Initial frames support

src/libexpr/eval.cc

@@ -836,6 +836,37 @@ void EvalState::runDebugRepl(const Error * error, const Env & env, const Expr &
    evaluator.  So here are some helper functions for throwing
    exceptions. */
 
+template <typename ErrorType>
+void EvalState::throwFrameErrorWithTrace(
+        PosIdx pos, const char* format,
+        const std::string_view s1, const std::string_view s2,
+        const Symbol * sym1, const Symbol * sym2,
+        Value * val1, Value * val2,
+        PosIdx pos1,
+        const std::string_view s3,
+        const Suggestions * suggestions,
+        PosIdx tracePos, const std::string_view traceStr,
+        Env * env, Expr * expr)
+{
+    hintformat f(format);
+    if (!s1.empty()) { f = f % s1; }
+    if (!s2.empty()) { f = f % s2; }
+    if (sym1) { f = f % symbols[*sym1]; }
+    if (sym2) { f = f % symbols[*sym2]; }
+    if (val1) { f = f % showType(*val1); }
+    if (val2) { f = f % showType(*val2); }
+    if (pos1) { f = f % positions[pos1]; }
+    if (!s3.empty()) { f = f % s3; }
+
+    auto e = ErrorType(ErrorInfo {
+        .msg = f,
+        .errPos = positions[pos],
+        .suggestions = suggestions ? *suggestions : Suggestions(),
+    });
+    e.addTrace(positions[tracePos], traceStr, true);
+    debugThrow(e, env, expr);
+}
+
 template <typename ErrorType>
 void EvalState::throwErrorWithTrace(
         PosIdx pos, const char* format,
@@ -901,9 +932,9 @@ void EvalState::addErrorTrace(Error & e, const char * s, const std::string & s2)
     e.addTrace(std::nullopt, s, s2);
 }
 
-void EvalState::addErrorTrace(Error & e, const PosIdx pos, const char * s, const std::string & s2) const
+void EvalState::addErrorTrace(Error & e, const PosIdx pos, const char * s, const std::string & s2, bool frame) const
 {
-    e.addTrace(positions[pos], s, s2);
+    e.addTrace(positions[pos], hintfmt(s, s2), frame);
 }
 
 static std::unique_ptr<DebugTraceStacker> makeDebugTraceStacker(
@@ -1164,7 +1195,7 @@ inline bool EvalState::evalBool(Env & env, Expr * e, const PosIdx pos, std::stri
         Value v;
         e->eval(*this, env, v);
         if (v.type() != nBool)
-            throwError<TypeError>(pos, "value is %1% while a Boolean was expected", "", "", 0, 0, &v, 0, noPos, "", 0, &env, e);
+            throwError<TypeError>(noPos, "value is %1% while a Boolean was expected", "", "", 0, 0, &v, 0, noPos, "", 0, &env, e);
         return v.boolean;
     } catch (Error & e) {
         e.addTrace(positions[pos], errorCtx);
@@ -1178,7 +1209,7 @@ inline void EvalState::evalAttrs(Env & env, Expr * e, Value & v, const PosIdx po
     try {
         e->eval(*this, env, v);
         if (v.type() != nAttrs)
-            throwError<TypeError>(pos, "value is %1% while a set was expected", "", "", 0, 0, &v, 0, noPos, "", 0, &env, e);
+            throwError<TypeError>(noPos, "value is %1% while a set was expected", "", "", 0, 0, &v, 0, noPos, "", 0, &env, e);
     } catch (Error & e) {
         e.addTrace(positions[pos], errorCtx);
         throw;
@@ -1502,7 +1533,7 @@ void EvalState::callFunction(Value & fun, size_t nrArgs, Value * * args, Value &
                     auto j = args[0]->attrs->get(i.name);
                     if (!j) {
                         if (!i.def) {
-                            throwErrorWithTrace<TypeError>(lambda.pos,
+                            throwFrameErrorWithTrace<TypeError>(lambda.pos,
                                     "function '%1%' called without required argument '%2%'",
                                     (lambda.name ? std::string(symbols[lambda.name]) : "anonymous lambda"), "",
                                     &i.name, 0, 0, 0, noPos, "", 0, pos, "from call site", fun.lambda.env, &lambda);
@@ -1525,7 +1556,7 @@ void EvalState::callFunction(Value & fun, size_t nrArgs, Value * * args, Value &
                             for (auto & formal : lambda.formals->formals)
                                 formalNames.insert(symbols[formal.name]);
                             auto suggestions = Suggestions::bestMatches(formalNames, symbols[i.name]);
-                            throwErrorWithTrace<TypeError>(lambda.pos,
+                            throwFrameErrorWithTrace<TypeError>(lambda.pos,
                                     "function '%1%' called with unexpected argument '%2%'",
                                     (lambda.name ? std::string(symbols[lambda.name]) : "anonymous lambda"), "",
                                     &i.name, 0, 0, 0, noPos, "", &suggestions, pos, "from call site", fun.lambda.env, &lambda);

