3 files changed, 62 insertions, 33 deletions

diff --git a/src/libutil/error.cc b/src/libutil/error.cc
index 1185a0204..10a5300cb 100644
--- a/src/libutil/error.cc
+++ b/src/libutil/error.cc
@@ -34,6 +34,7 @@ const string& BaseError::calcWhat() const
 }
 
 std::optional<string> ErrorInfo::programName = std::nullopt;
+bool ErrorInfo::showTrace = false;
 
 std::ostream& operator<<(std::ostream &os, const hintformat &hf)
 {
@@ -325,42 +326,44 @@ std::ostream& operator<<(std::ostream &out, const ErrorInfo &einfo)
     }
 
     // traces
-    for (auto iter = einfo.traces.rbegin(); iter != einfo.traces.rend(); ++iter)
-    {
-        try {
-            if (nl)
-                out << std::endl << prefix;
-
-            const string tracetitle(" show-trace output ");
-
-            int fill = errwidth - tracetitle.length();
-            int lw = 0;
-            int rw = 0;
-            const int min_dashes = 3;
-            if (fill > min_dashes * 2) {
-                if (fill % 2 != 0) {
-                    lw = fill / 2;
-                    rw = lw + 1;
+    if (ErrorInfo::showTrace) {
+        for (auto iter = einfo.traces.rbegin(); iter != einfo.traces.rend(); ++iter)
+        {
+            try {
+                if (nl)
+                    out << std::endl << prefix;
+
+                const string tracetitle(" show-trace output ");
+
+                int fill = errwidth - tracetitle.length();
+                int lw = 0;
+                int rw = 0;
+                const int min_dashes = 3;
+                if (fill > min_dashes * 2) {
+                    if (fill % 2 != 0) {
+                        lw = fill / 2;
+                        rw = lw + 1;
+                    }
+                    else
+                    {
+                        lw = rw = fill / 2;
+                    }
                 }
                 else
-                {
-                    lw = rw = fill / 2;
-                }
+                    lw = rw = min_dashes;
+
+                out << ANSI_BLUE << std::string(lw, '-') << tracetitle << std::string(rw, '-') << std::endl << prefix;
+                out << iter->hint.str() <<  std::endl;
+
+                auto pos = *iter->pos;
+                printAtPos(prefix, pos, out);
+                nl = true;
+                auto loc = getCodeLines(pos);
+                if (loc.has_value())
+                    printCodeLines(out, prefix, pos, *loc);
+            } catch(const std::bad_optional_access& e) {
+                out << iter->hint.str() << std::endl;
             }
-            else
-                lw = rw = min_dashes;
-
-            out << ANSI_BLUE << std::string(lw, '-') << tracetitle << std::string(rw, '-') << std::endl << prefix;
-            out << iter->hint.str() <<  std::endl;
-
-            auto pos = *iter->pos;
-            printAtPos(prefix, pos, out);
-            nl = true;
-            auto loc = getCodeLines(pos);
-            if (loc.has_value())
-                printCodeLines(out, prefix, pos, *loc);
-        } catch(const std::bad_optional_access& e) {
-            out << iter->hint.str() << std::endl;
         }
     }
 
diff --git a/src/libutil/error.hh b/src/libutil/error.hh
index d79ff8f8c..dcde28453 100644
--- a/src/libutil/error.hh
+++ b/src/libutil/error.hh
@@ -107,6 +107,7 @@ struct ErrorInfo {
     std::list<Trace> traces;
 
     static std::optional<string> programName;
+    static bool showTrace;
 };
 
 std::ostream& operator<<(std::ostream &out, const ErrorInfo &einfo);
diff --git a/src/libutil/tests/logging.cc b/src/libutil/tests/logging.cc
index 6d0431133..7531d6c7a 100644
--- a/src/libutil/tests/logging.cc
+++ b/src/libutil/tests/logging.cc
@@ -251,6 +251,7 @@ namespace nix {
 
     TEST(addTrace, showTracesWithShowTrace) {
         SymbolTable testTable;
+        ErrorInfo::showTrace = true;
         auto problem_file = testTable.create(test_file);
 
         auto oneliner_file = testTable.create(one_liner);
@@ -272,6 +273,30 @@ namespace nix {
         ASSERT_STREQ(str.c_str(), "\x1B[31;1merror:\x1B[0m\x1B[34;1m --- AssertionError --- error-unit-test\x1B[0m\n\x1B[34;1mat: \x1B[33;1m(2:13)\x1B[34;1m from command line argument\x1B[0m\n\na well-known problem occurred\n\n     1| previous line of code\n     2| this is the problem line of code\n      |             \x1B[31;1m^\x1B[0m\n     3| next line of code\n\nit has been \x1B[33;1mzero\x1B[0m days since our last error\n\x1B[34;1m--- show-trace output ---\nwhile trying to compute \x1B[33;1m42\x1B[0m\n\x1B[34;1mat: \x1B[33;1m(1:19)\x1B[34;1m from stdin\x1B[0m\n     1| this is the other problem line of code\n      |                   \x1B[31;1m^\x1B[0m\n");
     }
 
+    TEST(addTrace, hideTracesWithoutShowTrace) {
+        SymbolTable testTable;
+        ErrorInfo::showTrace = false;
+        auto problem_file = testTable.create(test_file);
+
+        auto oneliner_file = testTable.create(one_liner);
+
+        auto e = AssertionError(ErrorInfo {
+                .name = "wat",
+                .description = "a well-known problem occurred",
+                .hint = hintfmt("it has been %1% days since our last error", "zero"),
+                .errPos = Pos(foString, problem_file, 2, 13),
+            });
+
+        e.addTrace(Pos(foStdin, oneliner_file, 1, 19), "while trying to compute %1%", 42);
+
+        testing::internal::CaptureStderr();
+
+        logError(e.info());
+
+        auto str = testing::internal::GetCapturedStderr();
+        ASSERT_STREQ(str.c_str(), "\x1B[31;1merror:\x1B[0m\x1B[34;1m --- AssertionError --- error-unit-test\x1B[0m\n\x1B[34;1mat: \x1B[33;1m(2:13)\x1B[34;1m from command line argument\x1B[0m\n\na well-known problem occurred\n\n     1| previous line of code\n     2| this is the problem line of code\n      |             \x1B[31;1m^\x1B[0m\n     3| next line of code\n\nit has been \x1B[33;1mzero\x1B[0m days since our last error\n");
+    }
+
     /* ----------------------------------------------------------------------------
      * hintfmt
      * --------------------------------------------------------------------------*/