nixd/Controller: support "goto definition" for select expressions

nixd/lib/Controller/AST.cpp

@@ -247,6 +247,19 @@ nixd::Selector nixd::mkSelector(const nixf::ExprSelect &Select,
   return BaseSelector;
 }
 
+nixd::Selector nixd::mkSelector(const nixf::ExprSelect &Sel,
+                                const nixf::VariableLookupAnalysis &VLA,
+                                const nixf::ParentMapAnalysis &PM) {
+  if (Sel.expr().kind() != Node::NK_ExprVar)
+    throw NotVariableSelect();
+
+  const auto &Var = static_cast<ExprVar &>(Sel.expr());
+
+  auto BaseSelector = mkIdiomSelector(Var, VLA, PM);
+
+  return mkSelector(Sel, std::move(BaseSelector));
+}
+
 std::pair<std::vector<std::string>, std::string>
 nixd::getScopeAndPrefix(const Node &N, const ParentMapAnalysis &PM) {
   if (N.kind() != Node::NK_Identifer)

nixd/lib/Controller/AST.h

@@ -3,6 +3,7 @@
 
 #include "nixd/Protocol/AttrSet.h"
 
+#include <nixf/Basic/Nodes/Expr.h>
 #include <nixf/Sema/ParentMap.h>
 #include <nixf/Sema/VariableLookup.h>
 
@@ -49,6 +50,8 @@ upEnv(const nixf::Node &Desc, const nixf::VariableLookupAnalysis &VLA,
 std::pair<std::vector<std::string>, std::string>
 getScopeAndPrefix(const nixf::Node &N, const nixf::ParentMapAnalysis &PM);
 
+struct IdiomException : std::exception {};
+
 /// \brief Exceptions scoped in nixd::mkIdiomSelector
 struct IdiomSelectorException : std::exception {};
 
@@ -59,13 +62,21 @@ struct NotAnIdiomException : IdiomSelectorException {
   }
 };
 
+struct VLAException : std::exception {};
+
 /// \brief No such variable.
-struct NoSuchVarException : IdiomSelectorException {
+struct NoSuchVarException : VLAException {
   [[nodiscard]] const char *what() const noexcept override {
     return "no such variable";
   }
 };
 
+struct UndefinedVarException : VLAException {
+  [[nodiscard]] const char *what() const noexcept override {
+    return "undefined variable";
+  }
+};
+
 /// \brief Construct a nixd::Selector from \p Var.
 ///
 /// Try to heuristically find a selector of a variable, based on some known
@@ -74,22 +85,31 @@ Selector mkIdiomSelector(const nixf::ExprVar &Var,
                          const nixf::VariableLookupAnalysis &VLA,
                          const nixf::ParentMapAnalysis &PM);
 
-struct SelectorException : std::exception {};
-
 /// \brief The attrpath has a dynamic name, thus it cannot be trivially
 /// transformed to "static" selector.
-struct DynamicNameException : SelectorException {
+struct DynamicNameException : IdiomSelectorException {
   [[nodiscard]] const char *what() const noexcept override {
     return "dynamic attribute path encountered";
   }
 };
 
+struct NotVariableSelect : IdiomSelectorException {
+  [[nodiscard]] const char *what() const noexcept override {
+    return "the base expression of the select is not a variable";
+  }
+};
+
 /// \brief Construct a nixd::Selector from \p AP.
 Selector mkSelector(const nixf::AttrPath &AP, Selector BaseSelector);
 
 /// \brief Construct a nixd::Selector from \p Select.
 Selector mkSelector(const nixf::ExprSelect &Select, Selector BaseSelector);
 
+/// \brief Construct a nixd::Selector from \p Select.
+Selector mkSelector(const nixf::ExprSelect &Select,
+                    const nixf::VariableLookupAnalysis &VLA,
+                    const nixf::ParentMapAnalysis &PM);
+
 enum class FindAttrPathResult {
   OK,
   Inherit,

nixd/lib/Controller/Completion.cpp

@@ -351,17 +351,11 @@ void completeSelect(const nixf::ExprSelect &Select, AttrSetClient &Client,
   // Ask nixpkgs provider to get idioms completion.
   NixpkgsCompletionProvider NCP(Client);
 
-  const auto Handler = [](std::exception &E) noexcept {
-    log(DBG "skipped, reason: {0}", E.what());
-  };
   try {
     Selector Sel = mkSelector(Select, mkIdiomSelector(Var, VLA, PM));
     NCP.completePackages(mkParams(Sel, IsComplete), List);
   } catch (IdiomSelectorException &E) {
-    Handler(E);
-    return;
-  } catch (SelectorException &E) {
-    Handler(E);
+    log(DBG "skipped, reason: {0}", E.what());
     return;
   }