src/libexpr/eval.hh

@@ -312,6 +312,19 @@ public:
     std::string_view forceString(Value & v, PathSet & context, const PosIdx pos, std::string_view errorCtx);
     std::string_view forceStringNoCtx(Value & v, const PosIdx pos, std::string_view errorCtx);
 
+    template <typename ErrorType>
+    [[gnu::noinline, gnu::noreturn]]
+    void throwFrameErrorWithTrace(
+        PosIdx pos, const char* format,
+        const std::string_view s1, const std::string_view s2,
+        const Symbol * sym1, const Symbol * sym2,
+        Value * val1, Value * val2,
+        PosIdx pos1,
+        const std::string_view s3,
+        const Suggestions * suggestions,
+        PosIdx tracePos, const std::string_view traceStr,
+        Env * env, Expr * expr);
+
     template <typename ErrorType>
     [[gnu::noinline, gnu::noreturn]]
     void throwErrorWithTrace(
@@ -340,7 +353,7 @@ public:
     [[gnu::noinline]]
     void addErrorTrace(Error & e, const char * s, const std::string & s2) const;
     [[gnu::noinline]]
-    void addErrorTrace(Error & e, const PosIdx pos, const char * s, const std::string & s2) const;
+    void addErrorTrace(Error & e, const PosIdx pos, const char * s, const std::string & s2, bool frame = false) const;
 
 public:
     /* Return true iff the value `v' denotes a derivation (i.e. a

src/libexpr/primops.cc

@@ -1171,9 +1171,9 @@ static void prim_derivationStrict(EvalState & state, const PosIdx pos, Value * *
             }
 
         } catch (Error & e) {
-            e.addTrace(state.positions[posDrvName],
+            e.addTrace(state.positions[noPos],
-                "while evaluating the attribute '%1%' of the derivation '%2%'",
+                hintfmt("while evaluating the attribute '%1%' of the derivation '%2%'", key, drvName),
-                key, drvName);
+                true);
             throw;
         }
     }

src/libutil/error.cc

@@ -9,9 +9,9 @@ namespace nix {
 
 const std::string nativeSystem = SYSTEM;
 
-void BaseError::addTrace(std::optional<ErrPos> e, hintformat hint)
+void BaseError::addTrace(std::optional<ErrPos> e, hintformat hint, bool frame)
 {
-    err.traces.push_front(Trace { .pos = e, .hint = hint });
+    err.traces.push_front(Trace { .pos = e, .hint = hint, .frame = frame });
 }
 
 // c++ std::exception descendants must have a 'const char* what()' function.
@@ -382,6 +382,7 @@ std::ostream & showErrorInfo(std::ostream & out, const ErrorInfo & einfo, bool s
      *
      */
 
+    bool frameOnly = false;
     if (!einfo.traces.empty()) {
         unsigned int count = 0;
         for (auto iter = einfo.traces.rbegin(); iter != einfo.traces.rend(); ++iter) {
@@ -391,7 +392,11 @@ std::ostream & showErrorInfo(std::ostream & out, const ErrorInfo & einfo, bool s
             }
 
             if (iter->hint.str().empty()) continue;
+            if (frameOnly && !iter->frame) continue;
+
             count++;
+            frameOnly = iter->frame;
+
             oss << "\n" << "… " << iter->hint.str() << "\n";
 
             if (iter->pos.has_value() && (*iter->pos)) {

src/libutil/error.hh

@@ -110,6 +110,7 @@ void printAtPos(const ErrPos & pos, std::ostream & out);
 struct Trace {
     std::optional<ErrPos> pos;
     hintformat hint;
+    bool frame;
 };
 
 struct ErrorInfo {
@@ -188,7 +189,7 @@ public:
         addTrace(e, hintfmt(std::string(fs), args...));
     }
 
-    void addTrace(std::optional<ErrPos> e, hintformat hint);
+    void addTrace(std::optional<ErrPos> e, hintformat hint, bool frame = false);
 
     bool hasTrace() const { return !err.traces.empty(); }
 };