Remove trace item: while calling the 'addErrorContext' builtin

src/libexpr/eval.cc

@@ -1665,6 +1665,7 @@ void EvalState::callFunction(Value & fun, size_t nrArgs, Value * * args, Value &
                 try {
                     fn->fun(*this, vCur.determinePos(noPos), args, vCur);
                 } catch (Error & e) {
+                    if (fn->addTrace)
                         addErrorTrace(e, pos, "while calling the '%1%' builtin", fn->name);
                     throw;
                 }
@@ -1713,6 +1714,7 @@ void EvalState::callFunction(Value & fun, size_t nrArgs, Value * * args, Value &
                     //    so the debugger allows to inspect the wrong parameters passed to the builtin.
                     fn->fun(*this, vCur.determinePos(noPos), vArgs, vCur);
                 } catch (Error & e) {
+                    if (fn->addTrace)
                         addErrorTrace(e, pos, "while calling the '%1%' builtin", fn->name);
                     throw;
                 }

src/libexpr/eval.hh

@@ -69,6 +69,13 @@ struct PrimOp
      */
     const char * doc = nullptr;
 
+    /**
+     * Add a trace item, `while calling the '<name>' builtin`
+     *
+     * This is used to remove the redundant item for `builtins.addErrorContext`.
+     */
+    bool addTrace = true;
+
     /**
      * Implementation of the primop.
      */

src/libexpr/primops.cc

@@ -834,6 +834,8 @@ static void prim_addErrorContext(EvalState & state, const PosIdx pos, Value * *
 static RegisterPrimOp primop_addErrorContext(PrimOp {
     .name = "__addErrorContext",
     .arity = 2,
+    // The normal trace item is redundant
+    .addTrace = false,
     .fun = prim_addErrorContext,
 });
 

tests/functional/lang/eval-fail-addErrorContext-example.err.exp

@@ -1,20 +1,6 @@
 error:
-       … while calling the 'addErrorContext' builtin
-         at /pwd/lang/eval-fail-addErrorContext-example.nix:6:7:
-            5|     else
-            6|       builtins.addErrorContext
-             |       ^
-            7|         "while counting down; n = ${toString n}"
-
        … while counting down; n = 10
 
-       … while calling the 'addErrorContext' builtin
-         at /pwd/lang/eval-fail-addErrorContext-example.nix:6:7:
-            5|     else
-            6|       builtins.addErrorContext
-             |       ^
-            7|         "while counting down; n = ${toString n}"
-
        … while counting down; n = 9
 
        … while counting down; n = 8