiltinDescription &Params);
+bool fromJSON(const llvm::json::Value &Params, BuiltinDescription &R,
+              llvm::json::Path P);
+
+using BuiltinInfoResponse = BuiltinDescription;
+using BuiltinCompleteResponse = std::vector<std::string>;
+
 } // namespace nixd

nixd/lib/Eval/AttrSetProvider.cpp

@@ -5,6 +5,7 @@
 
 #include <nix/attr-path.hh>
 #include <nix/common-eval-args.hh>
+#include <nix/eval.hh>
 #include <nix/nixexpr.hh>
 #include <nix/store-api.hh>
 #include <nixt/Value.h>
@@ -156,6 +157,30 @@ void fillOptionDescription(nix::EvalState &State, nix::Value &V,
   }
 }
 
+std::vector<std::string> completeNames(nix::Value &Scope,
+                                       const nix::EvalState &State,
+                                       std::string_view Prefix) {
+  int Num = 0;
+  std::vector<std::string> Names;
+
+  // FIXME: we may want to use "Trie" to speedup the string searching.
+  // However as my (roughtly) profiling the critical in this loop is
+  // evaluating package details.
+  // "Trie"s may not beneficial because it cannot speedup eval.
+  for (const auto *AttrPtr : Scope.attrs()->lexicographicOrder(State.symbols)) {
+    const nix::Attr &Attr = *AttrPtr;
+    const std::string_view Name = State.symbols[Attr.name];
+    if (Name.starts_with(Prefix)) {
+      ++Num;
+      Names.emplace_back(Name);
+      // We set this a very limited number as to speedup
+      if (Num > MaxItems)
+        break;
+    }
+  }
+  return Names;
+}
+
 } // namespace
 
 AttrSetProvider::AttrSetProvider(std::unique_ptr<InboundPort> In,
@@ -172,6 +197,10 @@ AttrSetProvider::AttrSetProvider(std::unique_ptr<InboundPort> In,
                      &AttrSetProvider::onOptionInfo);
   Registry.addMethod(rpcMethod::OptionComplete, this,
                      &AttrSetProvider::onOptionComplete);
+  Registry.addMethod(rpcMethod::BuiltinInfo, this,
+                     &AttrSetProvider::onBuiltinInfo);
+  Registry.addMethod(rpcMethod::BuiltinComplete, this,
+                     &AttrSetProvider::onBuiltinComplete);
 }
 
 void AttrSetProvider::onEvalExpr(
@@ -227,33 +256,11 @@ void AttrSetProvider::onAttrPathComplete(
       return;
     }
 
-    std::vector<std::string> Names;
-    int Num = 0;
-
-    // FIXME: we may want to use "Trie" to speedup the string searching.
-    // However as my (roughtly) profiling the critical in this loop is
-    // evaluating package details.
-    // "Trie"s may not beneficial becausae it cannot speedup eval.
-    for (const auto *AttrPtr :
-         Scope.attrs()->lexicographicOrder(state().symbols)) {
-      const nix::Attr &Attr = *AttrPtr;
-      const std::string_view Name = state().symbols[Attr.name];
-      if (Name.starts_with(Params.Prefix)) {
-        ++Num;
-        Names.emplace_back(Name);
-        // We set this a very limited number as to speedup
-        if (Num > MaxItems)
-          break;
-      }
-    }
-    Reply(std::move(Names));
-    return;
+    return Reply(completeNames(Scope, state(), Params.Prefix));
   } catch (const nix::BaseError &Err) {
-    Reply(error(Err.info().msg.str()));
-    return;
+    return Reply(error(Err.info().msg.str()));
   } catch (const std::exception &Err) {
-    Reply(error(Err.what()));
-    return;
+    return Reply(error(Err.what()));
   }
 }
 
@@ -339,3 +346,33 @@ void AttrSetProvider::onOptionComplete(
     return;
   }
 }
+void nixd::AttrSetProvider::onBuiltinInfo(
+    const AttrPathInfoParams &AttrPath,
+    lspserver::Callback<BuiltinDescription> Reply) {
+  return Reply([&]() -> llvm::Expected<BuiltinDescription> {
+    auto &Builtins = nixt::getBuiltins(state());
+    if (AttrPath.empty())
+      return error("attrpath is empty!");
+
+    auto &TheBuiltin = nixt::selectStrings(state(), Builtins, AttrPath);
+    const auto &Doc = state().getDoc(TheBuiltin);
+    if (!Doc) {
+      return error("No documentation available");
+    } else {
+      return BuiltinDescription{
+          .Doc = Doc->doc,
+          .Arity = static_cast<int64_t>(Doc->arity),
+      };
+    }
+  }());
+}
+
+void nixd::AttrSetProvider::onBuiltinComplete(
+    const AttrPathCompleteParams &Params,
+    lspserver::Callback<BuiltinCompleteResponse> Reply) {
+  return Reply([&]() -> llvm::Expected<BuiltinCompleteResponse> {
+    auto &Builtins = nixt::getBuiltins(state());
+    auto &Scope = nixt::selectStrings(state(), Builtins, Params.Scope);
+    return completeNames(Scope, state(), Params.Prefix);
+  }());
+}

