Fix attrset completions

Display all available completion options within the current attrset even if it's empty or there is no text under the cursor.

Author: oandrew

nixd/lib/Controller/AST.cpp

@@ -313,6 +313,16 @@ nixd::FindAttrPathResult nixd::findAttrPath(const nixf::Node &N,
     }
   }
 
+  if (const Node *ExprAttrs = PM.upTo(N, Node::NK_ExprAttrs)) {
+    try {
+      getValueAttrPath(*ExprAttrs, PM, Path);
+      Path.emplace_back("");
+      return R::OK;
+    } catch (AttrPathHasDynamicError &E) {
+      return R::WithDynamic;
+    }
+  }
+
   return R::NotAttrPath;
 }
 

nixd/lib/Controller/Completion.cpp

@@ -384,13 +384,13 @@ void Controller::onCompletion(const CompletionParams &Params,
     return Reply([&]() -> llvm::Expected<CompletionList> {
       const auto TU = CheckDefault(getTU(File));
       const auto AST = CheckDefault(getAST(*TU));
-
       const auto *Desc = AST->descend({Pos, Pos});
-      CheckDefault(Desc && Desc->children().empty());
+      CheckDefault(Desc);
 
       const auto &N = *Desc;
       const auto &PM = *TU->parentMap();
       const auto &UpExpr = *CheckDefault(PM.upExpr(N));
+      CheckDefault(Desc->children().empty() || UpExpr.kind() == Node::NK_ExprAttrs);
 
       return [&]() {
         CompletionList List;