nixd/lib/Protocol/AttrSet.cpp

@@ -120,3 +120,19 @@ bool nixd::fromJSON(const llvm::json::Value &Params, AttrPathCompleteParams &R,
          && O.map("Prefix", R.Prefix) //
       ;
 }
+
+llvm::json::Value nixd::toJSON(const BuiltinDescription &Params) {
+  return Object{
+      {"arity", Params.Arity},
+      {"doc", Params.Doc},
+  };
+}
+bool nixd::fromJSON(const llvm::json::Value &Params, BuiltinDescription &R,
+                    llvm::json::Path P) {
+
+  ObjectMapper O(Params, P);
+  return O                          //
+         && O.map("arity", R.Arity) //
+         && O.map("doc", R.Doc)     //
+      ;
+}

nixd/tools/nixd-attrset-eval/test/builtin-completion.md

@@ -0,0 +1,56 @@
+# RUN: nixd-attrset-eval --lit-test < %s | FileCheck %s
+
+
+```json
+{
+   "jsonrpc":"2.0",
+   "id":1,
+   "method":"attrset/builtinComplete",
+   "params": {
+        "Scope": [ ],
+        "Prefix": ""
+   }
+}
+```
+
+```
+     CHECK: "id": 1,
+CHECK-NEXT:  "jsonrpc": "2.0",
+CHECK-NEXT:  "result": [
+CHECK-NEXT:    "abort",
+CHECK-NEXT:    "add",
+CHECK-NEXT:    "addDrvOutputDependencies",
+CHECK-NEXT:    "addErrorContext",
+CHECK-NEXT:    "all",
+CHECK-NEXT:    "any",
+CHECK-NEXT:    "appendContext",
+CHECK-NEXT:    "attrNames",
+CHECK-NEXT:    "attrValues",
+CHECK-NEXT:    "baseNameOf",
+CHECK-NEXT:    "bitAnd",
+CHECK-NEXT:    "bitOr",
+CHECK-NEXT:    "bitXor",
+CHECK-NEXT:    "break",
+CHECK-NEXT:    "builtins",
+CHECK-NEXT:    "catAttrs",
+CHECK-NEXT:    "ceil",
+CHECK-NEXT:    "compareVersions",
+CHECK-NEXT:    "concatLists",
+CHECK-NEXT:    "concatMap",
+CHECK-NEXT:    "concatStringsSep",
+CHECK-NEXT:    "convertHash",
+CHECK-NEXT:    "currentSystem",
+CHECK-NEXT:    "currentTime",
+CHECK-NEXT:    "deepSeq",
+CHECK-NEXT:    "derivation",
+CHECK-NEXT:    "derivationStrict",
+CHECK-NEXT:    "dirOf",
+CHECK-NEXT:    "div",
+CHECK-NEXT:    "elem",
+CHECK-NEXT:    "elemAt"
+CHECK-NEXT:  ]
+```
+
+```json
+{"jsonrpc":"2.0","method":"exit"}
+```

nixd/tools/nixd-attrset-eval/test/builtin-info.md

@@ -0,0 +1,25 @@
+# RUN: nixd-attrset-eval --lit-test < %s | FileCheck %s
+
+
+```json
+{
+   "jsonrpc":"2.0",
+   "id":1,
+   "method":"attrset/builtinInfo",
+   "params": [ "any" ]
+}
+```
+
+```
+     CHECK:  "id": 1,
+CHECK-NEXT:  "jsonrpc": "2.0",
+CHECK-NEXT:  "result": {
+CHECK-NEXT:    "arity": 2,
+CHECK-NEXT:    "doc": "{{.*}}"
+CHECK-NEXT:  }
+CHECK-NEXT:}
+```
+
+```json
+{"jsonrpc":"2.0","method":"exit"}
+```